Apollo Comms Part 2: Inside the Traveling Wave Amplifier
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- čas přidán 29. 06. 2024
- We take a closer look at the S-Band power amplifier from the Apollo command module, and learn how traveling wave tubes brought us voice, TV and data back from the Moon. The amplifier was manufactured by Collins, who was the prime contractor for the entire Apollo telecommunication system.
00:00 Recap of previous episodes
01:53 Physical location of the amp in the CM
02:35 Identifying the main functional elements
08:02 RF switches and emergency modes
11:14 Actual audio of Apollo 13 using the emergency mode
12:46 Making sense of the coax maze
16:03 Taking the amp apart
17:45 Broken connector scare and repair
20:08 Identification and history of the TWT tube
22:28 TWT explanation
25:33 Outro and future work
Full Playlist: • Apollo Comms Part 1: O...
Ken Shirriff’s article on this TWT amplifier:
www.righto.com/2021/07/inside...
Links to doc:
www.curiousmarc.com/space/apo...
virtualagc.github.io/virtuala...
www.ibiblio.org/apollo/
Music credits: Crinoline dreams by Kevin Macleod.
Thanks to our sponsors
- PCBs: www.pcbway.com
- Test instruments: www.keysight.com
- Connectors: www.samtec.com
Support the team on Patreon: / curiousmarc
Buy shirts on Teespring: teespring.com/stores/curiousm...
Learn more on the companion site: www.curiousmarc.com
Contact info: czcams.com/users/curiousmarca... - Věda a technologie
I’m an actual RF engineer. You know, the kind that thinks saying “anything below one GHz is DC” is funny. But I wouldn’t have the balls to claim that I *understand* a TWT. Just in case I run into one of the inventors at a cocktail party. You never know.
Microwaves "The blackest of black arts" yes you are entirely correct.
I work on very high power TWTs. They are interesting devices.
Apollo getting those smartphone notification "ding" sounds. Just cant get away from them, even on the moon.
DANGER: Will Robinson! (actually Marc & Mike)
When you solder the center-conductor tip, always use 'resistance-soldering' tweezers! With the tweezers, you will not get solder on the outside of the gold-tip and create a blob that can prevent it from locking in place. Most of the tips also have a solder-hole in the side to allow solder to be feed into the tip and wire once heated with the tweezers. If not, then you do have to feed it from the rear but Standards of Workmanship for Soldering, specify that there should NOT be a rear-fillet, and adhere to both contour soldering techniques, with no-wicking of the solder past the front of the insulation of the wire by one wire-diameter. I realize this is not going into space or even be used but that is the standard that was to be followed.
Anyway, really love your videos and 'crew'; thanks so much for these deep-dives as future generations will watch your videos to learn this important history!
Marc: "This very long video"
Me after this video finishes: proceeds to rewatch the Apollo AGC series.
Husband: " you see darling, i am not the only one..."
Wife: "i wish i would hang over with his wife while you two get fun watching these "entertainment" videos..."
I truly don't understand how these videos don't already have millions of views. This is amazing equipment.
One of my cats looked up concerned as my office vibrated when the Saturn V took off at the beginning of the video. We weren't expecting that 😀
Thanks for sharing, Marc!
That's 20 tons of oxygenated kerosene burning ever second for two full minutes during liftoff delivering 7.5 million pounds of sustained thrust.
@@projectartichoke mind boggling
This video brings back memories of the times when I learned about traveling wave tubes at the university in the early 1980s. Our professor had worked for RCA and has been involved in the development of the TWTs for the Mariner satellites, so he had a real passion for this topic.
Interesting to see that TWTs still have applications where they cannot be matched by semiconductors.
And one of mine warned us in no uncertain terms about the dangers lurking in these devices, as one of his past students had been electrocuted working on one
Came her for the tech. Delighted by the elevator music. Keep em coming Marc!!!
As a Amateur radio operater this equpment breakdown fasinates me this was way ahead of it's time.
I've got a 20W TWTA from Siemens. 50 dB gain@10GHz. It runs on 24 VDC and has a switched mode power supply. Very cool device, it has never failed the past 30 years. I use it mainly for 3cm wideband ATV.
Wow...how much power does it consume from the power supply?
@@WolfgangMahringer probably less than 100 watts. TWTAs are ludicrously efficient compared to other microwave amplifiers, even though it's still only 20-30%.
