Yagi – NT1K – Welcome

New Beam In The Air and I’m Swinging It Like I Just Don’t Care.

Since I got my first HF station up at my house, I’ve only used the G5RV (Both Jr. and fullsize) and the 10M dipole in my attic which is surrounded by aluminum siding. With these antennas I’ve been able to make thousands of contacts. I’ve manged to get basic DXCC and WAS awards. Even though a lot of people harp on the G5RV, it provided me countless hours of contacts and I think it was well worth putting up. I would still suggest the G5RV or its variants to others.

However I think I pushed the G5RV as far as it could go. The antenna has since stretched. More ladderline is laying on the ground. New entities are getting harder and harder and there are bands I haven’t really explored. 10 Meters on my G5RV hasn’t been really good to me and the dipole wasn’t going to cut it since it was basically surrounded by aluminum. I was also starting to get bored. I would only hop on to see if I can work a DX expedition or random JT-65 contacts. I needed an upgrade.

My first solution was to get a multiband vertical. In 2011 I purchased a used Butternut HF9V at a local hamfest. In 2013 I finally buried some coax and installed the antenna with a bunch of radials.

Upon getting it on the air, I found that it wasn’t really a performer. In a lot of cases, the G5RV was much better. The HF9V didn’t really give me the “WOW” factor I was looking for. But it work so it stays in my backyard. I needed something better. I needed a beam.

What Beam Should I Get?

That was one of the many questions I was asking myself. I didn’t want anything massive or anything that would require a large tower or rotor. I kept focusing on a Hex Beam type antenna, log periodic or a 3el tri-band antenna like the Mosley TA-33jr or Cushcraft A3S. I ended up going back and forth between the K4KIO type hex beam or TA-33.

The Hex Beam offers more coverage. It’s possible to get 20 through 6 meter coverage which includes the WARC bands. That’s 6 bands. In simple terms, it’s basically a 2 element beam with the elements folded in such a way that it still works. There is a claim 5dbi (or 2.95 dbd) gain. The claimed F/B (Front to Back) varies from approx 25db to 30db depending on the band. So in theory with perfect conditions and zero loss, if the antenna was fed with 100W, it would radiate around 192 watts. The hex beam would also attenuate signals from the back of the beam by 27db. This allows you to hear signals better in the direction it’s pointed in.

The TA-33jr can only really be used on 20, 15 and 10 meters. The antenna could be adapted for other bands with the addition of the WARC kit. The TA-33jr has anywhere from 5.8 to 8.0 dbd or claimed gain (or 7.95 to 10.15 dbi gain) and has a claimed front to back ratio of 20db. So once again, in theory with perfect conditions and zero loss, if the antenna was fed with 100W it would radiate anywhere from around 380w (on 20M) to around 631w (on 10M) and would also attenuate signals from the back of the beam by 20db

These comparisons are based from figures provided by manufacturers. That doesn’t mean that is how the antenna will perform in real world conditions. Things like height about ground, the type of ground, coupling to nearby antennas or other thanks and losses from coax and connectors play a major role in the performance and efficiency of the antenna.

On paper, the TA-33jr offers more gain on 10, 15 and 20 and looks easier to assemble but the multi band hex type beam has a better front to back (F/B) and offers more gain on the WARC bands. The TA-33 types of antennas have been in use much longer than the Hex type. If you were purchasing a beam on a small budget, the TA-33 type of beam would be much cheaper on the used market because they have been in use for decades (at least 50 years). I’ve seen TA-33 in decent shape for as low as $100.

How am I going to Mount The Beam?

No matter what I decide, I would need to mount the antenna to something. My first option was to obtain a tower and have it bracketed to my house at about 70′ in height. However that did not meet XYL approval because of possible guy wires in the yard and I want to keep my neighbors happy. Since a bracketed tower is out of the question, my next best bet was a roof mounted tower. My house at the peak is approx 40 feet above the ground level. With a 9ft roof tower and decent mast, I could get my beam 50 feet above the ground. So a roof tower it was.

