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HF 18AVT Vertical Fence Mounted with an Ugly-Balun

from Dale Kubichek, N6JSX on June 12, 2012
View comments about this article!

HF 18AVT Vertical Fence Mounted with an Ugly-Balun
(fixing the Hy-gain 18AVT)

by N6JSX /8

My previous article “HF Vertical fence mounted, Ugly-Balun, & extra band” posted on eHam.net on 04/02/2012 covered how I mounted my old dinosaur 18AVT onto the fence using an Ugly Balun. I was experimenting with this installation on my new chain-link fence (used as the counterpoise). It worked very well until winter hit that caused the AVT to suffer damage from high winds and freezing temperatures.

Even though Ohio had the mildest winter ever, we still got a few serious wind events. ATV top-hat spun in the wind. I could see from the ground the top-hat was loose indicating the aluminum tube insert-nut failed allowing free spinning. As you will read there was even more problems; here is my detailed how-I-fixed the 18AVT making it once again mechanically sound insuring many more decades of GOOD DX’ing.

MFJ/Hy-gain does NOT sell replacement aluminum tube with insert. Once again MFJ Quality failed me as they even sent me the wrong diameter tube. After some badgering they relented and sent me the proper diameter tube (at no cost). With a 3/8”- 24 one inch barrel nut and propane torch I heated the tube, then pressed the nut down inside the tube until flush with the tube end. That fixed the top most tube that affixes the top-hat to the AVT body.

During this top-hat repair I checked the 80m coil - finding it open. MFJ-Hy-gain does NOT sell replacement parts for this coil. I took the 80m coil apart to discover both brass 3/8”-24 caps must have spun inside the coil body as the coil solid wires had snapped off the caps. It looks like the glue used had let loose holding the coil form to the brass end caps allowing the wires to be twisted off.

The coil form was also cracked and very thin. The form required replacing which meant I would have to build a new coil. I had to dig deep into my bag of mechanical tricks to find a coil form that is 1.00” in diameter. I had an epiphany to measure Ύ” PVC and found it was a perfect 1.00” OD plus thicker walls too. Eureka my new coil form!

Top-down, WX coil cover/chrome ends : two brass coil caps : old gold coil : new red coil

The coil data is:

Coil: 1" OD x 10" long form
Turns: ~202 over 8.75",
Wire: 18AWG solid enamel coated

On eBay I purchased a 100’ spool of 18AWG magnet solid enameled wire as I needed at least 53’. I cut a 10” length of PVC and drilled two wire holes on each end (at the same measurement points as the old coil) then began my hand winding the new coil (this really makes your hands ache).

I have a new problem; the form wall thickness is very different as you can see in the picture. The brass end caps OD must be reduced in diameter to fit inside the PVC.

New coil - left : Old – right : below the two turned brass ends

I made a poor-mans mill from my drill press years ago by adding an X-Y vice. All I needed now was a good square lathe bit, which I bought from Harbor Freight.

I cut the hex bolt head off a 3/8”-24x2” bolt to be the bit for the chuck, screwed the brass end cap tight and turned down the two brass caps to fit very snuggle inside PVC. I estimate I removing nearly 0.125” of brass material. The brass ends remained nearly perfectly round for a very nice snug fit inside the PVC!

I stripped the enamel from the wires and soldered the coil wires to each cap.


Coil wire soldered to end cap

Coil with tapped hex insert

To insure the coil form never spins on the end caps again, I drilled a #29 hole into both ends of the coil through the PVC into the brass ends and thread tapped both for a #6-32x0.250” Allen-hex insert. Using thread-locker I placed the hex inserts so that one thread remains exposed. These brass ends will never spin inside the coil form again! (This is the right way – the way Hy-gain should have made this coil!)

I used hot glue on the last few coil wire turns, holes, and a worked a few dabs into the coil wires to insure the wires remain tight, found that hot glue very hot when working it into the wires. Then reassembled the coil to the WX cover and again used hot glue to seal the chrome end caps.

