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Re: AO-7 Mode A difficulties



Is there any issue with using circular polarization for uplink to AO-7?  I 
have heard that some sats prefer left-hand uplinks, while others prefer 
right-hand.  I presume that it is most likely linear-polarized up and down.

Personally, I think the big difference in modes could be to do with two 
issues:
1: the transverter design is  very different between those modes, the mode B 
is the newer "helaps " design that is aparently very efficient compared to 
conventional designs such as what makes up the mode-A portion.  This might 
be enough to make a difference in being heard in ssb.  Since there's limited 
power from the aging solar panels, it seems logical to assume that the 
less-efficient components would be struggling to work proplerly.
2: There's likely a lot of broadband QRM making it up to space on the145 
uplink... it would eat-up the available power without being detected unless 
you used a spectrum scope on the entire downlink band.  Also consider that 
the mode-A transverter is twice the bandwidth of the mode-B(50kHz compared 
to 100kHz), therfore there's twice as much input noise getting to the 
amplifier and hogging-up the available power even under ideal conditions.

I hope that this helps,
Auke, VE6PWN


----- Original Message ----- 
From: "Robert Turlington" <rob_g8ate@hotmail.com>
To: "Bob Stewart" <bob@evoria.net>
Cc: "Amsat Buleitin Board" <amsat-bb@amsat.org>
Sent: Sunday, November 04, 2007 1:21 AM
Subject: [amsat-bb] Re: AO-7 Mode A difficulties



Hi Bob
you are not the only one that struggles with AO7 mode A,I find that even 30w 
into a 6 el Quad pointed at the bird gives a good downlink ,it also depends 
on how good your Rx antenna is as well as things like background noise 
levels.Regards Robert G8ATE > Date: Sat, 3 Nov 2007 16:18:10 -0700> From: 
bob@evoria.net> To: amsat-bb@amsat.org> Subject: [amsat-bb] AO-7 Mode A 
difficulties> > I've made several attempts efforts to work AO-7 on > Mode A, 
but I just don't seem to be able to manage it. > I can hear CW signal, and 
if I whistle into the mike, but I > just can't hear my voice well enough to 
even attempt a > QSO.> > I'm using an 80 watt Mirage brick into an RHCP 
moxon > pair pointed straight up. I don't have any problems getting > into 
the FM sats with this setup. Is it because I'm only getting > about 40 watts 
EIRP from this and that's simply not enough> for AO-7 Mode A?> > Bob - 
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