Generator noise on radio

[TD&H]

During the last couple of flights I've started to get generator noise on the radio. Snap crackle and pop, not a regular frequency noise. Came to the conclusion it was the generator by turning it off, then the noise stoppped.

Old ('60s), PFA, wood and fabric aeroplane, O-200 with a Delco Remy generator into old fashioned (ie not electronic) voltage regulator. ICOM handheld with SPA 400 i/c. Had no problem with this set up before.

Could it be a faulty voltage regulator? If so could it be easily replaced by a new, electronic one, or do they only work with alternators? I did try cleaning the contact breakers on the voltage regulator to see if (like on a set of points) there were poor contacts causing the problem, ground run afterwards didn't show any improvement.

Any thoughts please?

[Three Blades]

I am afraid that I do not know a cure but I have recently suffered similar symptoms and manage to reduce the interference by loading up the electric system by turning on landing lights etc.
Not the end solution but it helped until I found an engineer to fix it properly.

[Avionic_Adonis]

Generator Noise

Bit of a 'chicken and egg' situation- of course it could be the generator, but it could alco be the intercom.

Firstly check all your earths/bonding etc. This is on all systems not just Radio and power generation, as well as aircraft structure.

I can only speculate on the intercom set-up but if you haven't lost an earth there, it may be just be a faulty intercom box or some screening failed somewhere.

Or why not just pay someone to come and sort it for you?! Good luck...

[Bus429]

I believe the SPA 400 does not use shielded cables. If the problem's just started, have a look at bonds and shields on all wiring. If OK, I'd go with the genny or voltage regulator (is it carbon pile or vibrating contact? (old!))

With genny online:
Switch off comm - can you still hear interference through intercom?
Switch off intercom - can you still hear interference with comm quiescent?

[L-Band]

Check the bonding of the engine to the battery ground.
Check the ground plane on the antenna is bonded to the ground point.
Check the routing of the mic and PTT wires from the SPA 400 to the sockets and the PTT switch and make sure it is not routed with the generator wiring.

Do a complete bonding check!
As with all wood and fabric a/c bonding is very important and over the years ground straps and instrument panel, etc get dirty and corroded.

Good luck
L

[Paradism]

Might be electrical arcing through carbon deposits in the genny itself. I've seen that a few times.