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MARS?
Is anyone hearing MARS activity (the military affiliates, not the planet)?
I never hear anything on the freq's I have. Greg |
"Greg" wrote: Is anyone hearing MARS activity (the military affiliates, not the planet)? I never hear anything on the freq's I have. I hear the MARS nets most often between 4.0 and 4.1 MHz mornings and evenings. Art N2AH |
Very timely request -- as from the ARRL is:
To celebrate the 54th US Armed Forces Day, the Army, Air Force, Navy, Marine Corps and Coast Guard are cosponsoring the annual Military/Amateur Radio communications tests on Saturday May 8. While Armed Forces Day is May 15, the Armed Forces Day on-air special event will take place a week earlier to avoid conflicting with Hamvention 2004, May 14-16. The event features military-to-amateur crossband voice operations and a digital message receiving test, with the text of the message prepared by US Secretary of Defense Donald Rumsfeld. URL: http://www.arrl.org/news/stories/2004/04/15/1/ For frequencies & locations -- see URL: http://www.arrl.org/news/stories/200.../ssb-sked.html -- el lector se guarda Amateur Radio is the best back-up communications system in the world, and that's the way it is. Walter Cronkite --------------------------------------------------------- "Greg" wrote in message ... Is anyone hearing MARS activity (the military affiliates, not the planet)? I never hear anything on the freq's I have. Greg |
"Greg" wrote in message ... Is anyone hearing MARS activity (the military affiliates, not the planet)? I never hear anything on the freq's I have. I'm pretty sure all the MARS stations here in S. Korea are gone. The reason being that it's easier for the GI's to just use the phone. Most of them buy cheap cell phones, and buy phone cards. We can actually call stateside from here cheaper than most of you can call the next state (the card I use is a bit under 5 cents per minute to the US). |
Thanks for the info everyone.
Greg |
Arthur Harris wrote:
"Greg" wrote: Is anyone hearing MARS activity (the military affiliates, not the planet)? I never hear anything on the freq's I have. I hear the MARS nets most often between 4.0 and 4.1 MHz mornings and evenings. Art N2AH The last MARS net I heard was on 4003 kHz at about 8:00 EDT. Jeff Seale Louisville, KY |
From: Jeff Seale Organization: Insight Broadband Newsgroups: rec.radio.shortwave Date: Sat, 08 May 2004 21:16:15 GMT Subject: MARS? Arthur Harris wrote: "Greg" wrote: Is anyone hearing MARS activity (the military affiliates, not the planet)? I never hear anything on the freq's I have. I hear the MARS nets most often between 4.0 and 4.1 MHz mornings and evenings. Art N2AH The last MARS net I heard was on 4003 kHz at about 8:00 EDT. Jeff Seale Louisville, KY There was already activity on that freq when I tuned in around 7:45 EDT. Also, I have heard the special Armed Forces Day traffic on 13985, 13996, and 14467 USA earlier and 14467 is still active. Greg |
Greg wrote:
There was already activity on that freq when I tuned in around 7:45 EDT. Also, I have heard the special Armed Forces Day traffic on 13985, 13996, and 14467 USA earlier and 14467 is still active. Greg That's cool, I don't do too much daytime/morning listening though except on the weekends when I don't have to work. The earliest you'll find me hitting the radio is about 3:00 PM EDT. Jeff Seale Louisville, KY |
On Sun, 09 May 2004 02:31:59 GMT, Jeff Seale
wrote: Greg wrote: There was already activity on that freq when I tuned in around 7:45 EDT. Also, I have heard the special Armed Forces Day traffic on 13985, 13996, and 14467 USA earlier and 14467 is still active. Greg That's cool, I don't do too much daytime/morning listening though except on the weekends when I don't have to work. The earliest you'll find me hitting the radio is about 3:00 PM EDT. Jeff Seale Louisville, KY I've been wondering: If a shortwave transmitter was put on Mars could I pick it up - at night I mean? Would I need an external antenna? BTW - I tune down. |
-=jd=- wrote:
I have no idea if it's an actual fact or not, but back in the mid 70's I was third party to a conversation in which it was mentioned that the moon missions communicated on something like 10 watts. I didn't believe it at the time - not that I would have known any better... Perhaps someone in here has the scoop on it? 10 watts is pretty typical for downlink for a space mission. High power transmitters are difficult in space: even if the power budget allows, it's hard to get rid of the heat without air to help. We tend to go with modest power and put in enough antenna gain to make the link work. NASA's Deep Space Network has some enormous dishes, more than adequate for a 10 watt voice link from the moon. One thing that helps is that losses in space are very small: you don't have ground absorption and ionospheric absorption is slight at the frequencies we use. I'm sitting here watching a 300 bps link from the HETE-2 satellite. Half a watt gives us 2000 km range using non-directional antennas at both ends. -jpd |