Going Shopping

I priced out a new Hex Beam from K4KIO, 9.5′ Tower from Glenn Martin, A new Rotor and Rotor Controller (Yaesu G-450), Mast, thrust bearing and cables. The price tag totaled almost $2,000. That is something I can not afford. However I was able to find a used TA-33, 5ft tower and rotor for much cheaper locally. I ended up purchasing the TA-33 package over the hexbeam. I am losing out on the WARC bands but the price made up for the loss.

A Pile Of Aluminum

Upon receiving the antenna, I noticed right away it’s not a TA-33 that I thought I was getting. The Boom is 2 inches in diameter and longer than the TA-33jr. After a little bit of investigation, I found that the antenna is a CL-33 or a TA-33 Classic. The CL-33 is 6ft longer and provides slightly more gain and slightly higher F/B ratio compared to the TA-33jr. I was trying to go as small as possible but since I already have the beam, it will have to do.

The tower and thrust bearing was in great shape but the rotor appears to seen better days. The terminals were rusty and the rotor would “struggle” in certain areas when turning it without an antenna attached. I need to restore the rotor.

I stripped the rotor down and found a group of really rusty ball bearings. I soda blasted and powder coated the case, ordered new ball bearings, new brake parts and a new style connector. After some cleaning and re-wiring, the rotor is good as new.

The antenna was taken apart and traps were checked for debris and broken parts

For the most part the traps were clean but some of the coils had cracks and even chunks of plastic missing. I ended up filling the cracks and voids with epoxy. Worst case is that I would have to get replacement traps. Being such a well-known antenna, it’s little easier to find parts.

After repairs I cleaned all the aluminum with scouring pads and applied an Anti Oxidation grease that will prevent the sections of elements from sticking to each other. I also applied anti-seize lubricant on clamps and other things.

I did a test fit to make sure everything is working and bolting correctly to the tower. You will notice a different rotor.

I have went with a Yaesu G-450 rotor because it was almost new and got it for much less. You will see WRTC spray painted on the rotor. It was used during the World Radiosport Team Championship (WRTC) here in New England. It’s not as heavy-duty compared to the Ham IV but I feel more safe using it.

There was only one concern I had with the tower and that was protecting the thrust bearing. I didn’t want rain, snow and ice to build up around the TB so I designed and fabricated a cone to slip over the TB shedding away anything from above.

Now it’s time to test the boom mounted to the mast

So far so good. The only concern I had was that the cone now provides a great home for hornets. I guess we’ll see.
The tower and antenna are now ready to be mounted on the roof.

Hurry Up And Wait… Now Hurry Up!

Now we have to get the tower mounted to my roof. I decided the best course of action is to mount the tower towards the rear of my house. That will allow the beam to clear a near-by tree and it makes it less visible from the street. Two trees in the front of my house hides the tower and beam quite well. I might provide some signal problems but we’ll see. I planned on using 10″ carriage bolts going through the roof into my attic and brace it using 2×4’s and a metal channel spanning over multiple rafters. I designed everything in CAD and put it through stress analysis. According to the results, it looks good.

Here is the problem. I don’t like going up on my roof. When I installed my X510, I almost fell off the roof and sort of been scared since. I don’t have the proper equipment to go up on my roof safely. the 10:12 pitch takes a toll on me. I am also stubborn and have a “do it yourself” attitude so I put the project off. It was planned to be put up in April before the New England QSO Party, but it’s now November and I still don’t have a tower on the roof.

I needed some roof work done before it got real cold outside. I had to hire a roofer to install venting and asked if he could install the tower at the same time.

Thankfully he agreed and there is now a tower on the roof. Ignore my leaning diamond X510. It could have been prevented from leaning if I used a couple of self tapping screws. Due to the weather and hourly cost of the roofer, I decided not to install the antenna on the same day. Let the neighbors sort of get used to the tower on top.

