[Milsurplus] more chopper information

[J. Forster]

Choppers were (are) expensive. I'd guess that a good one cost at least $50
in the 1960s.

The trick of having an amplifier with a gain of +1 or -1 depending on a
SPST switch was a common way of building a synchronous detector in those
days. It's easy w/ an opamp and a few resistors. I did several.

-John

===============




> More chopper fun! The choppers in the 618S1, ARC-38 and 38A are all
> Collins 354-1021-00 they also have an Airpax 300 part number on them. The
> 180L automatic antenna tuners use a larger chopper Collins 354-1014-00 or
> Oak NC600 All appear to be 6 volt 400 cycle  seven pin base and all have
> the same internal alignment of the pins, coil pins 3 and 4 ground and
> shield pins 2and 5 contacts pins 1 and 6 and arm on pin 7. Interesting
> that the chopper in the 180L dose double duty. The arm is grounded and one
> contact interrupts the feed to the loading servo and the other contact
> interrupts the feed to the phase servo so two different amplifiers only
> need one chopper, once again those guys in the fifties were good.
> Ray Fantini KA3EKH
>
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