PCM lock out servo mvt

[Bob Richards]

Ed,

I'm no expert on JR radios, but I'll take a stab at
it. If anything I say is not accurate, someone please
correct me.

As I understand it, the JR radios allow you to turn
off PCM altogether, which means that it will try to
respond to whatever signal comes along, whether it is
a real signal or interference. 

I suspect that what actually happens is that it turns
off the frame checking (checksum or CRC or whatever)
such that if the PCM receiver gets a data packet
(channel position information) with a bad checksum, it
will still try move the channels to the position
information in the bad packet -- if you have failsafe
turned off for those channels.

I believe most (if not all) receivers have some sort
of automatic gain control, such that if the received
signal is weak, it "turns up the volume". When you
turn off your transmitter altogether, then the AGC
will cause the receiver to open up to any signal that
comes along. The amount of RF floating around in the
air is getting worse every day, so there is a lot of
spurious signals floating around.

Like I said, I am no expert, but I don't think I would
be too worried about what you are seeing.

BTW, Futaba (at least the ones I have) does not allow
failsafe to be turned off. You do have the choice
whether you want to go to a preset position, or hold
at the last good position received. I usually do a
hold on every channel except throttle.

Bob R.



--- Ed Deaver <divesplat at yahoo.com> wrote:
> Need some opinions on a JR system.  Thanx in advance
>  
> Jr 10SX with a 955PCM rcvr.  The other day I turned
> off the transmitter and left the plane on for some
> reason.  I have the Failsafe set only to throttle to
> high idle.  All other failsafe channels are turned
> off.
>  
> For no reason, the elevator servo went to full up
> deflection.  Once I turned the radio back on it
> corrected.  No one else on my freq.
>  
> Today, while cleaning up, the plane was again left
> on, transmitter off.  For no reason L Ail full
> deflection up(nothing else) which returned to normal
> as I turned on the transmitter.
>  
> Range check is well within range, and actually very
> good.
>  
> Does anybody have any ideas to explain the above. 
> Am almost scared to fly now.
>  
> Ed
> 
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