From inside my attic, I braced the antenna using 2X4’s and a large metal U channel covering 5 rafters. Very sturdy.

I Wanted To Get It On The Air

There is an upcoming 10M contest in December that my local club is involved in. I wanted to participate and I know my G5RV, HF9V or my 10M dipole wasn’t going to perform. I finally folded and contacted members from my local club to come help me install the antenna. A lot of people responded and on cold windy Sunday in December, a bunch of people came to my house to help install the beam.

A Major thanks to Ed, KB1NWH for staying up on my roof for hours.

We removed the Diamond X510 as it would be in the way and decided to assemble the beam on the roof since the tower isn’t tall. We then installed the boom, each element and then the Diamond X3200. I didn’t want the X510 on the mast as it’s a much larger antenna.

Finally. I now have a beam! There is still cable work to be done but everyone was able to leave in just a few hours. I was on the air just after noon.

I would like to thank Ed (KB1NWH), Jim (KK1W), Steve (N1SR), Frandy (N1FJ) and Dave (AA1YW) for taking time out of their life to help me get an antenna on the air.

What’s the difference?

I never had a beam before and I have no clue how one would perform at my house. I hooked my radio up to a A/B switch so I can switch between the G5RV and the Beam. The bands were not great when I finally got on the air but I was able to hear a lot of West Coast stations on 20M. I had a real hard time getting my signal out west and was amazed to see the difference. Stations that were S2 on the G5RV were coming in S8-9 on the beam. The front to back ratio was okay. I was pointed to EU and hearing a Texas station at the same time. When pointed to EU the Texas station was S7 and when I turned the beam toward the Texas station, he became a S9+. I will have to do more comparisons.

Here is a quick and dirty A/B video I did for a Fellow redditor. I should have found a week station but that will be for another video. I just wanted to show the obvious difference in antennas.

Contest Time

Having the beam on the air for the ARRL 10M contest was great. I have never participated in it and felt the beam proved to work quite well. 10 meters was open to Europe both Saturday and Sunday morning. I did about 100,000 points which is not bad considering I operated only 10 hours using low power (Around 100W) and was not using spotting assistance. I knew I would not win SOHP so the amp stayed off.

Overall Feelings

I should have done a beam much sooner. Or maybe I shouldn’t. Starting off on wires provided a challenge. With the wires I was able to make contact with a lot of operators and even won some awards and contests. Now that I have a beam, hopefully it opens up the door to even more contacts with those ham radio operators around the world. My signal will now be a little bit stronger and I will be able to hear farther away. Getting the beam on the air has renewed my interest in actually getting on the air.

Thank for reading,
Jeffrey Bail (NT1K)

Antenna Reviews: Arrow Satellite II Vs. Elk Log Periodic

I was given two popular antennas to use for a decent amount of time. I figured to try them both out and share my feelings about each one. I was given the Arrow Satellite II from Arrow antennas and a dual band Log Periodic from Elk Antennas. We’ll look at each antenna individually and then compare them to each other.

Arrow Satellite II

Whenever someone mentions working amateur radio satellites (reapeaters in the sky), the Arrow Satellite II is almost always mentioned. It’s been mentioned so many times that I wanted one. However like most hams, I’m cheap! If I feel that I can make the exact same antenna, I will try my best to do so. I tried looking for the plans for that antenna but couldn’t find them. I was bummed out until someone I knew (N1KXR) purchased a used one from another ham. This was the perfect time to take the antenna and dissect it.

The first thing I did when I got the antenna was to assemble it and PLAY! The actual assembly of the antenna was OK. The reason it’s called an ARROW antenna is because the elements are made from aluminum arrow shafts that are used in archery. The great thing about using arrows is that they are light and built to some strict specs.

