Microair M760 Intermittentent Transmit

On Tuesday, April 2, 2013 at 9:38:04 AM UTC-7, Dan Marotta wrote:
Thanks, John.

The switch was already installed in my glider when I bought it and I've
upped the current demand with the installation of the transponder.

It's my intent (someday) to replace the DPDT with a couple of SPST switches
(one for each battery) and I'll buy them at the local electronics supply
store, not Radioshack (and they'll be beefy, literally and figuratively, and
designed for dc).

In the mean time, I find a 1.1v drop when all equipment is turned on and I
key the mic (down to about 13.9v), but that shouldn't prevent modulation.
My 14v battery is about 2 years old and is maintained on a smart charger.


"JohnDeRosa" wrote in message
...
On Apr 1, 6:29 pm, "Dan Marotta" wrote:
I switched the dc input to the radio to the hot side of the switch (on a
terminal strip) and it seems to be working. I'll need a few successful
flights before I call it good. If it fails to modulate again, I'll ship it
to microairusa for repair.


Dan - It seems hard to believe that the switch is your glider is so
"weak" that it cannot handle the amperage of your instruments. When
you say "delicate" could the switch be damaged? If it is intermittent
it could have built up some oxidation or carbon which is acting like a
resistor limiting the voltage to your devices. I've never seen this
myself but it is possible. Of course replacing the switch with
something NOT from Radio Shack is the next approach. Look for name
brands like Switchcraft, Alco or C&K. Maybe I am stating the obvious.

- John

1.1 V is a very large voltage drop. I would find where in the power distribution the largest portion of this drop is occurring and fix it. You are probable drawing 1 A in transmit, so 1.1 V equates to 1.1 ohm, a huge number for any power distribution component. If you have a good DVM you could just measure the resistance of the wiring. If not, just measure the voltage drop of each part of the wiring.

Tom