Apollo Comms Part 3: Inside the S-Band Transponder

We take a closer look at the S-Band transponder from the Apollo command module, and marvel at the 5 transmitters and receivers it contains. The transponder was manufactured by Motorola, and is entirely solid-state.

0:00 Recap of previous episodes
1:56 Overall block diagram
5:49 Looking inside
11:18 Detailed explanation (with elevator music!)
16:28 Every wire of the transponder explained (in technicolor!)

Links to doc:

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Music credits: Crinoline dreams by Kevin Macleod

[waltneitzel]

Interesting, I was a SDDS ( Signal Data Demodulator system ) technician at the time at a tracking station during Apollo. The equipment you are showing was unknown to me as I was downstream from the USB antenna system, about a half mile away, at the the actual tracking station where all the data was sent, decoded, and recorded and equipment called a PCM decoded all the down linked digital data. These signals had sub carriers PM and FM which contained voice and video which also had to to be decoded further by the SDDS for the digital and video data to be recorded and sent to Houston. It has been a long time, but I still remember some of the equipment and procedures. You might not be aware of it but all the timing for these systems used a Cesium beam time standard calibrated to the NBS time standard at Ft. Collins Colorado, because the spacecraft tracking with the USB required very precise timing.

[gusbert]

Bugger me. That is just microwave porn you have there. Black arts indeed, every time you show the Apollo hardware, I just realise that the Apollo engineers were so utterly brilliant, it makes me want to cry. I have often said that if I could make a wish it would be that I could have been involved in some small way in the Apollo program, I wish this so much that sometimes my heart would burst.

[Dennis-ucgm]

Designed by guys in white shirts and tie, a cig hanging from left lip and a slide rule in their hands . A brilliant designed piece of equipment for its time.. and to the people who questioned why we spent the money if they just could realize all the spin off's that came off of things like this we enjoy today.

[hightensionlabs]

Nothing like a bit of solid 60’s RF engineering to put a smile on ones face 👍😀

[ProdigalPorcupine]

I've got to admit - I'd love to see inside those modules! I'm fascinated to see how they managed to create this masterpiece with the components they had available back then. The compact size for such a complex device makes this a masterpiece IMO.

[senilyDeluxe]

Marc: Err hi, is this International Space Station?
ISS: Yes, but how did you get on this frequency?
Marc: Well you wouldn't believe this...

[finsterbarry]

Who the hell give such a video a thumbs down???
Please never stop making videos Marc!

[LMacNeill]

Wow! The *ABSOLUTE GENIUS* it took to design and build this system in the 1960s -- hell, it'd still be difficult to do TODAY! I can't imagine what it took to get it done in the '60s. Seriously, SERIOUSLY impressive stuff here!!

The more I learn, the more I realize how much I don't know. Absolutely LOVE these videos! Keep 'em coming!!

[BDJones]

I don't have a clue what the hell Marc just said but I absolutely love it. I hope he keeps doing more of these style videos. I love getting into the fundamentals of how things work. Fascinating.

[Sloxx]

Another video to add to my Curious Marc marathon tonight when I get some time to watch these! You get to play with the coolest stuff I tell you

[mlodzin]

So nice to watch this vintage Apollo stuff! It's
amazing to see that space-technology from years back.

[peep]

My dad worked on department of defense radar contracts in the 60s for GE and that was one of his great electronics loves that he passed on to me. So while not directly related, a lot of these parts are familiar. This is exceptionally cool and your knowledge is impressive

[repatch]

Holy crap! What an incredible job, both on your part, and of course the MANY engineers who built this thing! Amazing that so much of that can be done in a chip or two today

[Spookieham]

I have an Electronics Degree and an Amateur Radio licence and to be honest I have to concentrate on following some of these videos. Ironically you don't need to be an expert or even knowlegable to enjoy them which I what I love about Marc's channel.

[rubysausages]

Good day Marc... Since subscribing to your channel months ago one wish I have is for Voyager to come full circle back to Earth 🌍 and land in your garden for a CuriousMarc documentary.. Oh and to play that gold record with the sounds of the Earth... Romantic sigh... ♥

[DenDodde]

Can't wait for the next episode! This is so exiting!

[zeeclone]

I read microwave Comms at university. I still have the text books above my desk to remind me of how little I understand of how the damned things work.
My lecturer did pay me the highest complement I had at uni though: "You have one of the finest research minds of an undergraduate I have met in many years." I just wish my mental health had been in a place where I could have made a run at an EngD. Oh well. The paths left un-trodden.

[Aengus]

At 04:14 the time delay back at Houston when using "Ranging" gives distance but also the frequency shift gives velocity either away or towards the receiver using Doppler shift.

[AmauryJacquot]

"we could be silly and open it"
spit my coffee !

[PabloA]

Superb work Mark! Amazing to see your videos!