James,
Thanks for your email, which I have not included below, to save bandwidth.
You make a number of interesting points, and I might write more at a later time.
Regarding your point that there was little need to have good Doppler control of the uplink, as its FM:
In general terms, this is largely true, and for a 2m uplink, little or no tuning is required on AO-51/Echo etc. However, a number of earlier emails spoke of the more critical need for AO-16 as it appears to have tight filters compared to a typical FM uplink. Careful control of Doppler for the uplink would allow a more full use of the entire filter bandwidth, rather than using FM-Narrow, and having weak audio.
I still like the idea of attempting CTCSS, so may try this myself at some point. I have the sometimes great advantage that sat passes here may have only zero, one or two stations on, so it becomes possible to test or try things that might be considered unacceptable usage or sharing of the resource in many other locations around the world. If the sat makes a pass to my East, I can be close to 100% sure I would be the only station, so could test mostly anything I wanted that would not be harmful to the sat. (The downside is that its also impossible to make a contact too.)
Not related to AO-16, but something I intended to test on FO-29 at some point, was "two-station Doppler correction". Its not something I got around to, but the plan was to get the exact locations of both myself and the other station, and feed both sets of data into the Doppler corrections. The result could be that the other station would use a FIXED uplink and FIXED downlink for the entire pass, and the other station would do both. This would be ideal for someone to have their "first go" at working a contact via an SSB passband sat. HOWEVER, the signals would walk all over the passband on the sat, so would be totally unacceptable except for short tests, and when very few stations are in the footprint of the bird, as is mostly the case here in New Zealand. Sadly, its too late for FO-29, but it is still an idea I'd like to test. Again, I must repeat: This is NOT for use in busy parts of the world, were many stations are in the footprint, as it creates a more extreme use of the bandwidth.
Regards, Jim, ZL1TYF Wellington New Zealand
-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of James Whitfield Sent: Wednesday, 6 February 2008 1:58 p.m. To: amsat-bb@amsat.org Subject: [amsat-bb] Re: Automatic doppler tracking of DSB
Many thanks to each of you who have replied to my inquiry.
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