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noise in my radio

P

papa-papa

Active Member
I need some help with my radio noise from someone who may know what I should do.
Handheld with rubber antenna works wonderful for the last three years with no noise at all, I installed a real antenna on the belly of My RV-3 just forward of the spar. Now every time I use the electric fuel pump or the electric flaps, the noise in the radio is so loud that I want to remove the headset.
I have no wires running with the antenna coax, no noise filters (not sure what to get) the antenna has no BNC connector on the antenna, just a wire end connection and ground. Antenna is 6 inches from the fuel pump and 3 feet from the flap motor.

Any and all advice is welcome and appreciated.

Thanks in advance

Perry
 
Maybe

I'm sure someone that knows more than I do will chime in, but this is what I think could be the problem. On my aircraft I took all grounds to a central grounding point (forrest of tabs) on the firewall, which is grounded directly to the battery. I have no problems with noise. If your fuel pump and flap motor are grounded locally near those items, that might be why you are getting noise from them. If you run ground wire from those items to the battery it might eliminate the noise problem. Hope this helps.
 
I'm assuming you are using a handheld and no intercom.

The noise could be radiated (picked up by antenna) or conducted (running through power leads). Based on your description, it sounds like radiated noise.

As far as simple fixes (in order of cost)
1) Put a 0.1uF capacitor across the motor/pump leads. The brushes or contacts are acting like little spark gap transmitters, the capacitor should suppress the spark just like a condenser in an ignition system (conducted or radiated) http://www.radioshack.com/product/index.jsp?productId=2102589

2) In addition to the cap wrap a few turns of the power leads around a ferrite choke core. This should attenuate any remaining energy that wants to use the power leads as an antenna--closer to the source of the noise is better. (conducted or radiated) http://www.radioshack.com/product/index.jsp?productId=3012599

3) Replace your antenna--get one with a BNC connector, this will force the radiated energy to travel around the metal aircraft to the antenna instead of 6" from the pump to the wire center conductor (radiated)

4) Replace your coax with RG-400, the double shield might help prevent unwanted pickup inside the fuselage--this is pointless until you get an antenna with a connector (radiated)

Paige
 
Paige has the right ideas - and I would say that from my experience, it is very likely that your problem will be the antenna connection without a BNC - I've been there, and no matter how well you try to terminate the ground and antenna leads, you're going to reflect some RF energy back inside the metal box known as the fuselage.

Paul
 
radio

Thanks guys for the info, I guess I will go with the BNC connected antenna and see what comes from that. I have the radio shack feritte's but did not know that I was supposed to wrap leads.

Again thanks for the advice,, will let you know how it turns out

Perry
 
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