Indeed about 100 Watts give or take. These now obsolete (in fact they were abandoned in the late 90's) modular devices were used abundantly in Europe to establish video links between transmission towers.
My 10 GHz station uses a Siemens TWT. It makes 15 watts or so.
@@gertebert Were they also used for the huge grid of telecom microwave relay towers dotted around western Europe? I remember those round towers with a ring of small parabolic antennas around the tops being recognizable landmarks when traveling on freeways (as a passenger). I have noticed that many have been mostly disabled in recent decades as reliance on buried fibers and satellite links have grown.
This was a really cool video, it really surpassed my expectations :)
The favourite parts:
- 11:15 - including the Apollo 13 sound recording about the amiplifier
- 22:28 - never heard of travelling wave tubes - and now I know how they work ! -sort of :) + bonus point for the elevator music
PS: One could say, that the travelling wave tubes in the Vaoyagers have been really "travelling" for a long time....
Thanks for pointing the times out. I just added chapters to help navigate that longish video.
@@CuriousMarc Thank you for including the timestamps
It amazes me that anyone could have conceived a traveling wave tube, much less build a working one. Necessity is the mother of invention, and apparently genius.
I'm with you on that one. Hats off to people that invent microwave contraptions and manage to make them work!
Like all good ideas, the TWT appears to be a combination of the earlier Magnetron and Klyston tubes. I can imagine an off hand comment in a stairwell, something along the lines of "what if we unwrapped a magnetron into a straight tube....".
I'm surprised TWT's are still used, but then we haven't found anything better than the magnetron for our domestic microwave ovens either.
Great videos! Keep up the good work.🙂
@Noel Coward Ha Ha!!!
I didn't catch that..
@Stephen Ferree What does the F16 and F35 use (if it's not classified)?
Don't remember how long TWTs have been around - We were using S band, C band, and X band TWTs in 1959 in military systems. The S band tubes were good for about one octave bandwidth even for the high power tubes ( 1 kw out ). C band and X band, less bandwidth in those days. Early high power TWTs used external solenoids for beam focusing and were somewhat troublesome to establish and maintain reliable operation because of this. Made my life much easier when permanent magnet high power TWTs became available in the early 60s.
Thanks for the insights! I read that the big difficulty at the time for permanent magnet TWT was making rare earth magnet. Only Bell Labs could make such magnets early on!
@@CuriousMarc I believe you're correct on the PM development problems - I should have mentioned that the 1 kw output levels were at about 1 % duty cycle - Some of the low power tubes could run cw at 100 %, but we had to include protective circuitry to insure max duty cycle was no more than 1% on the high power tubes.
@@CuriousMarc I knew that Alnico was the highest power usually available, didn’t realise it was a manufacturing issue rather than a discovery issue though! I’m going to thank every little commodity neodymium now :)
Edit: I see it was a different type entirely, samarium-cobalt! Fascinating! I can see how they were more expensive in every way!
i checked my phone couple of times until i realise notification sound coming from the video
Yep. So did I
And conversely I should change the beep on my phone to an Apollo end of call switch tone...
18:45 holy holiness that's an awesome document and that picture is so much zeitgeist :-)
Marc, if you want to try it "on the air", I have a set of L and S-Band "antenna hats" leftover from the APEX mission in the mid '90s. Would love to find them a useful home! They're presently collecting dust in my garden shed.
Antenna hats allow you to radiate into a small space lined with RF-absorbing foam and give you a fixed coupling coefficient to a sampling port.
I’ve been in many elevators and this is the best elevator music I’ve ever heard.
By the gifted Kevin Macleod. Which reminds me that I should dig the attribution and put it in the vid description.
I've heard Led Zeppelin, Pink Floyd slowed down in an elevator. I was ok, but it was strange.
To arrive the moon safe and sound, includes more than just launching a rocket. Hats off to the engineers considering every detail, to make this mission a success back more than fifty years ago, including the one presented here, among all the others of course. Hats off.
The Apollo program was an astoundingly ambitious, ground breaking, and complex effort. It's absolutely amazing what they accomplished in just a few years. Compare that with the expendable Senate Launch System (SLS) that is years behind schedule and many billions over budget even though it's using modified components developed for the STS and an Apollo style capsule. How the mighty have fallen.
Senate Launch System - I like this one!
Yes. And truely an American effort. More rockets are launched today but they USA couldn't launch an *American* rocket today if lives depended on it (most parts from foreign sources today).
@@kippie80 Serious question, isn’t SpaceX all American ?
