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Operation Moon Bounce
linuxwrangler writes "Today marks the 50th anniversary of the first transmission of human voice via moon bounce. The voice was that of James Trexler and the technique became an important method of communication for the military that was used until the advent of the communications satellite. It is still a popular activity for ham radio operators."
At my local ham radio club, a guy just gave a talk about how he is attempting to implement a 47 GHz EME system. Is is interesting because of the technical challenges. Only a few other people actually operate 47 GHz stations. The travelling wave tube that most use was originally used for military work, for a project called Milstar. Interesting that at the time none of the traffic was coded to their satellites because it was considered intristically safe because it would be very hard to build a station for it.
Some operators do use voice, but have to use big time QRO (high power) stations because the path losses are so huge. Then with new DSP methods, voice communications can definetly work.
I read a SF book that used the moon bounce technique to store data. They had markers on the moon for navigation (just reflectors in the rock) People would use a transmitter on earth to send a burst of data to the moon and let it bounce back then retransmit it without storing it. just a loop. You could fit a certain amount of data in the lag. They used it on farther objects to get longer delays. Kind of a strange idea. Box
I haven't finished reading through the article, but I remember reading about this in one of James Bamford's book about the NSA, "Body of Secrets" or "The Puzzle Palace". Basically, when you bounce a directional radio beam off the moon, it can't be intercepted by anyone except those near the place on Earth where the beam bounces back to. This would allow Navy ships at sea to send a message from the open ocean, to the moon, then to Washington without having the message picked up by the Russians. Pretty neat trick, actually.
The reason this was in Bamford's book was that the USS Liberty, the Navy eavesdropping ship that was attacked by the Israelis in 1967, had this type of system on board and it was its primary method of communicating with the NSA people in the US. Unfortunately, the system was unreliable, and the hydraulics or pnumatics controlling the directional antenna often broke, making it unusable. Partly because of this, the ship never got the message to stay away from the conflict zone and was bombed. That's how I remember it, at least.
Maybe that's the danger of relying too much on bleeding-edge technology.
Anyone here heard of other stories of this technology?
"FIRST POST!!"
You are right for the lower frequency bands, but once you start moving up above 1000 MHz then EME is possible with much more modest systems. For example on 23cms (1296 MHz) you can work CW EME with 100W and a 3m dish, if you are peering with someone like HB9Q or HB9BBD then you can use a lot less than that.
The introduction of digital modes like JT44 and JT65 (using FFTs, correlation and strong FEC) has made a big difference and has made EME available for people with much smaller gardens and purses. Unfortunately there are a number of EME operators who insist that a digital mode somehow isn't "real" or that the contacts count for less. This is a shame and gives newcomers the wrong impression of a fine part of the hobby.
I intend to get active soon with a marginal system for CW work but more than adequate for the more advanced data modes.
For info about more reasonable microwave EME systems see G4CCH and N2UO
Well, CW *and* voice.
:)
I know a ham (I also have a ham license, but not the neccessary money for the equipment) who demonstrated this a few years ago and it was just amazing!
He has a lot of equipment and some agreements with the goverment for increased output power.
So he was able to do a few kW (5?)@2.5GHz on a 9m fully steerable dish and voice/SSB modulation if I recall correctly.
Now, the first beautiful thing was seeing the lights fade in sync with the voice because of the high power requirements of the transmitter
The response from the moon was clearly readable but noisy, this is very impressive if you calculate the minimum loss (in dB) that is just given by the geometry...
Amateur Radio Enthusiasts do CW (morse) communications using moonbounce, not voice. [Note for Non-Hams: SSB is "Single Sideband" (a form of voice communication) and CW is "Morse Code" (the old "di and dah.")] A few years back, I'd set up my 2m SSB/CW unit with a high gain directional antenna and listen in on EME. Most of it was, as you point out, CW, but occasionally there'd be some voice in there as well. Occasionally, you'd even hear an SSB station communicate with a CW station. I don't know why copying the CW portion of a SSB/CW conversation is hard, but for me it's far more difficult than pure CW.
This sig seemed like a good idea at the time....
" I don't know why copying the CW portion of a SSB/CW conversation is hard, but for me it's far more difficult than pure CW."
It's likely you are not used listening to SSB over a longer period of time. Switching between SSB and CW on the receiving side is extremely difficult, because you need to adapt your "internal" filters from very low bandwidth to rather large bandwidth.
I can listen to CW for hours and hours, but listening to SSB is extremely tiring and makes me want to throw away the headphones after a couple of minutes. Well, I drew the consequences and have lived without a microphone on my rig for the past 20 years or so.
It was widely rumoured that in the mid-to-late seventies some of the geostationary TV satellites got hijacked for various purposes. By 'widely rumoured' I mean that my ham radio boozing buddies talked about it quite a lot and several of them were broadcast technicians who used satellite up and downlinks at work. I have no first hand proof but they alleged that early geostationary satellites were simple transponders - if you pushed stuff up on the uplink frequency with the right amount of power and in the right direction it came back on the downlink. A popular trick was to slip a signal just to the side of the audio subcarrier at a modest level and then use it to send data or chat to friends. That is not easy to spot unless you look hard at the downlink spectrum.
This might all be speculation or not - I'd love to know. Maybe it's an urban legend.