Motorola 77XM21 AM / FM Radio

I had been on the prowl for an antique radio for a few months thinking that it would be nice to have a working vintage radio in my office for both a conversation piece and listening to of course.

After doing some research I decided on the 77XM21 by Motorola from 1948.  This is the perfect radio in my opinion.  First it is vintage but also incorporates FM which most people listen to today.  The best of both worlds so to speak, or at least in my mind, which of course is the only thing that is really important.... to me anyway.

I received my purchase in the mail and to my dismay the side cabinet was cracked in several places, but a little super-glue and then some ultra-fine grit sand paper good as new.  I powered it up and it sounds fantastic!  Hopefully in the next few days (who am I kidding.... maybe next few months) I will have the opportunity to go through the electronics and refresh the capacitors and fix the only issue that I was able to find with the radio which is that it has a hard time tuning at the upper end of either band.  This seems to be a problem with the mechanics of the tuner not the electronics, but we shall see.

Happy listening.

MotoTrbo XPR 4580 - 33cm (902 MHz) Amateur Radio

Well I finally upgraded the 900MHz radio in the car from a 12 watt GTX to a 30 watt /\/\otoTrbo.  So far, as in the last fifteen minutes, I like the radio.  The best in use feature is the expanded 16 character display instead of just the channel indicator as in the GTX.

The road to using this radio wasn't the easiest however but here is my story... maybe it will help.

First the instructions to program out of band here, http://www.qsl.net/n9zia/motortrbo_to_927MHz.html are what you need to actually program the radio in addition to the CPS and appropriate cable.  The CPS is RVN5115Y currently and the cable part number is HKN6184C.

My radio started off as the 800/900 3600bps trunking model which I thought was ideal since there is one public safety agency in the area that is still on an analog trunking system so in addition to the 33cm ham band I was going to use the radio as a scanner for that agency... or at least that was the plan.

After getting the cable and software from /\/\otorola I was off to the programming.  I got all of the local repeaters plugged in and logically it is time to test.  This is where things went south... the VCO wouldn't lock about 902.0000 MHz though receive on 927+ was perfect.

An afternoon of searching found a few posts of people having no problem programming their radio to do 33cm.  Come to find out that they all had conventional / DMR software in their radio.  I found a post or two that indicated that others with 3600 bps trunking had similar VCO lock issues that I experienced.

Off to the Business Online website to get convetional firmware.  An evening of upgrading the radio... or 30 minutes anyway, and now I have a conventional only radio. Programmed it up and viola... transmitting as expected on 902.XXXX.

Moral of the story is DMR / Conventional seems fine for 902 MHz but the 3600 bps option will produce the VCO lock issue.

Hope this helps someone else.

73