I like that it’s light weight and that I can setup the antenna to either VHF or UHF or Both. The duplexer inside the handle is a big plus. I don’t have a spectrum/network analyzer or lab equipment to give you the in-depth specs of the antenna (I just wish I knew) but it shows good SWR on my bridge (meter) and it performs. The only thing I would do if this was mine is to use different color electrical tape (or paint markers) to identify the correct pairs of elements. I lined them up by height. I would also drill a hole in the handle (away from the duplexer) so I could mount the antenna to a tripod better. As I found with the PVC Tape measure yagi, It gets heavy after holding it for awhile.

Let’s Reverse It!

I wanted to make this antenna almost exactly the same way it was purchased. From using arrows shafts all the way down to the micro-duplexer that is in the handle. I didn’t want to drift far away from the original design so out came the 5ft vernier calipers and went to town remaking the entire antenna in CAD.

After putting all the dimensions back into CAD this is what I got. I would like to say it’s within .005″ and the antenna is possible to reproduce if you have access to a drill press, arbor press (can’t tell if the BNCs are pressed) and lathe (Or a good fixture for the drill press) as most of the work would be focused on the driven element/gamma match.

Is it worth making your own?

Even though I have access to some of the material, I wanted to look at as if I had nothing and had to go out and buy all the material. So I started calling around for quotes on material. The more and more I got into it, the price kept climbing and climbing.

Let’s start off with the Arrows. I wanted to use the same aluminum arrows just like the ones that are used on this antenna. I went looking for the Arrows they used based on the dimensions I got from reverse engineering. While trying to find these arrows I learned a lot about all the different types of arrows used in archery. When it comes to aluminum arrows, they use a 4 digit number system. The first two digits are the diameter of the shaft in 1/64″ increments and the last two digits are the wall thickness in 1/1000″. I found out that they are using 1716 arrow and the only ones I can find are by Easton (Easton Blues/Jazz) and they are not cheap. Just the shafts would end up being $60-$70. That doesn’t include the 8-32 Inserts.

The tubing, square stock and bar stock for the boom and gamma match would add up to approx $30.

BNC connectors, Coax, plastic tubing, wire, screws and threaded rod would add up to approx $20.

So far we’re looking at least $100-$120 for the material and that doesn’t even include the micro duplexer. You can purchase the duplexer ready to go from Arrow Antennas for around $60 or you can make it yourself using the plans found on KI0AG’s Site that appears Arrow Antennas used as well. If you don’t have the means or equipment to make/etch your own boards then it will still cost a decent amount of money.

For me, It’s not worth building.

The price of material would meet or exceed the cost of the antenna if you were to buy it from Arrow. This doesn’t include the splitboom, duplexer and labor involved. As much pride as I take in building my own, it’s not worth it. I can buy the antenna already made for less then it would take to manufacture. I tried things like using 1/4″ solid aluminum rod to reduce the materials costs but now you are spending more time in labor in drilling and tapping for a 8-32 screw. A lathe would really help in this situation.

How does it perform?

I can’t get too technical because I don’t have any of the testing gear or the know how to give you exact figures. The following evaluation is just from my personal observations.

The way I received the antenna was in a tube with what appears to be the original plastic bag that separates the UHF and VHF Elements. Since this antenna is used, I am not sure how it comes from the factory. Assembling the Antenna is quite a challenge. The elements are NOT labeled! What I had to do was line up the elements by height and pair them together for both the VHF and UHF side of the beam. For me, most of the time assembling this antenna is spent finding out which element is which. This would be my only complaint about the antenna. However it can be fixed by doing a couple things. Buying multicolored electrical tape and put some tape on the elements and boom. You can also purchase or make your “Antenna” bag with pockets for each pair of elements.

Assembly is pretty much straight forward once you know what goes where, Just screw them together through the boom, hook up the BNC connector and you’re ready to go. I’d suggest the first time you put it together to check SWR and adjust the gamma match for optimal SWR.

I spent some time tracking Sats, hitting repeaters that I can’t normally hit with a rubber duck and some back yard RDF. The antenna performs, I was able to pickup some satellites like the NOAA and some Ham Sats and it performs just like you would expect. There is nothing much more I can say performance wise other than it works.

