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Can 4-stroke vibration cause RX interference?

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Old 07-22-2007, 01:07 PM
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Deadeye
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Default Can 4-stroke vibration cause RX interference?

I've noticed this on two planes.

#1, a UCD 60 with stock mount and a Magnum 91 with PPM RX. Over 80 flights glitch free. Shelved for two years, recently put back into flight using a Magnum 125. Noticed intermitten glitching. This is the same setup I had before, only exception is the engine and prop. Put a PCM RX, and the glitches are gone.

#2, a Sig Somethin Extra. Saito 82 15X4 prop, digital Spektrum standard servos, Futaba PPM RX. 40 + flights, no problems. Now I am getting hit hard. I can fly through it, and the glitching never happens on landing approach for some reason (throttle setting?).

Are digital servos noisy and more prone to cause RX interference? Can the harmonic noise generated by the engines cause problems? I'm getting tired of shelling out money for PCM...thanks.
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Old 07-22-2007, 02:30 PM
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Default RE: Can 4-stroke vibration cause RX interference?

Try having your receivers checked over. It could be a lot of things - even increased sun spot activity.
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Old 07-22-2007, 02:30 PM
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Default RE: Can 4-stroke vibration cause RX interference?

Vibration can cause loose or dirty connections to cause interference. I once a serious "glitch", with the engine running, and tried several times to cure it. When I plugged the battery directly into the receiver, glitch went away. Bad contact in the switch.
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Old 07-22-2007, 03:02 PM
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Default RE: Can 4-stroke vibration cause RX interference?


ORIGINAL: dirtybird

Try having your receivers checked over. It could be a lot of things - even increased sun spot activity.

RX's are just fine in other planes. I'll look into the dirty connections. I should've mentioned that my SSE has a rubber mounted mount. And there is no metal to metal contact on any linkages.
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Old 07-22-2007, 11:03 PM
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Default RE: Can 4-stroke vibration cause RX interference?

Absolutely. Especially if your equipment has been sitting around for some time. Dust, moisture, oxidation or a combination can do all sorts of crazy things. It's a fine idea to unplug, inspect and reinsert every connection in the plane after a long period of inactivity.

Just as an aside....buying PCM receivers is a great idea, but unless there's a problem with your old FM receiver, all your doing in this instance is putting a mask over the glitching. Whereas an AM or FM radio will respond (w/servo movements) to any old garbage that comes down the pike, a PCM radio uses checksums to "validate" the signal. If the numbers don't match for whatever reason....it drops that frame. The servos don't move at all. If it drops enough successive frames....the radio goes into fail safe.

It's basically a real fancy glitch. Instead of the servos jittering and chattering....they simply stop responding be it for a millisecond or an eternity. In this instance, an "eternity" is the amount of time it takes your plane to go from a safe altitude, to a point just below ground level at a high rate of speed. The results are never cause for celebration.

Investigate, and correct the source of the glitching, and you'll be all set.
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Old 07-23-2007, 11:10 PM
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Default RE: Can 4-stroke vibration cause RX interference?

Just curious.... are your receivers the "synthesized chip" type or do they use a channel chip?

I had a Hitec 2100 synthesized receiver that, when it was tied down too tight in the plane, would get vibration related lockouts. This was about a year ago, and it was the last Hitec receiver I ever flew. Now today, a year later without a glitch using JR radio equipment.... I'm setting up a 46cc Extreme Flight Yak and the radio will lock out if I go up to full throttle. The first thing I did was loosen up the tie-strap holding the receiver, and the problem seems to have gone away.

I'll be at the field tomorrow doing some serious testing before I try to get this plane in the air for the maiden.
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Old 07-23-2007, 11:25 PM
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Default RE: Can 4-stroke vibration cause RX interference?

RaceCity - Many years ago when PCM was first becoming popular, I had a guy I knew that worked for a radio manufacturer (who shall remain nameless) tell me

"pcm doesn't really fix radio problems, it just covers them up"..
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Old 07-24-2007, 10:39 AM
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Default RE: Can 4-stroke vibration cause RX interference?

do not "hard mount" your receiver. keep a large amount of foam between the receiver and the plane and don't strap it down tightly. It only needs to be tight enough so it doesn't flop around.
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Old 07-25-2007, 10:50 PM
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Default RE: Can 4-stroke vibration cause RX interference?

It is best to mount your receivers in or 0n foam - does not look as neat but reduces vibration related problemsy. I even do it in jets which, have very little vibration.
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Old 07-26-2007, 08:03 AM
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Default RE: Can 4-stroke vibration cause RX interference?


ORIGINAL: fizzwater2

RaceCity - Many years ago when PCM was first becoming popular, I had a guy I knew that worked for a radio manufacturer (who shall remain nameless) tell me

"pcm doesn't really fix radio problems, it just covers them up"..
PCM does in fact cover up the problems. Thats what it was designed to do. It also decreases the Minimum Discernable Signal (MDS) by nearly 3db. Thats the same as doubling the transmitter power.
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