Actually, its very bad as it barely supports 1 user at 3 times the proposed maximum power level. You could support 100 users on a HEO with the same SNR and power output. Most users will consider 10 dB SNR to be marginal and want another 10 dB of signal strength on the downlink. The same amount of power has been consumed by 10 stations on HEOs.
73,
John KD6OZH ----- Original Message ----- From: Joe To: John B. Stephensen ; amsat-bb@amsat.org Sent: Thursday, July 02, 2009 22:01 UTC Subject: Re: [amsat-bb] Re: The Moon is our Future
Now thats pretty good!
But why is it soo good, when the HEO birds were soo hard?
something missing?
John B. Stephensen wrote:
Path loss for a lunar downlink at 435 MHz is 197 dB and the sky temperature is about 75 K. If you assume a 2.5 kHz wide SSB voice downlink and 10dB average SNR (16 dB peak) a perfect receiver needs to see -130 dBm PEP input. Given 5 dBic of gain on the moon and 17 dBic (one long yagi) of gain on the earth, the lunar transmitter needs to provide +45 dBm PEP (32 Watts) per user.
73,
John KD6OZH
----- Original Message ----- From: "MM" ka1rrw@yahoo.com To: kg4zlb@gmail.com; amsat-bb@amsat.org; "Jack K." kd1pe.1@gmail.com Sent: Thursday, July 02, 2009 11:31 UTC Subject: [amsat-bb] The Moon is our Future
Theoretically we may have a free ride to the Moon for an Amateur radio repeater!
In the past, the flight to the moon for a Amateur radio project has been cost prohibitive. We just could not afford to pay for the ride to the Moon. NASA is going to the moon with unmanned landers. NASA is open to the idea of flying some public service projects to the moon on their landers.
Now there exists the possibility of getting a free ride to the moon, curtsy of NASA.
What we need are the following:
A stable club with funding to build a simple transponder project. A plan for a simple transponder (KISS no complex P3E). A link budget plan for a Moon transponder.
One theory: We need a simple Mode-J transponder (2-meters up, 440 down). Low power consumption. Assume minimal antenna gain from the Lander (3 dBd on each antenna) Assume transmitter power 5-10 watts.
Questions: What’s the link budget? How much gain will be needed on earth for such a setup? Can we build a working mockup in 1 year or less.
The Moon is within Reach. Let’s Go for IT.
Miles WF1F MarexMG.org
--- On Wed, 7/1/09, Jack K. kd1pe.1@gmail.com wrote:
From: Jack K. kd1pe.1@gmail.com Subject: [amsat-bb] Rebuttal - Re: Unused sats To: kg4zlb@gmail.com, amsat-bb@amsat.org Date: Wednesday, July 1, 2009, 4:46 PM I have to disagree in the strongest of terms about disregarding HEOs "for now" which in essence will mean to become forever. Until, or unless, we could come up with something along the lines of a "Cell" system of leos, we are missing one of the major advantages of Satellites and that is almost guaranteed communications for long periods (several hours) at a time... I am in no way denigrating LEOs as they have their place, but in the major schema of things HEOS will and always have rule given the state of communications art...
I understand the desire to "do something" but I suggest that the major thrust should be directed at getting a transponder on the moon (or Mars) or some more KISS type HEOs up... Cubesats can take care of themselves if we do, Heck I would even join in and participate in something like I just mentioned, I just can not get excited about "Contest style" contacts with a 5-12 min window most of the time... I do that on 2 meters scatter all I want,
DE Jack - KD1PE
----- Original Message ----- From: "David - KG4ZLB" kg4zlb@googlemail.com To: amsat-bb@amsat.org Sent: Wednesday, July 01, 2009 4:09 PM Subject: [amsat-bb] Re: Unused sats
All good points but forget the HEO's for now - we just need a good source of regularly launched easy sats in LEO to augment the few working birds we have and replace what we have to as they fall out of the sky or just stop working. _______________________________________________ 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
_______________________________________________ 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
_______________________________________________ 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 ----------------------------------------------------------------------------
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