Even though I have yet to participate in any type of Radio Direction Finding (RDF) event, I find myself buying and building stuff for it. This time I decided to build an offset (active) attenuator as I think it’s a must need for RDF. When I was testing out my 3EL tape measure Yagi, I placed a transmitter on my property and tried to find it with a Yagi and found that it was near impossible to pinpoint the source as my radio was showing full scale and dead full quieting no matter where I went.
Since I’ve been reading a lot about fox hunting, I knew I needed an attenuator. However there are different kinds of attenuators that you can make or buy commercially. I wasn’t sure what to get at the time. I narrowed it down to the offset attenuator and the step attenuator. I went with the offset attenuator because it appears to be cheaper, easy to make and better than a step attenuator.
The attenuator that I went with was found on HomingIn.com’s Website. The article was writen by Joel Moell (K0OV) and explained in detail about the attenuator. What the offset attenuator does is “Offset” the received signal by 4MHz using a diode, oscillator and some other passive components. You are now listening to the signal away from it’s transmitting frequency. Your antenna and radio is no longer being overloaded and you’ll be able to get even closer to the signal.
It appears to be quite easy to build, even for me! So I went with it. The parts that are listen in the article are a little outdated
Here is an updated list of parts that I purchased. I usually use Mouser for components but I wasn’t satisfied with their shipping to the North East so I used Digi-Key with better results
|1X||CAP CER 470PF 2KV 10% RADIAL||$0.23 ea||1286PH-ND||Digi-Key|
|2X||CAP CER 4700PF 50V 10% RADIAL||$0.30 ea||BC2683CT-ND||Digi-Key|
|2X||RES 2.2K OHM 1/4W 5% CARBON FILM||$0.10 ea||2.2KQBK-ND||Digi-Key|
|1X||RES 4.7K OHM 1/4W 5% CARBON FILM||$0.10 ea||4.7KQBK-ND||Digi-Key|
|1X||DIODE SMALL SIG 100V 200MA DO35||$0.10 ea||1N4148TACT-ND||Digi-Key|
|1X||OSC 4.0000 MHZ FULL SIZE||$2.49 ea||CTX774-ND||Digi-Key|
|1X||BNC FRONT MT RECEPT SHORT||$4.67 ea||ARF1064-ND||Digi-Key|
|1X||5K Audio Tape Pot||$3.49 ea||#271-1720||Radio Shack/In-Store|
|1X||Perf Board/PC-Board||$2.49 ea||Radio Shack / Instore|
|1X||SPST Swith||$2.49 ea||Radio Shack / Instore|
Total project cost: Approx $8.00-$18 USD
Making Sure Everything Works
Before putting it on any type of board I wanted to make sure that It works. I never really messed around with making electronic devices from a pile of parts. I put the entire project onto a breadboard following the schematic as close as possible
Here it is being tested out on the breadboard It went together pretty easy. I used a voltage meter to make sure the correct voltage is coming out of the LM7805 regulator. I was seeing around 5V
Here is a video of it in action
Now that I know it works, it’s time to transfer the design to a more permanent home. I wanted to compact it as short as possible to get it to fit into a small PVC box. Since I had a PVC box I wanted the board to go into, I measured a piece of perf board and cut it up
After cutting the board, I laid out all the components and attached all the wiring I could from underneath the board
Here its with most of the stuff attached.
Here is the Top view of the board. I had to use some jumpers (red and green wires) to get some of the components to make contact.
The black wires you see leading away from the board are for power and the adjustable resistor. I tried to test it out at this point to make sure it works before adding the coax and other things but It turned out not to be worth doing. But I did check the circuit wiring a couple times to make sure.
Getting it jammed into the small box was going to be difficult. I knew right away that I wouldn’t be able to fit the 9V battery and the circuit board into the same compartment without using a larger box.
Here is the PVC junction box with the circuit board, switch, POT and cabled jammed into it. I had to have shave some of the flange off on the cover as the Pot is almost the same size as the Inside dimension of the box.
To solve the battery issue, I fabricated a small aluminum box that can hold a 9V battery. I drilled a small hole in the side of the PVC case to route the power cable through. In the above picture you can also see the on/off switch and adjustable pot. I mounted the switch sideways to avoid any accidental switching even though it’s still possible.
Here is the fully assembled antenna. The PVC junction box is also used to mount the grip handle. This way most of the weight is sitting on top of my hand instead of out on the boom. I also didn’t want to put any kind of electronics/metal between the reflector and driven element. Not sure if it would make a difference but I think it’s better off this way
I learned a lot while making this attenuator. The circuit was simple enough to where I can understand what is going on.
If I were to build another one, I would make some changes to make it even better. The big problem is that the coax runs from the driven element straight into the attenuator from inside the PVC. This doesn’t allow me to swap out antennas. What I would do is put a BNC connector sticking out of the PVC box and have the coax come out the boom to make the connection. I could just make an attenuator that is seperate from the antenna but that is just another bulky piece of equipment to carry around. I wouldn’t want to attach it directly to the radio because I think it would put strain on the connector that is in the radio.
You also can’t TX using this antenna. If you do, you can kiss the diode and possibly other parts goodbye. I would try to install some kind of switch that would allow me to TX but I’ll just carry an extra antenna or extra radio for now.
Hopefully it will see a lot of use.
Thanks for reading!
Jeffrey Bail (NT1K)
Now that my station has grown, I have quite a bit of equipment that requires 12-14Vdc of power. In the past couple of years I decided to start using Anderson Power Poles. I decided to use them as it’s starting to be the standard of some organizations and It’s easy. My only complaint that I would have is that sometimes the connectors can loosen up and doesn’t require much force for them to come apart.
At this point I have a very minimal setup that needs to be expanded. I have a pigtail off the power supply and set of power poles on each device. If I wanted to use one device, I would have to disconnect power from one device and put it on another.
The obvious solution to my problem is the use a distribution panel. There are some commercially made panels that use Anderson power poles but being the cheap ham that I am, I figured I can find a cheaper way.
While at a local hamfest this past weekend, One of the vendors had a bunch of products that use the Anderson Power pole. Two of those products has caught my interest. One of the was the “EZ-Gate” by ham source and the other was distribution block by Quiksilver. The EZ-Gate is similar to the PWR-Gate by West Mountain Radio but doesn’t have LEDs or Fuses. The EZ-gate is half the cost of the PWR gate and this would allow my station to instantly switch to battery backup during events like field day or when the power goes out in my house. The power distribution block was just a simple 4-way connection using power poles and priced at $20. I thought the price was fair but I thought would be cheaper and fun to make my own at home, For the price of one block, I decided to get twenty pairs of power pole connectors.
Having no clue how the little distribution blocks were made, I thought of way that I think it was done with the commercially available ones. I used 12ga soild copper wire to connect everything together.
Here is a photo of what I started with and the final product.
I cut 4 wires about 1.5″ long and placed the connectors on each end and did a quick assembly to check the gap between the sets. I wanted the gap to be short as possible so the entire block would remain rigid. I also cut and bent two additional wires to act as a “link” to the top and bottom sets.
Here is one of the wires that I crimped the ends on. After crimping I soldered each end to make sure of a good connection. Please note that the connectors on each wire are opposite angles from the other side. At this point I installed the wire and marked the location where the link will go with a sharpie.
Two of the four wires, I soldered one “link” favoring one side of the wire.
Here it is halfway assembled. you will notice the link on the positive side very close to the connector. When the other side will be installed, the other link will be close to the negative block on the opposite side.
Before connecting the other side, I used a pair of pliers and curved the links around the top stack of the link.
After completely soldering the links and installing the other end, I wrapped the positive side in plastic. If I were to do this again, I would solder, install heat shrink tubing both leads and then install the other set of connectors.
For what I would have paid for ONE commercially produced block, I’ve made two blocks and had and also have an extra set to make a patch cable or pigtails/adapters.
It’s no rig runner but it works and does what I need it to do.
Thanks for reading!
When I first saw the FLEX3000 in action while I was at W1AW, I was suddenly interested in Software Defined Radio (SDR) and didn’t really have much idea about it. After playing around with it, I was amazed that you can see 96Khz of bandwidth. That means I can potentially see up to at least 24 SSB QSOs all at the same time. After leaving W1AW, I wanted to buy a flex but the problem is that I just spent a lot of money not to long ago on my FT-950. So I put the FLEX radio in the bin of dreams with the rest of the toys I wanted. When I was looking up the FT-950, I notice the DMU-2000 which provides a “Band Scope” which is like SDR. However the $1000 price tag and multiple negative reviews made that decision quick to make. Now I’m certain that I wouldn’t be using SDR.
Then one day I was looking around Youtube and saw a video of someone tuning around a FT-950 with SDR. I got excited thinking that I can finally have a SDR. After doing some more reasearch, I found that there is a company that makes a board that installs where the DMU-2000 would be installed at and it will provide an IF out signal. For $200 I was thinking that it would be well worth the money. What I didn’t know is that I still need another piece of hardware that takes the IF Signal from the radio converts it and sends it to the computer for processing. The same company (RFSpace) sells that hardware (SDR-IQ) for $524.00…. WOWZAS!!! It has great reviews and nothing but praise but it’s too rich for my wallet. That’s $724 to look at signals on a screen (it does more than that, I’ll explain later). The DMU-2000 is starting to look promising again.