Reassembled the top-hat and placed it back on the AVT, as shown below.

Another problem that winter caused was the disintegration of the WX trap caps. Another item MFJ/Hy-gain does NOT sell. The 10m & 15m traps are upside down on the AVT, without the WX caps they will become good rain/snow/ice catchers. Failed WX


Failed WX cap

Once again I had to dig into my bag of mechanical tricks to find a solution. Often I walk the aisles of ACE, Lowes, Menards, TrueValue, Harbor Freight, and other local hardware stores and even walk TSC, FleetFarm, Dicks, Gander, Bass Pro taking in what they have that could be used/modified for antenna projects. These walks help me visualize and create solutions or methods on how to build durable antennas.

I found the solution for this trap cap problem in using a PVC Ύ” to 2” reducer, shown below right. The Ύ” PVC OD is 1.00” making a perfect fit to the main AVT aluminum mast tubing after I removed the Ύ” PVC stop ‘collar’ inside the 1” hole.


Left – modified reducer : right as purchased reducer

I used a band-saw to cut-off the hex ends of the reducers and disk sander to true the face. This reduced the size and quad chamber rain/ice capture cups on top of my new WX caps.


Using clear Silicon outdoor rubber calk and a few judicious taps to insure the reducers were seated onto the traps, I made a very solid fitting WX trap caps, as pictured.

Clarification: my antenna project Ugly-Balun

Made with:

4” dia. x 24” PVC,
26 coil-turns of RG-8x (needing at least 30’ of coax just for the coil turns),
hot glued the two coax holes,
electrical taped the end coil turns,
bent/mounted two 8”x1.5” pieces of aluminum flat stock for the fence mounts.

I mounted the UB on the fence high enough to insure the lawn tractor misses it but not higher than the 18AVT coax connector. I did not want the UB to be in the same RF plane as the AVT. The fence gave me an added bonus in providing an off ground coax run to the house. Shown is my very first prototype UB. I plan on making a replacement that is far more compact and more WX durable to replace this proto. I will be using this same UB design on my Cushcraft A3 & A4 beams soon!!!

Ugly-Balun data can be found at: http://www.hamuniverse.com/balun.html

The Ugly-Balun really made this AVT a performer. I now get into EU, Med, Africa, and Asia (as well as all points North America). Some have diss’ed the UB, but for me it made a big difference and works – so I’ll keep it!


Here is my fixed 18AVT ‘SIX’-band vertical with Ugly-Balun fence mounted.

Writer BIO: Dale Kubichek, MS-EET, GROL/RADAR, N6JSX - Amateur Extra; first licensed in 1972. Served 10yrs USN, Vietnam Vet, FTG1 Gun/Missile systems & electronics instructor. Electronics Test/Manufacturing/Project/Quality Engineer/Manager in; aerospace - Hughes, Northrop, Rockwell, commercial - Magellan, Mitsubishi, Emerson; heavy construction – TEREX, Manitowoc Cranes, Magnetek; communications – STM, RockwellCollins. Currently, Sr Engineer on USAF UAV SIMs. Interests are designing/testing antennas, RDF hunting/training; published numerous articles in 73 Magazine & eHam.net. Owner of http://groups.yahoo.com/group/HAMSATs, http://groups.yahoo.com/group/RDF-USA, and many more.

Copyright 2012, N6JSX Sidney, OH
All rights reserved – only non-profits may copy or reprint.

Member Comments:
This article has expired. No more comments may be added.
 
HF 18AVT Vertical Fence Mounted with an Ugly-Balun  
by W9PMZ on June 12, 2012 Mail this to a friend!
"The Ugly-Balun really made this AVT a performer. I now get into EU, Med, Africa, and Asia (as well as all points North America). Some have diss’ed the UB, but for me it made a big difference and works – so I’ll keep it!"