"Bill Everhart" wrote in message ... I've been wondering: If a shortwave transmitter was put on Mars could I pick it up - at night I mean? Probably. The ionosphere would refract the received signals, but I think it would still come in if it hit the ionosphere at a the correct angle. If the signals were directly overhead, absorbtion would be the main problem. There's a couple of small bands in SW allocated to radio astronomy. One is around 13MHz and the other is around 26MHz. Would I need an external antenna? Only if the signal from Mars is weak when it gets to Earth. As long as this is hypothetical, let's give the Martians a terawatt transmitter and a steerable parabolic dish a mile across. In the real world, radio astronomy needs good antennas. BTW - I tune down. Never up? Frank Dresser |
"Bill Everhart" wrote:
I've been wondering: If a shortwave transmitter was put on Mars could I pick it up - at night I mean? Would I need an external antenna? Interesting question. When Mars is at its closest point to Earth, it's still about 35 million miles away. Only a tiny portion of the transmitted power would arrive on Earth (the rest would "miss" us and go out into space in all directions). The "free space path loss" between Earth and Mars at 15 MHz would be 211 dB. That's a HUGE loss. At UHF and microwave frequencies the path loss is even greater, BUT the use of very high gain dish antennas both on Earth and Mars, as well a low noise figure receivers, makes communication possible. At HF, antenna gain of more than about 10 dB is hard to obtain. And the atmosphereic noise at HF is a killer for weak signal reception. Plus, you'd have to be listening at a time when your side of the Earth was facing "their" side of Mars, and the E and F layers of the ionosphere were NOT refracting signals. BTW - I tune down. Huh? Art N2AH |
Very little power is necessary in space. I had a QSO with an astronaut on
MIR with a 3 watt ht. With nothing in the way, it will go on virtually forever. "-=jd=-" wrote in message ... I have no idea if it's an actual fact or not, but back in the mid 70's I was third party to a conversation in which it was mentioned that the moon missions communicated on something like 10 watts. I didn't believe it at the time - not that I would have known any better... Perhaps someone in here has the scoop on it? -=jd=- -- My Current Disposable Email: (Remove YOUR HAT to reply directly) |
In article ,
"Arthur Harris" wrote: snip The "free space path loss" between Earth and Mars at 15 MHz would be 211 dB. That's a HUGE loss. At UHF and microwave frequencies the path loss is even greater, BUT the use of very high gain dish antennas both on Earth and Mars, as well a low noise figure receivers, makes communication possible. At HF, antenna gain of more than about 10 dB is hard to obtain. And the atmosphereic noise at HF is a killer for weak signal reception. snip How did you calculate this loss? I'm assuming you mean the 211 dB to be an absorptive loss? Maybe you are considering the antenna on Mars to be a point source off a 180 degree ground plane so the loss figure is power distributed over a half sphere with the Earth - Mars distance? -- Telamon Ventura, California |
"Telamon" wrote"
"Arthur Harris" wrote: The "free space path loss" between Earth and Mars at 15 MHz would be 211 dB. That's a HUGE loss. At UHF and microwave frequencies the path loss is even greater, BUT the use of very high gain dish antennas both on Earth and Mars, as well a low noise figure receivers, makes communication possible. At HF, antenna gain of more than about 10 dB is hard to obtain. And the atmosphereic noise at HF is a killer for weak signal reception. snip How did you calculate this loss? I'm assuming you mean the 211 dB to be an absorptive loss? Maybe you are considering the antenna on Mars to be a point source off a 180 degree ground plane so the loss figure is power distributed over a half sphere with the Earth - Mars distance? The Free Space Path Loss Equation is: Path Loss (dB) = 36.6 + 20 Log F + 20 Log D Where F is freq in MHz and D is distance in miles. This assumes isotropic antennas as both ends. The "path loss" represents the portion of the transmitted signal that is NOT captured by the receiving antenna. It does not include absorptive losses (which should be negligible in free space). Some will argue that this is not a true dissipative loss, and that is correct. But by knowing the "path loss" you can determine your needs as to transmit power, receiver sensitivity, and antenna gain in order to assure successful communication. Art N2AH |
