[amsat-bb] Re: Heard on FO-29

i8cvs domenico.i8cvs at tin.it
Thu Jan 28 17:07:27 PST 2010

----- Original Message -----
From: "Hal Lund ZS6WB" <zs6wb at telkomsa.net>
To: "I8CVS Dom" <domenico.i8cvs at tin.it>
Sent: Thursday, January 28, 2010 7:59 AM
Subject: Heard on FO-29

> Hello Dom
> I just wanted to let you know that I heard you calling this morning on
> FO-29 at 0615 utc. You were on CW on a downlink of about 435.840 MHz. You
> were heard for several minutes and I copied your call distinctly several
> times.

> You were probably transmitting on AO-7 at the time as AO-7 and FO-29 were
> very close together but AO-7 was just below a ridge to the west of me and
> I could not hear it directly at that time.

> We could almost make it on AO-7 if my station wasn't sitting in a bit of a
> hole.
> It appears that FO-29 has been operational for several hours continuously
> now so that looks very promising.
> 73  -  Hal  ZS6WB
> Pretoria (KG44ee)

Hello Hal, ZS6WB and All on the List

Tank you very much for the above important information and I will try to
explain you what was really happening this night/morning on day 28 jan
at 06:15 UTC

Infact during orbit 61091 at 06:15 UTC  I was transmitting to AO-07 around
432.158 MHz searching to be translated exactly on 145.940 MHz at the exact
moment in wich AO-7 was at the very LOS for me with less than 0.3° elevation
on South at the end of the descending orbit 61091 from North to South when
AO-7 was about over ZS-land in South Africa and despite a few hills 20 km
away over my horizon I received back my CW succesfully up to 0.3° elevation.

To determine my exact uplink frequency in order to be translated by AO-7 at
145.940 MHz +/- at the very AOS moment when the bird comes to me from
South to North during an ascending orbit it was also very important for me
this night because in the following days I plan to contact on skedule at
145.940 +/- MHz  the friend ZS6BB, Pierre in KG43EU

But what was really happening this night ? You are right !

The distance into free space between AO-7 and FO-29 was about 1500 km at
06:15 UTC and both satellites where in mutual covisibility so that my
145.940 MHz CW signal that was translated by AO-7 was received by FO-29
and retranslated by FO-29 in 435.840 MHz at 06:15 UTC when you received
my CW signal in Pretoria  KG44EE through two satellites !

In more details at  06.15 UTC the subsatellite point (SSP) of AO7 was over
Nigeria at 8.557° Latitude North and 10.095° Longitude Est and his footprint
was not completely covering  ZS land while the SSP of FO-29 was over Zaire
at 6.482° Latitude South and  Longitude 16.500° Est but his footprint was
fully including ZS land where you was able to receive me in KG44EE

The above demonstrates that when the footprints of  two satellites about
overlaps a two way QSO between two satellites is possible particularly  on
CW provided that the uplink and downlink frequency bands  are the same and
one station transmit to one satellite in 70 cm listening in 2 meters while
the other one transmit to the other satellite in 2 meters listening in 70 cm

Unfortunately this is not the case betwen AO-7 and FO-29 because the 70 cm
bands are different 435.800 to 435.900 MHz for FO-29 and 432.125 to 432.175
MHz for AO-7 so that only one way two satellite link is possible as you Hal
experienced  because the same 2 meters band is in common between both

The above reception of my signal by you via FO-29 also demontrates that
actually FO-29 is working very well after a very long QRT because it was
so sensitive to receive my signal in 2 meters via AO-7 and retranslate it
into 70 cm with sufficient power to be received by you in 70 cm in Pretoria
South Africa

By the way since you in KG44EE are very close to Pierre in KG43EU I am
confident the at the end of testing and try with Pierre via AO-7 I can try a
QSO via AO-7 as well with you and I will informe you about if you agree.

The distance from my JN70ES and Pierre in KG43EU is 7548 km and with
you in KG44EE is 7511 km both no bad distances from South Italy and
South Africa via AO-7

Best 73" de

i8CVS Domenico

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