There must be a cheaper way. I have to live up to one of the stereotypes of an amateur radio operator and find a cheaper way. Well… There is… Sort of. I already know that In order for me to play with SDR and my FT-950, I would have to buy the RF-Space IF-2000 card. But there was no way in hell that I am going to get the SDR-IQ. So I went ahead and purchased the IF-2000 as it’s a must. The next best thing that kept coming up was the LP-Pan. For $225 (Now $250) I thought wow, I can do the same thing for half the cost. YES!!! Then I kept reading… You should always keep reading! I found that in order to get full use of the LP-Pan, I would have to purchase a Sound Card. Not just any ol’ sound card but one that has 192KHz of bandwidth on the input. Those can get expensive so now you have to tack on another $100 and more cables to run back and fourth. Unless you already have a 192kHz card, you can get away with the one built into your computer. However you’ll only get 96 or most likey 48kHz of bandwidth.
CHEAPER!!! CHEAPER!!! CHEAPER!!!
If I were to get the LP-PAN, I would get the costs down from $724 to $550. I’m also sacrificing features as the price goes down. Is there anything out there that is cheaper? Is there? Yes there is and it’s called SoftRock. You can purchase the Softrock Lite II (For 30M, Just tell him what you’re doing and ask for the correct crystal) for around $20. There are many SDR receiver options out there now. As long as it can receive a 10.55MHz signal then it can be used with the IF-2000 card. I ended up using a Softrock Ensemble II as I had one at the shack. With my computers built in sound card, softrock rcvr and IF-2000 board, I was able to add SDR to my FT-950 for around $220. THAT’S CHEAP!… Well is it? It’s cheap but you get what you pay for. Most of the money is spent just getting the IF signal out of the FT-950. You can use the softrock indepently. Since I didn’t invest in a decent sound card, I am stuck only receiving 48kHz of bandwidth. That means if the radio is on 14.160MHz, I can see anything going on from 14.112Mhz thru 14.208Mhz. If you were to get the proper sound card, you would be able to see from 13.968Mhz thru 14.352MHz which is the entire 20M US amateur band.
For the FT-950, the IF-2000 is a must. At this point in time, there are no other mass produced boards that can hook into the FT-950 (or FT-2000) that will give you an IF out. Here is the installation of the IF-2000 into the FT-950
IF-2000 In box form…. Whoopie dooo. Well, it’s not just going to sit there
Insides of the box. Doesn’t look like much for $200. But at least you get a serial cable to hook up the FT-950 to either the computer or SDR-IQ. This is if you didn’t hook up the radio to the computer for control (CAT)
To get at where you have to install the IF-2000 in the FT-950, remove all the many screws (except the feet) that hold on the bottom cover on. Once removed you will see this void with the taped wire. That is where the DMU would go. Bah! We’re putting the IF-2000 there instead.
Look at that pretty board installed. Not even 5 minutes of work.
Cable from the IF Out of the IF-2000 is hooked directly into the Softrock. You also can’t go wrong with the gold plated Radio Shack patch cable. Gold plated cables is what keeps Radio shack in business (Sense my sarcasm?) What you see is the USB cable that controls the Softrock, Audio cable that is hooked up the the Line input of the sound card, Power cable and the BNC cable from the IF-2000.
I am not going into detail about getting the SoftRock going as it’s a project by itself and not the point of this article. There are so many different SDR related software, it’s very hard to give you a how-to on each software. Please refer to other sites that provide help with getting the Softrock going.
Now that I have the Softrock hooked up to the computer and I have the IF-2000 hooked up to the softrock, time to have some fun!
I’m using SDR# as a panadapter. As you see (above image in green), I tuned the Softrock to 10.55Mhz which is tuned to the converted signal that the IF-2000 is putting out. So now if I spin the dial, I can see 24Khz of activity on each side of the center frequency which is giving me 48Khz of bandwidth (see above image in red). This is now just a basic panadapterY. If you have a decent sound card, you can display 96kHz or even 192kHz of bandwidth which is possibly all you need. The software (SDR#) doesn’t have rig control so it’s pretty difficult to link your transceiver to the software. Other software like SDR-RADIO, HDSDR, SpectraVue, Power SDR-IF and some others will allow you to link your rig and allow complete control so when you click around on the waterfall, the radio will be in sync for TX
As I mentioned before, you get what you pay for! Even though the softrock is a great and cheap way into SDR, it has it’s problems. If you look at the above picture, you will notice that in the center of the waterfall there is a big line (or sets of lines). The big line is the result of the SoftRock picking up groundloops. If you were to “Listen” to the hump you will get instant feedback which is very annoying. There are ways to combat this (using batteries instead of wall-warts amoung other things) to where it’s more manageable. Most operators offset the signal away from the DC offset.
I WANT MORE!
At this point all I have is a Panadapter that can see 48KHz. An extra $100 on a sound card would get me 96kHz or 192kHz which would be great. Just having the Panadapter capabilities allows me to find and tune into signals much faster. I can also find “Holes” in a packed band where I can setup shop and talk (or contest) much faster. I tried it in a contest and it made search and pouncing much more faster. It improved my Q rate by almost half. Well worth the money just having it as a panadapter. But depending on the software and your computer, you can do a lot more with SDR than just displaying signals. The software is now doing most of the filtering. You can adjust the filters really quickly to grab that SSB or CW signal. I am not saying in any way that the FT-950 w/ SDR is better than Flex-3000 or Flex-5000 but you now have similar features. A really good feature that I like compared to a Flex radio is that I still not dependent on having a computer hooked up to the radio. I can simply disconnect the IF out cable and will be able to still use my radio out in the field or during emergency power situations. I would lose SDR but I can still have a usable radio.
I am satisfied with that setup but I WANT MORE!
I hate having 48kHz of bandwidth and I hate having that DC Hump in the middle of the screen. I also want the software to control my rig and allow me to know exactly where that signal is. So I want more bandwidth. Well I could spend around $100 for a sound card to get 192kHz of bandwidth but I’m still stuck with the DC Hump in the middle of my screen. I could add toroids and use a battery pack to power the softrock which would dampen the DC hump. It would be okay if I were just using as a stand-alone receiver but when combining it with a radio, it makes it difficult to know what frequency your listening to than what is displayed on your VFO for TX.
That means I have to upgrade to a new SDR unit. As mentioned before, If it can tune to 10.55MHz then I can use it. I could get the LP-Pan or the SDR-IQ which was designed for my situation but that was a couple years ago. There are now other products out there that will give you similar or better results for a cheaper price and possibly while your reading this article, someone somewhere is making even something better. I ended up buying the AFEDRI SDR-NET.
Here it is! Awww so sweet. I lived up to the cheap ham stereotype and purchased the unit without a case to save $50. If you happen to buy one, I strongly suggest to buy it with the case. The case is made out of extruded aluminum and is well worth the the $50. Let me repeat, I strongly urge you to buy it with the case.
The AFEDRI SDR-Net costs around $250 (with the case). That is the same price as a LP-Pan. Why didn’t I just get the LP-Pan? Because the AFEDRI has much more to offer for the same price. With the AFEDRI, there is no need for a sound card which saves me an extra $100. It also samples at 1.2MHz!!! That means if I’m centered on 14.200MHz, I can see from 13.600Mhz to 14.800MHz!! I Can see activity on the entire 20M band and more! I can see almost 6X more bandwidth compared to the LP-Pan and SDR-IQ. The AFEDRI is compared to some of the more expensive SDR units and it can hold it’s ground.
Hooked up and ready to rock.
Getting the AFEDRI to run could be a little difficult. If it wasn’t for a fellow ham that owned one walking me through it, I would’ve had a hard time even though there are instructions sent over from the person selling these boards. To get full use (1.2Mhz bandwidth) you want to use the AFEDRI on your network (that is if you have one) or hooked directly to your LAN port on your computer. You can use USB but your limited to around 200KHz of bandwidth. That’s like buying a HF/VHF/UHF multimode base rig just to talk on a repeater. I have the AFEDRI hooked up to my switch/hub located in my office. When you first program the AFEDRI, you will need to also have it hooked up the USB on the computer. After it’s programmed and working (through the network), you can disconnect the USB. If you can make or get your hands on a 7.5V LINEAR power supply, that would work great on powering the AFEDRI (It does come with a DC plug). DO NOT FEED THE AFEDRI WITH 12V !!! I got lazy and had a bunch of cell phone chargers that had the Mini USB plug and 5V . I powered the AFEDRI through the USB port. It works but the problem is that it’s a switching power supply that creates noise. It is noticeable but not as bad as the softrock.
The AFEDRI is great but it does lack one thing… On board filtering. Due to the lack of filtering and being near (within 2mi) of 3 AM broadcast transmitters, The front end is overloaded when using the AFEDRI SDR-Net stand alone (without the FT-950)
YIKES! The Image above shows exactly what my problem is. What your seeing is 1.2Mhz of bandwidth showing the same 3 AM broadcast stations that are near my QTH. That almost makes the SDR useless unless I add filtering to get rid of the AM BCB signals. But when I hook it up to the FT-950, it shows something different.
