SB-200 Project: Update #2

This is the 3rd and update to my HeathKit SB-200 Amplifier Project.

See the orginal post here
See update  #1 here 

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 new fan came in and I just had to install it.

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.


Aluminum Spacers Used On Installtion

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.


The Installation is complete and we’ll see what happens!

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.

ty

New changes in the Shack as well as on this Site.

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.

Site Updates 

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.

RTL-SDR = CHEAP FUN

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.

 

My SB-200 Project – Update 1

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.

 

New Parasitic Suppressors on the SB200

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!

 

My SB-200 Project

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.

Here it is! Ain’t it purty! Arhajrhajr

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.

 

This is the box my SB-200 came in!

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 fans (top), Soft-Key (Left Green Board) and Soft-Start (W/ Expoxy glue on the top in-case it gets detached and bounces around(

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 New Parasitic Suppressors. Accidently wound of the coils with an extra loop. Thought it wasn’t a big deal… WRONG!

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.

Show me the tubes… SHOW ME THE TUBES!

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.

All new components! However it looks like a nest and needs cleaning

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.

Ohhhhh 600W mmmm…

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.

Let there be LIGHT! Hmmm electric sex.

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.

The original pressed in PEM nuts are long gone. The rubber feet that should screw into here holds the entire unit together. Found that Tinnerman (J) clips work great

 

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

SEE UPDATE #1 SINCE THIS ARTICLE

SEE UPDATE #2 SINCE THIS ARTICLE

Homebrew 5 Element VHF Yagi

 

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)
S1 =12.469″
S2 =20.492″
S3 =37.933″
S4 =58.000″

Element lengths
RL =40.495″
DE =38.363″
D1 =36.056″
D2 =36.086″
D3 =34.074″

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
(12.597*0.012362)-(114.5-(0.012362*0.012362))=.138226

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:

  • Hacksaw
  • Measuring Tape
  • Marker
  • Drill
  • *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
  • Marker
  • 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.


(elements shown cut to size with a band saw)

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


This photo shows the Pilot Holes drilled in each element

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.


This photo shows a element being tapped. Try to make sure your tap is 90 degree and straight.

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).

Software Sources:
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

Happy New Year!

Just want to wish those who visit this site a Happy New Year.  I haven’t been able to post many articles but that will change and stay tuned. I recently acquired a Heathkit SB-200 that needed some work so I’ll defiantly have a write-up on that. I also fabricated a 5EL VHF Yagi which I will show you step by step on how I designed, fabricated and tested (somewhat) the new antenna. And there is a possibility of my first HAM related home-brew equipment that I’ve seen in QST.  It’s in the planning stages but I think it’s going to happen.

Custom 19″ Cabinet for a portable repeater.

This project is more related to sheet metal design than Ham Radio because the fact that it could be used for more than just radios.

A friend/fellow operator asked me if I can build a 19″ rack mount for a portable repeater. I’ve learned over the years to NOT volunteer my time and/or services because it can lead to a lot of trouble and out-of-pocket expenses. But I owed it to him and I actually always wanted to design a desktop rack mount. Since time is of no worry, I felt comfortable working on this project.

For those who don’t know what a “19 Inch Rack Mount” is. It’s a standardized frame or cabinet/enclose for mounting equipment modules (i.e computers, radios, telecom equipment, and etc). These modules have a front plate that is 19″ wide which have holes/cut outs to allow the module to be mounted to the frame that has a standardized pattern. Since it’s a (EIA) standard in the industry, designers and fabricators have the basic foundation to design their product off of.  There is also a 23″ rack but the 19″ dominates the market at this point in time.

Having a standardized system makes the design aspect a lot easier to tackle. All I really had to figure out were the dimensions of the Motorola CM series radios.
Once I had that, It was actually quite easy to design.

I’ve personally dealt with these type of racks in fabrication, but I have never had a chance to actually design something using this standard. Hence the main reason I am making a this cabinet.  I’ve learned quite a lot from this project that will make me look just a little harder when it comes to similar projects.

Here are some pictures of the project.

Here is the 3D rendering of what I designed. On a lot of my projects that involves showing the image of the render before fabrication, I added a dollar bill to the project as a reference to size. It actually took about a couple of hours over a span of 3-5 months to design.

The laser doing it’s job. It’s about to cut on the front panels

Here is everything after laser cut in the flat. Little bit of deburring to take off any dross/slag  and off to the bender!


