paully_321

I have a troublesome 168df Futaba 8 channel RX. It seems no matter what servo I plug in to any of the channels, the servo goes crazy if the RX power is on and the TX power is off.

I have several other RXs on the same channel and none of them do that. It's not a locational problem, because it also does it at the field with no other radios on.

I pulled it out of my plane because I also started to notice (although I am really sensetive to it probably) some small glitches under TX power too.

Does this happen to others? What could it be besides a bad RX? I have tried different batteries, switches and servos. Even if I only plug one servo in (and try different channels) it does it.

Thanks,

Paully

onewasp

None of them (any brand) are to be used/tested/etc. with Tx power off.

Think!
What do you get with the TV or radio tuned to a band/frequency with zero transmission?
Hash right?

paully_321

Uhhh...

Sorry, but NONE of my other recievers ever does that...Not in my three cars or four other planes. And, I've never seen it before. It just seems unusual. Not just a little glitch, but a CRAZY full range of motion spastic freakshow.

stang

My Feedback: (1)

All mine do that so I don't think you have a problem. The receiver isn't getting any signal to drive the servos so they are doing what comes natural.

ggraham500

My Feedback: (4)

Your servo is trying to center itself but can't because it is not receiving a Tx signal.

Campgems

I ran into this the other day with my plane, Turns out that Ihad the wrong RF module in my Tx and was about 5 channels off the RX frequency. I can turn on my Rx alone at home with not problems, but this time at the field, I thought I was going to rip myservos out. I've even turned on the Rx by it's self at the field, but the combo of signals at the field resulted in a confused Rx and crazy servos.

Every thing in RFis signal to noise ratio. As long as the signal overides the noise, all is OK. When there is no signal, the noise wins every time. That is what you are seeing. As long as the RX and plane passes an engine running range test, you are good to go.

Don

A.T.

A very normal actionespecially with the recent"smart"receivers.
Transmitter On First - Off Last
See also sub Section "Glitches & Jitter in Receiver, Servo & ESC - causes and cures " under
"Radio Systems, Accessories, Alterations and FAQ." at:
Alan's Hobby, Model & RC FAQ Web Links

Regards
Alan T.

dirtybird

My Feedback: (5)

A receiver has a circuit called the Automatic Gain Control. When you turn on the TX the AGC reduces the receiver gain to prevent overload. So when you turn off the tx its just the same as turning the volume all the way up. With a PPM receiver the servo sees the noise spikes as random control spikes and tries to comply. Some receivers are worse than others. Also a nearby TX on another frequency can make this worse. Its nothing to worry about.

onewasp

None of them (any brand) are to be used/tested/etc. with Tx power off.

Think!
What do you get with the TV or radio tuned to a band/frequency with zero transmission?
Hash right?

Say again.?!

Ernie Misner

It can be downright dangerous to the health of your servos and control surfaces to turn the rx on before the tx is powered up. They may self destruct as in trying to move further than you expect them to.

Ernie

carrellh

Even though you never experienced it: as others have written, this is not at all unusual. I've forgotten to turn off the rx and 15 to 20 min later hear a servo moving.


If it is glitching when the tx is on I agree with pulling it.

Skarn

LOL, then you've been very lucky! I've been in RC since 1986 and every receiver I've ever used (except 2.4) does that if you turn the TX off while the Receiver is still powered on!

The severity depends on where you are and what other RF sources are around you at the time.

That's completely normal bro as everyone else here in this thread has pointed out.

Skarn

Campgems

Leave the RX on and TX off an then start your electric fuel pump. I did that this morning and about shook my plane apart. As soon as I quit pumping, it quit jumping, Signal to noice ratio. No signal and all noise and total confusion on the radio part.

Don