@@nigeljames6017 Certainly "assembled in usa" but many subcomponents, majority even, are from abroad. I don't know exact #s but just observations it is clear. not like 60's where majority are made in usa. It would be interesting to see an accurate breakdown.
@@nigeljames6017 Nah, Elon is South African born :-) but sure his Father was American. I think the ideas was that many of the jelly beans are imported. I expect the same in every space program, lots of parts imported even in Russia or china.
It sounds like it's time to build a faraday cage in your basement so you can power up the amplifier.
Yeah, but Faraday cages are way cooler ;-)
@@CuriousMarc Not to mention you'd be shielded from getting Corona through 5G!=P
@@notadream-tt3cn Guys used to heat up food in RF "Hats" used for our ECM pods..it was a bad smell.
I think this will be one of my favourite series of technical videos on CZcams. I have been waiting for someone to go over the comms on Apollo for ages.
Sir You and your team are AMAZING. Now BOUNCE a signal off the Moon.
In Australia I would regularly go out to Honey Suckle and stand on the concrete pad where the dish was. It is cool to see the boxes that were at the other end.
en.wikipedia.org/wiki/Honeysuckle_Creek_Tracking_Station
It's amazing how much of technology that was ground breaking in the 1960s is still in use today. What might be called old isn't necessarily bad.
Underappreciated perhaps is your good use of background music in these early videos. Enjoying this series!
Rudolf Kompfner; how come I've never heard of him before? Talk about unsung heroes! Architecture to amazing electronics! I feel that his name should have been first and foremost in this video. I only got to him on re-watching the piece because the first time I tried to watch it I fell asleep (well, I do have my senior's card).
Thanks for the explanation of the traveling wave tube. That's really cool! I remember Apolo13 and seeing how the power amp was bypassed to conserve power was awesome. As an electronic test technician, I like your dives into the technology.
Loved ur video. I love Looking at the old technology an my heart is glad that technology from my father's day still has a place in today's ever shrinking solid state midea.
My father worked on electron pre circuit board. At a time i feel was more art. Even the circuitry had interesting names. I watched my dad work on tv's radio's to rhe sounds of the world coming in on his ham radio. This wasat a time you could walk in a. Seven Eleven an look though a vacuumtube bin for horizontal and vertical tubes an any other needed. This was magic to me. A simple ole country boy.
Gave me the world. Alxo gave mea life long love with electronic. Thanks for the video an your time. God bless you and yours
I love microwave and wideband design because when you step back and look at what you've done it looks like you've scribed some kind of magical rune. Waveguide stuff feels different, but you still feel like a thaumaturge building an arcane apparatus to direct malevolent spirits. 10/10 would recommend EE dark arts.
I'm honestly not sure I've ever said "ah yessss! yesyesyes" upon seeing a new video get released before. This one is exciting!
My goodness I enjoyed this episode 🧘🏼♂️
The autonomous tracking dishes & how it operates would be very intriguing.
If these guys had the time and funding, they would totally build a functional Saturn V...
I half expect them to anyway somehow...in some future episode touring the stuff left on the moon, in person...
Most interesting. TWT's still used? Amazing!. I used them in nuclear experiments at Harwell in 1972.
I built these at Motorola's Military division in Scottsdale, Arizona in the mid 1960's. I was a final assembly, precision mechanic (PMA). There were two of us.
Incredible! You sure did a mighty fine job. Do you know if there are still any people with some documentation? Stories to share?
@@CuriousMarc Hi Marc, Unfortunately, that was a long time ago and the Motorola Military Division is gone. I'm busy right now, but I'll answer in more detail when I get a moment.
Dude this stuff is cooler than anything on cable TV. And it's available for us all to view for free. Thank you.
My favorite series yet! Can’t beat good old tube technology
Looks like a collaboration with Shariar at the Signal Path is in order, as he definitely has all the RF equipment you need to get that amplifier checked out and tested. Plus he can check just how good this technology is at handling modern signals as well.
That would be amazing! But they're on opposite coasts. I sense that Marc is going to be just fine bringing us some awe-inspiring analysis!
@@PixelSchnitzel Just need to take a flight then......
Thanks so much. This made my evening much more pleasant. I loved it all.
I love these videos, thank you Marc :)
looking forward this series... that bench full of RF test gear and antennas 😌 love it
Best explanation of the principle behind TWT amplification I've heard. Superb video, top quality as always.