Well it is an interesting article. Resoucefull.

But, looking at the 80M coil the Q is probably pretty poor. And without radials I can't imagine that it is very efficient on 80M/75M. Look at the size of the coils on screwdriver antennas for comparison.

But, what have you compared this antenna to; to determine that it is a "performer"?

73,

Carl - W9PMZ
 
RE: HF 18AVT Vertical Fence Mounted with an Ugly-Balun  
by K0IZ on June 12, 2012 Mail this to a friend!
Always interesting to see ways to utilize non-radio stuff in repairing radio equipment. Your sojurns pay off. Thanks.
 
RE: HF 18AVT Vertical Fence Mounted with an Ugly-Balun  
by WX7G on June 12, 2012 Mail this to a friend!
Dale, good work and very resourceful.
 
HF 18AVT Vertical Fence Mounted with an Ugly-Balun  
by KE6EE on June 12, 2012 Mail this to a friend!
Great, well-told, tale of doing the kind of problem-solving that is a big part of the pleasure of tinkering with antennas.
 
HF 18AVT Vertical Fence Mounted with an Ugly-Balun  
by KC8Y on June 12, 2012 Mail this to a friend!
very good detailed article showing how on making old equipment to operate, correctly

Ken KC8Y
 
RE: HF 18AVT Vertical Fence Mounted with an Ugly-Balun  
by AE6RV on June 12, 2012 Mail this to a friend!
"But, looking at the 80M coil the Q is probably pretty poor. And without radials I can't imagine that it is very efficient on 80M/75M."

Care to try to quantify that, Carl? Are we talking a 3 DB loss? 10 DB? 20?
 
RE: HF 18AVT Vertical Fence Mounted with an Ugly-Balun  
by W9PMZ on June 12, 2012 Mail this to a friend!
Need more information to quantify.

But based on experience on 75m I wouldn't expect the efficiency to be more than 1%.

Regarding the other bands read the books. A vertical needs an image and not a Balun to maximize performance. That is why I asked what does a performer mean? When the band is open a wet noodle could very well perform just as good as this antenna.

Certainly this is a good article on how to repair and use this antenna,but to claim to be a performer it would be nice to see some data other than a nonspecific statement on it's apparent capabilities.

73,

Carl - W9PMZ
 
RE: HF 18AVT Vertical Fence Mounted with an Ugly-Balun  
by KW6LA on June 13, 2012 Mail this to a friend!
Forget about the electrical crap ! ! ……….I love the tool bit in the vise to make the drill press a lathe > > Bravo !!
 
HF 18AVT Vertical Fence Mounted with an Ugly-Balun  
by W6CAW on June 13, 2012 Mail this to a friend!
I am glad to see I am not the only strange person wandering around hardware stores to find parts to make antennas with.
 
RE: HF 18AVT Vertical Fence Mounted with an Ugly-Balun  
by N2EY on June 13, 2012 Mail this to a friend!
It's not a balun. It's a line isolator.

A balun goes between a balanced and unbalanced system.

A line isolator keeps the coax from becoming a radial.

---

Using PVC plumbing stuff for antenna work is pretty standard. Been doing it for almost 30 years now.

73 de Jim, N2EY
 
RE: HF 18AVT Vertical Fence Mounted with an Ugly-Balun  
by KC2WI on June 13, 2012 Mail this to a friend!
"looking at the 80M coil the Q is probably pretty poor. And without radials I can't imagine that it is very efficient on 80M/75M. Look at the size of the coils on screwdriver antennas for comparison."

The Ugly Balun is not an 80 meter coil. It is not a loading or matching element. Actually despite the name "Ugly Balun" in this case it is a 1:1 unun - basically a choke that blocks RF from flowing on the outside of the coax.

"A vertical needs an image and not a Balun to maximize performance. That is why I asked what does a performer mean?"

