Hi all. Re: the power debate ... From http://observations.biz ........................................................................................................................................
POWER. How much is enough? . La2qaa Feb 2006.
There could be many answers to that question but the correct one regarding amateur satellite communications is ...
"Just enough to maintain effective communications".
For instance, how many people reduce their power as the satellite they're operating on approaches TCA ... (time of closest approach) ... a good operator will, because they know that the use of excessive power is *not* good for the transponder. Case in point. When AO-7 first comes up over the horizon you'll probably need "X" amount of power to communicate effectively.
However, after 10-15 minutes, as the range decreases you'll find that a 3dB ... (50%) ... reduction of power will have no effect whatsoever on the signal. A *VERY* sensitive S-meter might show a difference but your ears certainly won't.
Hands up those that actually regulate their power to maintain effective communications ... (No, I didn't think so) ... you should try it sometime, you might get a surprise.
By the way, we do know ... (don't we?) ... why most satellites have a beacon?. One of the principal reason, after telemetry, for a beacon is so that you can regulate your power to be consistent with that beacon, it's your reference. No signal should EVER be more powerful than the beacon.
Naturally, it will also serve as your propagation reference. .........................................................................................................................................
For those cases where a beacon isn't operative (read AO-7) you can use VE2DWE's sensible suggestion of tuning up and down the band and regulating your power to be consistent with known non-alligator stations.
Alligator = all mouth and no ears.
Remember the old adage, if you can't hear them you can't work them.
A decent receive aerial ought to be the most important part of an amateur satellite station.
73 John. la2qaa@amsat.org
The proceedure I follow is to ALWAYS wear HEADPHONES and CONTINUOUSLY MONITOR MYSELF. I set my tx/rx to the uplink and downlink freqs shown by SatPC-32 and will be on within a few hertz so I dont have to go up and down the transponder finding myself. I also have an SWR/Wattmeter in line all the time. I adjust my power to a bit bellow the point where I no longer hear an increase in my signal comming back. As the qso progresses I continue to adjust the power up or down to keep my signal at the point that if I reduce it farther I hear a definite drop in my signal comming back. For VO-52 the max power I need is about 20 watts (unless some strong alligator is on in which case my return signal will be very much reduced and increasing my power up to 50 watts or more will still result in an increase in my return signal) and the minimum is the lowest that the FT-847 will go which is about 1 watt. For AO-07 the uplink power can be anywhere from a 100 watts from my amp and still be just above the noise level to as low as 10 watts for an S7 return signal above noise level.
Operating on a transponder is not not like working HF or a repeater where it is push to talk. It is much more challanging, to tune for doppler, adjust az and el rotors and power. You can automate the first two but the power is a manual adjustment.
Clare VE3NPC
----- Original Message ----- From: "John Hackett" archie.hackett@hotmail.com
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POWER. How much is enough? . La2qaa Feb 2006.
There could be many answers to that question but the correct one regarding amateur satellite communications is ...
"Just enough to maintain effective communications".
For instance, how many people reduce their power as the satellite they're operating on approaches TCA ... (time of closest approach) ... a good operator will, because they know that the use of excessive power is *not* good for the transponder. Case in point. When AO-7 first comes up over the horizon you'll probably need "X" amount of power to communicate effectively.
However, after 10-15 minutes, as the range decreases you'll find that a 3dB ... (50%) ... reduction of power will have no effect whatsoever on the signal. A *VERY* sensitive S-meter might show a difference but your ears certainly won't.
Hands up those that actually regulate their power to maintain effective communications ... (No, I didn't think so) ... you should try it sometime, you might get a surprise.
I just recorded a pass of AO-51 from my home in Switzerland, this is not for the faint of heart. Equipment this side is TS-2000, SignaLink USB, crossed dipoles and an unreleased version of Ham Radio Deluxe.
Anyway - count the number of callsigns you hear, then the number of actual QSO's :-(
It's not always as bad as this, maybe too much coffee was drunk before the satellite sailed overhead.
The recording is a MP3 in the ZIP file http://forums.ham-radio.ch/attachment.php?attachmentid=667&d=1177577469
Antenna webcam: http://www.hb9drv.ch/webcam.htm Antenna picture: http://www.hb9drv.ch/PICT0003.JPG Forums topic: http://forums.ham-radio.ch/showthread.php?t=6860
Simon Brown, HB9DRV
For reasons which I don't understand the file was in a protected area of my forums. Here's a link to the same file in the public ftp area:
ftp://ftp.ham-radio.ch/common/sats/audio/AO-51%202007-04-26%201030.zip
The reason for the posting: even when running the correct power levels there are other reasons why one may not make contacts. Seems that many were calling CQ but not hearing anything.
Simon Brown, HB9DRV
----- Original Message ----- From: "Simon Brown (HB9DRV)" simon@hb9drv.ch
I just recorded a pass of AO-51 from my home in Switzerland, this is not for the faint of heart. Equipment this side is TS-2000, SignaLink USB, crossed dipoles and an unreleased version of Ham Radio Deluxe.
participants (3)
-
Clare Fowler -
John Hackett -
Simon Brown (HB9DRV)