Thank you for another fantastic episode. :)
Another fantastic technology deep-dive, today around S-Band microwave technology form the 1960's... just amazing! Thanks for sharing !
Absolutely fantastic! Being able to see how this stuff was done in the 1960's is amazing!
Excellent job.
An important part of the story is lived here in more detail.
It is still considered the masterpiece of engineering today.
and you are making all of that available.
Please show more.
Well i learnt something new today. Thank you Marc. 👍🏻
Always felt when I did my electronic engineering I should have taken a plumbing course too. Brilliant presentation as usual Marc...👍
Oh goodie! Been waiting for this one! Thanks, Marc!!
I had to describe the how the TWT worked in an exam question back in the early 80’s, there was a lot to remember on that one.
with how tightly packed everything is, an endoscope is probably the easiest way to inspect the components at the bottom of the box
When I was working on some military radio stuff, around 1980, I would occasionally rest my bare arms on a TWT (accidentally) while talking to someone. My arm would feel a test point and ground.. YOWZER! What a wake up call! Great video!
Absolute gold! Thanks for sharing.
Was really looking forward to this. Thank you.
After watching these can now see why the Apollo program cost so much.
Well it all has to be 'Man-Rated', so you have to make it the very best and still add redundancy.
And, since it has to be as light as possible and fit in an odd configuration all the enclosures have to be both custom engineered for strength with the minimum of material--then hermetically sealed. To me money very well spent.
Incredibly well explained, thank you !
11.6W Here I am impressed that I can exchange FT8 messages from Connecticut with people in Japan and Australia at under 100 watts. Then again I can be heard in Australia with 5W of power. Obviously the size means everything in this scenario 😃
Badass!!! Def do pass through. Turning on notifications. Great series. Thank you
And I thought working on my italian 125cc 2-stroke bike was complicated … great work, keep it coming !
Excellent presentation. Cool engineering.
These are fantastic! I'm an EE student with an emphasis in RF. I love anything to do with space comms and I am an amateur radio operator, so of course I like anything referring to Collins equipment. I also love the French style elevator music! AND TWTs are amazing ! I'll be finding out more about that.
I truly love the depth of knowledge you're handing out in these videos. Without going so far over my head as to make the information sound like gibberish. Wonderful job as always.
PS these engineers really made great strides in a very short amount of time considering the tools of the day and the lack of computer power. Bravo
Absolutely. Brilliant, entertaining presentation. And none of it goes over my head either. Nope. Not one bit. At all.
Agree 100%. I am in no way the target audience for Marc's videos, but he does an excellent job of explaining complex concepts in a relatable way. Happy to subscribe and support such an excellent channel.
That loose coax connection.... I am stunned.
Superb, thank you.
Color me impressed. What an artist.
Thank you for that lovely description of the TWT operation. Nice to know out domestic microwave and space communications are still using thermionic vacuum devices (with magnets nogal).
So Fascinating!!
Interesting video. I dealt with TWTs during my career in the U.S. Navy. Some were used strictly to amplify signals received by antennas. The largest was cooled by liquid coolant (FC-77) and transmitted 1 Kw of power.
11 watts into a dummy load should be just fine - power it up. And thank you for the great video's. 73
Depends on the size of the load and the frequency
@@TheFool2cool 11 watts into a proper microwave dummy load and the RF isn't escaping very far.
@@ve7fm447 It may be closer to the 20 watts of the TWT output this close to the amplifier. But yea, same thing, use a 20W dummy load.
Commencing count down, engines on.
Check ignition and may God's love be with you
Really cool tech! Time to get an endoscope to look closer inside these units :)
Can't wait for next episode
Thanks for the lovely traveling wave tube explanation. [I am reminded of various "particle cooling" mechanisms, used to "tighten the bunches" of particles in synchrotrons. In TWTs, the electron beam and microwave input/output form a kind of plasm transistor (if I may abuse the language a bit) I suppose similar "amplification", or alternately dampening, must happen in synchrotrons.]
I've been in wireless/RF for nearly 20 years, and I'm impressed at the range they achieved with so few watts at those freqs. Would love to check out the terrestrial rx antennas as they likely hide some magic and voodoo as well.
The terrestial antennas were crude parabolic antannas with gigantic diameter, precision pointing motors and triple positions around the globe, using only the one nearest the rocket at any given time of day/night.
I just love your channel.
That is just pure art.
Thanks for the good explan.
great video!