True but it also works better when there is no RF flowing on the outside of the coax. This antenna doesn't have a proper ground plane made with buried or elevated radials but is has a a counterpoise and maybe the the ground is fairly conductive.

As far as the refrerence to being a "performer" probably that means that it performs better with the ugly balun than without it. I'd say if you can get a noticable performance increase with the only investment being a bunch of turns of coax wrapped around a scrap piece of PVC pipe, that's a pretty good deal.
 
RE: HF 18AVT Vertical Fence Mounted with an Ugly-Balun  
by WB2WIK on June 13, 2012 Mail this to a friend!
The Q referred to the loading coil at the top of the antenna, not the "ugly balun" choke.

If the RF choke balun improved performance, that's because without it the outer conductor of the coaxial transmission line was part of the antenna and potentially reducing the current available to drive the monopole. With a good choke "balun," this is minimized, and more current might be available for desired radiation.

Simple stuff, but nice work!
 
HF 18AVT Vertical Fence Mounted with an Ugly-Balun  
by K4JC on June 13, 2012 Mail this to a friend!
I have to say, "Harbor Freight ROCKS!!" Yeah they have a lot of junk, but some pretty good stuff too. I can never get out of there without spending a few dollars.

I also like to wander around Lowe's, Home Depot, TSC, etc., to get antenna ideas. The local ACE I don't patronize very often. They're a little too helpful and want to pick out your items for you instead of letting you wander around. I figure that if I'm so clueless as to need the Helpful Hardware Folks to tell me what to buy then I have no business being in a hardware store!

Nice article, Dale. Good luck with the 18AVT.
 
RE: HF 18AVT Vertical Fence Mounted with an Ugly-Balun  
by KC2WI on June 13, 2012 Mail this to a friend!
"The Q referred to the loading coil at the top of the antenna, not the "ugly balun" choke."

OK I was not thinking about the top loading coil because so much of the discussion was reffering to the "ugly balun".

True, a long small diameter coil with fairly small diameter wire is probably not the best. An interesting experiment would be to make another coil with same inductance but much bigger diameter. Might have a problem with direct A-B comparisons but probably could get some idea of the difference in performance.
 
RE: HF 18AVT Vertical Fence Mounted with an Ugly-Balun  
by N4JTE on June 13, 2012 Mail this to a friend!
Performer; anything newly changed that works better than last experiment. Whether the efficency/ ERP went from 2% to 20% is the whole point of experimenting with antennas we have room for. Tnx for great pictures and your effort to share on eham.
Bob
 
RE: HF 18AVT Vertical Fence Mounted with an Ugly-Balun  
by WX7G on June 14, 2012 Mail this to a friend!
I'll take a whack at quantifying the 80 meter efficiency. The coil looks like the Hustler RM-80 resonator. That has a base-referred loss of 20 ohms. The radiation resistance of the vertical is 10 ohms. Now let's say the base-referred ground loss is 20 ohms. These resistances added together equal 50 ohms giving a 1:1 VSWR at resonance.

The radiation efficiency is 10/50 = 20% or 7 dB down from a 65' vertical having 120 quarter wavelength radials.
 
RE: HF 18AVT Vertical Fence Mounted with an Ugly-Balun  
by AE6RV on June 14, 2012 Mail this to a friend!
"I'll take a whack at quantifying the 80 meter efficiency."

Actually, my question was about the loss of efficiency from using smaller wire in the trap. I was trying to hint that it would be such a small loss that it wouldn't be noticed.
 
RE: HF 18AVT Vertical Fence Mounted with an Ugly-Balun  
by WX7G on June 14, 2012 Mail this to a friend!
The Q of the loading coil is about 100. Let's say it was wound with #14 wire and had a Q of 300. Now the loss has dropped from 20 ohms to 7 ohms. The antenna radiation efficiency is 10/37 = 27%, up from 20%. That's about 1 dB.
 
