[Milsurplus] BC-443/SCR-263 Radio Compass

[J. Forster]

Unserviceable but Repairable wrote:

> Sean I think you've hit on something that's bugged me a long time
>
> I know the BC-433 in the SCR-269 has a rear add-on package to steer the
> LP-19 loop.  Two of the 5 xtra tubes over the '443 are 2050 thyratrons.
> The SCR-269 is the precursor to the ARN-7 & if B24 Lady Be Good had one
> she wudn't have made that long unscheduled Sahara stop
>
> Amazing what 5 tubes, some physics/math, & a design genius will buy.
>
> Today the loop steering function would AT LEAST be a uP, dozens
> of glue chips, and a softwhere team of the largely arithmetic/ee-
> challenged to muddle it out.

Possibly. It could likely be done w/o ICs. Five transistors/SCRs would likely do
it.

The addition of automatic control to a loop is pretty straight forward:

The L-R indicator is basically a phase meter that indicates the difference
between the reference phase, the loop switch driving waveform, and the detected
RF signal.

The automatic function just takes this phase signal and uses it to drive the
loop in the direction of null. In an MN-31, which was an MN-26 with an added
Loop Control box,  some of the tubes were power amplifiers for the receiver and
reference outputs, and the phase detection was done with the 2050 thyratrons.
Really pretty simple.

-John