On Mon, 28 Jul 2003 22:24:11 +0100, Paul Burridge
wrote:

On Mon, 28 Jul 2003 13:20:27 GMT, (John Crighton)
wrote:

The rich guy is stunting around and decides to buzz
me at low level about 20 feet above the ground.
His model flies over me and then nose dives into
the ground near by. I could here his servos twitching
away as I walked past the wreckage.
After I retrieved my model and switched off my
transmitter, I stopped by the little gathering at the
wreck site. The rich guy was operating his servos OK
and scratching his head. " I spend thousands on
my model and that ******* John Crighton comes
here every weekend with 50 dollars worth of homebuilt
junk and flies. It just isn't fair." "Moan...grumble..moan."
I didn't try to explain that his receiver got swamped. His
mates put the crash down to pilot error at low level, and
that was that.

John, what in your experience causes this 'servo-twitching'?
In that incident with the rich guy, he was a few hundred yards
away from his model and my transmitter, only 20 feet away. even
though it was on a different channel upset his signal. Therefore
his servos twitched and his model crashed.

I've observed it myself at close hand many times.

Waving a transmitter with a fully extended antenna beside
the model will cause a bit of servo twitching. The signal
is too strong. That is why you see people doing close
range testing with the antenna retracted.

The last time it
happened, we cured it by isolating the die-cast box the rx was mounted
in from the chassis. I still can't figure out why this worked, as I'd
have thought grounding it *ought* to solve the problem.

I would have thought that grounding the RX to the box would
be good practice also.
Not having a circuit to guide you, maybe you were grounding
a spot on the PCB that should not be grounded.

But in this
instance, grounding it *created* the problem and isolating it solved
it! Sometimes when I see those servos behaving like they've got a mind
of their own it almost makes me believe in the supernatural.

You got some good advice from John R Strohm in regards
to fitting decoupling capacitors across the servo supply leads.

I am assuming that your R/C gear is operating from its
own battery supply not the main driving motor supply.
Using the same battery for the radio and main driving
motors could cause servo twitching.

Pity there isn't one of these fighting robot clubs
here in Sydney. I would like to have a go.

Paul you will have to put some pictures up
somewhere so we can have a look.

Regards,
John Crighton
Sydney