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  #1  
Old 11-12-2016, 11:39 AM
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MIPS MIPS is offline
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CB Bleedover

So I decided to do away with nasty home built antanna solutions for my base station and went with a 30' pole I was given because it had a shedding problem with the fiberglass. (until I clear coated it)



It has come with a major downside. While the base station is limited to 3W transmitting from the radio results on whatever you say blaring out of every FM radio in the house, plus the stereo upstairs breaks science completely and emits whatever I say, even when off.

I'm just about positive the base of the antenna and the coax to the basement are both properly grounded and there's no resistance or shorting issues within the cabling. CB is also so far away on the frequency spectrum to FM that even though the main antenna for the house is a few feet away the transmission shouldn't be doing this. The tuning rings on the antenna were likewise also adjusted and set during installation.

What am I doing wrong here?

Last edited by MIPS; 11-12-2016 at 11:55 AM.
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Old 11-12-2016, 04:26 PM
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Might be RF going back down the feedline getting into the house electrical system and maybe the speaker wires to that stereo which would explain why you are hearing your transmission while it's off. From your description and what I see looks like an old Antron A99 CB antenna. I have one I used on 10M that the fiberglass is shedding badly too. (I need to do something about that.) One thing that I did that helped keep RF off the feedline and getting back into the radio, was coiling up about 10 turns of coax just below the antenna feed point to make a common mode choke balun, but I also remember doing other things including the optional radial kit for that antenna before I mostly eliminated the problem. The coiled up cable forming a choke balun was the most effective in my situation.
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Old 11-12-2016, 08:03 PM
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Looks pretty easy to make the choke. Any preference on an open air coil or wrapped around a ferrite ring?
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Old 11-12-2016, 08:05 PM
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Quote:
Originally Posted by Ed in Tx View Post
I have one I used on 10M that the fiberglass is shedding badly too. (I need to do something about that.)
I found that while wearing gloves you could rub down the poles quickly to get rid of the loose fiberglass and then spray it all with clear coat or paint. Likely won't last forever because the antenna sways a bit but it at least seals it again.

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Old 11-12-2016, 09:00 PM
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My A99 has been out in the sun and elements since 1994 so it's pretty ragged. I've watched birds picking the fiberglass strands off of it to use for their nest building!

Might start with about 6-10 turns about 6" dia air core, just below the ant coax connector, form the coil around something like PVC pipe, try that.

Might try unplugging that stereo from the wall to see if that changes anything. If so maybe add some ferrite cores to the speaker leads right where they hook the amp-receiver. Check that they aren't some resonant length at or near 27 mHz wavelength that might be inducing RF into the stereo. 8 1/2 ft, (103 inches) is 1/4 wave, twice that, 17 ft, is 1/2 wave etc. You need to avoid resonant wire lengths.

I was getting into my next-door neighbor's sub-woofer, like wide-open hum and noise coming in blasts from my SSB transmissions. Worked on that a while. Finally, took an old ferrite core I had saved from from a flyback transformer, wound the audio coax from his AVR to the sub-woofer through it several turns, and that killed the RF getting into it completely. Took all day to figure that one out. Good luck!
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  #6  
Old 11-29-2016, 05:19 AM
Dude111 Dude111 is offline
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I wonder if the clear coating is doing something?
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Old 12-05-2016, 11:53 PM
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I can't see how it could be. It is neither metallic or conductive.

Anyways I picked up most of the fittings and cable I needed to make the choke so I'll work on fabricating something and getting it installed once the temperature rises back around 0.
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Old 12-06-2016, 04:53 AM
Dude111 Dude111 is offline
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Well I wish ya all the best getting her working properly

Last edited by Dude111; 01-14-2017 at 05:30 AM.
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  #9  
Old 12-29-2016, 08:08 PM
Dawg Dawg is offline
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Have you always had this problem?

When it comes to CB's, many people take them in to have them "peaked and tuned". Oftentimes this peak and tune involves disabling the modulation limiter and/or spreading the trap coils in the rear. Doing either of these will cause the radio to bleed. But it makes the CB techs Dosy meter show those "feel good" watts that aren't going out on the channel Nel you're on, but they ARE going out as harmonics on other frequencies.

First thing I'd try though are some snap chokes on the ends of the coax.

Has the radio been peaked and tuned?
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  #10  
Old 12-31-2016, 08:03 AM
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A half dozen turns of the coax directly under the antenna feedpoint will probably solve the problem. I've got a Ringo vertical for 6 meter FM, and it caused issues with the FM broadcast radio in the kitchen....the coax trick fixed the problem for me.
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Old 12-31-2016, 07:15 PM
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I still can't get up onto the roof. It warmed up a little, then we got another ten inches of snow.
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Old 02-04-2017, 11:13 PM
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Guess what?
It's still winter!



I'm still unable to go onto the roof and install the coil. It has however been built. Eight winds around a 6" coffee can, then strapped and taped together with ends soldered on.

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Old 04-13-2017, 07:34 PM
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The weather behaved enough this afternoon that I was able to get on the roof and install the coil, finally.



It did not work. What the $*&@?
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  #14  
Old 04-15-2017, 09:19 AM
madlabs madlabs is offline
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Do you have an SWR meter? Or a friend with an antenna analyzer? High SWR can lead to a lot of RF in the shack. When you wrapped your choke I see you said you used a coffee can. Was it metal? If so, take it out. And you likely need more turns, try doubling them.

On another note, looks like all your connections are not wrapped with tape. Moisture can cause SWR issues as well, aside from killing your signal.

Good luck!
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Old 04-15-2017, 09:23 AM
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Back in post #5 I suggested trying several things, not just a coil of coax as a choke. Did you try anything else or just read the first suggestion?
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