HF 18AVT Vertical Fence Mounted with an Ugly-Balun  
by K9ZW on June 15, 2012 Mail this to a friend!
Neat article and project! Resourceful use of tooling and hardware store supplies makes for a fun story. Awesome that the project antenna works nicely!


73

Steve
K9ZW
 
HF 18AVT Vertical Fence Mounted with an Ugly-Balun  
by WB0RXL on June 16, 2012 Mail this to a friend!
Dale, I want to thank you for this article. I have used this Hy Gain model for many years here in the US and for 20 years in Ecuador (where I was talked into selling it). Upon my return to the US I missed it so much I picked up a used one and am using it over a reduced radial field. Sometime during this past winter I noticed my 80 meter coverage had disappeared. I had previously repaired one of the higher band coils, but had put off digging into the 80 meter coil. Now that I have seen someone blaze the trail before me, I'm going to tackle that sometime this summer. Thank you!
John WB0RXL
 
RE: HF 18AVT Vertical Fence Mounted with an Ugly-Balun  
by W8JI on June 17, 2012 Mail this to a friend!
by WX7G on June 14, 2012

"The Q of the loading coil is about 100. Let's say it was wound with #14 wire and had a Q of 300. Now the loss has dropped from 20 ohms to 7 ohms. The antenna radiation efficiency is 10/37 = 27%, up from 20%. That's about 1 dB."

Not a correct analysis.

1.) The resistance of the coil is not directly in series with the base of the antenna, when the coil is not at the antenna base. This is because the antenna has standing waves along its length.

2.) The resistance of the coil is not the only resistance, it is part of many resistances. When the resistance of the loading coil is changed, it only changes part of the system resistance.

Like everyone else here, I have no idea what the ground loss or resonator ESR and current is, but at least we can look at a correct method.

The best method would be to know the inductor ESR, and current through that resistance.

Let's take a wild guess that 60% of base current is left at the point where the loading coil is, and that ground loss resistance with his fence, normalized at the base of the vertical, is 15 ohms. Let's go with a wild guess coil ESR is 15 ohms.

With one amp he has 15 watts loss in the ground system, and 5.4 watts in the coil, and some unknown amount elsewhere in the system.

Now if we change the coil to an ESR of 5 ohms, with the same current, we have 1.8 watts loss in the coil.

It went from 25% of total loss, or less, in the coil down to 11% in the coil.

This doesn't change the overall system performance much, because dominate loss is elsewhere.

Of course we all have to realize, all of this is just wild meaningless guesses. My point is more to remind others that, in system with standing waves like an antenna, resistance in one part of the system cannot randomly, without a plan, be directly applied to another point in the system. Current is not equal everywhere.


73 Tom
 
HF 18AVT Vertical Fence Mounted with an Ugly-Balun  
by KI4VJB on June 21, 2012 Mail this to a friend!
I have a 5btv mounted this way but it has alot of noise any ideas?
 
Forget all about it.  
by AI2IA on June 21, 2012 Mail this to a friend!
Choose your favorite bands. Put up resonant wire antennas. Don't worry. Be happy.
 
HF 18AVT Vertical Fence Mounted with an Ugly-Balun  
by K5WZI on July 2, 2012 Mail this to a friend!
Great article Dale! Thanks for sharing your ideas. I'm
sure this antenna performs as well or better than it did
before and with out a doubt, it is much stronger mechanically.
 
HF 18AVT Vertical Fence Mounted with an Ugly-Balun  
by KO3D on July 3, 2012 Mail this to a friend!
"MFJ/Hy-gain does NOT sell replacement aluminum tube with insert. Once again MFJ Quality failed me as they even sent me the wrong diameter tube. After some badgering they relented and sent me the proper diameter tube (at no cost)."

