[Motorola] 1960s Motorola Base

[Geoff Fors]

The old BY base station should tune down to 146.52 with just a couple of
mods.  The receiver will have a problem, however, going too far below that
because the cavity pipes run out of electrical length.  Unless you happen to
have a rare 130-150 MHz military version.

The transmitters were available in several models such as the 829B model.
Usually the transmitter will not tune properly down to the 146 range by the
time you get to the final amplifier.  There is a set of round disks on the
plate lines which should be screwed close together (without shorting them!)
and in all likelihood you will need to add some capacity across the tuned
lines to fully resonate it at 146.52.  This was often done with a
couple-inch piece of RG-58 soldered across the lines, open-ended.

The Sensicon-A high band receiver is a wonderful thing which will last
virtually forever and should give you a bit better than 0.5 microvolt
sensitivity when you are finished.  I used to use ex-radar 5654 tubes in the
front ends.

You can find the manuals on eBay regularly, usually described as a "Research
Line" manual.  The base manuals show up less frequently but the Research and
Twin-V mobiles used the same TX and RX strips (in the older 15" cased high
power models.)  You can also find the Motorola test sets there although the
BY series usually had a metering kit built-in.  I have the documentation in
my library but I won't be able to help anybody until after April 15th due to
work pressures.

For anyone interested in working on "historic" tube type Motorola equipment,
try to get a copy of the "FM Schematic Digest" by S. Wolf.  They show up on
eBay from time to time and usually go begging.  This huge book has
schematics of all the Motorola FM gear from 1942-62 including tune-up guides
and crystal data.  There were at least a couple editions.  The last one is
red, and there is an earlier, slightly smaller yellow edition.  There is
also an excellent small booklet titled "Converting Commercial FM Gear" by
Glenn Zook, K9STH which was published in the early 1970's by 73 Magazine and
has lots of useful information, although today it seems very rare.  I think
Glenn is actually a subscriber to this list!

Finally, don't worry if your unit is wideband (15 KHz deviation.)  Just
crank the deviation down to 5 KHz.  The receiver doesn't care one way or the
other.

Geoff Fors
WB6NVH