Joe,
I think you forgot another likely reason: The HIGH PASS FILTER in the
mic circuit. Like the high frequency energy, there is also a lot of low
frequency energy (below 300 Hz) on simplex that is being stripped by the
high pass filter in the mic circuit that ensures CTCSS frequencies in
the user's voice don't false decoders or interfere with the transmitted
CTCSS. I don't think that HPF is on the PL board on a Mitrek, but I
could be wrong. I don't have any books at home right now for one.
I think your best solution is to run unprocessed audio (no de-emph - no
preemph). If you do, most of your audio coloring should go away. I don't
recall the audio chain of the Mitrek exciter, so you may have to add
limiting and LPF'ing to the TX audio (Joe, weren't you working on an
aftermarket board to do that?). I know in some units, you can still use
the stock filtering, as the preemphasis (that you need to eliminate) is
before those stages. Of course, this would only apply to a FM exciter
(which the Mitrek is). It would not apply to a PM exciter.
Joe M.
Joe Montierth wrote:
>
> 2: The LPF filter in the Mitrek tends to start some
> rolloff at 2KHz or so, causing some loss in high end
> energy that is still there on simplex.
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