"CW" wrote: Very little power is necessary in space. I had a QSO with an astronaut on MIR with a 3 watt ht. With nothing in the way, it will go on virtually forever. The signal will decrease by 6 dB every time you double the distance. MIR was about 250 miles above Earth, and you could establish communicaion with fairly low power when it was overhead. On the other hand, Mars is about 35 million miles away! You'd need a LOT more power and antenna gain to contact Mars. Art N2AH |
"Arthur Harris" wrote in message t... "CW" wrote: Very little power is necessary in space. I had a QSO with an astronaut on MIR with a 3 watt ht. With nothing in the way, it will go on virtually forever. The signal will decrease by 6 dB every time you double the distance. MIR was about 250 miles above Earth, and you could establish communicaion with fairly low power when it was overhead. On the other hand, Mars is about 35 million miles away! You'd need a LOT more power and antenna gain to contact Mars. I presume that the Mars rovers do not have extensive antenna arrays, nor more than a few watts of power. Of course, NASA does have large receiving arrays.. |
Arthur Harris wrote:
The Free Space Path Loss Equation is: Path Loss (dB) = 36.6 + 20 Log F + 20 Log D Where F is freq in MHz and D is distance in miles. This assumes isotropic antennas as both ends. The "path loss" represents the portion of the transmitted signal that is NOT captured by the receiving antenna. It does not include absorptive losses (which should be negligible in free space). Some will argue that this is not a true dissipative loss, and that is correct. But by knowing the "path loss" you can determine your needs as to transmit power, receiver sensitivity, and antenna gain in order to assure successful communication. The key here is a theorem that shows that the "capture area" of a perfectly efficient isotropic antenna is (wavelength)^2/(4 Pi). -jpd |
for all of you who were speaking about what times you listen, here is what
happened to me when I was real young. I heard an advertisement on a shortwave station for a program I wanted to hear, but at the time, I didn't understand 24 hour time since I had never heard of it before. However, when I asked about it, either my uncle or my grandpa (maybe both) explained it to me. and I then understood it. But I STILL missed the program when I tuned in at the time said to hear it. I didn't find out until later that the reason why I missed it is even though I understood 24 hour time, I wasn't aware of different time zones in different parts of the world. The time given was in GMT and I was tuning in according to Eastern Time instead of GMT. |
The signal will decrease by 6 dB every time you double the distance. MIR
was about 250 mi but I believe that some people have dx'ed Mars in either the AM or FM broadcast band. That is, Mars, Pennsylvania. ;) |
No ****. Do you think or just flame?
"Arthur Harris" wrote in message t... On the other hand, Mars is about 35 million miles away! You'd need a LOT more power and antenna gain to contact Mars. Art N2AH |
"CW" wrote: No ****. Do you think or just flame? "Arthur Harris" wrote in message t... On the other hand, Mars is about 35 million miles away! You'd need a LOT more power and antenna gain to contact Mars. Take it easy! You're the one who claimed signals in space "go on virtually forever." Art N2AH |
Arthur Harris wrote: "CW" wrote: No ****. Do you think or just flame? "Arthur Harris" wrote in message t... On the other hand, Mars is about 35 million miles away! You'd need a LOT more power and antenna gain to contact Mars. Take it easy! You're the one who claimed signals in space "go on virtually forever." To the best of my knowledge signals in space DO go on virtually forever. Elsewise what would be the point of looking for life via the search for signals from deep in space. A project that has been ongoing for some time. Steve Holland, MI Drake R7, R8 and R8B http://www.iserv.net/~n8kdv/dxpage.htm |
Interesting how my original post about the Military Affiliate Radio System
turned into a discussion on communications in space. Interesting stuff! This is a very lively group. And thanks all for avoiding any discussion of signals radiating from Uranus! Greg |
Settie's (sp?) got that covered.
