[JMS] WTB: Millen 90700 Vari-Arm Coupling Unit

[Robert Nickels]

My understanding is the Variarm VFO originated with an article in QST in 
January 1941 by Henry B Rice W9YZH, "The "Variarm 150" - A simple ECO 
Exciter and it's Power Supply".    It was the cover article and I 
presume Millen picked up the design and offered it commercially.   The 
resemblance to Rice's original is very strong.     A few years ago I 
picked up a homebrew clone that was quite nicely done including an 
output coupler mounted in a small tin can that used a 4-pin plug-in 
coil.  The one that I have was for 80 meters but is identical in design 
to the schematic:

It  should be simple enough to wind up a coil and make a homebrew clone 
of the output coupler, although since the output of the 25L6 amplifier 
already has an identical tuned circuit, I don't really see the need for 
it.  Recall that back then it was a bit of a challenge to put a stable 
VFO signal on the higher bands, so it was common to run the oscillator 
at a low frequency and multiply up to the desired band.   Hams were 
expected to figure these things out and most transmitters were homebrew 
so a typical setup might be to make a 7 MHz output from the VFO and 
mulitiply in the transmitter to reach 10 meters, for example.     Most 
"modern" transmitters should be happy with the up-to-2 watts from the 
Variarm VFO.

73, Bob W9RAN