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Re: Echo Ground Station Simplicity!



Error in the URL below:
It should be ...usna... not ...unsa....

On Sun, 22 Jun 2003, Bob Bruninga wrote:

> On Fri, 20 Jun 2003, Rick Hambly (W2GPS) summarised ECHO's features:
>
> > . Mode V/U, L/S and HF/U.  Also V/S, L/U and HF/S sometimes....
> > . Analog operation including FM voice.
> > . Digital modes. Store and forward. Bauds of 9.6, 38.4, 57.6, 76.8
> > . PSK31 repeater using 10-meter SSB uplink and UHF FM downlink.
> > . Four VHF receivers and two UHF high power 8-Watt transmitters.
> > . Multi-band, multi-mode receiver.  Analog and Digital simultaneous.
> > . Can have geographical personalities.
> > . Digital Voice Recorder (DVR)
>
> This is FANTASTIC!
>
> Although I frequently post about the 9 dB benefits of operating Mode-B
> for EASY sats 'to-omni-antenna-users', I must point out, that all of that
> advantage is lost -IF- one decides to use a small UHF beam.  THis is an
> important thing for everyone to understand.
>
> Now, since ECHO is to be a super-satellite, and since half the 'fun' of
> operating satetllites (and using them in education about satellites) is
> to POINT something at them, then Mode-J is EQUAL to Mode-B.  This is
> because a Handheld 4 element UHF beam is about the same SIZE as a VHF
> omni, so this balances the LINK budget using antenna size as the
> comparison.
>
> Now, another IMPORTANT thing that often gets overlooked is that it does
> NOT take an "OSCAR" array with AZ/EL rotators to work a mode-J LEO bird!
> It only takes a $60 TV antenna rotator and a small 4 to 7 element UHF
> beam the hear ANY mode-J low-earth orbiting satellite.  We do ourselves a
> disservice by implying that every satellite operators needs an OSCAR
> array.
>
> A small 10 dB gain UHF vertical beam canted up at about 10 degrees from
> the horizon can work  ALL terrestrial uses of 440 as well as work all
> the LEO satellites perfectly well.  Remember, you only need gain on the
> horizon where the satellite is 10 dB further away and spends 70% of its
> time.  When it is above 45 degrees (5% of the time) it is 10 dB stronger!
> See the table on http://www.ew.unsa.edu/~bruninga/rotator1.html

<error above.  Swap ...usna... for ...unsa...>

> We need to make sure the membership understands that ECHO will not need
> an OSCAR array, and in fact a TV rotator and a small UHF beam is perfect.
> ANything BIGGER just makes the beam narrower and tracking harder...
>
> Of course, with 8W of power, ECHO will also be able to communicate
> DIRECTLY to stations with an OMNI antenna under those modes when all the
> power is dedicated to one or two downlinks too.  But I think it will be
> better to have several modes running at the same time sharing the power to
> let more people use it at once.
>
> So make sure you have a working TV rotator.  In a few years you might
> not be able to buy them as everyone wants you to go cable and satellite and
> fiber...
>
> de WB4APR, Bob
>
>
> ----
> Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
> Not an AMSAT member? Join now to support the amateur satellite program!
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>

de WB4APR@amsat.org, Bob

PCsat WEB  page     http://www.ew.usna.edu/~bruninga/pcsat.html
ISS-APRS FAQ:       http://www.ew.usna.edu/~bruninga/iss-faq.html
CUBESAT Designs     http://www.ew.usna.edu/~bruninga/cubesat.html
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APRS SATELLITES     http://www.ew.usna.edu/~bruninga/astars.html
MIM/Mic-E/Mic-Lite  http://ssdl.stanford.edu/mims/

----
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