Base A99 Antenna Feedline Question

[338_MtRushmore]

Who'd a thought this thread would run this course.
I think DB got this one, but the coax termination vs feed point diagram by Bob had me rolling.

 

[Riverman]

Who'd a thought this thread would run this course.
I think DB got this one, but the coax termination vs feed point diagram by Bob had me rolling.

In hindsight, the thread was unnecessary. I answered my original question with my remembrance of the handling of my Patriot 12 (Post #14). Am sure the same would hold true for the A99.
Still, it's always fun to sift through all the posts and try and determine who's pulling your leg and who isn't.

 

[undertaker]

My first antenna was the A99 always had good luck with it...

 

[Marconi]

Check out this article, The End Fed Half Wave Antenna, by Steve Yates AA5TB, at this link.

http://www.aa5tb.com/efha.html

Personally I've had several A99's over the years. One was really bad acting with spatter and TVI, but it still seemed to work on TX/RX just fine. My other A99's worked just fine as far as I could tell, with and without radials...and they did not act bad on the air.

I have an A99 GPK, but for the most part I seldom use it except when testing the effects. I did a lot of antenna work on my A99's but unfortunately I lost my files.

 

[Riverman]

Check out this article, The End Fed Half Wave Antenna, by Steve Yates AA5TB, at this link.

http://www.aa5tb.com/efha.html

Personally I've had several A99's over the years. One was really bad acting with spatter and TVI, but it still seemed to work on TX/RX just fine. My other A99's worked just fine as far as I could tell, with and without radials...and they did not act bad on the air.

I have an A99 GPK, but for the most part I seldom use it except when testing the effects. I did a lot of antenna work on my A99's but unfortunately I lost my files.

Thanks, Marconi.
I followed the link, read the entire article, and will be gathering the items depicted in Figure 9 for use with my next Patriot 12.

 

[Marconi]

Antennas that include a matching system don't need radials to tune and function, but in some ways said radials will benefit the antenna. If you used the antenna before adding such radials, and then after adding a set of radials you notice a change in performance, you had a common mode currents problem before putting the radials on.

DB, I figure you are describing a real life A99 antenna above, but do you have a model for an A99 that includes a match that takes care of the mismatch?

If so, how does the model compare to a model without the match?

 

[The DB]

DB, I figure you are describing a real life A99 antenna above, but do you have a model for an A99 that includes a match that takes care of the mismatch?

If so, how does the model compare to a model without the match?

No, the schematic I've seen multiple places including above don't give enough detail, namely the values of the components.

I've played with components in essentially that layout once or twice, but as of yet have not been able to simulate a good SWR match. I just don't have enough information...


The DB

 

[Marconi]

I haven't had any luck either. Thanks for the reply.

 

[bob85]

It will be very difficult to simulate the a99 matching accurately,
measuring the two series capacitors is easy enough but the coil is concentric wound,

small coil in the schematic sits inside the larger coil with the tuning rings moving up & down the outside of the large coil.

 

[The DB]

It will be very difficult to simulate the a99 matching accurately,
measuring the two series capacitors is easy enough but the coil is concentric wound,

small coil in the schematic sits inside the larger coil with the tuning rings moving up & down the outside of the large coil.

I am aware. The schematic is actually wrong, they are not acting like two independent inductors, they are actually working together as a single impedance transformer. That layout is very similar to how some ununs are layed out. The two inductors are actually a step up impedance transformer.

I don't think I would be able to model such a device...


The DB

 

[LeapFrog]

Not 45 degrees (coax to "bottom leg"), but close; supposed to be a vertical dipole center cut for .64 w/l @ 27.285 MHz, free to me just had to measure, cut, & solder. I could use more ferrite beads or a tighter network of loops (and closer to the SO-239) if I had bamboo laying around this would be a true horizontal dipole.
[album=medium]627[/album]
Worked great horizontally (the coax came out at 90 degrees), but I like the current configuration (vertical polarization) for local contacts, I call it "The Lambda". Right or wrong I'm "gettin' out and gettin' down", neighborhood wide!!

 

[JAF0]

Look at the a99, there's 18" of coax plus the aluminum tube to act as somewhere for return currents, the so239 connector is not the feed-point.

I measured the coax inside my (dead) A99 base tube at 12", me thinks you're dreaming about having 6" more.

 

[Old_Crow]

I used an MFJ-259b to get the best SWR at around ch20. Those rings at the base are tricky, sometime just being to close to it give a false reading.

 

[bob85]

I think DB said about 12" earlier, the top end of that is the end of your feed-line,
its easy enough to determine who's pulling your leg, buy an a99 and see that they don't go crazy when you tape the coax to the pole..