I wasn’t able to snap a picture of the machine actually bending up the cabinet but this is the machine that did it. It’s called a Panel Bender and works great for projects like this. The tooling is already installed and all you do is punch in a couple of numbers and off to the races. With this project and the time constraints, I bent every part by eye without using the CNC gauging system (takes longer to program the machine). I knew I was going to bend by eye so when I programed the part for laser cutting, I added little cutouts to physically show where I am going to place a bend. Line up the little cutouts with the tooling on the machine and it will put the bend within the tolerance that I need for assembly.

Here is the box after bending. I did a test fit by assembling all the parts. In the design I added 1/8″ diameter alignment holes. These holes when lined up and used with cleco pins (sort of like removable rivets) , will temporarily hold the panels together. This will allow me to either weld, spot weld or take one cleco pin out at time and replace it with an actual rivet.

Here it is all assembled and ready for paint. I decided on a black texture powder coat because it’s used often in the industry. Plus it hides my fat greasy fingerprints quite well.

And there she is… Ain’t  that a thing of beauty? I placed a 2U power strip just to illustrate that how universal it can be. Well that’s basically it. This little article is to show to process from the thought to design and from design to build. If I were to even build something like this, I would use thicker material and stick to the specs on the standard a little more closely. I would also add handles and reinforce the area where the handles are mounted.

Edit (9/30/2011): Here are some more photos (Click to enlarge)

Here is it at the house…

Here is a different view. On the bottom of the unit is a surge strip. When I fabricated I only made 3U panels so if I were to install devices that took up 1u or 2u then I would have a gap. So I made some additonal panels which haven’t been painted

Here is a upclose  shot that will show how the panels or modules are mounted. Depending on the design, some rack systems have sliding frame rails to extra weight support. The silver looking thing you see is actually a spring clip with a floating #10-32 nut. Back when these racks were first being designed, instead of using a square hole with a captive nut, they just had regular round holes that were drilled and tapped. Problem was if the threaded hole were to become stripped due to major use or misalignment, then the entire unit could be scrapped if it couldn’t be repaired. With the new system, you can just pop in a nut where ever there is one needed. If it gets stripped, just replace the nut!

Here a picture of the back of the unit. I created a 2X3″ in opening to allow cables to be routed through. When not in use, the gasket-ed cover can bolt right into place using two #10-32 screws that screw into pressed inserts on the main body to create a nice air/weather tight fit (even though the rest of the unit is not air tight).


Here it is with the radios installed. Considering this is the first time I actually got to physically handle the radios, everything lined up okay considering I was using the specs from a similar radio for it’s dimensions.

Overall it was a great build, I just might build another one and apply what I’ve learned on the new box If by some chance you have the chance to fabricate something similar, I would use 1/8″ Aluminum or 12ga (.105″) steel.

 

Hello APRS My old friend.

I’ve come to talk with you again.


APRS – ™ By:  Bob Bruninga, WB4APR Http://www.aprs.org

Back in 2001 when I first got my license. I was interested in APRS because it was something I can do with my new license. I went as far as setting up a part time digipeater and after only a couple of months, the digipeater went down and lost interest in APRS because the cost of a GPS receiver at the time (even though GPS is NOT a requirement to listen or participate on the APRS network).
GPS receivers are a lot cheaper compared to 10 years ago and I have a old Garmin GPS-V lying around. So I figured this would be the perfect time to get back into APRS. For those who don’t know what APRS is, It’s Automatic Packet Reporting System which is an Amateur (Ham) based system for real-time communications of information using a digital protocal (AX.25). There are many possible things you can do with APRS. You can send (Short) text E-mail, SMS Messages,  send weather data (Which the NWS uses) and when hooked up to a GPS , will send position data.  I am not going to go into much detail because there are websites that are dedicated to APRS.
I am going to be doing a couple of things with APRS. One thing is that I am going to set up a part-time iGate (internet gateway) to make use of the frequency scanner and antenna that is not being used. Packets of Information received from the scanner (tuned to 144.39mhz) will be sent over the internet using the APRS-IS network so it can be databased and displayed on such websites as aprs.fi .

