[amsat-bb] Re: The Moon is our Future

Fri Jul 3 10:43:32 PDT 2009

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 at 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 at yahoo.com>
To: <kg4zlb at gmail.com>; <amsat-bb at amsat.org>; "Jack K." <kd1pe.1 at 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 at gmail.com> wrote:

    From: Jack K. <kd1pe.1 at gmail.com>
Subject: [amsat-bb]  Rebuttal -  Re: Unused sats
To: kg4zlb at gmail.com, amsat-bb at 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 at googlemail.com>
To: <amsat-bb at 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.
        _______________________________________________
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Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
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