If two sats like Hamsat (or Echo) were in orbit at the same time and could see each other ...
Could User#1 uplink to Sat-A and then Sat-A would link to Sat-B (probably on one of the higher microwave bands) then Sat-B would downlink to User#2 and User#2 would uplink to Sat-B and be relayed to Sat-A and down to User#1 ??
If this could be done there would be a much larger footprint and launch costs would be far less expensive, correct?
Les W4SCO
Years ago AO-6 and 7 use to do this...one way of course...but it was fun to listen to.
Robert Oler WB5MZO/portable Life member AMSAT/ARRL
If two sats like Hamsat (or Echo) were in orbit at the same
time and
could see each other ...
Could User#1 uplink to Sat-A and then Sat-A would link to
Sat-B
Its rather easy to evaluate that situation. Look at what it takes for a user uplink and downlink station just to hit the satellite. Now imagine that you are asking for all that power and gain antennas to be added to one satelite just so now this one satellite can work another satellite. As you can see, it is pretty much impractical.
Bob, WB4APR
Bob, Just asking...
Wouldn't you have less loss as you don't have to go through all that atmosphere? I'm trying to recall the specs on the MILSTAR sats that support that type of technology but I'm having trouble coming up with the figures for the "link" system.
Of course we did it on PCSAT and ISS... :)
73s, de Eric KF4OTN
Robert Bruninga wrote:
If two sats like Hamsat (or Echo) were in orbit at the same
time and
could see each other ...
Could User#1 uplink to Sat-A and then Sat-A would link to
Sat-B
Its rather easy to evaluate that situation. Look at what it takes for a user uplink and downlink station just to hit the satellite. Now imagine that you are asking for all that power and gain antennas to be added to one satelite just so now this one satellite can work another satellite. As you can see, it is pretty much impractical.
Bob, WB4APR
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Wouldn't you have less loss as you don't have to go through all that atmosphere?... Of course we did it on PCSAT and ISS... :)
Yes, but communictions loss is almost insignificant going through Atmosphere except at some very high microwave frequencies. The Biggest loss in any comm link is the DISTANCE term. It is 192dB
for going 40,000 km at 2.4 GHz. 192 dB is 10 to the 19th. That is, the signal is one divided by 16,000,000,000,000,000,000.
It takes power and/or a lot of antenna gain to make up for that. Bob
73s, de Eric KF4OTN
Robert Bruninga wrote:
If two sats like Hamsat (or Echo) were in orbit at the same
time and
could see each other ...
Could User#1 uplink to Sat-A and then Sat-A would link to
Sat-B
Its rather easy to evaluate that situation. Look at what it takes for a user uplink and downlink station just to hit the satellite. Now imagine that you are asking for all that
power
and gain antennas to be added to one satelite just so now
this
one satellite can work another satellite. As you can see,
it is
pretty much impractical.
Bob, WB4APR
Sent via AMSAT-BB@amsat.org. Opinions expressed are those
of the author.
Not an AMSAT-NA member? Join now to support the amateur
satellite program!
Subscription settings:
http://amsat.org/mailman/listinfo/amsat-bb
Sorry all,
My email below wrongly thought we were still talking about EAGLE HEO type satellites doing cross links. And so my answer was correct but for the wrong question.
So YES, two LEO satellites can communicate if they are like PCSAT or PCSAT2 or our future RAFT and ANDE satellites because they all share the same uplink and downlink. And since they are designed for APRS users with OMNI antennas, they can hear each other just as well as they can hear users. The longest two-hop PCSAT1-PCSAT2 contct is shown on our web page: http://www.ew.usna.edu/~bruninga/pec/pc2ops.html covering 4426 miles from Algeria to the USA. In fact we WELCOME more and future packet satelites on the 145.825 space digipeater frequency! The more the better. More often coverage, and logner hops.
-----Original Message----- Subject: [amsat-bb] Re: Two Sats
If two sats like Hamsat (or Echo) were in orbit at the same time and could see each other ... Could User#1 uplink to Sat-A and then Sat-A would link to
Sat-B
Its rather easy to evaluate that situation. Look at what it takes for a user uplink and downlink station just to hit the satellite. Now imagine that you are asking for all that power and gain antennas to be added to one satelite just so now this one satellite can work another satellite. As you can see, it
is
pretty much impractical.
Bob, WB4APR
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings:
Sorry, My email below wrongly thought we were still talking about EAGLE HEO type satellites doing cross links. And so my answer was correct but for the wrong question.
So YES, two LEO satellites can communicate if they are like PCSAT or PCSAT2 or our future RAFT and ANDE satellites because they all share the same uplink and downlink. And since they are designed for APRS users with OMNI antennas, they can hear each other just as well as they can hear users. The longest two-hop PCSAT1-PCSAT2 contct is shown on our web page: http://www.ew.usna.edu/~bruninga/pec/pc2ops.html covering 4426 miles from Algeria to the USA. In fact we WELCOME more and future packet satelites on the 145.825 space digipeater frequency! The more the better. More often coverage, and logner hops.
-----Original Message----- Subject: [amsat-bb] Re: Two Sats
If two sats like Hamsat (or Echo) were in orbit at the same time and could see each other ... Could User#1 uplink to Sat-A and then Sat-A would link to
Sat-B
Its rather easy to evaluate that situation. Look at what it takes for a user uplink and downlink station just to hit the satellite. Now imagine that you are asking for all that power and gain antennas to be added to one satelite just so now this one satellite can work another satellite. As you can see, it
is
pretty much impractical.
Bob, WB4APR
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings:
The satellite has to be either inside or outside the Van Allen radiation belts. LEOs are limited to 1200 km (usually 800 km) so you need dozens of them to provide decent coverage. Once the satellite is above the radiation belts, you get almost 50% coverage anyway.
73,
John KD6OZH
----- Original Message ----- From: sco@sco-inc.com To: amsat-bb@amsat.org Sent: Sunday, September 10, 2006 14:41 UTC Subject: [amsat-bb] Two Sats
If two sats like Hamsat (or Echo) were in orbit at the same time and could see each other ...
Could User#1 uplink to Sat-A and then Sat-A would link to Sat-B (probably on one of the higher microwave bands) then Sat-B would downlink to User#2 and User#2 would uplink to Sat-B and be relayed to Sat-A and down to User#1 ??
If this could be done there would be a much larger footprint and launch costs would be far less expensive, correct?
Les W4SCO
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
participants (5)
-
Eric H Christensen -
John B. Stephensen -
Robert Bruninga -
Robert Oler -
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