[SMCARA] GM300 servicing

[Daniel Metcalf - W3DMJ]

For those who haven't heard yet a small group of us are building two
"portable" UHF repeaters. Portable meaning everything needed, except
antenna and mast, is in a single container that could be setup anywhere.
We are working to make work off of solar and batteries. The trouble is
the power for the radios and the controller is easy to manage. It is the
amplifier that is going to be the power hog (at least in theory).

Anyway having found a supplier of GM300 radios we now have several.
Being I got these off of EBay used I have been testing them out and
really getting to know these radios. 

First challenge, the previous users liked the ignition sense feature of
these radio but to activate it a fuse on the main board has to be
"removed". I say "removed" because they physically exist in the board
but are blown (I have 50 on the way from China only paid $12). Should be
easy enough to replace.

Second Challenge, getting the radios programmed. I became a member of
the Radio Doctor yahoo group and they have the Motorola RSS software on
their site for the Radius GM300 as well as a visual basic program to
program the radio. There is a real disadvantage using the VB program as
once you use it to program a radio you will not be able to use the RSS
software again. At least not until I figure out which value is out of
range and crashes the rss software. The RSS software is tricky as it
will not run natively on modern machines as it is a dos program. I have
found, being I run linux as the main OS on my laptop, that I have to run
Windows inside of a VirtualBox virtual machine and then run dosbox in
the virtual machine. Setting the clock speed to 191 in dosbox has been
working for me.

Third Challenge, Squelch. It seems the previous user only wanted the
best signals coming through as they had the potentiometer on the main
board that sets the squelch level cranked full on. The potentiometer was
easy to find once I had an idea where to look as it was labeled "SQ" on
the board. Bring the squelch down was key to communicating with Ken
(KB3YPY) last night on Pete's repeater before having to go participate
in "Forced Family Fun Time" (we watched a movie). With the squelch as
high as it was nothing was getting through except for my HT that we only
feet away. Thank You YouTube!

Fourth Challenge, Now that I have 5 of the 8 (the other three are
waiting for the fuses) radios programmed with two channels using 446.000
MHz for channel 1 and Pete's WA3UMY repeater for channel 2 I have found
that not all were putting out their rated 40Watts. So I had to borrow a
Bird Wattmeter with a UHF slug from Rob (K3RWR) and had to learn the RSS
software to make the RF board adjustments which as it turns out is done
in real time. Now I have them all set to the appropriate power levels I
noticed in my testing last night that some are better receivers than
others which tells me I have some servicing to do. 

Which brings me to my question. Has anyone serviced a Motorola Radius
GM300 UHF 40W radio to include adjusting the receiver sensitivity and
receiver alignment (making sure it is listening where I tell it to
listen)? Does any one have the gear or knows what gear would be needed
to perform such a task?

I have the schematics, users manual and service manual. I am not sure
the service manual is complete because at first glance it didn't seem
very instructive. 

Well just another way to have fun in the Amateur Radio Hobby!

73,
Dan Metcalf - W3DMJ
c. 301 769 1111