Much Much Better… This is showing the 80/75m band even though the display says 10.56 (should be 10.55). At this point I am still using the software as a panadapter tuned the converted IF output frequency of the IF-2000 . I’m assuming it’s better because the signal is passing through the FT-950′s bandpass filters before the signal is sampled. I am assuming this because If I made adjustments to the Attenuator and pre-amp on the front of the rig, I can see instant changes on the screen. If you are going to use the AFEDRI by itself. Don’t be alarmed. You can purchase or even make your own high pass filters that will solve a lot of the issues.
You will also notice that I am sampling at 1.2MHz even though I am using the FT-950 w/ the IF-2000. The reason why I brought this up is that RF Space claims on their website that the IF-2000 adds a 190KHz of display. That was my biggest fear when I was purchasing the AFEDRI that when I hooked it up to the FT-950 and IF-2000, I was only going to get 190KHz of bandwidth due to any limitations on the IF-2000. When I hooked it up, I was glad to see that I am taking full advantage of the AFEDRI.
The only issue I have at this time is calibration. If you spin the dial to a known frequency and listen it to it on SDR, you will notice compared to your radio that the signal is off. This can be fixed partially by calibrating the AFEDRI using the supplied software. I am now within 1-3Hz of a signal on LSB. However when I switch it to USB, I am off by .500KHz. Depending on the software, you can make a different correction (offset) for each mode.
Now I have a pretty Panadapter that allows me to view the entire band for most of the HF bands. It makes it easier to see if the band is “alive” and it allows me to dial in a station faster but what if I could just “CLICK” on a signal and have my radio automatically tune the VFO to that frequency so I can talk?
The AFEDRI by itself is a receiver. You can hook up your antenna to it and away you go! But I have it hooked up to my transceiver which adds a whole new element to having an SDR rig. by having it as a panadapter, I can just spin the dial to the signal on the screen and talk. But what if the signal is 100Khz away? I would have to spin the dial pretty quick. Depending on your rig and SDR software being used, it’s possible just to click on a signal that you see on the screen and the radio will automatically put will put it’s VFO right on or near the frequency you want to talk on. During contesting, that would allow me just to click on signals instead of spining the knob during search and pounce.
The ability to “Click And Tune” all has to do with the software. The software has to have a CAT control option. I ended using a slightly older version SpectraVue because of it’s ease of use but I also successfully used HDSDR and SDR-RADIO to where both the FT-950 and AFEDRI work together in RX and TX.
Here is a video of the FT-950 and AFEDRI in action
I find that SpectaVue is the easiest to use but lacks features found in both HDSDR and SDR-RADIO.
LOOSING A COM PORT
I like to use software such as N1MM, HRD and DX Labs Suite for logging, contesting and working “Digital” stations. However I won’t be able to use my SDR software because the port is being used by the logging/CAT control software and vise versa. For me, logging software is just as important as having SDR in my book. Have no fear but yet another piece of software to use to “Emulate” the com port allowing multiple applications to share the same com port. One such software I has success with is “Virtual Serial Ports Emulator”. If you happen to use the same software. “Create a new device” as a “Splittler”. Choose the regular comport that was normally used with the FT-950 and then choose the “Virtual” port. You will have to reconfigure all the software to communicate with the “Virtual” port. Another tip is to make sure the settings in VSPE are the exact same as what is used in the other programs used with your rig.
SO FAR SO GOOD
I’ve been messing around with this setup for about a week now and I am impressed. SpectraVue doesn’t allow custom offsets per mode (just has one main offset) but I fixed that by using the “Shift” feature on the FT-950. There are a couple issues that I see but don’t annoy me enough to get rid of SDR and I am sure it’s going to improve as more people get into SDR. The biggest annoyance is that when I TX, the software doesn’t catch on for a bit and I can hear my TX audio for a second. There is also a slight delay (as expected) between hearing the signal on the radio and the computer. I am not sure how it’s going to fair in a contest but the worst case is that I’ll use the SDR as a controllable panadapter and use the audio from the radio instead of the SDR.
Now I have to make a case!
Thanks for reading,
Jeff – NT1K
IF-2000 from RF Space – Allows the FT-950 to become a whole different beast
Softrock Lite – A simple means of SDR with the FT-950 and IF-2000
AFEDRI SDR-NET – My personal choice for SDR. Alex is a great guy and is very helpful
SpectraVue – SDR software that I use. It’s also on RF Spaces website. I suggest getting a version previous to 3.25 if your using the AFEDRI.
HDSDR - Another SDR software that I use. A modified version that works with the AFEDRI is included on a CD that comes with the AFEDRI.
Virtual Serial Ports Emulator – Allows the FT-950 to be used with both logging/CAT control software and the SDR software at the same time
After seeing a lot of articles written about making a three element Yagi using PVC and a tape measure, I was interested but not excited about it. That was until I made a QSO with K1MAZ (Nick) while he was doing a SOTA Activation. I decided to try to make contact with Nick on VHF as it was spotted on the SOTA website. Nick was on top of Burley Hill in Union CT which is about 30mi from my QTH. He tried using his stock antenna on his Yaesu Handheld but it’s just a little too far out of range. I knew someone was trying to get in but there was no copy. A couple of minutes later I hear him again, but it sounded like he was in front of my house. He was S9+ and very clear audio. After meeting up with him I asked what antenna he used and he said that he was using his Tape Measure Yagi. I was somewhat amazed that it worked that well.
Now I want to make this antenna. It appears to be real easy to make and requires only hand tools. I ended going with a mixture of three designs
The first design I went with was from WB2HOL which appears to the origin of this particular antenna. It’s designed to be a RDF (Radio Direction Finding) antenna. It could also be used in portable operations like SOTA or Field Day. I obtained all the dimensions needed from his website.
I got the boom design from the Camden County Radio Society’s website which is slightly different from WB2HOL. It replaced the tee used by the director with another cross tee and added a 5″ stub. I have no particular reason why I went with this book design. I just liked it and it avoids adding a different part even though it’s no big deal.
Finally I got the choke from an article published in QST Magazine (May 2007)
Is the choke/balun needed? I’m not experienced enough to give you a yes or no answer. I decided to use it because it wasn’t going to cost me anything to do it. If it didn’t work our or was causing an issue then I can just simply un-wind it.
I am not going to go into detail about making the beam as it’s already done for you in the those articles that I linked to above.
However I will provide a detailed blueprint that is a little better than what I’ve seen out there.
Please use all safety cautions while working with tools and parts!
I tried as best as possible to get the exact dimensions of the PVC caps and cross tees but I found that the dimensions vary between manufacturers. That will explain the 0.060″ (1.5mm) differnce in element spacing as noted on the print.
Along with the instructions on the blueprint, I would like to share some of my personal experiences when it comes to building and using the antenna.
Working with PVC Tubing
I didn’t have a PVC cutter as I rarely do PVC work. I also didn’t have a vice or clamp setup to use a regular saw or sawzall with. I ended up using a tubing cutter that is normally used on copper tubing for plumbing. It worked but it wasn’t pretty. It pushed the PVC to form a flange or lip around the entire diameter of the tube. I had to use a sander to remove the burr/lip.
PVC Cut into lengths
I also decided NOT to use PVC primer and cement. The parts fit together so tight that I didn’t even bother using it.
Antenna Boom Dry Fit – PVC was so tight fitting that I didn’t bother using glue
Tape Measure Sharpness
The tape measure is somewhat sharp along the long edge. It’s not razor sharp but it’s sharp. Cutting the tape measure creates a real sharp edge. You can combat this by either wrapping the exposed edge with electrical tape or cutting a chamfer (corner) or both. I’m going to use a product call “Plasti-Dip) and coat the tips of each element with it.
Hopefully you will be careful running around with the beam. Doing this will make things just a tad bit safer.
I’d would either dismantle or cut out the bad sections of tape. If you already have a 1″ wide (or bigger) tape measure, I’d suggest buying a new one and cut apart your old one. I’ve notice coating usually wears out within the first couple of feet. My suggestion would be to start cutting the tape up from the oppisiet end.
Soldering the Hairpin and Coax
There is also an issue when it comes to soldering the tape measure. If you have normal flux core solder, you might have a hard time soldering the wires to the tape measure to where it won’t stick. I ended up using a liquid flux that is commonly used in the plumbing/welding industry. It’s an acidic flux that works great.
After grinding away the paint/coating on the tape measure, I put just a teensy drop of flux on the exposed metal of the driven elements. After soldering the hairpin match and coax using a 100W iron, I took it over to the sink and washed off any left over residue that was still on the tape. I’ve been told and I’ve read that using this type of flux is pretty corrosive and will eat away at the metal it was applied to causing a bad connect. So please be careful. After a week of playing around with it, I have not noticed anything.
Running the cable through the boom.
You will notice that I drilled some holes extra holes. I want to run the coax through the center of the boom, have it come out to start the coil and back through. I did that so the cable couldn’t drag across or get snagged in the reflector and to provide a little more security with the coil. It’s not a big deal but I found it to be cleaner than having it zip-tied or taped to the boom.
Cable Through Boom
You can build this antenna for under $20. Since I work in trade where a lot of people accidentally cut off or destroy their tape measures, I have quite the collection of tape measures.
