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Re: AO-50 now open to all



Robin and all,

I have been enabling the repeater automatically over the U.S. for well over 6 months now. When within site of Florida for more than 3 minutes, and given no serious competition on the uplink, the satellite is automatically enabled.

Please!!! All new users be advised, be VERY SURE that your equipment is good enough to hear the satellite before attempting to enable it with the 74.4 hertz tone. If you have any doubts at all, let someone else turn it on. What will be disastrous is if some of the users that have marginal receive systems spend half the pass transmitting the 74.4 tone at 50 watts. 2 seconds is enough, and the receiver is VERY senstive.

Also, for those trying this sat out for the first time, bear in mind that with a single 1/4 wave whip for the downlink transmitter on the satellite you will experience occasional severe fades caused by A) cross polarization if using a linear antenna or B) the spacecraft body blocking your view of the antenna. B happens even with large AO-13 class stations with a preamp. This week I've noticed the downlink is particularly good at the beginning of the ascending passes, and not so good near the end of the pass.

Altogether this little bird is quite a winner, and I hope to see more folks on it soon.

73, Drew KO4MA



-----Original Message-----
From: VEFRH@aol.com
Sent: Jun 10, 2004 10:27 AM
To: amsat-bb@AMSAT.Org, Advisors@AMSAT.Org, bod@AMSAT.Org
Subject: [amsat-bb] AO-50  now open to all

Greetings,
I have been advised that I can now publish the tone to Open AO-50 to all  
users as the power availability appears to be good.
To switch the transmitter on you need to send a CTCSS tone of  74.4  Hz.
the order of operation is thus:
 
 (allow for Doppler as necessary)
 
1) Transmit on 145.850 MHz with a tone of 74.4 Hz to arm the 10 minute  timer 
on board the spacecraft.
 
2) Now transmit on 145.850 MHz  (FM Voice) using 67.0 Hz to PT the  repeater 
on and off within the 10 Minute window.
 
3) Sending the 74.4 tone again within the 10 minute window will reset the  10 
minute timer.
 
Some additional information ...
 
The spacecraft repeater consists of a miniature VHF repeater with a  
sensitivity of -124 dbm, having an IF bandwidth of 15 KHz. The receive antenna  is a 
1/4 wave vertical mounted in the top corner of the spacecraft. The receive  
audio is filtered and conditioned then gated in the control electronics prior to  
feeding it to the 250 mW Transmitter.
The downlink antenna is a 1/4 wave mounted in the bottom corner of the  
spacecraft and canted at 45 degrees inward.
 
73
Robin Haighton VE3FRH
President AMSAT-NA
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