skipp025 wrote:
>Sometimes there is no free Commercial radio lunch... a standard converted
>Micor Mobile will start in chassis desense at power levels above 30-40 watts.
>
I have converted about 100 Motorola Micor Mobiles to repeaters. They
have included types from Low Band, High Band, and UHF, and RailRoad
versions.
I have *never* seen an in cabinet desense issue, even with a 6 meter
unit at 500 Kc separation, or a 2M unit with 600 Kc separation, either
one running 110 watts, or more. Some Micor Low Band mobiles will easily
do 150 watts. While I won't run a mobile at those levels continuously,
I have thoroughly tested them and have never seen one ounce of desense.
In the units you have experienced these problems, have they been
properly converted? Double shielded RX cabling? What band? Have the
Audio & Squelch Boards had the duplex RF bypassing done? Where do you
believe the desense to have been ingressing, at an RF level, or audio?
Realize that the Micor Mobile AF amplifier will exhibit desense issues.
I have traced these issues back to the large filter capacitor on the
interconnect board; which has dried out. Also, even when the AF amp is
experiencing difficulty, the audio from the Emitter Follower is clean,
and since this is where I choose to get the audio that is to be
repeated, no ill effects are ever seen in real practice. So, are you
sure the desense you heard was being retransmitted, or was it simply
disturbing the local speaker?
Brian Martens of ICS Controllers will be releasing a custom controller
for the Motorola Micor Mobile repeater conversion (if he hasn't
already). At my recommendation, he has included an on-board AF amp that
allows the OEM Micor AF PA to be removed, resulting in less current
draw, and it gets around the Micor's audio amplifier's shortcomings when
a mobile radio is used as a repeater.
>I'm sure the converted high powered mitreks also suffer from the same problem.
>
I have experienced desense in *some* of the 2M conversions I have done
on the Mitrek.
Kevin Custer
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