8FT of 1/2″ Schedual 40 PVC Pipe - $3 (Home Depot)
3 PVC Cross Tees 1/2″ – $1.50 Ea ($4.50) (Home Depot)
2 PVC Caps 1/2″ – $0.40 Ea ($0.80) (Home Depot)
6 SS Hose Clamps – $1 Ea ($6.00) (Home Depot)
1 Tape Measure – $3 (Harbor Freight)
Grand Total – Approx $17
If you already have a 1″ wide or bigger tape measure in your tool box, I’d suggest on purchasing a decent tape measure and use your old one for this project. When it comes to using used tape measures, I would make my cuts starting from the other end of the tape. Most used tapes have lots of wear and tear on the first 12″.
Also don’t cheap out and get regular steel and electrical grade PVC conduit. The clamps will rust and the electrical PVC has a thinner wall and will easily flex. It may not happen right away but time will take it’s toll. I know it’s a cheap antenna but it would be more cost effective in the long run.
Well Did it work? I would say so, I don’t have an analyzer to tell you for sure. I hooked up the antenna to a SWR meter (bridge) and was seeing 1.2-1.5 on the meter. I went out in the back yard of my house and I’m sure my neighbors think that I’m training to be a JEDI fighter or something with the way I was waving the antenna around. I ended up hitting a couple of repeaters that I couldn’t normally hit with the stock antenna
Here is a video I made really quick to show it in action
Nothing exciting but it was fun.
Here is the complete setup. I gave myself enough slack on the coax incase I decided to mount the yagi on a tripod.
Overall it was a really fun build. It didn’t require any type of heavy equipment or tedious work. I have a feeling that running around the woods with a tape measure will end up with crimped or broken tape measure. However it would be much better that running around with 1/4″ (6.35mm) aluminum rod. Replacing the director and reflector would be easy as cutting the tape measure. So fart so good!
Thanks for reading,
This is the 3rd and update to my HeathKit SB-200 Amplifier Project.
The amp has been running fine since I’ve got it going. I had a resistor pop in the parasitic suppressors and I think that the amp is running too hot in temperature for little time I use it. At this point I am placing the blame on the two muffin fans that are currently “Cooling” the tubes. I am thinking that the fans are not providing enough air to cool the tubes fast enough. When I was replacing the parasitic suppressors, I performed some modifications (see update #1) and ordered a new fan from Harbach Electronics to see if it would make a difference.
I also held out on performing a couple more modifications because I had to fabricate some parts to encase the glitch resistor so if it were to pop, most of the resistor mess would be contained. The fan was placed on back order so It gave me time mark up and cut the lexon glass to sandwich the resistor with.
The fan kit does come with installation instructions which at first were a little difficult for me to understand. This was due to the fact that the new fan is a modified replacement of the original fan that came from Heathkit and I had purchased the amp with PC type fans. There is pre-assembly you have to do to the fan before installing. It involves removing a couple of screws on the fan that stick out and replacing them with shortened screws. Then you have attach aluminum spacer blocks to the fan which the block also has holes spaced out to fit in the orignal pattern of the fan from Heathkit.
The installation is pretty simple and straightforward. The kit comes with new rubber grommets to absorb any minor vibration that the fan causes.
You can either cut the wires near the old fan and tie into them or what I did was un-solder the old wires and wire the new ones in place.
I initially wrote this article in early may. I wanted to do some other upgrades at the same time but the New England QSO party was really close so I decided just to do the fan. The install went easy and would like to thank those at Harbach for rushing out the part. I made sure the fan was balanced as much as possible and I was able to use the amp during the entire contest. It’s a tad bit louder than the PC Muffin type fans that were in there but you can actually feel more air being pushed with the replacement fan. Over the past months the amp has performed very well. I should find more screws to secure the hood and the sheet metal covering the tubes/rf deck as it tends to rattle during operation.
Things have been kind of slow since Field Day. I Don’t have the drive to pickup the microphone (or practice on the key). It doesn’t stop me from doing stuff in the background. I was looking at my station and was disgusted by how it was setup. I had equipment on top of equipment and a rat’s nest of wires behind my desk.
I recently saw an Antenna Tuner” come up for sale on eBay that matched what I needed which consisted of having a variable inductor and that it can handle at least 1000 watts. It was also within the price range that I could afford so I took a chance.
It was the Heathkit SA-2060A tuner. After reading review after review, I put this on my list of potential tuners. The only complaints I hear about this particular tuner is that the hardware becomes loose after use. Since they are kits when they were first sold, The build quality depends on the operator who built it. When I received the tuner, I opened it up and made sure everything was tight and soldered correctly. It appears that it’s in great shape and I did no work to it other than some light sanding using a fine scotch-brite pad.
The reason I decided to get a tuner is because of my antenna(s). At the time I really have only one HF antenna which is my home-brew G5RV wire dipole antenna. Once you started getting away from 20 meters, the mis-matched antenna places a strain on my tubes that are located in the amplifier. The “tuner” should help that out.
However I had no room for it. I didn’t want to stack the amplifier or anything else on it so I decided that I need to do something about my desk to keep everyone happy. I ended up fabricating a shelf that spans across the entire desk which would allow for me to put more stuff on my desk.
I’m liking it better than the previous setup. The most important piece is right in the middle and a tiny bit easier to get to.
I had a chance to work some DX with the new layout. Here it is in action with LA4UOA (Tor in Norway)
Now I just have to clean the rest of the office.
I am debating on placing advertising on this site. I am not a fan of advertisements and wanted to keep this site AD free but running this site isn’t free. It’s not much compared to other websites but any income I can get that would offset the costs would help greatly. I also might place ads on my YouTube videos. Not looking to make AMAZING profits but hopefully enough to cover the hosting.
I am sure some of you have been hearing the letters RTL-SDR come up more often. At the time all I knew was what the SDR part meant (Software Defined Radio) and didn’t really care about the subject. After hearing more and more I decided to see what all the buzz was about.
The company Realtek (sounds familiar?) designed an IC chip called the RTL2832/RTL2832U (USB 2.0) that was originally used by electronics manufacturers that made DVB-T (Digital Video Broadcast - Terrestrial) receivers. These devices will display Digital TV signals from nearby TV stations (Remember the whole Digital TV upgrade that made older TV’s useless unless it has a converter) as well as digital FM radio onto your computer/laptop. The actual RTL chip demodulates the signal, cleans it up and processes the signal using a built in ADC (Analog to Digital Converter). All the software does is display the information that is coming out of the RTL and it will also control the frequency and filtering of the signal through a tuning chip on the board. It’s way more technical than that but I’m just giving you the basics.
Someone found out that RTL chip with the tuner could allow you do sample/listen to signals from 64Mhz up to 1678Mhz (Varies depending on the tuner) which is quite impressive. These chips could also decode many different modulations and you can view/sample megahertz at a time. All of this for around $20 USD and some software. With some other tricks you can decode APCO25 (P25) or other digtal and digital type signals with this dongle.
What does all this mean to me?
In short terms you have a Software Defined Receiver (SDR) that you can listen and actually SEE any signals from around 64Mhz to around 1678Mhz at around 2Mhz at a time.
For example you can listen/watch a good portion of the 2M (Let’s say from 146.000-148.000Mhz) band and see all the conversations going on in that 2Mhz span. Depending on the software you’re using, you can filter just what you want to hear while seeing what else is happening . If you’re listening to a repeater, you can view the station on the input as well as hear and see the same station on the output frequency on 2M. If you tried to get the same features in a police scanner, you could be spending at hundreds of dollars.
Is this too good to be true? What’s the catch? Is this a Scam?
It does seem to be too good to be true but it’s actually true. For around $20 USD, you can have a VHF/UHF SDR receiver. I have a feeling the price will go up as retailers are seeing a huge increase in sales of these “Cheap” devices. There are some catches however. It doesn’t have the best filtering so signals could get cross and mixed in. You’ll sometimes hear “Birdies” and there are times where the frequency displayed is not correct to the frequency you’re listening too (So far I’ve seen if off around 6khz). Another issue is with the dongle itself, depending on the manufacture the cases don’t have really any shielding and the antenna connection and the supplied antenna is basically crap. At the time of writing this, there are a couple companies seeing the demand for these RTLSDR’s and are making units with the correct case and antenna connection. But for the issues it has and for the price they are being sold at the moment, it’s well worth having. It’s almost comparable to purchasing a FunCube dongle for around $190 that is similar even though I think the FunCube is better and helps support AMSAT.
Ok ok ok… You’ve sold me. How do I get one these $20 dongles?
This should be the only battle you have to do. Securing the Proper Dongle at the correct price. There are many manufactures of dongles that do almost the same things. You want to find a dongle with the correct RTL chip and the correct tuner chip. The Cat’s meow of Chipsets are the RTL2832U and the Elonics E4000 (AKA E4K) tuner chip. Why? I have no clue. Some dongles have this configuration and some use other Tuners like the Fitipower FC0013 and FC0012 that work also. Some of the differences are the Bandsplit of what frequencies the tuner chip can tune.
