[aprssig] Ham Radio MOBILE Traveler PL-FIND device?

Robert Bruninga bruninga at usna.edu
Wed Nov 29 10:09:18 CST 2017

APRSSIG thoughts about Mobile TRAVEL operations.

In the USA, at least everywhere that I travel, almost all voice repeaters
are PL.  This PL, removes the fun of traveling and joining new
conversations.  Fortunately, some brands (Kenwood does) have PL SCAN which
helps to find the PL of an existing QSO, but it takes a few button pushes
on each frequency to operate.  The wife does not like me touching buttons
while I am driving.

But when there is no existing QSO and traveling in a new area, would it be
practical to make an Emergency FIND-PL dongle to plug into the ACC jack on
the back of a mobile that when activated on a given frequency, would
automatically KERCHUNK while trying every PL until there is a response…

In the old days “KERCHUNKING” was a bad thing, because people did not like
to hear a dead kerchunk without someone IDing.  But now, most repeaters are
NOT USED much.  And PL keeps them quiet from noise. QSO’s are rare, its
hard to find a contact…  And so maybe to increase activity, people wouldn’t
mind an occasional PL-FIND search?

Plugging the dongle into the ACC jack gives all the access that is needed.
The PTT and SQL detect as well as the modulator input (with passband to
pass PL tones generated by the dongle).

This idea of course violates some conventional thinking about kerchunking
(up to 38 times till found).  But for the listener to a repeater that is
being FIND-PL-searched, the other users will not hear anything until the
correct PL is found and they will only hear the found repeater come up
once, and then the person activating the FIND-PL search will of course
voice ID.  SO to the casual observer, nothing unusual happened other than a
Traveler just found a way in to call CQ..

The only second thought is that for up to maybe a minute the input to the
repeater was being kerchunked causing some possible other user blockage.
But again, the timing could be such that if a real user with correct PL
keyed up, then the auto-FIND-PL would stop anyway, so I don’t think there
is any jamming issue either.

To do this, we would need to understand the typical ANTI-CHUNK delays in
most repeaters.  If it was a full second, then it might take over a minute
worst case to try all 38 tones while waiting to hear a response and while
allowing some time every try for another user to bring up the repeater
without any collision.

Just thinking…

Traveling without being able to play on repeaters due to inaccessible PL’s
is no fun anymore.

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