Noisy Cobra 29 LTD

Sounds like a grounding issue. Just because your last radio did not do it does not mean that it is grounded good. May be internal ground but if it's new I doubt it. Some electronics puck it up worse than others.


Sent from somewhere out there on the road.

 

Look around in the truck stops for a noise filter. The one you want is a 10 or 15 amp which is a black rectangle shape which appears to have heat fins (not, just molded plastic), and 4 wires. Do not buy a 3 wire noise filter since you want to attack both common mode and transverse mode noise. Install it per directions in the power cord between the fuse and plug head, keeping wires short but leave enough length so you can stick the filter out of the way. You want it after the fuse in the power cord (which you just cut the wires for the install) just after the plug head since they have been known to short out so why not take advantage of the fuse for protection. May not help in extreme cases but it is a good starting point in solving your troubles. Assuming the radio is not the problem of course. Radio Shack used to carry a 10 amp 4 wire filter which was good, shaped like a cylinder. I would also use 4 lengths of heat shrink tubing for insulation so you can do a good job on the install.

 

Magnum (RF Limited) makes a CB power cord with a filter in it that should plug right up to your radio. They work well for noise on your radio's power line and no cutting necessary.

 

The old Regency radios were really bad when it came to line noise and th filters worked wonders ...

 

If you tend to the "thrifty" side and want to learn a little about how it works, here's a 30-minute project you can build yourself. I've made 4 so far and they've been as good as anything I've bought from Radio Shack ("You've got questions, we've got blank stares!") or the commercial radio wholesalers I've dealt with. Also works great for removing the same whine from your transmitted signal -- if you can hear it in your speaker, it's likely that it's also affecting your signal when you talk.
http://www.worldwidedx.com/home-brew/31492-building-simple-alternator-whine-ignition-filter.html

Feel free to ignore that it appears on one of the dreaded "ham sites".......but RF is RF......
Hope that helps,
-- Handlebar --