humm noise cobra 25ltd classic

[p38]

if my rf gain is turned up too much i get a humm/buzz noise tfrom my radio?!? even with the noise blanker on sometimes. can anyone explain this?

[231]

Maybe...
- Is it mobile mounted?
- Where do you have the power leads coming from (i.e. both +/- directly to the battery)
- If it's base mounted, what are you using for a power supply?

There will be more questions...but it's impossible for anyone to say with the limited info' you've provided. It could be anything from an electrical device(s) from from your neighbors to a problem with the power source, and everything in between. More info' will help us determine where to start looking first.

Good luck.

231

[p38]

yes it is in my mobile a 1998 blazer 4 door. i have the power direct to the battery with a noise filter xterminator 250 watt 15 amp . 102 whip with a quick disconnect k4a stud on a steel plate mounted too my bumper which is steel all the connections are good the antenna I the stock have a power mic as well.
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[231]

Make sure you aren't parked under (or next to) a power line, house, or anything else where noise can be generated.

The antenna may be picking up fuel pump noise being the rear bumper isn't the best place to locate the antenna. Not an uncommon problem when antennas are located there either. With the radio on and engine running remove the antenna and see if the noise goes away (or at least seriously cut down). If it does, there (most likely) lay your problem. Half the battle is identifying where the problem is and where the noise is getting into the radio from.

Honestly, options may be to relocate the antenna (my first choice). A good heavy duty fender mount will not only improve your performance, but likely remove the noise if in fact it's fuel pump causing it. The other option is to find the power leads to the fuel pump and run run ferrite cores on it, maybe even adding a capacitor. That's what I had to do with my diesel pick up after being left no option but a performance upgrade when my fuel pump failed. It caused all kinds of racket on my Icom IC-7000 which has some of the best filtering available in it. The ferrites and capacitor solved the problem though and no additional filtering was required. But on an OEM submersed fuel pump (like you probably have) it can be a pain to do. Relocating the antenna is almost always easier (not to mention will work better). Just may not look as good.

Just a few thoughts. Good luck.

[str8stroke]

Could be a short in the mic cable? That can make some gosh awful noises.

[Z-MAN]

Good call on the Fuel pump but i would shorten the ground wire to the chasis. Just like with Car stereo amps, so there's no noise, if nothing works maybe turn the recieve down in the radio? Could be too high?

[p38]

Z man thats what is was thinking! Some.one.has been inside it before . It has a short ground strap and its mounted too a steel bumper with the pain ground.off ! Only hear it once and awhile now on both of my radios! The other one is a 29ltd turned up past mudd duck power

[721HACKSAW]

Does the noise go away when you turn the vehicle off? Does it go away when you disconnect the coax? We need to narrow things down to determine if the noise is external and how its entering the radio.

[p38]

Truck on or off no difference. When its running it humms if the nb is off.