understanding the A99,, the 1/2 wave over 1/4 wave bit

[HomerBB]

One of the questions that arises for me is when a vertically mounted and modeled antenna such as the A99 is compared to the dipole and no mention of the dipole being vertically modeled. Is the model free space, or over earth? Does the model include a mast for either or both? Are both vertical or horizontal?

Things change when an end fed has been provided a counterpoise. With no counterpoise, a comparison is like racing two cars with half of one car still on the assembly line.
Horizontal to vertical are not apples to apples comparison.
I will add that I agree that a 1/4 wave can be the superior DX antenna over an end fed 1/2 or 5/8 wave. Why? Because it is the only complete car on the race track.

 

[Riverman]

It may very well be the Son of Satan, but there’s no escaping the fact a person can purchase an Antron 99, screw a couple of sections together, put it in a 12’ mast, attach it to the house eave, talk to the locals, shoot skip and talk all over the world on a some ham bands for around a hundred bucks. Oh, and the thing is bulletproof as far as the weather goes.

 

[HomerBB]

Sure you can. Happens all the time. You gave it at least two counterpoise, the mast and the coax braid.
However, their are many people who've tried the A99 and despised it because it produced such bad common mode currents. As W8JI states, they were not the lucky ones who chanced upon a working combination of height and mast/coax length. The manufacturers are depending upon the necessity of a mast and coax to complete the missing part of the antenna.

 

[S&W357]

Good thing my A99 can’t read. It would probably feel unworthy and suffer from depression.

 

[HomerBB]

I've owned several. And I certainly don't dislike them, nor anyone having them. I just am aware of the nature of the antenna. When I build an EFHW I always know I will need an counterpoise or suffer the consequences.

 

[Riverman]

I've owned several. And I certainly don't dislike them, nor anyone having them. I just am aware of the nature of the antenna. When I build an EFHW I always know I will need an counterpoise or suffer the consequences.

Homer,
I have never used a counterpoise with an end fed designed by Dale Parfitt.
Rather, like countless others I’ve just strung up his Endfedz and talked all over the world with them.

When it comes to EFHW antenna theory, I side with him and John Huggins.

https://www.hamradio.me/antennas/of-fields-and-feedpoints.html

 

[HomerBB]

So do I.

 

[Marconi]

It may very well be the Son of Satan, but there’s no escaping the fact a person can purchase an Antron 99, screw a couple of sections together, put it in a 12’ mast, attach it to the house eave, talk to the locals, shoot skip and talk all over the world on a some ham bands for around a hundred bucks. Oh, and the thing is bulletproof as far as the weather goes.

Riverman, I agree totally.

For the early years when skip was really big in CB I would hear 100's of reports from folks far away claiming they used an A99, and they also most likely stated they used no GPK.

I wasn't tracking this information or comparing antennas in those day...it was just a fact back then when I was on the air, plus I heard the same echoed repeatedly. I also recall I probably heard some folks complaining about their A99, and mostly saying it was noise. None of this was complicated by science or technical conversation either.

I had the GPK, but I seldom used it and when I compared it with and without the GPK, I could tell NO difference. This was probably back when I first started trying to compare CB vertical antennas.

Homer,
I have never used a counterpoise with an end fed designed by Dale Parfitt.
Rather, like countless others I’ve just strung up his Endfedz and talked all over the world with them.

When it comes to EFHW antenna theory, I side with him and John Huggins.

https://www.hamradio.me/antennas/of-fields-and-feedpoints.html

Long ago I remember reading what Steve Yates - AA5TB, reported back in the days on EFHW verticals and it made sense to me. Basically saying, the EFHW needed only a very small 0.05 WL of wire to provide the design with the required and effective current return path in order to work. The article was a lot more complicated than this description, but that is what I took away form Steve's ideas.

Here is the link: http://www.aa5tb.com/efha.html

 

[Marconi]

One of the questions that arises for me is when a vertically mounted and modeled antenna such as the A99 is compared to the dipole and no mention of the dipole being vertically modeled. Is the model free space, or over earth? Does the model include a mast for either or both? Are both vertical or horizontal?

Good questions Homer. I'm sure you see a lot of such omissions of descriptive information in modeling on the Internet. In particular when only model results are posted, with little or no details, not even an image of the antenna...often being the case.

1. In Free Space the models should have all the losses switched off. I also remove the mast if included in the Real Earth version of the model.

Switches are:
Ground type = Free Space
Wire loss = Zero
Plot type set to = 3D

In Eznec if the Control Panel (CP) is published, the Free Space (FS) or Real Earth (RE) patterns are often easily determined, see model below.