At the time of writing this, If you can get your hands on a EzCap EzTv668 (or EzTv666) with the RTL2832U and E4000 tuner then you are golden. However the company that designed and manufactured the E4000 is no longer in business and the company is now being liquidated. This means at this point in time the E4K is no longer being produced. Most companies are switching over to the FITIPOWER FC0013. So you want to make sure that you are getting a unit with the E4K. There are some ebay sellers that are claiming to ship dongles with the E4K but they are really the FC0013.
If you happen to get stuck with one, don’t worry. It will still work.
JUST TELL ME WHICH ONE!!! Grrrrr.
That’s the thing… I can’t! Things are changing so much that its possible for something to be different next week. Have no fear! The good people over at /r/rtlsdr over at Reddit.Com (http://www.reddit.com/r/RTLSDR) have a very nice up-to-date list of dongles as well as places to purchase these dongles. Just take note that you’re still gambling when purchasing a Dongle. A lot of these are drop shipped from China and you’ll never know what you’ll get until it lands on your doorstep.
Here is a Ebay “EzCap EzTV668″ screen shot of one I actually purchased on Ebay.
(Click to enlarge)
I purchased this from a seller on Ebay as well as one from Deal Extreme (DealExtreme.Com). The reason I purchased it from Ebay is the one I ordered from DealExtreme was taking way too long and when I contacted their customer service, I was told they were out of stock and could take almost another month for it to come in.
If you notice the Ebay Auction says RTL2832U and E4000 tuner… Well… This is what I got!
It’s a EzTv645 and it has the Fitipower FC0013. This dongle is NOTHING like the advertised dongle on Ebay.
I could have complained and returned it but as you can tell, I hacked it up already. I just wanted to warn you that you might not get what is advertised on Ebay.
I added a Pigtail with a PL-259 which voided any warranty (if any) it had. I wasn’t going to waste time with trying to return someone that was sold over ebay and shipped from china.
When soldering on the coax to the board. I messed up and used a powerful (too powerful) soldering iron without any grounding or ESD protection.
Here is a Video of the dongle with the FC0013 in action
You’ll see some of the signals being mixed and some other horrible stuff.
I am not sure if this is how it is normally is or damage done from my soldering job.
Also for some reason the video lost sync with the audio.
The dongle still works but it’s in the hands of my co-worker who would really have fun with this.
The very next day after screwing up the Ebay EzTV645 purchase, My order from DealExtreme showed up
After reading posts on Reddit of people saying their recent DealExtreme orders have the FC0013 tuner got me a little bit worried. I opened the dongle and is happy to see this
This is what you’re looking for. It’s the advertised 668 with the Elonics E4000 Chip (Little square chip to the right of the Antenna Jack) and the RTL2832U (Under the IR Sensor).
I dared not to touch this one with a soldering iron. For now I went to Radio Shack and got a couple connectors (PAL to BNC). I would suggest going on ebay and getting the correct adapters or if you have a really good soldering station, solder in a SMA pigtail and/or connector.
Here is a video of the new dongle
It looks and sounds much better than the one I purchased from Ebay. But I can’t tell you for sure since I hacked up the Ebay one before I can make a comparison between the two.
The hardware finally came in… What now?
You now have to obtain software to display the information from the dongle. At this point while writing the article, the best choice for RTLSDR software is SDR# (SDR Sharp). There are others out there depending on the operating system you are running. I’ve chosen SDR# because it’s really easy to setup and use (compared to some of the others) and it works on some other SDR hardware I have. Plus IMO it’s best choice for beginners like myself. If you do end up using SDR#, make sure to download the DEVELOPMENT (DEV) Version as well has ZADIG which will replace the driver that was automatically installed (or attemped) when you plugged in the dongle with the one that is needed to run in SDR#
I would follow these instructions as it’s worked for me
That’s It!! It should be working. Tune around and have fun. If you’re using the antenna that came with the dongle, good luck! You will not pick up much with the stock antenna. I ended up cutting the plug off the antenna and soldering it to some RG-58 as to not mess up the board. You can also find adapters online and possibly at Radio Shack. The plug looks like an RCA but it’s really a “Belling Lee” (IEC 169-2) connector or PAL connector.
Here are some RTLSDR websites that were helped me out and are resources for this article.
Http://www.reddit.com/r/RTLSDR – Huge community with tons of information on the dongles that are being sold
http://sdr.osmocom.org/trac/wiki/rtl-sdr - RTLSDR website with more technical information than I’ll ever know.
http://www.rtlsdr.com/ - Just catalogs RTLSDR feeds from websites and video sites.
http://www.sdrsharp.com – Website for SDR#. My personal choice for SDR software
Possibly where the RTLSDR idea came from
Just want to say thanks to all those on Reddit.Com (/R/RTLSDR and /R/amateurradio) and those on ##RTLSDR and other IRC channels on freenode/geekshed for helping me out.
Well, after a month or so of operation with the SB-200, my first “oops” happened. I went to turn on the amplifier and I thought I had everything correct and when I went to TX I heard a loud “Pop” sound. Quickly shut off the amp and disconnected the power. Opened the case to find that one of the resistors and the parasitic suppressors popped. I knew something was going to happen because the resistors were turning black.
Since I had to fix the suppressors, I figured this was the time to do some other “Modifications” to the amp. When I first rebuilt the amp, I ordered all the parts to do almost all the mods that you see on KL7FM’s SB-200 Page. I figured since it’s opened up, this would be the time to do SOME of those mods listed on his site. Are these mods needed?.. Nope! If they were then I would assume that they would have been incorporated a long time ago. I just figured if it makes it run a fraction of a percent better, why not invest the extra couple of dollars.
First thing I did is replaced the Parasitic Suppressors and I also replaced the .001uF 1kV ceramic Disk cap with a .0025uF 10kV disk cap (as seen in orange in the picture above),
Apparently it allow less RF to leak back into the power supply on the lower bands. Cap was around $2.00US
In this photo I replaced the two 33ohm carbon resistors that I had with some higher wattage metal oxide resistors. I then replaced the 3300Ohm resistor with a high wattage metal oxide type as well. I also replaced the 2 200pF caps with 4 470pf 1kV. I guess by replacing the caps, there will be decrease the grid-to-ground reactance for better improvement on the lower bands.
In this photo I replaced the nylon protected wire for the input to the cathode and replaced it with a 10Ohm 3W resistor. I guess this will help dampen the VHF oscillations as well as help by prevent over driving the amplifier.
After hooking everything up, The amp turned on and sprung back to life. After messing around with it for a couple house, I haven’t really notice really any improvements. doesn’t mean nothing is happening which is WAY better than having it break on me. So it was a success.
Since the AMP has been operational, I’ve notice that it gets very hot with little use. My gut is telling me that the Pancake AC fans are not doing the job efficiently. The fins are quite small and most of the room is taken up by the motor in the center. I am seriously considering the purchase and installation of a replacement of the type of fan originally used in the SB200. The company that sells the fan kit want over $60 and I am still tossing it around in my head. So far I keep my eye on the temp and I’m using a bigger fan that sits on top of the case to exhaust the heat. |
When the time comes to install the new fan, I am also going to do more modifications that were on that website that have to do with protecting the power supply and the meter. I might even go as far as replacing the meter light with an LED that turns Red when I’m TX. I also might change the “REL Power Sense” POT with a Switched POT so I can put the AMP in standby mode. Hopefully after this, I will never have to go in that amp ever again!
I felt that it was time to put some “Fire In the Wire”. However I wanted to learn about amplifiers since I have no clue how one really works other than giving my signal a boost. The original plan was to build one from scratch but after some attempt at collecting parts I decided that building one from scratch was not going to work out since I didn’t have knowledge to even start one. The next best thing was to buy an amplifier and rebuild it.
I ended up getting a Heathkit SB200 Amplifier. The reason I went with the SB200 is that it appears to have a huge following and (some) parts are still being sold for it. There are also many articles written about this amplifier and it’s still being used in a lot of stations to this day.
What is an amplifier and what does it do? Or what does an RF amplifier do since we’re dealing with RF (Radio Frequency). A RF amplifier is a electronic device that takes a low-power radio frequency signal and turns the signal into larger signal with more power without changing the characteristics of the signal . This can be done by at least a couple of different ways. It can be done using Vacuum Tubes or Field Effect transistors (FET) which act very different but produce similar results. Vacuum tubes use High voltage with low amperage and FETS use low voltage with high amperage. There are many different types of amplifiers that are divided into classes depending on the type of circuitry used in the construction and its final use.
Do you really need an amplifier? This question could lead to a lot of debate between hams. There are hams that take pride on making all their contacts by only using the power provided from the transceiver (and some using under 10 watts/QRP) and there are hams that prefer using amplifier at almost all times. It all depends on your situation and needs. I would prefer a nice antenna setup that can be directed and have gain over a amplifier but at this point in my life, it’s very unlikely that it will happen. I went with an amplifier as a “Pile-Up” buster. An example for me is when 9K2UU (Barrak in Kuwait) was on the other day. There were so many people trying to contact Barrak that it felt impossible that I was going to establish contact with him. The last time he was on I tried for over an hour to make a QSO without luck. Mostly due to the other operators using Amplifiers. This time I had the amplifier so after a couple of times of trying to contact him, I turned on the amp and made a QSO with Barrak with the first try.
