Solarcon A99 Experimental Results and Analysis of Ground Plane Radials

[Lil'Yeshua]

According to one website,the guy described the tuning section and the short section of coax leading down to the SO-239 as the 1/4 wave part of the antenna. My A99 has a GPK-1 kit but with 102" SS whips for radials. Most everyone in my neck of the woods have their A99's without ground radials and are 60-130' high up in the tops of pine trees. That limits the ground underneath from detracting from the antenna's performance. It also means that the coax is being used as the other half including the tuning section/short connector coax. I've already had a local alledged ham dispute my antenna configuration saying that I needed to take off the ground plane kit because my antenna needed a higher TOA than the EZNEC'd 10 degree angle of it's biggest lobe.


P.S. The GPK-1 goes right underneath the running rings and is electrically connected with the SO-239

 

[Marconi]

kaosfm, concerning the idea for the need of a mast, coax, or radials necessarily being attached to an A99...else it will not work properly.

When considering the test I presumed if the idea the A99 needed some conductive element attached to the feed point in order for it to work properly was true...then the antenna's match would be ill-effected if at least one of these elements was not attached at the feed point. So, I decided to test using my VA1 meter attached directly at the feed point.

Several years ago I tested this idea and I reported that I did not see any difference when I hooked my analyzer directly to my A99 vs. testing using a feed line at 27.205 mhz. This original test was done without isolating the antenna from the mast, and I also did not use radials.

Later on it was suggested that the test I did above probably used the mast as the other 1/2 of the antenna, and therefore it was understandable that I saw similar results, and that revelation rendered my prior results as inconclusive.

So I did this test over using a 20" fiberglass insulator inserted into the top end of my telescoping 20" mast. I effectively raised the antenna up on the insulator an inches or so above the mast.

I first tested and recorded the results from my Autek VA1 analyzer directly connected to my dummy load. I also compared those results using a tuned feed line jumper cut at 27.205 mhz between the meter and the dummy load. This was done to test the meter ,and to set some control and comparison values for when testing the A99 directly at the feed point in the next step in the process.

Sorry about all the camera shaking...it is a sign of old age. I hope you can see all of the results.

A99 test with my VA1 analyzer - YouTube

 

[Lil'Yeshua]

Marconi,in other words,your A99 is tuned correctly without the need for a metal mast or coax to tune it any further. Like I said in my previous post is that I read on one website,the man said that the A99's tuning section and the short length of coax from that to the SO-239 connector is the 1/4 wave(half wave over quarter wave) part of the antenna.

 

[Marconi]

Marconi,in other words,your A99 is tuned correctly without the need for a metal mast or coax to tune it any further. Like I said in my previous post is that I read on one website,the man said that the A99's tuning section and the short length of coax from that to the SO-239 connector is the 1/4 wave(half wave over quarter wave) part of the antenna.

Lil'Yeshua my A99 was tuned, but I did not change or try and retune. Tuning was not the point of this test. The key issue I was trying to demonstrate was whether the A99 will work, as noted by kasofm, without one of at least one of the following...a mast, coax, or radials attached at the feed point.

Yes, I've talked to Steve Yates about the A99 matching as compared to what he designed and tested in his article. He said his antennas was not the same as the A99, but if the circuits produce similar results then the circuits are similar...even if they look nothing alike.

I was amazed with what this article suggested, because I could find little to no difference in the matching results with my VA1 analyzer connected directly to the feed point or using a random or tuned feed line.

I don't have a clue how it is possible to voltage feed an antenna at a current node, but I see it work. Yates is the first I've ever seen that spoke on the subject and I don't read many critics of his idea.

I've read a lot of naysayer claims that the EFHW will not work, but they were not very convincing. This is probably why many CBr's find little to like about a 1/2 wave antenna.

 

[HomerBB]

The central thesis of kaosfm's thread is the performance of his antenna.
He refers to his anecdotal experience with the A99 under three differing setups.

1. his original directly set near/on his metal mast with no other modifications. He noted the performance with a drive around and radio checks, and his buddies providing feed back..

2. He made the modifications to the antenna system with angled GP radials of a given length and did the drive around with radio checks again, and his buddies providing feed back.

3. He removed his GP radials, and, unlike Marconi's A99 sitting within an inch or two of the 20' long metal mast, isolated the A99 from the mast by 4 - 5 feet, once again did his performance test with feed back.

His thesis has been the A99 worked under number one conditions with noticeable CMC indicated as TVI, worked much better with GP radials and reduced CMC indicated by a lack of noticeable TVI, and was by far worse in performance compared to either of the number one or number two setups.

