[Milsurplus] I-81-A Radio Compass Indicator

[J. Forster]

That is what I thought.

It's just amazing what the engineers did with selsyns, gears, and motors
in WW II.

The Battleship Massachusetts has a bunch of such computing mechanisms in
the Dead Reckoning and other systems. The mechanisms can:

Add
Subtract
Multiply
Divide
Integrate
Differentiate
Trig functions.

All without a single tube or transistoe. AND, they are still working
accurately after 70+ years.


Take that iPods!

-John

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



>
> All the radiocompass selsyn indicators I-81, I-82, MN-92 ( MN-92 is a rare
> lighted I-82) used with SCR 269 and ARN 7 run on about 26 VAC 400 hz. If
> you are using a square wave 400 hz source they will be very noisy
> (actually screechy) and a bit sluggish and jumpy. They run smooth and
> quiet on a pure harmonic free sine wave from a rotary inverter.
>
> Funny how much radiocompass gear was bought surplus. I-82s in seemingly
> endless numbers show up serially on eBay. At a ham swap last month a guy
> had a bunch of brand new loop compensators and selsyns for the LP 21 loop
> antenna. They were too pricey ($30 each) and those things never ever wear
> out so I passed.
>
> That MC 203? loop compensator is a really ingenious piece of mechanical
> engineering. Nowadays you'd need shaft encoders, azimuth offset lookup
> tables and some software to accomplish the same thing.
>
> 73,
> Mark
> AF6IM
> See photos from Pacificon 2010 Parachute Mobile jumps.
> https://sites.google.com/site/boeing377/parachute-mobile-pacificon-2010-jumps
>
>
>
> =
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