The other thing I want to do is location tracking. In order to do tracking you’ll need 2 or 3 things. You’ll need a GPS receiver that has an output for NMEA data, TNC (Terminal Node Connector) and a transceiver (VHF [144-148mhz] is Most used). As stated earlier, I have a Garmin GPS-V lying around and I also have a Kenwood TH-78A.  All that is missing is a packet TNC.  A Real TNC can cost $100+ and needs a computer. However there are units designed and built for APRS that will encode the data from the GPS to the AX.25 protocol and transmit the signal using the transceiver. I’ve purchased one of these units called ” TinyTrack3+” from a company called Byonics. It’s as basic as it gets. You can either buy it as a kit or assembled, with or without a GPS Receiver, with or without cables for your transciver or with or without cables for various GPS models.  I ended up going with a solder and assemble your self kit without any extra cables because I wanted to invest the least amount of money in it as possible.

Here is the kit as you would get it in the mail. It comes with the componets, board, case and instructions.

Here is the board soldered up. I used a 35W Pencil type soldering Iron. I filed the tip a little bit to assure that solder flows to the tip. It took about 1/2 to 3/4 of an hour to solder. If your new to assembling boards, I would go to the Byonics website and download the manual because the online .pdf manual will cover the assembly and everything else in great detail. As long as you follow the step by step instructions, it will turn out great. For newbies make sure the diodes are going in the right direction, LEDs in the right direction and make sure the notch (little cutout) is aligned with the silk screen image.

Now that board is done, time to make some cables! (Since I didn’t order any)

Here is the cable all assembled! It’s a DB-9 Connector  (Radio shack P/n: 276-1538 US$2.69) , Pos and Neg power cords with Anderson power poles attached so it could powered by many different sources (7-35vDC), Sacrificed  speaker microphone from the Wouxun for its cable, Ferrite Core choke (Optional, Radio Shack P/N: 273-105) and the DB-9 Case (Radio Shack P/n: 276-1539 US$2.09). I Got the wiring diagram from the  Byonics website and took about 1/2 hour to make which ended up costing me around $5 since I already had the cable, choke and power connector

Just an FYI, I sacrificed a speaker microphone from my Wouxun. Power-Werx which distributes Wouxun products (as well as the power poles), has the exact same cable for this application for sale on their website. They also have a similar one but with a cigarette lighter plug (Both for US$20). Byonics also sells cables for this and many different radios. Also note that that wouxun speaker mic layout is the same for kenwood HT’s!

After you assemble the tracker and the cable. Apply power to unit and hopefully it comes to life by flashing the yellow and green LEDS three times. Only thing left to do is to program the tracker using your computer. This point it can get tricky. The TinyTrak3 needs a NULL modem cable (Or adapter) to program it and possibly a gender changer. I found that I didn’t have a null modem cable, all I have are straight through cables. Since I didn’t want to wait for an adapter I made one from old computer parts lying around my house

Here is the cable that I made from parts out of an old 486 that I had in the attic. It’s not pretty or rugged enough for daily use but once you program the Tracker and are satisfied with the operation then you will most likely not have to program it again.

Here is the complete setup. Right now I have the unit running off a 9V battery. I also used a cigarette lighter plug with power poles connected to it. Depending on how you programmed the tracker, It will only send when there is data from GPS. There are limitless things you can do with this setup. For SOTA members (Summits On The Air), They can bring this along with them so others can see their progress in their hike. If you helping out in a public service or public events which ham radio operators are helping, you can show your location to HQ without even telling them. It makes things a lot easier.

Here is my first track. I learned a lot when doing this. I found that my handheld in the truck has a hard time communicating with the digipeaters in the area. I might purchase a small 1/4″ wave mag-mount  or a duplexer and switch to my dual band antenna for when I am running APRS in the truck.

Modifications

I added things to the Tinytrak3+ which I think will make it better for me to run. If I had to be really critical about the tracker is that the DB-9 connectors did not come with mounting screws. The first test out with my truck the power/radio connector became loose and eventually lost power to the tracker. To fix this I went scavenging parts off  a old computer.

Now I can secure both the power and GPS connections. The screws came off the LPT and monitor ports of an old mother board. There is a small amount of space between the back plate of the connector and the board. So I had to grind down the bolts and nuts so It would not touch the board.

Another issue that might come is when I am portable (walking). More likely the power source for the tracker for this purpose will be a 9V battery. The tracker with all the LEDS running will consume around 18.6ma which means a 9V battery (.370Ah avg) could possibly last for about 9-12 hours (60% discharged). If  you turn off the LEDs, the power consumption is 6.6ma. On a 9V battery, the tracker could last around 30 hours. The TinyTrak3+ can run without the LEDS by cutting a lead (tells you how in the directions). If you using a high-capacity 9V (.580Ah)with no LEDs it could last for more than 50 hours so it might be beneficial to cut the lead and add a jumper. The down side is that you will not know the status of the Tinytrak.

