[Motorola] Motorola PT Radios

[Geoff Fors]

The PT-200/300/400 receivers sometimes have bad Permakay filters in them so
if you can't get one to align, that may be the reason.  I used to work on a
lot of these back about 25 years ago and we were seeing maybe a 5-10%
failure rate in those sealed filters at that time.  I don't know why.

You'll need to make up an extension cable to service them, the usual
procedure is to clamp the handle in a bench vise with the boards facing you
and go from there.

It's very hard to measure the oscillator peak on the receiver with an
ordinary VTVM or the equivalent.  I found that you have to use an RF probe
capable of reading small signals and do it that way, or use an RF
millivoltmeter (preferred way.)

There's also a weird radio, the MP-500, which I think was a special item
made for Amtrak or some big railroads.  It's basically an MH-10 HT with a
high power RF PA added, sitting on a lantern battery power supply.  There's
no speaker in it, it just uses an old MH-10 Handie-Talkie speaker mike.
About 10W RF out.  Otherwise unremarkable.

Geoff
WB6NVH