[Boatanchors] RE: Collins 180L auto tuner

[Dave Maples]

WARNING: LONG POST.  SKIP IF NOT INTERESTED IN THE TUNER...

Keith: I had a Collins 180L antenna tuner for a number of years.  Never got
it to work, although I fiddled with it for a while.

This is a really interesting tuner, for those who have never seen one.  It's
basically the following in series from the radio connection to the antenna
connection:

a. Impedance discriminator (really neat Collins design).  These could be
purchased independently from Fair Radio Sales at one time (don't know if
they are still available). They provided two separate outputs for reactance
and resistance; when 50+j0 is reached, zero output occurred from both
outputs.  Truly very neat.

b. Center-tapped roller inductor used as an autotransformer between the
radio and the rest of the tuner.  This roller inductor is driven from the
400 Hz power supply through a vacuum-tube amplifier.  This is another neat
piece...good way to adjust for odd resistive impedances.

c. Roller inductor--this is really interesting.  Collins solved the problem
of decreasing the Q of the inductor when turns are shorted by having TWO
rollers geared together--one metal and one phenolic.  A strip of silver wire
is rolled from one roller to the other to increase or decrease the
inductance (as the silver wire lands on the metal roller, it is, of course,
all shorted together).

d. Vacuum-variable capacitor (6-1000 pf, I believe).

e. Switched fixed capacitor from the antenna connection to ground (the tuner
engages this only if it can't get a match otherwise).

Basic operation:

1. Prestage inductor, capacitor, and center-tapped autotransformer.

2. Adjust inductor and capacitor to zero out reactance in line.

3. Adjust autotranformer to provide 50-ohm match.

The detailed tuning algorithm is rather unusual due to the response
characteristic of the impedance discriminator in the unit.  This and a lot
of other good data is in the manual.

If you don't have a complete manual, I believe you can get a repro from Fair
Radio Sales.  Without the manual (particularly the part on the tuning
algorithm) I think you'd have a pretty hard time getting it to work again.

You will also need a 24 VDC supply, a 250 VDC supply, and a supply that puts
out 115 VAC @ 400 Hz.  The 400 Hz supply drives  The last can be obtained
with a 400 Hz oscillator driving a complementary pair, or a relatively cheap
audio amplifier.  You could pick up a 400 Hz transformer on the surplus
market (again, Fair Radio or elsewhere) and build a pretty good 400 Hz
supply for not a lot of effort.  The other thing you might (or might not)
want to spend $$ on is the matching connector for the front panel.  William
A. Perry Co can probably supply that, but I really don't know another place
to find one.  It's a real booger to find (very wierd, very expensive
connector from ITT Cannon).

If you have time to devote to it, it might be a pleasure to make the thing
work.  On the other hand, if you DON'T have a lot of time to tinker, you may
not want to wade into it.

It's an interesting winter project, methinks.  I had notions of getting mine
to work with an ARC-38A aircraft SSB transceiver.  I still have the power
supplies, but got rid of the radio and the tuner when I moved from Louisiana
to here in Northern VA 6 years ago.

Hope this helps.

Dave WB4FUR
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