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Ham Hears Mars Orbiter 45 Million Miles From Earth
Richard L. James writes "As reported on the Mars-net email list Flight Refuelling Amateur Radio Society's resident satcom + WLAN guru Paul J. Marsh (M0EYT) has managed to detect and receive NASA's Mars Reconnaissance Orbiter on
X band at a staggering range of 45 million miles from Earth using a home made receiver setup and a RFspace SDR-14 software radio."
Oh, nevermind. You were refering to a civilian finding and keeping it then reverse-engineering it.
Though your point is still mute. I doubt they use the same scheme for all their assets. That would be retarded.
How many of you remember the articles in QST and Ham Radio from the 1970's about the ham radio operators that received and decoded the pulse-coded modulation transmissions directly from the moon during the Apollo missions? Yeah, I think we really did go there.
This new feat comes on the heels of the success of ham radio in Louisiana. I've been licensed since high school in the early 1970's. These new-fangled computers are nice and convenient, but nothing beats ham radio! It works where nothing else will.
Ray
you're ... moot.
/me out
"mute" is not the same word as "moot". They have different meanings and different pronunciations.
Furry cows moo and decompress.
I'm sort of splitting hairs here, but only the command link is secured on most NASA satellites. The telemetry back to the ground isn't necessarily encrypted (it isn't on the shuttle and ISS), although you'd definitely need to have some pretty expensive equipment and know-how to decode the carrier into anything useful (like voice and data). Then again, it's only fun because it's hard...
There's a few more details on how it works for ISS in a NASA training manual here. (It's a 6 Mb pdf, communications is section 4).
Worst...sig...ever!
Bullshit. You have absolutely no idea as to what you are talking about.
Can you imagine the damage some antisocial radio vandal could do to the Mars Rovers, for instance, if the command traffic was sent in the clear?
More bullshit. Many spacecraft command uplinks are not encrypted. You need to know a lot of things and have some very expensive hardware before you are going to be able to command a spacecraft. Just knowing the uplink frequency is a small piece of the puzzle.
Mea navis aericumbens anguillis abundat
*** uhf-satcom.com website MIRROR HERE ***
There is a bit mroe to it than just ading more power gets you a higher data rate. If you send a .25 watt signal with all the power in a .5 khz bandwidth signal, you are not going to get more than about 300 bits per second data transfer. Increasing your power level does not improve the data rate, though it may improve your receive capability over a longer distance. I.e. increasing the power from that original .25 watt to say 25 megawatts doesn't improve the data rate, but it may mean you can receive the signal somewhat further away.
.5khz wide signal, you are going to need more power spread across that bandwidth. Going to a 2.5 khz signal means you will need a 1.25 watt signal. 5khz means a 2.5 watt signal. For that uncompressed live video feed, if you use a 5mhz wide signal (this gives a comfortable 1 mhz separation for most people, which is probably sufficient to toss in an audio stream of some sort) you are going to need a 2500 watt signal to start with. If you need to be able to receive it at a significant distance, you will need to be able to either increase the radiated power, or the gain of the signal in the direction the receiver is located in. Gain is measured in db, and for the purposes of this posting are compared to an omnidirectional signal. If you can get an effective four times the power radiated in the direction of your receiver, you have effectively increased the gain by 6db. (3db is double the signal.) You can also improve the signal reception by increasing the gain of the receiving antenna. In the case of the article the improvement in gain was done via a 1 meter offset sattelite dish.
If you want to increas the data rate, you need to expand the transmited bandwidth. Most of the comercial handheld 2-way radios out there use about a 2.5 khz bandwidth, which is OK for voice, though Hams and older (much older actually) comercial equipment uses a 5 khz bandwidth for voice. This bandwidth also works fairly well for slow scan vidio, which is basically single images sent over a period of between 5 and 20 minutes, depending upon the data rate, (1200 bps, or 9600 bps are common on ham frequencies) and image resolution and color depth.
If you want to send live video, you have to step up the bandwidth significantly. Standard TV uses a channel separation of 6 mhz, You can do a lot better with compression, and by reducing the frame rates. If you are video conferencing over your dsl or cable modem line, with an uplink cap of 128kbps, the signal your video chat partner receives is going to be somewhat less impressive than they get off the air for TV.
Now if you want to reach the same distances with the higher bandwidth signal as you would with that
For the most part the desire is to get the gain of the desired signal to be some power level over the noise floor of the environment you are working. The noise floor is generated by background radiation, as well as radiation of the environment you live in. If you happen to have mountains between you and all the local cities, or can work from an island over the horizon from significant RF sources, you can improve your separation somewhat. That doesn't help with the univeral background radiation, so he had to add some filtering to lower the signal level for signals outside of the desired bandwidth. As he was able to reduce those sigals by an effective 50db with his waveguide filter, he significantly improves his ability to receive the desired signals.
Granted he still has to be able to point the receiving system at the sending system. Sounds like he was able to.
The radiated power that the Mars Express transmits with is published data, as well as the effective gain of its transmitting antennas. The range between earth and Mars is reasonably easily calculable. It sounds like M0EYT got the rest of the calculations to work out as well.
Some of the above is not exact. Feel free to do more research to learn more about it yourself.
-Rusty - kc0vcu
You never know...
Hi, re the bpf, its only a 2 cavity filter made in wg16, cf=8420 with about 50MHz bandwidth, and RF coupled in and out via the standard probed with appropriate matching screws. Using that dish, the signal isnt that strong, its detectable though on an FFT as per the article. There is a nice page on x-band space probe reception with some example audio at http://www.setileague.org/photos/probes.htm
The next plan is to try to hear the orbiters that are currently at Mars, but that will need the 3.7m dish.
regards,
Paul (uhf-satcom.com contributor)
HI,
Yep its probably a victory for ham radio - since I'm licensed and operate >1GHz only, its experience with building ham transmitters / receivers etc that gave me knowledge etc, to build an 8.4GHz rx. The whole project was done to see if it was technically possible to build a receiver - I've not really got the time / interest to delve into the telemetry formats or to work out how to decode the tt&c data.
Next, I'm waiting for the 'New Horizons' mission to pluto, that will provide an interesting signal to track for a number of years.....
regards,
Paul (uhf-satcom.com contributor)
Here is your link.
Hi Voltageaav, you have misread the context of the article, I built the receiver and have no connection with nasa at all - it was done out of technical curiosity just to see if it was possible with simple equipment to hear anything, the answer turns out to be a "yes".
regards
Paul (www.uhf-satcom.com contributor)