Still having issues. The carrier is stable, but SWR's are around 2.8 with the amp on and 1.1 with the amp off. If I put the carrier to around 50 watts, the SWR's go down to 1.3. Again I'm using high quality 8X coax now on the antenna and jumpers with the Sirio magmount with a Sirio 5000 antenna. I tried my Wilson whip and same thing. I'm thinking the driver is getting reflect back from the main transistors in the amp. Don't know what else to do except to service the amp.
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High SWR's, trouble with carrier on amp
- Thread starter bassman21
- Start date
I don't believe that you've mentioned what kind of radio you are using - and if it had been modded.
A dirty output from the radio is commonplace thing, and things only get worse when hooking it up to an amp. If I had a nickel for every radio that I've had to restore from all of those hack 'mods' . . .
Lincoln II, no mods done, just modulation turned up a bit and carrier turned back to 1 watt. Same issue with my Cobra 25. That isn't the issue.
Might try a longer coax jumper. Or a different length at least and let me ask, how close is the amp to the radio/s?? May have to move the amp away from the radios if they are close together.
Not sure if any of this will actually work, but it's worth a try.
Not sure if any of this will actually work, but it's worth a try.
Thanks for all your help. This amp is picker than a spoiled 3 year old. I put a high quality RG58u 4 foot jumper between the radio and the amp and the SWR's are now 1.2 with the box on, dead key is stable. Two, high quality 6 foot 8x jumpers and 1 8x 3 foot jumper had SWR issues. It's working great now!
I ended up fixing this problem better by extending the length of the coax after the amp. When I installed my MK3, the oscillation came back above channel 28 or so. Adding 6 feet to to the coax after the amp eliminated it through and through. It also lowered my reflect power. I sold the amp and I'm back on my Dave Made 1X4.
What are you using as a ground plane for the antenna (and please don't tell me you don't have one!) Without a ground plane, you have HALF an antenna. A mobile antenna uses the car's sheet meta and other metallic structures (properly bonded together is best) as the ground plane.
If changing the coax length improves things, it really hasn't. The problem is still there with a bandaid on it.
I used a steel patio table and had an swr below 2:1 with k40 mobile hardmount, now I have an Antron 99.
My idea was to connect the power supply hooked to the radio (dc ground) to the antennas steel table counterpoise with a wire running to the table (Which had several radials extending out from the edge). (I never bothered to run a "dc" wire to the table antenna as I found I had a bad coax Jumper!)
73
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OK, that sounds better than what was going through my mind. As long as the table radius plus the length of the radials was equal to the vertical length of the antenna (or maybe just a couple of inches longer, that should have worked acceptably. You don't need to run a "dc wire" to the table; the cable shield takes care of that. If the shield doesn't have continuity from the radio to the antenna, that's your first hint of something being wrong, but don't just run a piece of wire. Repair the coax or replace it.
Thank you Beetle, yes I had to find & remove the bad coax jumper and the issue seemed to go away.
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