"Greg" wrote in message ... Interesting how my original post about the Military Affiliate Radio System turned into a discussion on communications in space. Interesting stuff! This is a very lively group. And thanks all for avoiding any discussion of signals radiating from Uranus! Greg |
Pretty much. The real limiting factor is how much they spread out over
distance. "N8KDV" wrote in message ... To the best of my knowledge signals in space DO go on virtually forever. Elsewise what would be the point of looking for life via the search for signals from deep in space. A project that has been ongoing for some time. Steve Holland, MI Drake R7, R8 and R8B http://www.iserv.net/~n8kdv/dxpage.htm |
"CW" wrote in message ... Settie's (sp?) got that covered. SETI? The Search for Extra Terrestrial Intelligence? They aren't looking in the solar system. They are trying to find signals which might indicate intelligence in solar systems far away. Some of the Art Bell types say SETI is a diversionary tactic to keep us from finding out the Aliens are here right now. Signals from Uranus would be heard by Radio Astronomers. Well, heard by the Radio Astronomers who aren't aware that there's a Government-Alien space program which flies regular missions to the Martian bases. Frank Dresser |
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Arthur Harris wrote:
"CW" wrote: Very little power is necessary in space. I had a QSO with an astronaut on MIR with a 3 watt ht. With nothing in the way, it will go on virtually forever. The signal will decrease by 6 dB every time you double the distance. MIR was about 250 miles above Earth, and you could establish communicaion with fairly low power when it was overhead. On the other hand, Mars is about 35 million miles away! You'd need a LOT more power and antenna gain to contact Mars. Art N2AH Voyager 1 is just over 90 Astronomical Units or 8.4 billion miles from the sun, transmitting with approximately 2 watts and signals are still being received here on earth. How do you account for that? |
JJ wrote:
Voyager 1 is just over 90 Astronomical Units or 8.4 billion miles from the sun, transmitting with approximately 2 watts and signals are still being received here on earth. How do you account for that? Inspired design, careful implementation, meticulous attention to nit-picky details, enormous antennas, cryogenic cooling of the receiver front ends, and 65535-bit-long GOLD codes sent straight-up for "1" and inverted for "0". It's amazing what can be pulled out from under the noise floor when only (50% of the sequence)+1 bits need to be received correctly to achieve unambigous decoding. -- Should array indices start at 0 or 1? My compromise of 0.5 was rejected without, I thought, proper consideration. (Stan Kelly-Bootle) |
= = = Greg wrote in message
= = = ... Interesting how my original post about the Military Affiliate Radio System turned into a discussion on communications in space. Interesting stuff! This is a very lively group. And thanks all for avoiding any discussion of signals radiating from Uranus! Greg GREG, Good Come Back :o) Just a Thought - Isn't there a book that was written: Women are from Venus .. . . Men are from Mars ! Considering that the majority of posters here are Men, it is easy to see why "MARS" became 'Mars' :o] Although the Men may have originated from Mars, I believe that you are right that a few of then must have been raised on Uranus because they are such ***-***** at times ;- Just for the Fun of It ~ RHF .. |
From: (RHF) Organization: http://groups.google.com Newsgroups: rec.radio.shortwave Date: 10 May 2004 14:49:05 -0700 Subject: MARS? = = = Greg wrote in message = = = ... Interesting how my original post about the Military Affiliate Radio System turned into a discussion on communications in space. Interesting stuff! This is a very lively group. And thanks all for avoiding any discussion of signals radiating from Uranus! Greg GREG, Good Come Back :o) Just a Thought - Isn't there a book that was written: Women are from Venus . . . Men are from Mars ! Considering that the majority of posters here are Men, it is easy to see why "MARS" became 'Mars' :o] Although the Men may have originated from Mars, I believe that you are right that a few of then must have been raised on Uranus because they are such ***-***** at times ;- Just for the Fun of It ~ RHF My wife teaches middle school science and her kids love it whenever she mentions Uranus! Greg |
Harris wrote:
JJ wrote: Arthur Harris wrote: The signal will decrease by 6 dB every time you double the distance. MIR was about 250 miles above Earth, and you could establish communicaion with fairly low power when it was overhead. On the other hand, Mars is about 35 million miles away! You'd need a LOT more power and antenna gain to contact Mars. Voyager 1 is just over 90 Astronomical Units or 8.4 billion miles from the sun, transmitting with approximately 2 watts and signals are still being received here on earth. How do you account for that? A steerable 12-foot dish on the spacecraft, and HUGE antenna arrays on Earth. So you don't need a LOT of power to contact Mars. |