So what I did is cut the lead on the board and installed a bridge (shown in the picture above with the blue jumper). When jumped the LEDs are operational.
Also pictured are 2 bridges installed (on the left side) for jumpers J5 (outside pair) and J6 (inside pair). If J5 is jumped it will switch to what was programed in the secondary tab in the program (Program 2) . This would work great for an event which required either a different call and/or different settings. After the event, you can switch back to the primary settings. If J6 is jumped it will send a signal to power on the transceiver. This would involve another board with a relay to put power into the transceiver or modifying the transceiver. I don’t plan on messing around with it any time soon but since I am soldering on jumper bridges, why not.

Overall it was a really great build and I am having a blast with APRS. My plans are to find a way to make it all fit into a nice tiny package that I could carry when hiking or driving.

73 and thanks for reading!

 

Homebrew GMRS 3 Element Yagi

Since I’ve built a ton of J-Poles and wire Antennas, I’ve wanted to build something different. I decided on a 3 element YAGI built for GMRS that is directly fed with 50ohm coax. After a couple of failed yagis and the help of another ham on QRZ.com forums, I finally built a Yagi that works! The reason I’ve chosen a Yagi built for GMRS is due to the ultra high frequency, which ends up being a small antenna. If I were to mess up (Which I did), the material cost would be low. I also wanted to use it on a GMRS repeater in the area.

The first Design I used is with a Web Site that has a Java base applet to design the Yagi, After getting all the Dimensions from the website, I went to work building the antenna. After everything was done, I learned two things. One is that my drill press does not drill straight (90 Degrees) through the tubing. The other thing is that when I hooked up the antenna to a simple SWR Meter, That didn’t work either (Pegged the Meter). At this point I got frustrated  and posted my issue on QRZ.com. A Ham by the call of WB3BEL (Harry) took my dimensions (That I got from the applet) and plotted my antenna into 4NEC2 software (Like EZNEC but freeware) and it would not work for the center frequency of the GMRS Band (or any part of the GMRS band).
WB3BEL actually re-designed the antenna to where it would work so I give him credit and major thanks for help. I took his Dimensions, Modeled the antenna for fabrication and built the antenna. I Hooked up the antenna to a transceiver and SWR meter and got a 1.2:1 SWR and a 1.5:1 SWR on the outsides of the GMRS band. The Design is calculated to yield 7.5Dbi of Gain. Considering connector and cable loss (Lets say 4Dbi using 50ft RG-213 W/ 3 SO-259 Ends and a Barrel Connector) still yields gain of around 3.5Dbi which is not too bad.

Here is rendered Image of the Antenna. The elements are Insulated from the boom using plastic shoulder washers for the Reflector and director. The Driven Element is insulated using a 0.750(OD)X.375(ID)X1.5″(L) Plastic spacer. Since the elements are going THROUGH the boom, It will make the elements electrically shorter so you have to compensate for the loss by adding 0.279528″ (7.1mm) to the element to correct the effect (Boom correction). The elements are secured using #8-32 Screws screwed to the boom. The screws are also insulated from touching the boom. The screws do not make any significant changes to radiation pattern of the antenna as long as it’s insulated from (not touching) the boom. I did notice that the screws actually lowered the SWR a tad which is great.

I didn’t add a matching network to the antenna because I wanted an easy to build and assemble antenna which is the entire point of this article. The antenna is fed using RG-213 Coax with terminals soldered to the core and shield. I tried to keep everything as short as possible because this and the ring terminals effect the performance and SWR of the antenna.

Here are a couple of screen shots from the antenna software that show the Radiation Pattern and gain. Nothing special here.


Here is the calculated results for the SWR of this Yagi. Please note that it’s in the ball park. By adding screws, coax leads and the ring terminals, it could or will effect the final pattern and/or performance of the antenna.


Here is a SWR Shot. As you can see, I don’t have a very good meter. I would like to buy a HF/VHF/UHF Antenna analyzer for my Antenna builds but I don’t think that will happen in the near future.


Here is the complete Antenna.
Overall it was a fun little project. It took a short time to build and it’s a great directional antenna with some gain to help your signal on GMRS reach its destination.

Continue reading if you want to build this antenna.

Continue reading “Homebrew GMRS 3 Element Yagi”