Slashdot Mirror
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."
...how soon can I get this sort of range/reliability for my home Wifi?
I am Spartacus
and here I can't get a decent fucking picture from DirecTV.
"Can you hear me now?"
We better start encrypting our space chats or the aliens will surely hear us.
Orbiter: "Beep beep beep bo beep" Base station: "Da deet da da deet deet da"
Jesus fucking christ! What link do they want me to click?! My slashdot honed senses are confused by the lack of more then one link in the article summary!!!
:)
Oh, wait, nevermind, since when did I read articles? Crisis averted!
So, how long will it take for this guy to be reprimanded for space war driving of satellites ?
Which one?
Don't know something? Look it up. Still don't know? Then ask.
So what? This guy's basicly just taking his work home for fun. Yeah, he tinkered and built one on his own, but he should be able to if he's the NASA expert on it.
Someone save me from this sanity.
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
It's nice having so many links embedded in the summary, but which one links to where it's actually reported ? I'd expect a link on the "reported" word.....
because that's one helluva Pringle's can. Defcon contests, you're over.
---- Teach Peace. It's Cheaper Than War.
The problem with this layout is that there's too much shit to click on. Seriously, who's ever going to click on all those links? The worst blogs are the ones that make every other word a hyperlink to another website so by the time you finish reading this sentence, you've forgotten what you were reading, or why you were reading it in the first place. Hey, this article is great but you know what would make it better? If I could read another article in the middle of it. Great design, morons.
The guy, a human being with clothes and bad breath and pimples as a kid and all of those things that level the playing field for all of us, is communicating with something 45 million miles away!
Even the most boring, predictable, well-funded case of this occurring should be celebrated with what is left of the adverturer in you.
"So what". Puh! Why exactly are you at Slashdot then?
You are checking your backups, aren't you?
Gonna need a lot fo postage on that QSL Card....
As with most things in life, the correct answer is "it depends". All NASA communcations to/from the shuttle are NOT necessarily encrypted but can be. Uplink from the ground to the shuttle always is encrypted (we don't want someone sending bogus commands). In addition, the crew has the option of disabling all commands coming from the ground. Direct downlink from the shuttle to the ground can be encrypted but that is not always done. It depends on the mission configuration. DOD-based classified missions back in the 80s always were encrypted on both the uplink and downlink.
There are also other communications paths between the shuttle and the ground. Indirect communications, known as forward and return links via, TDRSS are always encrypted.
I am waiting patiently for the equipment webpage to load so that I can see what sort of filters he used. That's the main tricky part for doing such an experiment - you need to build a custom filter to reject everything that isn't in the spacecraft's frequency band. The rest of the equipment is apparently a modified satellite TV receiver and a generic software radio.
The determined Real Programmer can write Fortran programs in any language.
Did anyone else read that title as:
"Ham Nears Mars Orbit 45 Million Miles From Earth"
I thought it was going to a story about Piiiigs in Spaaaaace!
When information is power, privacy is freedom.
Slashdot is a public forum where everything is dicussed in far too much depth and 90% of it is pointless
Working on the (alleged by some) premise that we never went to the moon - how do we know that NASA isn't pumping out a fake, weak signal from a research lab just to fool us!!? I won't believe it until we get some triangulation on that signal!
AT&ROFLMAO
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)