JJ wrote:
Arthur Harris wrote: The signal will decrease by 6 dB every time you double the distance. MIR was about 250 miles above Earth, and you could establish communicaion with fairly low power when it was overhead. On the other hand, Mars is about 35 million miles away! You'd need a LOT more power and antenna gain to contact Mars. Voyager 1 is just over 90 Astronomical Units or 8.4 billion miles from the sun, transmitting with approximately 2 watts and signals are still being received here on earth. How do you account for that? A steerable 12-foot dish on the spacecraft, and HUGE antenna arrays on Earth. See: http://www.spectrum.ieee.org/pubs/tr...c06-stone.html The article says in part: "The science data from this 12-year journey of exploration completely altered our understanding of these planetary systems. A number of first-time telecommunications achievements made this possible, including the first operational X-band (8.4-GHz) system. During the course of the mission, there were a number of significant changes to the communications system on the spacecraft and on Earth which provided in aggregate a factor of six higher data return at Neptune than was possible at launch. Data compression programmed into the flight data system gave the largest single increment, and switching from a Golay code to a Reed-Solomon code helped enable the use of the data compression. The other major contribution came from increases in effective receiving area by arraying of multiple Deep Space Network (DSN) antennas and increasing the size and efficiency of the largest DSN antennas from 64 m to 70 m. For the Neptune encounter, an array of 29 antennas consisting of 70- and 34-m antennas in California and 27 additional 25-m antennas (comprising the National Science Foundation's Very Large Array in New Mexico) provided fully steerable equivalent aperture of 150 m." Art N2AH |
"JJ" wrote in message ... Harris wrote: JJ wrote: Arthur Harris wrote: The signal will decrease by 6 dB every time you double the distance. MIR was about 250 miles above Earth, and you could establish communicaion with fairly low power when it was overhead. On the other hand, Mars is about 35 million miles away! You'd need a LOT more power and antenna gain to contact Mars. Voyager 1 is just over 90 Astronomical Units or 8.4 billion miles from the sun, transmitting with approximately 2 watts and signals are still being received here on earth. How do you account for that? A steerable 12-foot dish on the spacecraft, and HUGE antenna arrays on Earth. So you don't need a LOT of power to contact Mars. It takes lots of ERP (Effective Radiated Power). You can get high ERP by using high power or a high gain antenna (or both). The 12-foot dish on Voyager has over 40 dB of gain at X Band. In conjuction with Voyager's 20 watt (not 2 watt) transmitter, that produced over 200,000 watts of ERP. See: http://www.spacetoday.org/SolSys/Voyagers20years.html The statement I took issue with was: "Very little power is necessary in space. I had a QSO with an astronaut on MIR with a 3 watt ht. With nothing in the way, it will go on virtually forever." That implied that a simple low power transceiver and mediocre antenna could communicate over unlimited distances in space. That is simply not true. The Mars missions and Voyager mission used very sophisticated engineering to accomplish what they did. Art N2AH |
Arthur Harris wrote:
"JJ" wrote in message ... Harris wrote: JJ wrote: Arthur Harris wrote: The signal will decrease by 6 dB every time you double the distance. MIR was about 250 miles above Earth, and you could establish communicaion with fairly low power when it was overhead. On the other hand, Mars is about 35 million miles away! You'd need a LOT more power and antenna gain to contact Mars. Voyager 1 is just over 90 Astronomical Units or 8.4 billion miles from the sun, transmitting with approximately 2 watts and signals are still being received here on earth. How do you account for that? A steerable 12-foot dish on the spacecraft, and HUGE antenna arrays on Earth. So you don't need a LOT of power to contact Mars. It takes lots of ERP (Effective Radiated Power). You can get high ERP by using high power or a high gain antenna (or both). The 12-foot dish on Voyager has over 40 dB of gain at X Band. In conjuction with Voyager's 20 watt (not 2 watt) transmitter, that produced over 200,000 watts of ERP. The Voyager's power is now down to 2 watts and has been for some time to conserve power. So you don't need a LOT of power to communicate long distances in space. Real power from the transmitter and ERP are two different things. |
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