[amsat-bb] AO-7 CW Telemetry

[John Papay]

It is very rare to hear clear CW from the AO-7B
telemetry beacon around 145.972.  Most of the time
there is no beacon at all.  Sometimes there is
jibberish.  Usually the signal is very weak.

With AO-7 going through eclipse on every orbit, the
satellite can come out of eclipse in different modes/
options.  Recently there have been times where the
beacon has transmitted clear CW over North America,
something I have not heard over the years.

According to the DK3WN website, there was some cw
telemetry back in 2002 when the satellite was discovered
to be working again.  And there was some discussion about
what is valid data based on the last 3 digits sent in the
24 group block of data.  If the value is 649, 650, or 651,
the data is likely valid.

I first heard the image of the cw signal around 958.  It was
so loud I thought it was a valid user at first.  But since
the cw was all numbers I tuned up to the beacon frequency and
there the signal was louder than anything I have ever heard
on AO-7.  It took a while for me to get the recorder running
but I managed to capture some data.  After playing it back I
found that there was only one block of data where the last
group was valid, a 649.  Other later transmissions were loud
but the data was much different and the last group was not
correct.

I couldn't locate a telemetry calculator at first so I decided to
build one on Excel using the formulae provided by DK3WN.  The
data follows:

AO-7B Telemetry 24July2014   2318UTC
POS  Parameter                Range     Raw  Real

1A Total Solar Array Current  0-3000ma  171 2094.5ma
1B +X Solar Panel Current     0-2000ma  193  110ma
1C -X Solar Panel Current     0-2000ma  157  830ma
1D +Y Solar Panel Current     0-2000ma  108  1810ma
2A -Y Solar Panel Current     0-2000ma  286  250ma
2B RF Power Out 70/2          0-8watts  204 7.3728W
2C 24 Hour Clock Time         0-1440min 201 15.16min
2D Batt Ch/Discharge Current-2000/+2000 207  -1720ma
3A Batt Voltage               6.5-16.4  361  12.7V
3B Half Batt Voltage          0-10v     397   9.7V
3C Batt Charge Reg #1         0-15v     340   6V
3D Batt Temperature         -30 to +50C 300   95.8C
4A Baseplate Temperature    -30 to +50C 446   27.72C
4B PA Temperature 2/10      -30 to +50C 401   94.32C
4C +X Face Temperature      -30 to +50C 430   51.4C
4D +Z Face Temperature      -30 to +50C 498  -49.24C
5A PA Temp 70/2             -30 to +50C 545   29.2C
5B PA Emitter Current 2/10    0-1167ma  502   92.84MA
5C Module Temp 70/2         -30 to +50C 543   32.16C
5D Inst. SW Regulator         0-93ma    527   33.14MA
6A RF Power Out 2/10         0-10,000mw 606   23.076MW
6B RF Power Out 435           0-1000mw  643   219.9MW
6C RF Power Out 2304          0-100mw   679   255.881MW
6D Midrange Telemetry Cal     0-.5v     649   0.49

There are some values which are obviously not correct.
Some sensors might not be working properly since some
values are out of range.  However, the solar panel numbers
might be somewhat correct.  I wouldn't doubt it if the
transmitter was putting out 7 watts at the time.

Perhaps there are those who are familiar with the AO-7
telemetry that can make some sense out of the data.
Unfortunately we don't have multiple blocks of good data
to compare readings.  Maybe some have recorded recent CW
data and can find some good blocks that can be shared here.

The data was copied on my Arizona remote and Skype was being
used to listen.  But I am fairly confident that the cw copied
is correct.

73,
John K8YSE