[R-390] Mason Labs R-390A?

[Tisha Hayes]

Some people romanticize the idea that the R-390A was used to listen to
Apollo moon landings but the reality was different;

The Apollo missions primarily operated in the S-Band (around 2.1 GHz) with
some backup capability at 296.9 MHz. If you dig in the references you will
see that the Gemini capsules did have HF capability at 15.016 MHz but it is
not documented if it was ever used. By Apollo the references to the 15.016
MHz system was dropped but maybe it was something available as a
post-splashdown SAR/recovery unit in addition to the 296.9 (and maybe
243.0) aviation-type radios.

In the S-Band the system operated off of a PM (like FM) carrier with
sub-carriers for voice and telemetry. Some of the sub-carriers could be
turned off and the main carrier was also used for position/ velocity
tracking with a pretty high degree of accuracy.

At one time I thought that the capability of putting an external oscillator
on an R-390A might have something to do with compensating for doppler shift
(from spacecraft motion) but it makes more sense that it would be used for
high-stability operations with HF RTTY/Data on fixed or maybe even
shipboard operations. During Apollo, NASA had lots of tracking stations on
land and at sea.

*Ms. Tisha Hayes*

*AA4HA*