[Motorola] Funny-Acting Micor Question

[Eric Lemmon]

Jay,

Carrier-squelch MICOR radios are not intended to deal with users who are
transmitting CTCSS tones.  One solution is to install a TRN6002 PL
decoder on the Audio & Squelch board.  A high-pass filter on this board
does a very good job of cutting off anything below 300 Hz, so PL tones
won't get through.  Just set the PL Disable switch on the Station
Control module to ON, and be sure to cut JU201 on the A&S card so that
audio is routed through the filter.  (I am surprised that this repeater
is not required by the coordinating body to have CTCSS decode.)

Another potential cause of your problem is the sad fact that many
Amateur transceivers have the CTCSS tone deviation set far higher than
necessary, sometimes nearly triple the proper value of 400-600 Hz. 
Actually, I should not use the term "set," because this parameter is
seldom adjustable in Amateur radios, and the makers apparently think
that "more is better."  Alinco radios seem to be the worst; every Alinco
radio I have tested had CTCSS deviation above 1000 Hz.  It took some
creative surgery to pad it down to around 500 Hz.  Excessive CTCSS
deviation is bad, because the voice deviation is summed with the CTCSS
deviation, and when the total reaches the deviation limit of 4.8 to 5.0
kHz, the PL may be distorted enough that the repeater mutes itself.

The worst-case scenario occurs when two inexpensive radios are using a
repeater that does not have a CTCSS filter:  The transmitting radio may
have excessive CTCSS deviation, and the receiving radios have no
high-pass filter in the audio chain.  The result is an annoying buzz
heard by everyone.

I strongly suggest that you add PL decode to this repeater, using
standard MICOR modules.  Good luck!

73, Eric Lemmon WB6FLY

James Coote wrote:
> 
> I will be helping someone with a repeater problem on a distant mountain top.
> 
> A carrier-squelched Micor repeater seems to boost or emphasize PL signals on
> the repeater input.  A subscriber radio PL is set to the norm, but on the
> output, the repeater is distorting the subscribers audio.  It happens on all
> subscribers in this carrier-operated repeater, when they forget and have PL
> enabled in their radios...