So how does the SB200 work. We know it takes the signal from the transceiver, amplifies it and sends it out to the antenna. But how? The SB200 has three areas that make amplification possible. You have the power supply, input circuit and the output circuit. There is a relay that is controlled by either a switch or the transceiver that activates the amp. The signal comes out transceiver into the “Input Circuit of the amp. The input circuit consists of coils and capacitors that are adjusted and controlled from the band switch on the front panel that provide the tubes with the proper impedance. The signal then passes through the tubes where amplification takes place using the components in the tubes and the very High voltage provided from the power supply to power the tubes. After the tubes do their work the signal passes through the “Output Circuit” consisting of more capacitors and Coils to clean up the signal even more and is fed to the antenna. This is just a basic summary of how the SB200 works. There are websites that explain how amplifiers work in great detail and I’ll link to them at the end of the article.
Now to my SB200. I found this amp on the for sale section on QRZ.com. The amp needed work and thought that this amp would be the perfect project to get my feet wet in amplifier building. Thing about Heathkit amps is that they are kits. They are as good as the person that built the amp. If the original builder had no clue what they were doing (examples are cross wiring, swapping components and poor soldering to name a few), the amp will perform poorly if it performs at all.
The seller did a poor job at packaging the amp for shipping and my pants almost turned brown when I saw the box come off the truck. The seller then blamed me since “I didn’t pay enough for shipping” when it was the seller who gave me the shipping quote. The amp showed some signs of damage from shipping which appears to be cosmetic but I was worried about the High voltage power supply so I hooked it up to find that I was getting the 2300-2400vdc that I needed. A bit of relief. I’ve learned to inquire how the item is going to be shipped from now on.
When I got this amp it was in the middle of being restored. There were no tubes, the components were missing on the tube sockets and there were no parasitic suppressors (Which I was well aware). It appears that previous owner replaced the original cooling fan with a couple of PC type fans and installed a “Soft-Start” circuit as well as “Soft-Key” circuit but removed the “Soft-Key” before it got to me. The power supply that provides the High Voltage also appears to been replaced/upgraded. Since this amp was designed back in the 1960′s where the circuit that activates the amplifier used -110vdc. It would ruin modern transceivers keying circuits by putting high voltage into the transceiver. To combat this people install a “Soft-Key” which basically converts the -110Vdc to around 1Vdc which plays nice with the modern transceivers. Another modification that was done before I got the amp was the addition of a “Soft-Start” module that prevents a “Rush” of current hitting the tubes. when you push the on button, the amp is supplied with a load that is restricted for a couple of milliseconds and then switches to the full load using resistors and relays. Even though I’ve read on many sites that the “Soft-Soft” is not really needed for this amp but since it’s installed, I’ll keep it. It can do no harm.
The previous owner also shipped some components that will make bringing this amp back to life a lot easier. I received the filament choke and a couple kits from AG6K (Not sure if he still sells kits) with detailed instructions on installation.
The only thing I have to do is obtain the rest of the parts. The tubes were available from RF parts. The tubes were about $120 for the pair, A new “Soft-Key” kit for around $30 from Harbach electronics and the rest of the components were about $20 from Mouser. I have around $350 invested in this project.
After all the parts came in. I found a manual with a schematic online and used it to install all the missing parts and installed with “Soft-Start”. After installation of the parts I went back to the manual and double checked the entire installation and everything seemed to check out.
Before turning the amplifier on, I preformed some checks to lower my chances of a smoke and/or light show. The manual states to perform a couple of “Resistance” checks. The first one is to put a multimeter on the anode clip (nipple of the tube) and the chassis. When the meter stabilizes, it should read around 180k ohms. However I was seeing 240K ohms which made me a little bit worried. After searching google I learned that this is due to the replacement of the High voltage board. The other resistance test is to place an ohm meter on lug 3 (V3) of the tube and place the other lead to the chassis. The resistance should be somewhere between 5k-15k ohm. I ended up with 10K which is right in the middle.
After performing all the checks I can do with the amp off, I was still hesitant on turning the amp on since I never really messed around with an amplifier before. I wanted the amp to be checked out by someone else but I got impatient one weekend and decided to go for it. I removed the tubes from the amplifier and powered the amplifier. To my relief there was no smoke/light show and was still seeing around 2400v on the meter. I turned the amp off and waited till the caps were discharged. Placed the tubes in and turned the amp back on. To my amazment, the tubes sprung to life and produced a comforting glow. I left the amp on for an hour and nothing happened in that time so I decided to put a signal through the amp to see what happens. I went on the 20m band, put the radio into CW and did a tune. I was glad to see around 600W on my watt meter.
I decided at that point to make some contact with the amp on. Spinning around the dial I hear a Northern Ireland DX station and threw my call out. He responded to my call the very first time and gave me a report of 59 20+. That made me a very happy operator to know that my amp was working.
The only place where I have 220V that I can get to was in the basement. So that’s where my equipment was until I had the chance to get 240v wired to my office. Once in my office I wanted to really use it so I turned it on and went through all the check to find that I was not seeing any grid current show up on my meter. That started to scare me so I shut the amp off and went searching for the answer to “What’s causing this to happen?” I asked the HeathKit Amps Yahoo group and I also asked help from my local club. There was a major block in the road and it seemed that the help I was getting was leading me to nowhere. Some people said I have shorted tube(s) and others said that something is wrong with the wiring. Both can be plausible since I never really worked on an amp and I’ve heard of people receiving bad tubes. But then someone ask me if I had a dummy load. Of course I don’t! So another member of the club let me use his Oil can dummy load. When I hooked up the dummy load I noticed everything is now looking good.
I now have a working amplifier! Just in time for the ARRL DX SSB contest. I was happy that I was going to get to use my new amplifier and put it to the test. On Sat morning well into the contest I decided to start. Amp on and 20m is quite busy. I was making a good amount of contacts while only searching & pouncing until I started to hear a sizzle sound coming from the amp. Found out that one the resistors in the parasitic suppressor kit has become broken and was arcing to the resistor it broke from. That kept me out of the contest till I had the nerver to solder it back together and get back on towards the end of the contest.
I still have some issues but I am leaning toward my antenna setup to be the cause. For some reason the tubes get very hot on 80 and 40m. I would have to either get a tuner that can handle the power or get a resonate antenna before I can continue on other things. I am also thinking that the PC type fans are not doing their job. The chassis and case get hot to the point where I can’t touch it. Tubes are not glowing but I want to keep it that way.
Future plans for the amp are the following
- New HV board – The one I currently have is newer that original but I think if I’m going to keep this amp that it should have a new board
- Glitch Resistor – This will save the tubes if anything goes wrong with the HV board.
- Meter Protection – Since the meters are rare and get expensive when they come up for sale, I’d rather spend a couple cents on some diodes.
- LED Meter Conversion – I want some nice white/bluish LED to light up my meter to match my FT-950
- Various upgrades – There are websites out there that have a ton of things to do to this amp to make it much better. I already got the parts for most of the mods but want to make sure the amp is fully functional before I even attempt modifying the amp.
- New Chassis, Cover and face – I want to design a more modern looking case around the same chassis and incorporate some more RFI shielding and better ventilation and the use of a thermostat for fan operation.
- Clean Up – When the new chassis is made I would like to DE-oxidize all connections, coils and plates.
Some cool sites I cam across when rebuilding this amp
Rick Measures (AG6K) - Boat loads of AMP info
Yahoo groups – HeathKit HF Amps - Helped me out a couple times, worth joining
Robert Norgards (KL7FM) SB200 page – I plan on doing almost all his suggestions
Okay, enough of UHF/GMRS antennas. Now it’s time to step it up (just a little bit) and fabricate a bigger antenna.
Due to material, I decided on a 5 element Yagi built for VHF since all I would have to buy is more 3/8″ round stock. I’ve taken what I learned from the GMRS Yagi and applying it to the design and fabrication of this VHF Antenna. I am writing this article in a way in which I hope newer hams can understand, build and learn about antennas. So please excuse if I go into details about things that you consider simple and “common sense”.
In order to design a Yagi we have to learn what a Yagi is. A Yagi is a Directional antenna made of up elements.
The 3 Major parts which make a yagi are the driven element, reflector and director. When cut and placed at a calculated distance (On a Boom), the elements will cause the RF (Power) to be sent (radiated) or received in whichever direction the antenna is pointing to. In the radio world this is a great because you can basically “Focus” the power and direct it in the direction you want. Whereas a Vertical (Omni-Directional) radiates its energy in a 360 degree pattern (think of throwing a rock in a still lake and watch the ripple pattern in the water.) which will send out your signal “everywhere” but will dissipate quicker.
