[amsat-bb] Re: bird to bird fun
domenico.i8cvs at tin.it
Fri Aug 29 06:01:04 PDT 2008
----- Original Message -----
From: "SV1BSX" <sv1bsx at yahoo.gr>
To: "i8cvs" <domenico.i8cvs at tin.it>; <w7lrd at comcast.net>; "AMSAT-BB"
<AMSAT-BB at amsat.org>
Sent: Thursday, August 28, 2008 9:34 PM
Subject: Re: [amsat-bb] Re: bird to bird fun
> Hi Domenico, Bob & all
> it's a nice idea but I am thinking also that, the relay between AO-7 &
> FO-29 needs UHF Uplink and UHF Downlink as well !
> Therefore, we need two UHF systems (TX-RX) working simultaneously
> for Full-Duplex operation.
> And even if the AO-7 Uplink is 3.7 MHZ lower than FO-29 downlink,
> we need two antennas in the same band and probably
> a repeater-style *Hi-Q duplexer* in order to avoid the desense.
> Or just a UHF antenna and a circulator dr Domenico ?
> Difficult components for the most of us!
Hi Mak, SV1BSX, Bob W7LRD & All
It's not a problem for me Mak because I currently use a 70 cm TX only
connected to a RHCP 10 turn Helix antenna and another different RHCP
10 turn Helix antenna connected to a 70 cm RX only and both Helices are
separated about 10 meters over the roof.
I tried to transmit to AO-7 uplink at 432.150 MHz center frequency with
about 100 watt without experiencing desensitivity at 435.850 MHz downlink
center frequency of FO-29 even using a low noise and high dinamic range
homebrewed cavity input GaAsFET preamplifier.
> However, it's a great challenge. For example @ 18:30 UTC the overlap took
> place between the 2 footprints over W.Asia. From E.Canada, Atlantic
> Ocean, Europe, Asia upto E.Siberia it was possible a QSO... !
But at 18:30 UTC of day 28 august during the overlap the orbit of AO-7 was
ascending northbound while the orbit of FO-29 was descending soutbound so
that the relative speeds by which each satellite see at the other one add
togheter and this make the doppler shift compensation another challenge to
> Amazing distance for LEOs ! Can you imagine that ?!?!?
> Yes, I know.. it's difficult, yes. But a great-great challenge for the
> hibernal months !
> And the AO-7 is working 24/7 for the next months - out of eclipse.
> Great opportunity !
> 73 de Mak, SV1BSX
OK Mak, we will try on CW as soon you are ready to go.
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