At the bottom of the CP image you will also see the Average Gain (AG) Results...which should be close = 1, and indicates the accuracy of the model as constructed. This AG only works if all losses are switched off correctly. I also add "FS" at the end of the title for my free space models, if I don't forget.

2. In most cases the pattern will show a typical Free Space pattern image, but not always. With antennas that are irregular in constructions an shape, the pattern can look much different, and for sure when they have asymmetrical parts.

3. Some models may show both Vertical and Horizontal RF patterns with the gain and angle. There is a switch for this feature that is indicated in the upper left portion of the Pattern Screen, and is under "Total Field."

Note: A small (*) indicates which polarity is active, indicting both the gain and angle at that polarity.

 

[Riverman]

Riverman, I agree totally.

For the early years when skip was really big in CB I would hear 100's of reports from folks far away claiming they used an A99, and they also most likely stated they used no GPK.

I wasn't tracking this information or comparing antennas in those day...it was just a fact back then when I was on the air, plus I heard the same echoed repeatedly. I also recall I probably heard some folks complaining about their A99, and mostly saying it was noise. None of this was complicated by science or technical conversation either.

I had the GPK, but I seldom used it and when I compared it with and without the GPK, I could tell NO difference. This was probably back when I first started trying to compare CB vertical antennas.



Long ago I remember reading what Steve Yates - AA5TB, reported back in the days on EFHW verticals and it made sense to me. Basically saying, the EFHW needed only a very small 0.05 WL of wire to provide the design with the required and effective current return path in order to work. The article was a lot more complicated than this description, but that is what I took away form Steve's ideas.

Here is the link: http://www.aa5tb.com/efha.html

Marconi,
Concerning noise and the broader subject of CMC, my experience through the years has been that both are lessened, or eliminated, if the coax is routed along the ground rather than simply strung through the air to a window or such. The more lying on the ground the better. If buried, even better.

Any thoughts on that?

Jim

 

[Marconi]

Jim, I have experienced the same and done the same, but several times I was surprised to see the CMC effects return. So, I figured the idea might be doing something good for the RF on the line that was laying on the ground, but I always wondered about the line going up to the antenna.

I've even see CM chokes seem to work fine, and a while later they were back making problems.

I guess it's like Homer says...sometimes you're lucky and sometimes you're not.

For years I tended to discount their effectiveness with so many different ideas, with everyone saying my idea works best. Then I got my Sirio Gain Master and I saw a choke really working as it should. It never failed me in that regard.

 

[Riverman]

Jim, I have experienced the same and done the same, but several times I was surprised to see the CMC effects return. So, I figured the idea might be doing something good for the RF on the line that was laying on the ground, but I always wondered about the line going up to the antenna.

I've even see CM chokes seem to work fine, and a while later they were back making problems.

I guess it's like Homer says...sometimes you're lucky and sometimes you're not.

For years I tended to discount their effectiveness with so many different ideas, with everyone saying my idea works best. Then I got my Sirio Gain Master and I saw a choke really working as it should. It never failed me in that regard.

Would like to have a Gain Master but worry about wind. Blew 69 mph here last night in a thunderstorm. My A99 is standing proud this morning. Not sure a GM would be.

 

[HarryUSA]

While this is an old post, some things need to be addressed. First, the Antron 99 is a 1/2 wave antenna, and if anyone said that someone calls it a 1/2wave over a 1/4 wave, I can only imagine they were referencing the input impedance is the same as a 1/4 wave ground plane antenna, because a half wave over a 1/4 wave is 3/4 wave, which has the same input impedance as a 1/4 wave, but slightly less gain at the horizon. But to be clear, the Antron 99 is just a half wave antenna, with no less gain than a half wave dipole, and there is no way to get a radiator of one length to impersonate a radiator of another length.

If the schematic above for the matching network is accurate, then it is a very effective and fairly broad banded solution, that they avoid using a transformer and a counterpoise for impedance matching. So here's the lumped solution:

 

[BC Coyote]

A-99 and it's clones are a great antenna as long as they are mounted at least 36 feet above ground.
The ground plane kit does nothing to improve transmit or receive, but DOES help dramatically reduce common mode currents which enter the shack on the coax braid and cause all kinds of problems (like squealing mics).....
Hanging four 108 inch wires from the base of the antenna achieves the same effect and is much cheaper !
I've talked all over the world on A-99's. They'll never perform like a beam or other directional antenna but for a vertical they work well.

 

[Rwb]

i want to sell my A99 and get another sirrio 2008