crossflow235

Hi I am looking for some advice on clearing up some glitches with my radio xcvr. I am running a gas boat and have the throttle servo mounted on the motor mounts. The only way I could cleanly connect servo to carb and have accurate throttle. As everyone knows vibrations can do strange things to your xcvr. My rudder and throttle glitch momentarily when motor is running. I think I am sending noise to the Xcvr via the throttle servo due to magneto and motr vibrations. The batt and xcvr are wrapped in foam inside the radio box, the throttle servo lead is covered in shielding and grounded to the motor. I recall several years ago there was a company that sells line noise cancel device that connect between the servo and the xcvr and the batt and xcvr as well. Has anyone ever used these with success? If so where can I purchase them.

Thanks

vsop

Look at the site advertisments here, there is one company that sells them who has a banner on this site..

You are probably having a grounding issue with the engine..

crossflow235

Grounding issue? What is the correct way to ground a motor in a boat. The shield I have the servo cable run through is grounded to the motor..

Thanks for the info for the link on this site I will take a look when I find it.

LtDoc

Mechanical vibrations don't cause RF interference. Electrical pulses, or anything that makes a spark does cause RF interference. There are two ways of getting rid of this kind of interference, by shielding the electronics from the 'spark', or by 'by-passing' the empulses from the spark to ground. (The third way is to stop making the spark, but that may cause other problems too.)
There are several sources for ferric type thingys to wrap leads around/through. They can help but may not 'cure' the problem. Capacitors from leads to ground 'by-pass' (pass AC currents to ground) the pulses to ground instead of to the electronics.
The first thing to do is determine where the interference is comming from (also the hardest part). From there you can get a clue of how to stop the problem.
One easy thing to do is twist the servo leads, how ever many twists you can mannage and the lead still reach where it's supposed to go. If it helps, even a little bit, then one of the ferrite thingys should help even more. [Those thingys look sort of like a metal donut.]
If you want to try capacitors for by-passing there are two values you need to be aware of. One is the voltage it will have to handle, the capacitor's rating should be at least twice whatever the voltage through it is. The other value is of the capacitance it's self. In general, the larger the better. Theres a point where that large value gets to be impractical, as in the thing gets too big to fit in the boat easily. Something in the 'micro' range, not the 'pico' range, will work.
Resistor spark plugs or wires can help. And when everything else fails, try wrapping things in foil (except for the radio's antenna of course).
Ain't this 'fun'?
- 'Doc

crossflow235

Wow thanks for the info.. Looks like I have my work cut out for me. I have already twisted the servo wire and the extension cable, The communication wire I use for DDC controls can pickup stray voltages ect so its twisted and I thought of trying that first along with a outer braided shield. I have experienced strange glitches on xcvrs when the batts are not wrapped in foam on glow engones which have no induction system.. Also have seen glitches when a loose metal object is bouncing around against another metal object.

I will try a choke on the servo lead and see if the plug for the motor is the resistor type, if not I will replace that first. The leads for the servo cable are as far away from the motor as they can get once it leaves the servo. Could the wire that I soldered to the shield that is bolted to the motor be causing problems. Typically when using shielded cable you ground one end so I thought grounding it to the motor would help cancel stray signals.. Thanks again