smoke pump placement? any interference issues when close to rx?

[husker]

I am planning on placing my smoke pump behind the tank however it is about 6 inches away from the rx(futaba fasst). Are there any potential issues putting it there?

[WangoTango]

Husker,
I just installed a Don Harris about a foot away from my JR 955 on 72 Mhz. and I'm not getting any problems. Do a range check with engine and pump running or not and see if you get any jitters on the ground.
WT

[husker]

Good to hear. I don't think there would be a problem but a little reassurance is what I am looking for.

[Pistolera]

I've also got a Harris pump about 3" from my Futaba 72mHz PCM Rx...no probs in over 150 flights...you can see the Harris pump just behind the spar. Rx is behind that.
Earle

[husker]

Good deal! I think I will be fine now

[rdgood]

Well,

There are a few good rules to follow to reduce the chances of FM radio interference.
Most of the smoke pump motors are brushed (I say Most!). If they are indeed brushed they are creating sparks just by their very nature by transfering current to the armature(arcing). The arcing in RF form is very broad spectrum RF. Now to help block the wide spectrum RF there should be a capacitor across the + and - terminal of the motor. One other rule I always follow is make sure that your battery source for the smoke pump is not shared with the receiver. I know - I know alot of folks are doing just fine plugging smoke pumps into their receivers. What alot of folks don't realize is if the cap fails open - wide band rf noise is now riding on your ground buss on the receiver. This is not good! Why risk it - IMHO!
Just use a seperate battery for the smoke pump and you should be fine.

This is my two cents.

Ronster

[WangoTango]

Ron,
My Harris pump is new and has the cap you mentioned. It's also plugged into the receiver. In the drawing that came with the pump, it showed a simple line drawing on a model of Don Harris pump that could use a separate battery to power the pump and keep things from messing with the receiver. (I called Brian but he wasn't familiar with the old style brushed pumps systems.) So my question: Is there a solder mod or fix to take care of this?
WT

[Pistolera]

Interesting. My Harris is the newer "Comp" pump, and uses a small brushless inrunner motor. It is plugged directly into one of my open Rx channels, and has performed flawlessly. I'm running a single A123, 2300mAh battery to power the Rx, servos and smoke pump. I have considered powering the smoke pump from the ignition battery, just haven't gotten around to try it.

Earle