Electrical Interference

[stephendmarcus@aol.com]

I have Tac Tic wireless speed/depth instruments on a 1977 Pearson 28 with an Atomic 4 engine. The depth gauge goes crazy with the engine on but works fine when the engine is off. I have resister plugs and new wires (from Don Moyer.)

All of the parts for the system have been replaced except for the display. The display is the only wireless part of the system. Any suggestions?

[Dave Neptune]

Quick check!

stephan, first welcome the MMI forum!!

Since the wires are fresh and the plugs are resistor things should be OK as far as ignition.
It could be the alt, try getting it running and disconnect the alt field (exciter) to kill the charging. If this eleminates the issue it can be fixed by mounting an interferance condensr to the alt, really not to uncommon.
I'm sure someone more qualified in electronics will chime in soon.

Good luck
Dave Neptune

[hanleyclifford]

I had the same problem with a depth sounder even though I have a 150 amp suppressor for the alternator. I solved the problem by putting a 1 ohm 10 watt resistor just ahead of the sounder + terminal. It seems the sounder didn't like the 14 volts the alternator was furnishing.

[ndutton]

Like the others said, you'll need to find the source and then suppress it. Dave's suggestion covers all things alternator and Hanley's experience is worth a try too. I suspect you're more vulnerable to electronic noise due to being wireless. It takes shielded cable, typical with depth sounders, off the list of possible remedies.

Points or electronic ignition?

[romantic comedy]

I had a lot of noise in my depth sounder too. It was not wireless. I put a capacitor across the positive and negative terminals on the gauge. I also put a choke in line in the power wire.

I may have the details a bit wrong, it was 10 years ago. It is 430 am and i cant sleep so I decided to see what was up here.

Maybe someone else can give more details...

Radio shack has the capacitor and choke.

[hanleyclifford]

I'm not familiar with the term "choke" as used in this application. Do you mean "resistor"?

[smosher]

Choke is an inductor, its meant to impede the change of current(amps)

The other item I would look at for interfere is the grounds.

Steve

[roadnsky]

I'm not familiar with the term "choke" as used in this application. Do you mean "resistor"?

Most likely referring to a FERRITE CHOKE or BEAD...

"A ferrite bead is a passive electric component used to suppress high frequency noise in electronic circuits.
It is a specific type of electronic choke.
Ferrite beads employ the dissipation of high frequency currents in a ferrite ceramic to build high frequency noise suppression devices.
Ferrite beads may also be called blocks, cores, rings, EMI filters, or chokes."