MTS2000 mute problem

[TechHead]

3 x MTS2000 model II are exhibiting a mute issue when programmed with conventional 12.5khz non-PL frequencies (the new local UHF CB channel set). The units were decommissioned from various commercial services using 12.5khz spacing, but with PL on the frequencies programmed.

With the TX deviation to 2.5khz so the steps suit 12.5khz, the radio's mute is loose i.e. it opens on many channels with noise. No other services are using adjacent channels to cause the mute to open and being 3 different units from different sources, suggests it is a programming or common radio setup issue rather than a fault.

Increasing the squelch factor even up to its max of 31 has no effect. Change the deviation back to 5khz so the radio reverts to 25khz spacing and the mute behaves i.e. it closes, although it does not appear well advanced nor does it snap closed.

The same issue occurs over the full frequency range of the units, so they do not appear to have been tweaked for a particular range.

They have been programmed with CPS R01.13.00
Receive squelch type is set CSQ
Unmute/mute type is set Unmute, or mute
Receive unmute delay is set 1ms
Squelch (fine tune) is set to 3 (but as above, advancing it doesn’t have any effect)
TX & RX Emphasis are both set on.

Suggestions would be appreciated ……..

[TechHead]

For posterity, in case someone is searching in the future with the same issue, the solution is to use MTS2000 Tuner, which allows the mute to be set with different thresholds for various band segments.