I would have to prepare rebuttal, or at least information of merit to argue contrary-wise to any depth to Marconi's result of presumed A99 integrity by way of the analyzer, but on the surface of things I see the proximity of that A99 to the metal mast as being such that although there is no feedline or GP radials present, there is certainly a mast present to provide the balance for the sake of the analyzer readings.

I think kaosfm may have demonstrated exactly what we referred to before, the EFHW needs to be presented with material sufficient to fulfill the laws of physics, which is an antenna needs yin/yang or the antenna efficiency fails.

I find it interesting in the video that the A99 has to be so long in order to render nearly identical readings as the little dummy load.

Maybe kaosfm will put radials on his dummy load and tell us how well it doesn't do with a great SWR. Mine don't do so well as an antenna, and I get 1.0 SWR, R=50, and X=0

My neighbor 125' behind me talks to me with his dummy load, but another fellow 1.5 miles away thinks I'm ghost talking when we converse.


I don't have an A99, but I do have a very well tuned EFHW. If I can get a break in weather and my work obligations at the same time I'll certainly put the EFHW on a long non-conducting pole at least 20' in the air with the MFJ-259 hooked directly beneath it and see whether my results are similar. That said, I will only show that my EFHW without another half reads as well as my dummy load without another half.

 

[Lil'Yeshua]

Well what about the A99's tuning section and short coax to the SO-239 connector? I read on a Website where the guy said that that was the 1/4 wave part of the antenna. What do you think ?

 

[kaosfm]

While doing research prior to my recent post, I inadvertently came across the original patent for the variable mutual transductance tuning system that forms the heart of the A99. Interesting read and quite a bit of detail present. I can't quite interpret everything present with my knowledge-base. I wonder if there are any hints in there as to what precisely forms the 1/4 wave section of this antenna design (i.e. the matching device + coax stub) or some segment of the mast or feedline, etc...

Patent US4280129 - Variable mutual transductance tuned antenna - Google Patents

 

[kaosfm]

Well what about the A99's tuning section and short coax to the SO-239 connector? I read on a Website where the guy said that that was the 1/4 wave part of the antenna. What do you think ?

I wonder if you were to cut open the A99 and uncoil the matching coil if it would equal 1/4 wavelength with the short coax stub factored in. In essence, the A99 would be like an improved jpole, where it uses a 1/4 wave tuning "stub" of sorts to drive the 1/2 wave element, but that 1/4 wave stub takes the form of a coil. If that were the case, then some type of ground system wouldn't be needed as stated by the manufacturer. However, as practical experience shows with j-poles, this 1/4 wave "cheat" doesn't really solve all of the inherent problems with the design, forcing interaction with the mast and/or feedline.

I love topics like this that test theory vs. reality and try to make sense of a very abstract situation. Too bad an Engineer from Solarcon can't jump in here. You'd think they would want to address these issues if it drove up revenues from their GPK-1 kit.

I know there is about a 50/50 split as to whether the addition of a GP really helps an A99 in the eyes of the general public. I don't see nearly as much debate as to the value of adding a GP kit to the Imax-2000 antenna. I would think it would be even more desirable to add a GP to the Imax since it is a 5/8 wave design.

 

[Marconi]

Homer, I read kaosfm's comments to mean he was wondering if the A99 would fail to work if there was no return path (counterpoise) provided at the feed point. I had a similar thought several years ago, so I did a video on the subject to test the idea as I saw it at the time.

This video was just another test to again compare how my VA1 analyzer scanned the load with nothing conductive attached to the feed point...except the analyzer.

You can see by the VA1 meter results there is little to nothing wrong with the feed point match, so we see no failure even without considering the results from the dummy load.

I've explained already that I did the dummy load idea to test my VA1 to see how close it was when directly connected...compared to when using a feed line and a known load. I recorded the results the VA1 showed in order to have something to compare too when I connected the VA1 to the antenna.

I made no reference to the other issues kaosfm's noted including his performance results, I addressed that issue in my first post in his thread.

If you get all fire up to do a rebuttal please note that I was also wearing blue vinyl gloves. That no doubt had some bad effects on results too.

Homer, if I placed the antenna on a 10' foot wooden dowel pole do you really think the results would be different? Remember the analyzer is only producing a very small amount of power. Maybe if I put 500 watts into the setup, the mast would play a part.

Homer, maybe when the weather gets better you can try the idea with your 259b and check it for changes in match considering each way mentioned above? I don't believe you will see the A99 fail either.