On the lower frequencies (HF), a Yagi would be the antenna of choice by Hams. Well then how come every ham doesn’t have a Yagi (on HF)? There is a couple of down sides to having a Yagi or Beam antenna (on HF). First off, HF Yagis are huge. In order to use a Yagi/Beam to it’s fullest you would have to install an antenna tower/mast and rotor. HF Yagis are expensive and so is the tower and rotor, so the parts alone could add up to couple thousand dollars. I’ve seen cases where someone moved or is SK (Passed on) and sold their equipment cheap. There are also several other factors that would steer someone away from a Yagi. Those factors could be age, housing restrictions, living in an apartment, permits, handicap, property size, neighbors, and more stuff than I list. However the Yagi I’m building does not take much space and could be transported to be used in events where I am portable. Yagi’s come in many different sizes depending on the frequency and the efficiency of the antenna. The lower the frequency, the larger the antenna. The higher the frequency, the smaller at antenna. The length of the antenna will vary depending on how much efficiency/gain you want. Increasing the length (boom) and adding more director elements will increase the gain/efficiency of the antenna. On the Yagi that I am building, the design is based on the length of the (boom) antenna rather than the gain.
So you want to build a Yagi. To start off your going to have to know what material your going to be using. Most Yagi antennas are built using Aluminum since it’s light and is a great conductor (Well, compared to steel/stainless). There are many different types of aluminum and I would say that 6061-T6 Aluminum would be the best choice for antenna building. The reason is that 6061-T6 is more weather durable and easier to work with compared to other aluminums. The downside of 6061-T6 is when it comes to bending. 6061-T6 tends to crack when bending using a tight radius. Since we’re not bending anything on the yagi we’re building then It won’t matter. If it comes to other designs of yagis that use a Hairpin or folded dipole then I would take the type of aluminum into consideration.
Okay, we’re using Aluminum. What’s next? Now we need to figure the sizes of the material we’re going to use. This all depends on personal preference. For HF Yagis, you’re going to need Tubing ranging from 2″, telescoping in diameter down to 1/2″ because the antenna is going to be big and will need to support the weight of the elements. Since we’re dealing with smaller VHF/UHF antennas, the material doesn’t have to be large. For the antenna that we’re building we will be using 3/8″ (.375″/9.5mm) round solid aluminum and 1″ (1.00″/25.4mm) square tubing to mount the elements to. You can also use 1/4″ solid round aluminum instead of the 3/8″ to save a couple of dollars but realize that it’s easier to damage 1/4″ rod. If you decide to go with 1/4″ round please note that the dimensions and calculations you see in this article will NOT work using 1/4″ rod because 3/8″ rod has more surface area for the signal to travel on and all the calculations are made with 3/8″ In mind. You can change it to work with 1/4″ which I will cover later on.
Now that we have the material and size in mind that we’ll need, we now need to know what frequency we want to transmit on. Since this is a VHF yagi that we’re building, it will most likely be in the 144-148 range. Are you going to use this antenna for sideband (ssb/usb) only, or both ssb and FM (repeater/general operation)? Reason I ask that is if your designing this to be on sideband only, you will only need it to design it to work best over the span from 144.000Mhz to 144.500Mhz whereas FM would need to be designed over the entire band (144.000mMhz to 148.000Mhz). Since we’re building an antenna for the entire 2m band, we going to use 146.000Mhz as the design frequency since it’s directly center of the band and would allow for a somewhat even performance throughout out the band.
Another downfall of the Yagi is that it has a narrow bandwidth.What I mean is that the antenna will work the best over the span anywhere from 100khz to 10mhz depending on the design (Could be more or less). If you start transmitting out of that span, it could create signal loss and high SWR causing the transmitter to step down power to prevent damage (or actually damage older radios). Why build an antenna that is not going to radiate the power going to it? If the antenna is designed and fabricated correctly and you have at least a SWR Meter/Bridge then this should not be an issue.
So now we have everything we need to start designing a Yagi-Udi Antenna. Well… How do you design one? This is a fork in the road and there are many different ways you could design one (too many to list). There are different programs for different types of Yagis and there are different mathematical formulas for different (or the same) types of yagis. The method I am going to use is a Antenna modeling (software) program called 4NEC2. This program is based off the Numerical Electromagnetics Code for modeling antennas. The great thing about 4NEC2 is that you can model almost any antenna and the best part is that its FREE! What this software allows you to do is to design/draw an antenna using X,Y,Z Coordinates and then run the antenna through a simulator to see it’s efficiency, SWR, impedance and many other things that I have yet to look at. Basically it will tell you if your antenna is going to work and how well it will work on or near the frequency you designed it for. Another great thing about 4NEC2 is that it will perform adjustments on your antenna to optimize it for the best results. So if you are somewhat close to a good antenna, the software (if the programed right) will make it even closer. This software however is slightly (or very) difficult to use for a new person in the hobby. I adapted to the design portion of the software because I have knowledge in CAD (Computer Aided Drafting), but I had to do a lot of reading about the electrical properties and how to make the software do what I want. I am not going to dive in depth explaining this software. However, I will show you how I used the software to create the antenna. If you find the software to difficult then skip the section and use the final results in building your antenna.
Before we start using the software, we’re going to need to know what dimensions to input in the software. We can’t just throw random numbers into the software and expect magic to occur and produce the “Perfect” Yagi antenna. The U.S Department of Commerce and the National Bureau Of Standards released a document which helps in Yagi Design. Information based off the manual has lead to the following Dimensions
300 (speed of light in meters)/146.000(mhz) = 2.0547 wavelength or(WL) (in meters). This will be used as reference for the following dimensions.
Length of each element as follows:
Reflector Length = 0.493 X WL=1.01297m (or 39.880″)
Driven Element Length = 0.473 X WL = 0.971873m (or 38.262″)
Director 1 length = 0.440 X WL = 0.904068m (or 35.593″)
Director 2 length = 0.435 X WL = 0.893795m (or 35.188″)
Director 3 length = 0.430 X WL = 0.883521 (or 34.7843″)
Spacing of each elements from the reflector as follows (WL = 2.0547 in meters)
Reflector to Driven element = 0.125 X WL = .256838m (or 10.1117″)
Reflector to Director 1 = 0.250 X WL = .513675m (or 20.223″)
Reflector to Director 2 = 0.500 X WL = 1.02735m (or 40.446″)
Reflector to Director 3 = 0.750 X WL = 1.54103m (or 60.670″)
Now that we have all the dimensions that will put our Yagi in the “Ball Park” of a good VHF Antenna. The software will end up fine tuning the elements and spacing between elements to obtain the best SWR for the giving variables (i.e Element diameter, Boom length and etc).
Open the 4NEC2 and plot the antenna using the dimensions above. At some point in the near future, I will post a video on how I plotted the antenna. If you don’t know how to use 4NEC2 I suggest searching using google for results because that’s how I learned.
Please note that using the “Optimization” will give different results what I came up with. So do not get alarmed or worried. If it was done right then there shouldn’t be any issues to the design that the software gave you. DO NOT START CUTTING ANYTHING!! These dimensions will change!
Here are the Dimensions and spacings from 4NEC2 that I got! (Note that these dimensions will be the ones used for the rest of the article and that they will be different than your results if you decided to use the software)
Spacings (Each from the reflector)
Now you should have all the Dimensions (lengths) of the elements and the spacing. Now we need to work on the BOOM. The Boom is the tube that we are going to mount the elements on. At this point we have to decide what material, size and length we’re going to use for the boom and how we’re going to mount the elements. I have decided on 1.000″ square aluminum tubing because it’s commonly used and that it’s easier to work with compared to round tubing. The length that we’re going to need is based on the location of your last (furthest away) director.
I also decided to mount the elements by drilling through the boom and using plastic shoulder washers so we can slide the elements through the boom without the elements contacting the boom. At any point we DO NOT WANT THE ELEMENTS TO CONTACT THE BOOM!! Because we’re putting the elements through the boom, the elements will become electrically shorter because of the inductance change. So we would have to increase each element which is called “Boom Correction”.
There is a formula to calculate the “Boom Correction”. In fact, there are many different formulas to calculate the correction so I am going to use the one that I see most on the internet
C= (12.597B) – (114.5B^2)
The C equals the correction, and B equals boom diameter in wavelengths. This formula will work on boom diameters smaller than .055 wavelengths (Smaller than 4-1/2″ boom diameter on VHF and smaller than 1.5″ boom diameter on UHF). So let’s dissect this problem to make it easier.
To find B we’re going to need the wavelength of the frequency (146Mhz) that were going to use in millimeters.
300/146 = 2.0547 meters or 2054.7 millimeters.
Now we need to take the boom diameter in mm (1.0″ = 25.4mm) and divide it by the wavelength (in MM) of 146Mhz
25.4/2054.7 =0 .012362 (B is .012362)
Now we can do the problem
Now we take the correction and multiply it by the boom diameter (in MM)
.138226X25.4 = 3.510mm or .138″ is out correction
We now have to ADD .138″ to EACH element. So our NEW element lengths (in inches) are as follows.
RL = 40.633″
DE = 38.501″
D1 = 36.301″
D2 = 36.224″
D3 = 34.212″
At this point we should have all the lengths of the elements, spacing distances from the reflector to each element, boom diameter, boom length and the type of material we’re going to need for fabrication… Right?
We need to go shopping before we build. Here is a list of what we need to build
- 5ft (60″) of 1X1″ Sq Aluminum tubing (1/16″ Wall/Thick)
- 16ft (192″) of 3/8″ Round Aluminum Rod
I would suggest that you google for a local “metal supply” shop. I would avoid the big chain stores (like Home Depot, Lowes) or stores that have every type building material under one roof because the markup on material is very high. I was able to purchase 12ft of sq tubing and 24ft (2 12ft lengths) of rod for around US $30. There was enough material to build this antenna and two UHF 3 Element beams.
