We get NASA Apollo Comms Test Equipment! (Patreon)

We recently got quite a few more mystery boxes from Steve Jurvetson's garage. Steve had bought a large lot, mostly for the flown artifacts in it. But it also came with a pile of somewhat generic ground equipment boxes, and he was unsure whether he was going to keep them in his collection or put them up for sale. However, he brought them to our attention, and looking at the pictures, it seemed that they might be related to Apollo S-band communications. So we picked them all up for a closer look in the lab, to the great excitement of his wife, whom did not particularly appreciate the big pile of old stuff in the garage...

We ended up with 7 large boxes, with no description nor documentation whatsoever. But our suspicions were quickly confirmed. Not only were they related to S-Band communication, but we figured out that taken together, they formed the ground test set for the Apollo command module transponder he had just given us in our previous visit! What a timely find! We don't have everything, but we have a lot of it.

In particular, we have the two earth-side microwave receivers: the PM (Phase Modulation) and the FM (Frequency Modulation) receivers, made by Motorola, that we would have to otherwise reproduce on our own to establish a link with our transponder.

See the PM receiver below. This was used for primary voice downlink, data downlink, backup voice, ranging and doppler telemetry (in connection with several other boxes). The PM receiver was going to be a bit difficult to replicate, so that's super good news.

And see the FM receiver below. This one was used for the all important TV downlink from the moon, as well as recorded data/voice tape dumps and backup data downlink.

But these only do the front-end microwave S-Band receiving. You have to follow them up with all the subcarrier demodulating equipment for voice, data, and telemetry. Which then has to be followed up by more data decoding and ranging equipment.

Fortunately, this next box seems to do some subcarrier work for both the ground uplink side (labeled STE MOD) and the space transponder downlink side (labeled USBE). At least that's my thinking, as there is no documentation on any of these.

But the box that we first turned most of our attention to was the more esoteric "Transponder Mount" box. It made little sense, unless you had just studied the USB transponder in detail like we did. 

It appeared to have the row of buttons that we were about to remake to power and control the transponder!

It also has all kinds of interesting RF and IF stuff inside. Some cables were missing, cut, or had been re-routed in our box, which kept us on our toes.

We eventually figured it all out, and we think we understand what every screw does. We rewired it correctly, repaired a few things, and powered it up.  Once all the contacts and lamps issues were ironed out, it lit up like a Christmas tree.

The transponder under test is supposed to fit in the drawer below (hence the "Transponder Mount" moniker).

The transponder then connects to the RF ports above, to the two multiple pin round connectors (one above, one on the side), as well as 4 coaxes that had been cut (you can see some remnants lying in the drawer). If we can redo all the cabling harnesses, we should be ready to test our transponder like in the good old NASA Apollo days!

Marc