I had a similar saga with Hy-Gain/ MFJ over this antenna. Parts were missing etc. Called them and the guy said he would send them right out. Two weeks later no parts had arrived and I called Hy-Gain back. A woman said the guy hadn't entered the order in the system. Got the parts sent and when they arrived they were for a different antenna. They wouldn't ship me a new antenna until the old one wasn't just sent back but returned and refunded minus S+H. So much for their "no matter what" guarantee...
 
RE: Forget all about it.  
by K4YZ on July 3, 2012 Mail this to a friend!

by AI2IA on June 21, 2012

"Choose your favorite bands. Put up resonant wire antennas. Don't worry. Be happy"

...and when you live on a city lot where your 'back yard' is 20'x30' and you're a low-band fan, what's your next smart alec answer?

(Don't worry about replying...that was a rhetorical question...I've already found a solution that works for me...I just love guys who have some dim-witted, 'why doesn't everyone do it my way' posting made primarily just to get their call sign in the line-up as if the universe might seize up if they didn't...)

K4YZ
 
Great Article!! I need some advice  
by W6HDG on July 13, 2012 Mail this to a friend!
Hi Kuby,
This is an outstanding article. Thank you very much for posting this. I don't know if you remember me but we communicated about 12 years ago when you built the $10 CI-V Icom interface - my call has changed since I wrote that article...

Well, I've been off the air but your vertical antenna on a fence has inspired me to put up a multiband fan dipole on my 12 foot tennis court fence. The center top of the antenna is only 20 feet. The SWR is pretty good but the performance is only middling. Do you think a vertical mounted the same way at the top of the 12 foot fence would be a better performer? See a couple of pictures below. Best 73, Howard

[image]http://www.quickharness.com/support-tube.jpg[/image]

[image]http://www.quickharness.com/multiband-fan-fence-dipole.jpg[/image]


 
HF 18AVT Vertical Fence Mounted with an Ugly-Balun  
by AF6OF on July 14, 2012 Mail this to a friend!
I love your drill press/Lathe!

Allen AF6OF
 
HF 18AVT Vertical Fence Mounted with an Ugly-Balun  
by KE4ZHN on July 15, 2012 Mail this to a friend!
I still cant understand why amateurs refer to those coax wound coils as a balun. Its a choke and a pretty poor one at that. W8JI ran tests on many commercially made baluns and included the classic coax coil choke balun as their often called. In effect...they suck. It performed the worst of even the cheapest balun tested. The coil of coax only acts like a choke over a very narrow frequency range and does little if anything to truly isolate your feed line from the antenna system. So on some bands your coax shield also becomes a radial hot with RF usually right at the shack end of the system.

Its just a hams cheap way out. In the case of this vertical use a real UNUN and do it right. Along with putting a proper radial field under the antenna. A fence is hardly a good counterpoise for a vertical. The chain link has poor electrical connections and in fact can aggravate TVI/RFI problems by creating "diodes" in the chain link due to corrosion. Would you really want your radial system to contain dozens of rusty "diodes" in it? Think Im crazy? Look up how the soldiers made trench radios in WW 1....using rusty razor blades and pencil leads as very crude detector diodes. Being a retired welder and having had the displeasure of welding galvanized crap...its electrical properties suck. You have to grind the coating off to get a good weld..so if it doesnt even conduct DC well...how good can it be for RF?

Im not trying to slam Dale for his project so please dont take offense. I like the work you did to repair the radiator itself but the problems in the installation are obvious. Every time I see these coax chokes I cringe. Cushcraft even used to recommend this method for feeding the A3. They probably still do and frankly this approach is asking for trouble. If you spent several hundred dollars on a tribander..why cheap charlie and use a coax coil when a nice 1:1 balun would do much better and feed the driven element properly? Its not as if a 1:1 balun or a line isolator costs a fortune...you can buy them for around a hundred bucks or less. Unfortunately, many hams have a phobia about baluns in general. Usually because they misused one or bought a cheap crappy one and melted it..so that automatically makes all baluns taboo in their eyes.
 
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