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AO-40 S band telemetry / reception report



Hello all!

I was able to hear AO-40 today and post this to share my observations.

My station is in FN20ah, Reading, PA. (40.3316N, 75.9870W).

I am using 2 Directive Systems Blowtorch loop yagis in a 1 x 2 array.  They
are cut for 2304 and are really for terrestrial weak signal work.  The
rotors are M2 MT-3000 and RCP2800.

I have an SSB Electronics preamp on the mast near the power divider; also
centered on 2304.

I run 100 feet of LMR-600 UF to the house where I have 50 feet of 7/8 inch
hardline bringing the signal to the shack.  Then I have 10 more feet of
LMR-600 to the rig.  (Its a good thing the SSB Preamp has lots of gain!)

The rig is an ICOM IC-970H with the ICOM 2400MHz module installed.

Frequency control was via Wisp, using a homebrew visual basic program to
pick off the doppler info from Wisp's DDE output,to control the 970H via the
CT-17 system thru COM5. (Keps Set #18)

I used a center frequency of 2401.317.240 and found that I had to use
3.6-4.6 KHz of RIT. This would suggest that the center freq is on the order
of 2401.321-2401.322 MHz, if the ICOM is on frequency.  I suspect that it
is, as UO-11 center frequency was right on at 2401.500 MHz for me today.

The TNC was an AEA DSP-2232 with the new AO-40 400 B DSP modem loaded.

Results:
UO-11 is Q5 copy here but S meter moves little if at all with it.

AO-40 AOS here was 940 UTC today. Initial range was 7622.6 km, phase 4.2,
squint 41.  Squint minimized at 28 at 0950 UTC when distance was 9462 km.
(I used Nova which I believe gives the correct squint with alon 2 and alat
260).

Initially AO-40 was peaking at S8 (meter is at 0 with no signal), with a a
good bit of fade.  The DSP-2232 was able to copy telemetry out to 1120 UTC
at a range of 29000 km, but I got no good CRC after 951 UTC, just after the
optimal squint time noted above.  AT 1120, beyond which the DSP-2232 lost
lock, the squint was 63.7 degrees.

Once the bird was a ways out (between 35 and 40K km) I was able to check the
pointing of my antenna as I lost the signal with just a few (less than 5)
degrees of mispointing.  The antenna was 'right on' with Nova doing the
tracking.

At 40 K I essentially lost the bird in the noise, not hearing it at all,
although I could still see the traces at times using AO40r, which I also
found helpful for getting the signal frequency centered at first.

I am sending my telemetry files (mostly bad crc) to the repository.

Thanks to all who helped me with this...I hope this helps someone else who
is like me just getting started at S band satellite work.

PS I used the loop array because it is already up there on the tower.  I
also have one of the barbeque grill dishes, but with stock feed it won't
handle the 50 watts I use for terrestrial work on 2304, so it is currently
not being used.  I may or may not end up putting it up for AO-40, depending
on how this setup works.

73,

Roger Rehr
W3SZ ex AA3QK, WA3JYM  FN20ah
2 Merrymount Road
Reading, PA  19609-1718
http://www.epix.net/~rrehr/w3sz.htm

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