 

[HomerBB]

I'm not wanting to appear to be all fired up, but I feared you might get there should I post as I did. I did it anyway hoping it would clarify the distinction between what a load can read on an analyzer and/or meter, and whether that meant anything in terms of efficiency or performance. It appears to have had the result I was looking for in that you returned to post exactly what your test was hoping to discover, and what it was not designed to prove. This is good.
You know that I am an empiricist first of all - tasting is the proof of a pudding - so I have nothing but respect for what either of you are doing. But I also want there to be complete clarity as to what is actually going on, what might be going on, and what a test can or can not unequivocally prove.

I will do the test because I think it could lead to more learning discussion on the matter.

Thanks for sharing it with us. It is impossible to dispute what you showed us, now it is time to determine what it may or may not mean. Speculation helps to get us there.

 

[Marconi]

Well what about the A99's tuning section and short coax to the SO-239 connector? I read on a Website where the guy said that that was the 1/4 wave part of the antenna. What do you think ?

If you are asking me Lil'Yeshua, and you are talking about Steve Yates article on EFHW Antennas...below is a copy of the email Steve sent me.

As I read the article I think Steve is suggesting the length of wire needed for a suitable return current path necessary for a resonant EFHW radiator is .05 wavelength, and that length is a far cry from a typical 1/4 wavelength at resonance we tend to think is needed.


----- Original Message -----

From: Steve Yates, AA5TB
To: Eddie - Marconi
Sent: Monday, August 12, 2013 8:33 PM
Subject: Re: Questions on the EFHW


Hi Eddie,


Thanks for the note.


I have never used a Solarcon A99 so I can't give an opinion based on experience. I have been very skeptical of all of the hype it has received ever since I first heard about it a couple of decades ago.


Below is a link the describes what is in the antenna and a reversed engineered schematic. I don't really understand reason for the circuit configuration that is used. I don't see anything that would prevent common mode currents on the coax although if operated at a frequency where the antenna is truly a half wave there may not be too much to worry about. At other frequencies where the antenna's impedance would start to drop I'd expect the currents in the shield of the coax to increase.


http://xoomer.virgilio.it/ham-radio-manuals/a99.pdf



From what I can see the antenna is no different than any other end fed half wave vertical such as a J-Pole, Ringo, etc. except for the unusual matching network that may be very lossy as the author indicates. This loss is probably what gives it the wide band response everyone seems to brag about. At 27 MHz it is possible that the coils may have enough reactance (>>Z) on their own to function as a simple broadband, high impedance transformer and therefore not need a resonating capacitor to bring the antenna coil up to many thousands of Ohms reactance (in a transformer the reactance of the windings should be at least 4 times the impedance on a given side of the transformer). However, there are capacitors of sorts in the design so I am not sure.


Sorry I can't be of more help.


Take care,
Steve - AA5TB

From: Eddie - Marconi <edromans@comcast.net>
To: Steve Yates <Steve@aa5tb.com>
Sent: Saturday, August 10, 2013 9:09 PM
Subject: Questions on the EFHW


Steve, I am Eddie Romans. I am not a Ham, but as a hobby I do try and understand antennas, and the ideas that make them work. I've read your article on EFHW's many times, and use it as a reference link from time to time. I find your ideas revealing to me.


We are discussing the Solarcon's A99, for CB, at the moment.

As noted, I have read you article on EFHW antennas, and would be curious if you have ever consider that matching design, and have a brief opinion that you could share?


My main interest is, does this design almost guarantee to manifest common mode currents unless we add radials and isolate the antenna from the support mast, or do you think the design could produce a balance similar to your idea in your article?


Thanks,


Eddie
edromans@comcast.net















​

​

 

[Lil'Yeshua]

Yes,it is a question I'm throwing out for whomever to pick up the gauntlet on. There appears to be a trend on this forum that if something isn't new and exciting,it gets virtually not hardly any attention. The A99 may not be a desirable antenna among so many good performers but there ought to be people out there that knows exactly what's going on with this antenna and could share it's means of operation rather than dismissing the idea of further discussion on the topic.

 

[kaosfm]

As a follow up to my previous post, I think "Big Hair" of BigHairAntennas.com is onto something with his custom built "half-wave over quarter wave" antenna. He suggests it is superior to a standard A99 because it actually has a quarter wave section on the bottom (in the form of radials it would appear). I think chances are good that myself and others that have added 1/4 wavelength radials, such as Lil'Yeshua, to our A99's are experiencing effects and performance advantages of the same scale. If you look at what he writes, it is quite revealing.

