----- Original Message ----- From: "SV1BSX" [email protected] To: "i8cvs" [email protected]; [email protected]; "AMSAT-BB" [email protected] 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 play with. !
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.
73" de
i8CVS Domenico