I need a new base antenna

[Lil'Yeshua]

I just got my first A99 yesterday and just trying to help with info I have so far. A RF choke might could help and as long as you have the antenna up 9' or more above the roof and 18' away from anything else. I'm not familiar with amp swr problems. Maybe somebody with more expertise and knowledge can help you solve this issue.
RF Choke Coil - K3DAV - Amateur Radio Operator

 

[Lil'Yeshua]

Haven't heard that one before! What does it mean for the amplifier to be installed 'out of phase'?
- 'Doc

It's in this link. I'm still interpreting the grammar.

 

[nosepc]

here is a pic of my antenna

the rubber sleeve is not in the way of the drain hole I even installed ground straps on all the joints..

Hello

Well, I think the problem is the mast, and length.

I would sort reins pulling three insulators at 10 feet from the anchors and mounting the antenna.(first ground strap)

These three reins, both would work as a ground plane.

He always did so to my monopoles and the result was 100 x 100 good.

greetings from Argentina

 

[Lil'Yeshua]

The guy lines look non-conductive to me. Still could use a RF choke.

 

[Shockwave]

This problem will almost certainly trace back to the RCI radio with the built in amp. Do you have a bypass switch on the internal amp? Was this radio used to drive the other two amps you ran the tests with?

I ask this because some early versions of the board they used in the 2950 did have self oscillation problems. They added a VC variable capacitor near the finals in this radio. It is likely this cap is some type of negative feedback loop to stabilize the RF amp.

To the best of my knowledge I've never seen this VC mentioned in any of the service manuals or alignment procedures. I had one 2959 board that would self oscillate so bad it looked like it had a big carrier on SSB! Any time you see this condition it will be impossible to get a good VSWR into any resonant load.

I would suspect the RCI and continue using process of elimination until you can identify the trouble as being in the radio or can eliminate this possibility.

 

[Lil'Yeshua]

Electrically Isolating the mast????
http://www.worldwidedx.com/amateur-radio-antennas/139576-need-advice-putting-up-antron-a99.html

 

[KD2GOE]

This problem will almost certainly trace back to the RCI radio with the built in amp. Do you have a bypass switch on the internal amp? Was this radio used to drive the other two amps you ran the tests with?

I tested it with the internal amp disabled on the RCI-2990

I all so tested the 2 amps with my Uniden Washington with the same results in SWR.

Electrically Isolating the mast????
http://www.worldwidedx.com/amateur-radio-antennas/139576-need-advice-putting-up-antron-a99.html

hmmmm? I guess I can try it.......

 

[KD2GOE]

The guy lines look non-conductive to me. Still could use a RF choke.

yes there a UV resistant rope

 

[Shockwave]

Keep in mind, things like isolating the mast and installing a coax choke at the feedpoint do reduce the percentage of CMC radiation. However, changing your power level does not change the percentage of CMC or the ratio between it and forward power.

This means I don't think we should expect CMC to cause large changes in VSWR that are directly effected by power applied to the antenna. Once the meter is calibrated at that power level, any existing CMC should have the same effect on VSWR as it did at the lower power level.

What is the VSWR with the amp off and with it on?

 

[Lil'Yeshua]

Something I found earlier in my research about matching up amp.
Amplifiers, Care & Feeding
Worth brushing up on:
http://www.k0bg.com/

 

[KD2GOE]

Something I found earlier in my research about matching up amp.
Amplifiers, Care & Feeding
Worth brushing up on:
KØBG.COM

Ok thanks ill take a look and read them over.

 

[KD2GOE]

Keep in mind, things like isolating the mast and installing a coax choke at the feedpoint do reduce the percentage of CMC radiation. However, changing your power level does not change the percentage of CMC or the ratio between it and forward power.

This means I don't think we should expect CMC to cause large changes in VSWR that are directly effected by power applied to the antenna. Once the meter is calibrated at that power level, any existing CMC should have the same effect on VSWR as it did at the lower power level.

What is the VSWR with the amp off and with it on?

I'll look it over tonight

 

[Lil'Yeshua]

Ok thanks ill take a look and read them over.

Marconi's done research on this antenna. I'm thinking that A99's have to be grounded only as to provide a path for lightning to follow to earth ground and not one's equipment. I did find a website where the guy rebuilt the coil inside and got a perfect 1:1 match. I'll have to look for that again.
Here's Marconi's take on analyzing a A99
http://www.worldwidedx.com/cb-anten...testing-his-a99-without-feed-line-mast-2.html

 

[Lil'Yeshua]

Do you think that the ground is inviting CMC into the equation? I still think that a RF choke will help along with electrically half wave length of coax. The RF choke probably will change things. Maybe an antenna analyzer will help nail this problem down.

 

[Lil'Yeshua]

End fed antenna problems
End-fed Vertical and J-pole