[Milsurplus] Aircraft comms on MF

[Hue Miller]

>From time to time comes up the question of aircraft comm equipment working 
on LF and MF.
We are not, of course, dealing with the usual RDF equipment. The issue is 
raised by the existence,
for example, of the most noteworthy transmitters of this kind, the 
super-rare Command Sets in the
500 - 1300 kHz range. The theories, if I understand correctly, are that this 
makes possible communicating
with ships, or for working at overseas, foreign country airfields working 
with maybe antiquated
equipment in this frequency range. I promoted the fact that aircraft could 
send homing signals for
other planes equipped with usual DF equipment to form up with them. My 
memory is a little sketchy
on this, but I think this was done in the case of the locating of the 
Indianapolis survivors - one
plane sent homing signals for others to center on. Another use of LF and MF 
transmit is to get
bearing information from ground DF stations - the QTE request. This is 
pretty well documented and
I mentioned in the past a book memoir of an aircraft radio operator which 
recounts frequent
instances of this.
These uses may leave open the question, why then the smaller aircraft 
transmitters in the LF and
MF bands. What were they about?
I am cleaning up around here and I found a manual for the U.S. Navy MB-1 
radio. The date is
nowhere to be found in the manual, even on the drawings - but, the 
manufacturer is Westinghouse
and there is a loose page included which lists Westinghouse manufacturing 
plants, sales offices,
and repair locations. This page is from the 'Westinghouse Press' and dated 
10-1929. Note that
date. Broadcasting in the U.S.A. was in full swing at that date. The MB-1 
operates 545-995 kHz.

The manual:  "This equipment is intended primarily for use on observation 
and certain scouting planes
of the U.S. Navy. It is to be used to effect communication with ship 
stations and other aircraft within
the vicinity.....
Model MB-1 radio equipment is designed to U.S. Navy Specifications for use 
on airplanes and is
especially intended for fire control spotting work."

End quote. The transmitter uses 2 CG-2566 tubes driven by one in a crystal 
oscillator. The plate
current total is approx 300 mA at 500 volts. Now here's an odd statement:
"When the tube is used as an oscillator or R. F. amplifier....The D. C. 
plate current should be held
below the maximum figure of 060 M.A. which is not possible in this set 
because of the large output
required. "

W.E.P. ?  ( War Emergency Power ) ( joking. )

Broadcasters were using these frequencies in 1929. Why would the Navy use 
the same band?
They needed frequencies. And, THEY COULD.  Basically the same reasons you 
see WW2 German armored
vehicles and radio trucks using frequencies in the 1 - 3 MHz band.

I do not have an MB-1. The radio I have is an ME-1, which tunes 3000 - 4000 
kHz; otherwise the circuit is
similar. The date is the same, 1929. The receiver on both is 4-tube 
regenerative.
-Hue Miller