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

[BC Coyote]

I know of a couple people who replaced A-99's with Sirio antennas. One to a 2008 the other to a 2016. Both reported very little difference in receive or transmit, but both reported the Sirio to be somewhat quieter in terms of static and noise.
So unless you live in an electrically noisy location, you probably won't gain much by changing antennas.
Not sure about the U.S., but up here in Canada those Sirios are hard to get and cost twice as much as an A-99.
Another consideration.... the Sirios are not all that well built and have been known to shed screws etc. during high wind conditions......

 

[S&W357]

Mine is a keeper

 

[The DB]

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:

I'm surprised I didn't post anything about this back then, I must have been busy when this conversation was happening...

I agree, the a99 is not a 1/2 wave over 1/4 wave. That came from advertising for said antenna, which is apparently enough to get some people to believe it regardless of any evidence actually brought up. It is hype that many believe without question, nothing more.

Henry, when it comes to the schematic (the one in the first post, not the the other shown later), there is an error in said schematic. The two coils are actually placed one inside of the other, so it would be more accurate to call the two coils a single transformer. It is actually very close to an UNUN design.

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).....

Unless there are many buildings/hills that are taller than that in the area, any CB antenna mounted at 36 feet will perform well. If it doesn't you have a problem with your antenna setup.

Also you are correct, if the a99 is set up and has no issues, adding a ground plane kit is nothing but extra weight and wind load added to the antenna. When it comes to common mode currents, it is one way of dealing with them, but definitely not the only way.


The DB

 

[Rwb]

i disagree.antron a 99 i have has low swr.when i got my sirro 2008 i put it up 10 ft to the base,used small coax.set it for low swr. radio was putting out 50 watts. distant friend n i started talking,id switch to the a 99 that was 30 ft to base n he would say you dropped way down. switch back to 2008 n he would say bending my needle. a friend of his about 12 miles farther away got on n said very first time ive heard you. yhen when i traded places with the a 99,it was great.
my first a99 was lot better than new a 99 n several said that.
greg t will attest to a 2008 being superior too

 

[lonestarbandit]

I "heard" they shortened the sections on the new one like they did my Imax. If that is so, that is probably why.

 

[W4KVW]

I don't know what the antenna really is by design but I have been using mine at 30 feet for over 10 years with 100 watts & I have worked the world on 10-17 meters & if it's really quiet even on 20 meters with the tuner in the ICOM 7610. It's the only HF antenna I currently have since my tower with my yagi's & wires all came down during a Hurricane here in Norh Florida. The Antron withstood the storm with no guy wires on the push up mast. I will continue using it until the New tower & beams are up & operational & it will then be connected to my 2nd radio. It was a gift from a close friend who is now a SK so I have no plans of ever taking it down if possible since it just works.

 

[HarryUSA]

I don't know what the antenna really is by design but I have been using mine at 30 feet for over 10 years with 100 watts & I have worked the world on 10-17 meters & if it's really quiet even on 20 meters with the tuner in the ICOM 7610. It's the only HF antenna I currently have since my tower with my yagi's & wires all came down during a Hurricane here in Norh Florida. The Antron withstood the storm with no guy wires on the push up mast. I will continue using it until the New tower & beams are up & operational & it will then be connected to my 2nd radio. It was a gift from a close friend who is now a SK so I have no plans of ever taking it down if possible since it just works.

I said what the A99 antena really is; so to quote myself: "...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."
...and I like it too.

 

[W4KVW]

I said what the A99 antena really is; so to quote myself: "...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."
...and I like it too.

I have read many descriptions of the antenna since it’s release so long ag.I have seen the cut away pictures and I have heard people Praise and Trash them.I praise it for what it has done for me for more than 10 years when a friend who is now a SK gave it to me for my Birthday.He nor I had any idea how many QSO’s I would make with it.It’s still going strong and I will use it until either it or me fails.