His design supposedly sports 3dB gain over a dipole alone by its lower angle of radiation. It appears to mimic a 5/8 wave in a sense. My modified A99 seems to cast a strong consistent signal downward where there is practically no observable multipath distortion or other anomalies within the first mile radius of the testing zone. The only other vertical I have ever encountered these reception characteristics with was my 5/8 wave in the FM broadcast band. I tested a standard vertical dipole during my time on the FM band and its inconsistent reception characteristics locally remind me greatly of the A99 in stock form.

If you look at Bighair's antenna photo, it almost looks like it is using a square PVC ring to which ground radials are attached. This is quite similar to my curtain rod supports with speaker wire radials. The only part that doesn't fit is his assertion that the 1/4 wave GP section significantly lowers the feedpoint impedance. Yet, with the A99 we see minimal effect on impedance with or without the GP.

The half wave over a quarter wave is better than any other half wave antenna (including an Antron 99..),
because its truly a 1/2 wave over a quarter wave, meaning both portions of the antenna actually do radiate!
The Ground Plane at the bottom, creates two significant perks for the 1/2 wave antenna. First being, is that it
actually lowers its angle or radiation, and second being, is that it also lowers the overall impedance of the
antenna from 3,000 to approximately 850 ohms. This means less matching is needed, to achieve the
desired 50 ohm impedance. This makes it easier to reduce matching network/inductor loss, when
performing the impedance matching transformation.

The 1/2 wave can be mounted on a tower, a pipe, or even tree mounted. It also has a great bandwidth, and
with the 1/4 ground plane element underneath it, it also achieves a decent low angle of radiation gain thats
superior to conventional 1/2 wave base antennas. Unlike other half wave 18 foot CB antennas, this 1/4 wave
section is truly an active part of the antenna, and will affect SWR and performance significantly if it were to be
removed.

I used an optimum parallel matching technique, to efficiently match the antenna to 50 ohms. The drawback
of the antenna, is that it requires both an inductor and a Hi-Q transmitting capacitor to achieve such
efficiency, which also limits its power handling to 5000 watts approx. Its nearly impossible to find affordable
transmitting capacitors that can handle more than 5000 watts. The capacitors I use are ceramic, and are
rated to handle 15,000 "peak" volts at 15 amps of sustainable RF current, which equates to about 5000
watts max.​

Let the A99 dead horse beating games continue! :bdh:

 

[Lil'Yeshua]

The A99 still uses the mast/coax/ground plane as it's other half. The matching section is just provide a 50 ohm load. According to Solarcon,the mounting base of the A99 must be grounded as to provide a discharge path for lightning and power line contact. Still,a ground plane,a rf choke one quarter wavelength down from the SO-239,a metal mast would be required for the A99 to function properly. Either that or the whole idea of an other half of the antenna is nothing but a farce.


P.S. And then we talk about lossy ground providing the antenna is close enough to the ground to influence it

 

[The DB]

Just for kicks I modeled a pair of half wavelength antennas, one is end fed with no radials and the other is end fed with four radials at 45 degrees. The left pictures are the no radial variety the pictures on the right have the four 45 degree radials.

First the data...

It looks to me like the 45 degree radials raises feedpoint impedance over no radials significantly...

And now the current distribution...

Hmm, next to no current is flowing in the radials. 3 dB gain over a dipole seems like kind of a stretch to me based on this information...

This shows that the additional gain is insignificant, 0.12 dB additional gain really doesn't amount to anything. The take off angle, if there is a change, isn't enough for NEC to pick it up. As a matter of fact, the patterns look identical to me so I would be surprised if there was anywhere near one degree difference in "take off angle"...

Now for a few notes...

1) These models didn't include any feedline or mast, and simply compare antenna to antenna in near ideal, if not lab like conditions. The a99 would be affected by the feedline and mast more simply because it doesn't have a low impedance option such as radials for said current to flow. Because of this, the electrical length and running of the feedline and the electrical length of the mast can change the radiation pattern, current distribution and phase of said currents, and feedpoint impedance properties of said antenna as there is no low impedance option for the RF to flow that a set of radials would provide.

2) This potential in variance in potential feedpoint impedances may explain why many people claim that the A99 is a lossy antenna, such losses would help make tuning an antenna with such a problem easier by lowering the feedpoint impedance over the entire useable range of the antenna and beyond.

3) One thing to watch out for with the Big Hair design is the overall length of the vertical element. As you pass a half wavelength mark the radials are no longer in phase with most of the vertical element. This causes an initial drop in gain then a switch to a much higher angle dominant node. Because of this if there is anything in the area of the antenna that effectively lengthens the electrical length then the benefits of that design quickly evaporate.


The DB