Re: [amsat-bb] PSAT - power requirements
WB4APR recommends no more than 25 watts.
That was the design goal, but until we get more experience, we wont know for sure. But since everyone can see their own downlink just like everyone else can see it, it should be no problem adjusting for minimum uplink power.
But with any shared transponder it can also become an arms race. As one person increases power it drives the AGC down and everyone else goes down, so they also increase power and this just keeps going until the AGC is maximally tightened and everyone is transmitting max power and everyone is weak.
What we really need (BEFORE this happens) is for everyone to give us feedback as to the minimum power they needed to maintain a minimum signal in the passband and of course, what kind of antenna they are using under those conditions. And this is best early on when there are only 1 or 2 usewrs at a time..
If you don't yet have PSK31, but want to get some data, team up with an HF friend in your area and ask him to just transmit for the next 10 minutes and you can then receie his downlink while commenting on his signal strength throughout the pass.
The prelaunch orbit estimate I saw was a 700 km x 350 km orbit with an
expected orbital lifespan of 3 years. I'm not sure how close that is to the final orbit. We don't know yet either, but perigee is nearer the morning passes and apogee is nearer the later passes (THis is for the Northern Hemisphere.). Both apogee and perigee being near the equator.
Bob, WB4aPR On family travel and with very spotty Email till next week.
On Thu, May 28, 2015 at 2:58 PM, Red Willoughby redski@bellsouth.net wrote:
A couple of questions:
How much power (to a dipole) is recommended for uplinking on 28.120 PSK31?
Also, what is it's altitude?
And, how long is its expected lifespan?
Thanks in advance.
Red KC4LE
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Quoting Robert Bruninga who wrote on Thu 2015-05-28 at 17:40:
If you don't yet have PSK31, but want to get some data, team up with an HF friend in your area and ask him to just transmit for the next 10 minutes and you can then receie his downlink while commenting on his signal strength throughout the pass.
At this moment in the year HF propagation on 10 meters is almost non-existant in Europe (from time to time http://dxheat.com/dxc/ suggests there is good propagation in the americas). This means the PSK31 uplink band for PSAT is usually quiet.
A good time for testing this. I can do uplink on HF or downlink on 70cm, but not both during the same pass. My locator JO22NC and my time is limited due to work/family life ;). HF uplink is easier since that's all set up in the shack.
Koos PD4KH
Quoting Robert Bruninga who wrote on Thu 2015-05-28 at 17:40:
What we really need (BEFORE this happens) is for everyone to give us feedback as to the minimum power they needed to maintain a minimum signal in the passband and of course, what kind of antenna they are using under those conditions. And this is best early on when there are only 1 or 2 usewrs at a time..
If you don't yet have PSK31, but want to get some data, team up with an HF friend in your area and ask him to just transmit for the next 10 minutes and you can then receie his downlink while commenting on his signal strength throughout the pass.
I decided to play the role of the HF friend and Jan van Gils PE0SAT was kind enough to record the downlink for me in a pass that started at 09:59 UTC this morning for me in JO22NC.
The short conclusions:
- I needed 20 watts on HF to get through the satellite (when the telemetry signal was active) and produce a readable signal.
- The automatic switch in the transponder does not recognize PSK31 from earth very well. Every time it switched off when the beacon packets stopped, even with reasonable strong PSK31 from earth.
The complete story of how this was done and the telemetry seen at
http://idefix.net/~koos/newsitem.cgi/1433017519
Koos van den Hout PD4KH
participants (2)
-
Koos van den Hout -
Robert Bruninga