If you regenerate PL you will end up with two PL decode
time delays, the first at the outlying site, the second at
the voter comparator site. Multiple cascaded PL decoders
will cause unacceptable pickup delays - figure a worst-case
scenario of 2/3 of a second per decoder - do you really want
your users to have to squeeze the PTT and have to say to
themselves "one thousand and one, one thousand and two,
OK, now I can talk". Unless you are desperate never put
more than one PL decoder between the user and the system
transmitter.
One of the systems I helped set up used 146-to-420MHz
at the outlying sites with the discriminator audio fed to a
brick-wall amplitude limiter fed to the link TX modulator.
The link RXs were 420MHz Maxtracs. Up to this point in
the hardware the entire system was carrier squelch. The
main user PL decoder (100hz) was on the voter output
and fed the PL decode line of the repeater controller.
This way if you came up with 100hz any RX would work.
Later the individual link Maxtrac RXs were programmed
for different PLs and diode OR'ed together with the main
user PL decoder. The unique PL tones were intended for
the repeater committee members to RX test site coverage
with but ended up with the users using them as well. If
you came up with, for example, 107.2Hz only link #1 RX
would open, or 123.0HZ brought up RX #3, but the OR'ed
PL decode lines caused the repeater controller to see a
PL decode signal and the system came up. So for the
cost of programming the Maxtracs for active-low-PL
decode and a few diodes the system had remote system
diagnosis... it didn't take knowing the 420mhz link
frequencies and a scanner to determine that, for example,
the south receiver was numb.... the end-user could use his
HT with the proper unique PL tone and see how quieting
they were.
Mike WA6ILQ
At 03:00 PM 2/23/05, you wrote:
>Definately,single point decoding is the way to go here,let the remote
>pass all that it hears and let the decoder and voter sort it out. Also
>allows the use of multiple tones thru the system instead of being
>limited to just one. BTDT...73,Lee
>
>Bob wrote:
>
> >Another in my periodic series of questions dealing with "best
> >practices" (dontcha love bidness buzzwords?!) regarding remote
> >receivers:
> >
> >In a system using remote receivers RF-linked back to a voter at the
> >main site, should each satellite (remote receiver, that is,
> >not "orbiting body") strip out and regenerate PL, or is it sufficient
> >to simply let PL pass through and let all decoding occur at the main
> >site? Assume "flat" audio throughout.
> >
> >Tnx es 73 de Bob
> >K5IQ
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