[Collins] 18S-4 & ARC-38A

[Michael Tauson]

Hi, Jerry,

> There might be a couple ways to get LSB. Surely its more than single
> conversion, moving either oscillator to the other side can change the
> side band without wrecking the calibration, probably. 

If it's like the 618S-1 from which it was derived (via a long and curlycue
path), it's single conversion.  However, I don't know what all Collins did in
converting it to a Stabilized Master Oscillator & SSB rig.  

> Then many Collins mechanical filters were made in USB/LSB pairs for
> the same carrier frequency so all it would take to get LSB would be to
> switch in the other half of the pair. Those pairs tended to be
> asymmetrical with a sharper cutoff at the carrier side than the high
> audio side of the pass band.

I don't rememebr seeing a pair like that for 250 KHz but I'll look again.

> Rubbering is most likely easiest by rubbering the reference oscillator
> for the synthesizer, unless there is an offset oscillator and then
> rubbering the offset oscillator also works. Often in vintage
> synthesizers there is an offset crystal because the programmable TTL
> counters couldn't count to 30 MHz reliably.

Food for thought.  Thanks. <G>

> I'd guess that the connectors are standard Mil Spec, probably catalog
> items, but they could have been permuted for insert position compared to
> shell indices. The makers allowed for that, but distributors often
> don't. Could be threaded series or bayonet series and still be in the
> Mouser, Allied, or Newark catalogs.

The ones for the RT sets are attached to the rack and are more like ... um,
Winchester? connectors.  The control box connectors are likely Cannon
connectors of some order so shouldn't be that difficult to either find or
fabricate.  On the other talon, if they were that easy to find, others looking
for the same connectors would already have a known source and thus far it's
been no joy.  

Okay, off to fix a compound cross slide ... <G>

BEst regards and thanks,

Michael, K3MXO


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