[amsat-bb] AO-85 TRANSMITTER POWER
n0jy at amsat.org
Tue Jul 4 06:55:51 UTC 2017
On 7/3/2017 22:37, jeffory broughton wrote:
> I am curious what the transmitter power of AO-85 is in either watts or dbm.
The PA was characterized over a range of temperatures and battery
voltages in its final design, in 2013. Unfortunately, those projected
temperatures (-50C to +10C) in the thermal analysis were quite lower
than are actually seen on AO-85. FWIW from my best eyeballing of the
graphs and given the reset 693 uptime 335876 telemetry (05:51 UTC July
4) with an RX temperature of 41.7C and battery voltage of 3.91, I would
guess that the output power could be just under 600 mW.
The output power increases with battery voltage but decreases with
temperature as the efficiency is lower in warmer temperatures.
800 mW is the maximum output we claim for the launch profiles, about 775
mW was the max measured in this characterization at 4.2V and a
temperature of -50C. Given the temperatures we see in orbit (about 10C
to 50C), AO-85 probably ranges from about 700 mW during eclipse when
it's not in a full sun phase (so cooler overall) at 10C and 4.1V, to 550
mW when it's in a full sun phase (warmer overall) at 50C and 3.8V.
All of that is scientifically based on my possibly debatable
extrapolation from the PA characterization data we have on file!
So Paul and John are both right in theory.
Jerry Buxton, NØJY
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