[eagle] Re: what is going on?, some technical content at last.

John B. Stephensen kd6ozh at comcast.net
Tue Jul 15 21:01:50 PDT 2008

The S band downlink was very useful on AO-13. Mode BS allowed me to copy 
weak signals using the S downlink and others to copy me on the V downlink. 
By the time of AO-40 I had periodic long duration interference from WiFi 
devices in the neighborhood so the S downlink was unusable for hours at a 



----- Original Message ----- 
From: "Lyle Johnson" <kk7p at wavecable.com>
To: "John B. Stephensen" <kd6ozh at comcast.net>
Cc: "Andrew Glasbrenner" <glasbrenner at mindspring.com>; "Bob McGwier" 
<rwmcgwier at gmail.com>; "'Bill Ress'" <bill at hsmicrowave.com>; "'David 
Goncalves'" <davegoncalves at gmail.com>; "'AMSAT BoD'" <bod at amsat.org>; 
<eagle at amsat.org>
Sent: Wednesday, July 16, 2008 03:01 UTC
Subject: Re: [eagle] Re: what is going on?, some technical content at last.

>> AO-40 was heavily promoted in QST and downlinks were 10 dB stronger than 
>> AO-13 so activity went up.
> Yep, sometimes I heard 4 or 5 stations in addition to the Colorado 
> continuous SSTV downlink! And LEILA stepping on everything it could find 
> (except the SSTV downlink :-(
>> I don't know how long it would have lasted. One interesting fact was that 
>> the AO-13 70 cm downlink worked much better in Los Angeles than the 2 
>> meter downlink. Ambient noise was about 15 dB lower.
> AO-40 had downlinks strong enough to actually use.  AO-13 was definitely 
> for weak-signal operation and needed serious antennas.  Karl's analog 
> HELAPS was realy pushing the envelope to get near 100 kHz bandwidth.  An 
> SDX could do it easier - but we really need to prove the SDX can tolerate 
> the radiation and recover from a hit.  A reliable narrowband transponder 
> is to be preferred over an unreliable wideband transponder :-)  The 
> original Eagle proposal, if memory serves me correctly 9it often does not) 
> was to have a linear transponder and the SDX was goign to be an experiment 
> on the 2 meter downlink, 50kHz wide or so, with a bypass at the IF so if 
> it became unreliable we could still get engineering beacon data on that 
> downlink.  A coded S-band downlink is probably even better, though, based 
> on AO-40 experience.
> 73,
> Lyle KK7P

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