Pros:

Uses aluminum
Lightweight
Tuneable (Gamma Match)
Built in duplexor
Use either 144 or 440 or both.
Breaks down into a small area

Cons:

Elements not marked
Arrows can break
Built in duplexor
Very bulky when assembled
Hard to transport

If you noticed I put duplexor in both the pros and cons. The reason is because it’s great that you just one connection to the radio but you will have loss at the duplexor. I would assume the loss isn’t much at all so I wouldn’t be to concerned.

When you assemble both the VHF and UHF side of the beam, it turns into quite a bulky object and would be harder to transport inside your car. Not saying it’s impossible but you would most likely have to break down one band of the antenna.

Overall a great antenna and would recommend it to anyone that is serious about portable sat work, RDF and low power operations (<10W)

Elk Log Periodic

Whenever the Arrow antenna is mentioned, the Log Periodic by Elk Antennas is also mentioned and vice verse. The antenna is known as a log periodic which is a little bit similar to a Yagi. Instead of one boom, It uses two booms which the elements that are attached to each boom are 180 degrees from the elements on the other boom. In a simple way I can put it is that it’s a bunch of dipoles of different lengths. When the signal enters the antenna, it will find the best pair of “Dipoles” for that frequency and the other pairs help direct the signal.

Lets reverse it!

Well I didn’t. I didn’t think it was worth it.

The antenna is made with some quality parts. The Booms are thick walled aluminum tubing. They are spaced part using plastic spacers and plastic bolts and it has tapped holes along the boom with #10 screws to hold the elements. The boom is mounted/supported by two different grades of PVC tubing. The PVC used for mounting is schedual 40 and the other appears to be electrical conduit. The elements are also aluminum tubing that appears to have been either wet or powder coated with vinyl caps to protect the ends. They also have pressed in threads (10-32). They are high end tent poles. Included is a Handle made from PVC tubing that has a foam grip fitted to one side. This handle allows for portable ops.

Is it worth making your own?

I priced everything out as if you didn’t have any of this material laying around the house and you started from scratch.

4Ft Aluminum tubing for the boom – $25
12ft Aluminum tubing for the elements – $35
PVC for mounting – $10
Vinyl caps – $5
Stainless Screws/Nuts (Nylock) – $15
Plastic Screws/spacers – $10
SO-239 Chassis mount – $5

Total Materials cost – Approx $105

Just based on materials alone, It’s cheaper than if you were to purchase one.

For Me, It’s not worth building

Even though the materials are cheaper than what it’s being sold for, there is quite a bit of work that has to go into this antenna. One of the booms will have to be machined for a notch to allow the SO-239 connector to sit flush. There is also a LOT of drilling and tapping going on. That means you need a drillpress that is almost perfectly 90 degrees and fixtures/jigs available to drill nicely through round stock. If you don’t have the time or you highly value your time, I can see 4 or so hours in manufacturing and assembly. If you wanted to go all out and powder/wet paint the elements, then you are add more time and costs.

How does it perform?

Once again, I don’t have the equipment to give you a proper assessment of the antenna. The following evaluation is just from my personal observations.

I got the antenna mostly un-assembled in a bag. I am not sure how it comes from the factory as this is also a used antenna. Assembly is easy with this antenna. The elements and boom are marked with different colors. All you have to do is match up the colors and screw them to the booms (Yep, still calling it that), connect the coax and away you go!

I was able to receive some Sats, and hit some distant repeaters with my HT. I also mounted this to my simple TV rotor in my attic and used it with my FT-1900R.

I even did a night time SOTA activation with it. Worked quite well.

