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Aligning Keychain Remotes Redux

Hi folks,

About a month ago, I asked about aligning these little Multicode
remotes that give a squirt of 300MHz RF when you press the button.
Solution found. I bought a second gate control receiver for $29.95
plus shipping. Fixed 10 of those puppies yesterday morning.

The receiver board had a couple of clearly marked test points:
"GND" and "DATA". Doing the obvious thing with my scope, I was
presented with a pulse stream that I could easiliy peak with the
tuning cap of the remote.

Strangely enough, only three of them were out of tune. The rest
had other problems, such as cracked solder joints. A couple had
bad on/off switches. And a couple were just clogged with dirt. The
out of tune ones were WAY out of tune, as if somebody had messed
with them.

The test setup showed clearly if the remote was oscillating, and
also whether there was a data stream. I could read the switch
positions right off the pulse train - ON switches had short pulses,
and OFF switches had long ones.

Each remote had a pot for adjusting the pulse width. Strangely,
it made no difference in performance or sensitivity wherever I adjusted
it. You'd think Multicode would have figured that out and
just stuck in a resistor :). After all, this is a VERY cost sensitive
application.

- Jerry Kaidor ( [email protected] Ihatespam 2.com )
 
N

NSM

Jan 1, 1970
0
The
out of tune ones were WAY out of tune, as if somebody had messed
with them.

I suggest you mark these internally as to how they were out (high or low).
If you find yourself readjusting them later replace them - they are jumping
frequency.
 
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