radio noise 41 cadillac

[mr41cadillac]

I have installed a 12 volt radio that's runs totally seperatedl from the wiring in the rest of the 6 volt system. I'm having radio static and lower volume only when the car runs. sounds fantastic when the engine s not running.  anyone have any idea how to cure this ? thanks john

[C Gorgas]

Place a noise suppressor in the coil wire and that should solve the problem. It is easy to install. I had the same problem and it took care of the noise. I have an extra for small fee if interested; return for refund should it not work. Chet Gorgas 25441

[Bobby B]

Check your plug wires? Solid Core? Change to Resistor type wires if you're not showing the car. At least you can enjoy some tunes.......
                                                                                                         Bobby

[bcroe]

In addition there are probably a couple noise suppression caps associated
with the V reg and the ignition, make sure they are in place.  You may find
turning on the heater blower or other motor causes more noise; these can
be addressed individually.  And all grounding straps around the engine
should be in place.  I wonder how you run a 12V radio in a 6V car? 

I cured my generator noise by converting to an internally regulated alternator. 
There are cures for all your own noise; how serious are you?  Bruce Roe

[mr41cadillac]

my radio runs directly to a 12 volt battery in the trunk. I ran the ground wire from the radio directly to the battery.

[J. Gomez]

my radio runs directly to a 12 volt battery in the trunk. I ran the ground wire from the radio directly to the battery.

Hmm you failed to mention if the radio is single band (AM) or dual band (AM/FM)?

Is the noise a buzzing/popping type which increases with engine rpm’s or a humming (which most likely would be a radio problem )?

Is the noise predominant on the AM, FM or both (if dual band)?

You mention the radio runs from a separate 12V battery, assuming the 12V is totally isolated from the 6V (positive ground) system.

Assuming the charging and overall electrical system on the car remains at 6V?

If the 12V is totally independent from the 6V system on the car, remember both have different grounds potential so they would need to be totally isolated from each other, as do the radio (especially any grounding contacts on the radio with the chassis).

In addition to the aforementioned suggestions on the condensers/capacitors noise suppressors.

The antenna lead shield would be grounded to the chassis (6V positive ground). Disconnect the car antenna and try using a temporary one to see if the noise goes away or if diminishes the noise.

Good luck..!

[Steve Passmore]

Suppressors are still needed.    Connecting a radio to its own supply will not avoid static. The engine will send the static outwards and any receiver will be affected.  Decades ago when I messed with my cars outside my mothers house hers and the neighbours TVs were affected and did they ever cuss?

[bcroe]

I don't agree, that there is a need, or any advantage to isolating the 12v
negative ground, from the cars positive 6V ground system.  Probably all
the noise is radiated from the offending systems, not conducted directly
via the wiring. 

My Mom bought a vacuum about 1948 which which wiped out the radios I
got later.  I got a hold of it and installed a couple filter caps, problem solved. 
Don't use 50V caps in car wiring (like I tried); starters can generate very
short spikes of hundreds of volts. 

Caps can cure a lot of noise when installed the right place, but there are
places they can't be used, like the field current to the generator (one reason
I changed to an alternator).  If the problem persists, the generator to V reg
wires could be shielded.  The resistor ignition wires help.  There are completely
shielded ignition systems to 100% cure this, mostly us radio amateurs go to
this extreme to kill all noise.  The parts I think are derived from aircraft ign;
they had the additional advantage of being immune to water washing over
the engine.  Then you get to listen to the noise of all the vehicles around you. 
Bruce Roe   K9MQG since 1958

[mr41cadillac]

i read an article that says just use a distributor condenser on the generator and coil to stop radio noise.  i tried one on the generator but didn't work.

[bcroe]

A distributor cap will take any primary voltages.  Placement is important; if
it is too far from the noise generator, the connecting wire will be an antenna
radiating the noise.  A cap mounted by and connected to the generator main
output terminal should help there.  No cap can be put on the field terminal,
as it would damage the V regulator contacts.  Shielding the wire to the V reg
and then putting a cap on the battery terminal of the V reg could help.  A
solid state linear V reg substitute could cure this, but none may be available
for 6V positive ground.  Bruce Roe

[mr41cadillac]

sorry but you lost me. what is a cap? what is the noise generator ?

[bcroe]

Oh yea, they were called condensers long ago; capacitor became the favored
industry name more recently.  Then some of us who don't type so well just
call them caps. 

I meant, a noise generator, or noise source, is any component that produces
the (radio) interfering radiation.  Bruce Roe

[mr41cadillac]

thanks I get there it just takes me longer