Howdy Andy.....Reread what Ralph described to you carefully and, when
you
think about it, you'll see that he's described exactly the same
reasoning
amateur repeaters use PL tones, with the same benefits and consequences
if their use is misunderstood (a user who, using the correct PL tones,
and is accessing a repeater may be interferred with by another station
transmitting on the same frequency but not using PL tones or who may be
using a different PL tone...of course the difference in signal strengths
received by the repeater will determine the degree of interference).

Maybe some amateur repeaters are transmitting a PL tone....if so I
didn't realize that, and persons in the coverage area could be open to
interference if for some reason they attempted to share the frequency
using a different tone or no tone (and vice versa).

Quite a few repeaters here in SCV-land do put a tone on their output
(almost always the same one they use for their primary receiver).
There are a couple of reasons for having tone-squelch turned on, on a
mobile rig using these repeaters:

- There's quite a lot of QRM on certain 2-meter repeater output
frequencies - commonest cause seems to be leakage from improperly-
installed cable TV systems in homes and apartments. It's often
strong enough to unmute a rig driving through the area of the QRM
emitter, unless tone-squelch is used or carrier-squelch is cranked
*way* up.

- We occasionally get tropospheric "skip" from repeaters on the same
frequencies, 100 miles or more away, which use different
(usually county-based) PL tones.

The best bet, as
we all (should) know, is to listen first, ensure the frequency is clear,
then transmit.

Definitely agreed!

My own mobile and HT rigs will show the incoming signal strength, or a
BUSY indication, even if the tone squelch is suppressing the audio...
so "look before transmit" works pretty well with these rigs ;-)
Unfortunately this isn't possible with all rigs, or in an eyes-are-
busy-elsewhere situation.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
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