Pros:

Easy to assemble
East to transport when assembled
Dual band
No duplexor
Easy to break down
Can be semi permanent install
Can accept up to 200w VHF and 100W UHF

Cons:

Uses PVC
Coax has to be positioned correctly to avoid SWR issues

Even though the antenna works and does a great job, The use of PVC just makes me feel that the build quality is… meh. It has a home-brew feel to it, that’s all. When hooking up the coax, you have to keep at least 8″ of the coax 90 degrees from the boom as suggested on their website. In order to get the most out of this antenna, you would have to make some sort of fixture to mount the coax correctly which could be a hassle depending on how you’re looking at it.

Dueling Antennas.

Cue the banjos and setup the octagon because we have a fight on our hands. Well… Not really. There is no winner and there is nothing that would make one WAY BETTER than the other. They both have their unique features and they both pretty much perform equally in my book. I like the Elk because it’s not as bulky and can handle more power but I like the Arrow because it doesn’t use Plumbers\Electrical PVC and it’s easy to adjust. If push came to shove and I had to make a choice, I would lean toward the Elk. If they redesigned the boom holder/mount using something other than PVC tubing then I would prefer the Elk over the Arrow.

I decided to make a carrying case for the elk. I used outdoor canvas and my sewing skills are absolutely horrible. But it’s better than the nylon tent bag that was being ripped up by the screws that are sticking out of the boom. Now all the elements are organized and I have a pocket to put coax or a small handheld radio. The green tube in the background is what holds the arrow that was created by the owner of the Arrow. It appears to be a pool stick bag with a PVC pipe. It’s long because at the time, it was one solid length of boom

Here is a photo of both the antennas un-assembled. At the point of taking this photo, the Arrow still has a one piece boom. They both pretty much take up the space if the boom was split on the arrow.

Here is the duplexor that is located within the handle of the Arrow. Wasn’t going to cut the shrink wrap to show the circuit but it’s no secret. the plans are out on the internet.

Here are both antennas assembled. You can see that the Arrow is bulkier due to it’s cross polarization and it’s a bit longer than the Elk. But I will say that the arrow “Feels” lighter. I wouldn’t be holding either antenna for an extended amount of time.

Here is the “Split Boom” modification I did to the arrow antenna. This is available as an option from Arrow Antennas and I would suggest spending the extra money to have it done for you. What’s great is even though arrow sells a split boom model, they published the modification to make your one piece boom into a split. I followed the directions on the site except for the angle. I used a piece of 1/2″ plumbing copper pipe. I should have turned it down in the lathe as it was a really tight fit. Once I got the copper pipe a couple inches in the boom, I drilled a hole through the boom and tube and used aluminum pop rivets to secure the copper tube. Once I got the other end of the boom to slide on the copper pipe and meet the angle, I drilled a hole through copper tube using the hole for the first director element for the UHF side of the antenna. This way when you thread the arrows through the boom and tube, it will “Lock” the booms together. Nice move on arrows part.

Overall there is no clear winner. They both have their strengths and weeknesses. My personal preferance would be the elk even though I wouldn’t mind the arrow at all. Tasters choice I guess.

Thanks for reading!

73,
NT1K

My Offset Attenuator Project

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

Qty	Desc	Price	P/N	Source
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.

Final Assembly

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

Lessons Learned

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!

73,
Jeffrey Bail (NT1K)

VHF 3EL Tape Measure Yagi.

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.
http://theleggios.net/wb2hol/projects/rdf/tape_bm.htm

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)
http://www.arrl.org/files/file/Technology/HANDSON.pdf

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!

3EL Tape Measure Yagi PDF

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.

(Chamfering the corners and sanding down the points)

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

Prices Involved

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.

End Result

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.

Here it is with the elements folded up. I would do this before a fox hunt so I can place it in the back of my truck

Here it is folded up for extended storage. I use the clamps that hold on the driven element to secure the tape measure to the boom

Here is a plot of the Yagi using the miniVNA Pro. Testing conditions involved hooking the calibrated analyzer to the end of the feed line and taking multiple readings while holding the antenna in my office. Increasing the gap lowers the center frequency.

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,
73

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.

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”