- 8pcs – 3/8″ Inside Diameter Plastic Shoulder Washer
- 6pcs – 3/16″ Inside Diameter Plastic Shoulder Washer
- 1pcs – 3/8″ Inside Diameter X 3/4″ Diameter X 1-1/2″ Long Plastic Spacer
These Items will be a little tricky to get. If you’re in the US, you can go online and order from a company called McMaster Carr. I have the part numbers listed on the blue prints that I’ve used. However when I put the antenna through the ringer (tests), I will see if I have to change the part numbers to something else. I have been considering using plastic rivets instead of shoulder washers because I am afraid that the adhesive (epoxy) will not hold the plastic shoulder washers to the boom. If you get different washers or insulators, The dimensions will differ from what I have on my blue prints, so please change dimensions accordingly. If you do order through McMaster Carr, They will only sell the washers and spacer in packaged amounts. If I recall the small shoulder washer came in a pack of 100pcs, the larger shoulder washers came in a pack of 50pcs and the Spacers came in a pack of 10. It’s great because I ended up making a bunch of antennas w/o having to make an extra order.
- Glue or epoxy.
Anything that you know will bond plastic to metal and will survive the elements (rain, cold, ice, snow, heat, wind). Still a good idea to use even if your using plastic rivets.
- 6pcs – 9/16″ Long #8-32 Screws
I would suggest using stainless steel screw as it will survive in the elements longer
There are optional things that you buy like Sq caps for the boom and vinyl caps for the ends of the elements for water and safety protection.
There is some more paper work to do (Grrrrr). Now that we have all these neat numbers and material, We should at least have some kind of drawing to help us when it comes to actually cutting, drilling and tapping these parts. I assume that your building the antenna for one or two reasons which are that you either don’t have enough cash to purchase a commercially made (and tunable) Yagi, or that you actually want to learn how these types of antennas work. So let’s take some more time to layout the antenna so we can have something to use when we’re cutting, drilling and tapping.
I am going to use software called “AutoDesk Inventor 2011″ which is a 3D design software that is used for CAD (Computer Aided Drafting) purposes. This software will let me make each part in 3D and assemble all the parts to make sure of proper fitment. This software will also let me create Blueprints based on the information I typed into the software. If you can’t get your hands on any type of this software, no worries. You can do the same thing on graph paper.
My Results are posted below. Please note that I’ve included all the information that is needed IN the Blueprint for those who just want to download the prints and fabricate w/o reading this article. However the information listed on the prints (other than the dimensions) have only basic information for experienced fabricators/ antenna builders.
**** INSERT BLUE PRINTS ****
(Still working on them, please check back)
Now that we have all the dimensions and a print, LETS GET FABRICATING!
Here is a list of basic tools that are needed. Most Hams have these tools or can get access to them. Following this list will be a list with the preferred tools that would make the job faster, smoother and more accurate. However the majority of people do not have a lot of the items
Basic Tools Suggested:
- Measuring Tape
- *Various Drill Bits (Ranging from .125″ to .750″)
- 8-32 Bottoming Tap (With T Handle)
- Bench Vise
- Sandpaper (120 grit)
- Scratch Awl/Scriber/Etching pen (or anything that has a sharp point that you can easily handle)
Preferred List Of Tools
- Metal Chop Saw (With vise)
- Vernier Calipers (6″ or bigger)
- Automatic Center Punch
- Drill Press (With a vice able to hold SQ and Round tubing/stock)
- *Drill Bits (Various to .750″ [or 3/4])
- Files or deburring device
* – For those who don’t have .750″ drill bit, depending on where you live, a 3/4″ Drill bit can get expensive. I would suggest either a step bit (still expensive) or a 3/4″ countersink (at 82 degrees). Drill the specified hole up to the biggest bit and then finish it off with the 3/4″ countersink. Since it’s aluminum, it will not damage the countersink and you will be able to counter sinks holes on other projects (DO NOT COUNTERSINK HOLES ON THIS PROJECT!
Lets start off by cutting all the aluminum rods (elements) and tubing (boom) to the correct lengths by using the tape measure. The blueprint posted in this article shows both decimal and fraction to the nearest 32nd of an inch.
After you cut the elements and boom to length, It’s time to layout the hole pattern on the boom and each element
I used a red pencil to mark the location along the boom. Then I marked the center of each location using a pair of verniers and used a marker to make the center point more visible.
When marking the elements it’s a good idea to mark the center point twice. Once from each end so you know that your exactly on center of the element. With the driven elements, you just need to place a mark at 3/16″ in from only one edge.
Using a drill or drill press with a small (>.125″) drill bit. Drill pilot holes on every center mark on the boom. DO NOT DRILL THROUGH THE BOOM! Only drill through the side you marked unless your using a bridge port mill that has a perfect 90 degree head.
Also drill pilot holes at the marks of each element. Once again, DO NOT DRILL THROUGH THE ELEMENT! You will only want to drill half way through the element. A bit of advice is to measure from the tip of the drill bit 1/4″ up and use the edge of some masking tape to tell you where to stop when drilling. If you feel un-easy about drilling the element, you should have a couple of inches of scrap rod that you can test both drilling and tapping on.
This photo shows pilot hole being drilled into the boom
After drilling the pilot holes, time to open the holes according the blue print. With the elements, I suggest using a .120″ (or #31) drill bit as the element could wobble causing the hole to open up a little more. With the boom I would start with opening the holes where the elements slide through first! Then switch to the 3/4″ bit and open up the holes where the driven element slides through. Switch back to the pilot drill bit, insert the plastic spacer that will hold the driven elements and using the two holes on the top of the boom as guides and drill halfway through the plastic spacer. Then open the rest of the holes to the correct size.
The next step is to tap each element with a #8-32 bottoming tap. If you can get your hands on a bottoming tap, you can take a regular tap and break the head off it and grind/file it flat.
After everything is cut and drilled and tapped to size. It’s time for assembly. Assembly is pretty stright foward.
Glue/Epoxy all shoulder washers/rivets into place and let dry. The driven elements are going to slide into the plastic round spacer. Make sure that each side of the driven elements does not come in contact with each other. Then slide in the reflector and directors and secure them with the 6-32 screws. When finished I placed more epoxy around the elements (NOT THE DRIVEN ELEMENT) at the point where they meet the boom. I did this because I don’t plan on taking apart the antenna.
Attache your coax to the driven element making sure you don’t have the connections contacting the boom.
You should hopefully have a functional 5el VHF Yagi
Here are some reading I’ve taken with a analyzer that I borrowed.
At 144.42Mhz, I got a 1:1 SWR with an Impedance of 48ohm.
At 146.02Mhz, I got a reading of 1:1 SWR with an impedance of 46ohms
At 147.72Mhz, I got a SWR of 1:1 and an impedance of 44Ohms
These readings were taken in my house with the antenna mounted to a wood broom stick. When I got the antenna into the attic I took another set of readings before I gave the meter back and I saw that a slight change on the values. Can’t wait to get it outside.
If you plan on making your own Yagi, please take ALL SAFETY considerations into effect. Know and respect all the tools you are using and when it comes to installing your Yagi, make sure the antenna with not come in contact with any utility lines.
If you are using the plans from this page, please note that your results may/will vary from what I’ve made. Since I’m new to antenna making, I would not want you to risk any material/money. Please confirm your findings with someone who does know before purchasing or building. These are just my notes on what I did to create an antenna.
Sources Of Information:
Peter P. Viezbicke, National Bureau Of Standards. “Yagi Antenna Design”. U.S Department of Commerce/NBS Tech Note 688 (Dec 1976). PDF (Sept 2011)
G.R Jessob, and R.S. Hewes. “Radio Data Reference Book” (ISBN: 1872309305) Radio Society of Great Britain; 6th edition (November 1995)
Unknown Author (N4UJW?). “Basic Yagi Antenna Design For The Experimenter”. YAGI ANTENNA DESIGN BASICS. Web (Sept 2011)
Martin Steyer (DK7ZB). “DK7ZB Yagi – 144Mhz-Yagis”. DK7ZB Website. Web (Sept 2011)
ARRL, R. Deam Straw. “The ARRL Antenna Book: The Ultimate Reference for Amateur Radio Antennas, Transmission Lines And Propagation.” American Radio Relay Leauge; 21st edition (May 2007)
Peter Knott. “Wire Antenna Modelling with NEC-2″. Antenna Engineer 8/12/2009. PDF (Sept 2011)
Daniel C Lester (KE9SE). “The Effects Of A Conductive Boom On Element Lengths”. VHF-UHF Basics (9/17/2009). Web (Sept 2011)
Guy Fletcher (VK2KU). “Effects of Boom and Element Diameters on Yagi Element Lengths at 144, 432 and1296 MHz”. ARRL QEX Magazine (Jan/Feb 2000).
Arie Voors . “4NEC2″ – Web – (Freeware) Program Used to Design and Simulate Yagi (and other) antennas
Autodesk Corp. “Autodesk Inventor 2011″ – Web – (Trial/Edu/Paid) Program used to Design and create blueprints