FYI it's not just satellites using TWTs...both the american Patriot and russian S-300 AA missile systems use a TWT as the main transmit amplifier for their radar(s), despite everything else in them being solid state. The only reason solid-state will eventually push them out of military service are active phased antenna arrays, TWTs are physically too big to fit into those.
I used to test TWTs for Varian Canada back in the early 1980s. That company is now CPI the vendor in this video.
Clearly, the enclosure is an old V8 valve-cover. : )
Time to work on the roughing and high vacuum pumps.
Even a Technician license would let let you use that, as long as it fits in the bandplan.
I remember reading that the travelilng wave tube, obtained from surplus, was a favored high-quality wideband amplifier used by amateur radio operators. Basically, there was nothing else like it.
Wow, 11.6W, that's a lot considering HAM's bounce signals off of the moon using about 50W with a link budget for voice
They barely made it. They had just 3dB margin for B&W TV with the high gain antenna, and negative margin for voice and data comms with the omnis. Borrowing the military 210 ft Goldstone antenna basically saved their butts on the Apollo 11 landing. They’d have lost the LM coms when they were forced to go to the omnis. All the later color TV transmissions mandated the 210 ft Goldstone.
I used to work on TWTAs in a previous employment, including fault finding the PSUs and optimising the tubes with permanent magnets to minimise helix current. I've worked on some 2kW C band TWT amplifiers, they use scary high voltages and the entire cathode heater supply sits the EHT voltage as they operate in depressed cathode mode with the collector (anode) at near ground potential.
Thank you Marc. That was an outstandingly interesting and enjoyable video. This series is fascinating.
I don't though understand how this video could be down-voted. Non-Engineers perhaps who don't understand the technical brilliance of it?
Fascinating!
5:44 hmm someone had an iPhone back then
10:10 damn, there's probably a chunking trick to this I would think
great video
Kampfner, a new name in my pantheon of unsung heroes. People Who are incredibly important in our daily lines, of whom we have never heard. Watts Davies is another. Internet choccy if you tell me who he is. 😀
I was going to look up TWT...but then you explained it so simply, a caveman (like me) could understand!
Cool, thank you!
11 watts from the moon... that is impressive!
Oh my! I want the next chapter nowwww! Hahaha. Point the antenna to the moon and send "Hello Moon" text and wait for the bounce. Find a local Radio Amatuer with the specific license for that band and mode.!!
Hey! This is what Senku is building in the future!
Never be surprised that analog hollow state electronics can beat transistors! Klystrons are also fairly well renowned devices for incredible RF power transmission that still exist to this day, simply because solid state would either be hideously expensive and complex or because the output power and sensitivity are not yet matched
TWTs are still a fantastic way to generate high power over a very broad band too. Even as wide as 2-18GHz.
There are very fancy TWTs that go up to 220GHz and beyond. I think these are used in missile seekers and have very tight export controls around them.
You should explain the Quindar tones. I once saw a Quindar decoder at a ham swap meet in Sonoma, CA many years ago.
I recently became active on the 13Cm ham band, 2.3Ghz and have a 20W pa that is only about 10x10x4cm and runs off 28v. Had they had that on Apollo it sure would have saved weight!! Some hams still use TWT for EME I believe.
Those tubes have spent an awful long time cold. They rely on an extremely hard internal vacuum. Sadly molecular-level microleaks can soften the vacuum to the point where there are enough ions floating about to intercept the electron beam. Operating the tube has the effect of “pumping” the leakage ions and improves the tube interception current (a measure of the tube health). However, if the tube has been cold a long time and it has a high level of microleaks, when the beam is enabled it will scatter due the the presence of ions and hit the helix rather than the collector. The tube helix interception current will instantly rise to trip level. The result is a tube that accepts heater voltage, might well accept cathode and collector volts, but trips immediately the anode or grid is biased on which switches on the beam. If the tube is soft or gassy, the only way to get it on is to pulse the beam switch at kHz so as to establish a beam long enough to pump but short enough not to trip the tube or cook the helix winding. That assumes these tubes have a switchable anode/grid. The tube is fairly short so cathode volts are likely to be 3-8kVish. Enough to kill the unwary.
If the tubes were well made, and have stayed hard all these years, make sure to run them for at least 15 minutes to allow them time to pump themselves. Then they’ll switch on as if new again. If they are space-qualified in the modern sense, they’ll have 3 or more collectors and be very efficient, as well as being the highest quality build achievable. Oh, and INCREDIBLY expensive.
Wooo! Time for RF voodoo!