Hi Greg, Drew, etc
This conversation is starting to make my head hurt! My example is to connect with some of our European friends. Some of them I share maybe a 60 second window, with PA1TNO it is less than 30 seconds. I have had several false starts in that I heard Paul 2E1EUB, by the time I located my downlink on his, he was gone. I want to predetermine where to set my uplink for a given downlink. There just is no the time be looking around. Like I said this is probably simple I'm just have trouble getting my thinking around the concept. Also if say I am planning on a downlink of 145.950 will Paul be looking at the same frequency? In the past these concepts never concerned me as there was always plenty of time to yak it up with the locals on AO-7. 73 Bob W7LRD CN87 Seattle, Wa. ----- Original Message ----- From: "Andrew Glasbrenner" <[email protected]> To: "Greg D." <[email protected]> Cc: [email protected], [email protected] Sent: Thursday, January 7, 2010 9:30:44 PM GMT -08:00 US/Canada Pacific Subject: Re: [amsat-bb] Re: probably simple > > > But any pass where you are really stretching the footprint is going to > be a low elevation pass. The more you stretch, the lower the pass. > In the limit, I think Bob's ultimate pass has a peak at .001-degrees > for both stations. If you're doing that, then you're at TCA, and zero > doppler. > > That's all I meant to convey, > > Greg KO6TH I understand, but with all due respect your assumption is incorrect that long distance QSOs are always at TCA and zero Doppler, even theoretically . This is only the case when the two stations are at near right angles to the track of the satellite. Use the following example. If I want to work LU5BOJ/O in FG75 from EL88 on HO-68, my only windows are at either LOS or AOS, depending on whether it is an ascending or descending pass. Neither pass will be a low pass for either station, and neither QSO will occur at TCA or zero Doppler. In Bob's case, let's look at his next possible window with Paul, 2E1EUB in IO92. Bob is in CN76. At the beginning of the 1 minute window tomorrow at 1251Z, Bob's Doppler shift on 432 is -3.68 khz. On the next mutual window at 1452Z, the beginning Doppler is -7.93 khz. On the next, at 2020Z, it's -8.3 khz. None of these windows are over 2 degrees elevation, and none are at TCA for either station. When you have 60s to make the QSO, being right dead on frequency is essential. Respectfully, Drew KO4MA _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
