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Mikefromms
Posted on Saturday, February 07, 2004 - 9:39 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

If the amplifier is turned on in your car and you hear yourself coming in on fm radio in the car but more pronounced at given frequency would you call this power overload on the fm antenna or would this be receiving a harmonic from the cb with amp on? I ask this question because, again, the interference is much more pronounced on given frequencies on fm.

mikefromms
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Kc0gxz
Posted on Saturday, February 07, 2004 - 6:16 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Mikefromms

There's a possiblity that you may be getting RF into the speaker leads of the car-radio. If not, then you are experiencing front-end overload.

Make sure everything is grounded well. Good grounding is first and foremost. There are other things you can try but we'll start from here.

Jeff, kc0gxz.
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Ca346
Posted on Saturday, February 07, 2004 - 8:01 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Mike:

I'm SURE you don't have the California STEREO's that vibrate the windows when someone has their car stereo turned up so loud that everybody within 4 blocks gets to enjoy it too, BUT.... (Hang in there, I'm going to get on subject...), BUT, whenever I experience that nearby me I switch to AM and hold the key down with no voice.... It stops them dead. There is always this panicked look that their stereo died....

Anyway, don't preclude the fact that depending on how much power you run out of your transmitter, it is going to be heard all around you. I cannot use my FM radio when transmitting in my pick-up.
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Rattlesnakejake
Intermediate Member
Username: Rattlesnakejake

Post Number: 137
Registered: 12-2003


Posted on Thursday, May 06, 2004 - 12:10 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

That's ahlarious, Ca346, I gotsa try that sometime. We got many people that do that blast hideous music LOUD on their stereos down here.
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Tech237
Moderator
Username: Tech237

Post Number: 12
Registered: 4-2004
Posted on Thursday, May 06, 2004 - 9:06 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

It could be front end overload, getting in via speaker leads or simple thru the power leads.

Make sure everything is correctly earthed, all connections are solid and tight. Try winding the speaker leads through toroid cores, in such a way that half the core is wound clockwise and the other half anti-clockwise. You may even try the same thing on both power leads.

If you have enough slack on the FM coax try wrapping two of three turns around a ferrite core too.

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