Not to mention the coherence between uplink and downlink. One high pass I was showing a 3.5KHz offset between uplink and downlink frequencies. The next pass (15'ish degs) the downlink was drifting severly (yes, my Doppler was accounted for)....I think they have some thermal issues to work out. It's a new spacecraft so some issues is a given.
Herb
On 12/31/21, 6:41 PM, "D. Craig Fox" DCFox@rwglaw.com wrote:
John, I was on a 12 deg CAS-3 pass earlier today. I really did not hear myself until max elevation and even then my downlink was marginal with TS2Kx, 5el up, 11 el down, no preamps. I have been on several evening passes including my first QSO on it with Christy, KB6LTY. Very few stations heard. While I lack the technical skills of John K8YSE to provide any graphical analysis, speaking entirely subjectively, I can confirm that the downlink is not particularly strong compared to, say, XW-2F or CAS4B, especially on the earlier 12 deg pass, and the transponder's passband noise is quite noticeable and definitely would cover weaker stations. The noise reminds me of the noise in JO-97's passband. When I worked Christy it was a much higher pass and the downlink was sufficiently strong until I lost it somewhere around the 15 deg point when descending. My Doppler file is set up right at .180 for the downlink and that is where I have hovered, except to move up or down to avoid the noise.
I believe my first uplink calibration was around 900 hz, so it was already pretty close and did not require much searching for my downlink. Of course, YMMV
I am sure others would appreciate a summary of operation suggestions.
HNY satops!
73, Craig N6RSX DM 13
-----Original Message----- From: John Brier johnbrier@gmail.com Sent: Friday, December 31, 2021 3:44 PM To: AMSAT BB amsat-bb@amsat.org Subject: [AMSAT-BB] XW-3 issues and tips for success?
So, I tried XW-3/CAS-9 on the first orbit and once later but didn't have any luck finding myself on the downlink. I want to try again but it seems the bird has issues and I'd like to understand more about those issues so I can have better luck next time I try.
On Twitter I've heard others say the sat is weak, has high SWR, not a sensitive receiver, noisy at TCA, fluctuating AGC, etc. It's also possible that the RX sensitivity issue is only bad at the edges of the passband, forcing people to work in the center. Has anyone confirmed that? What's up with the AGC?
What kind of uplink power/ERP is required/recommended?
Maybe we can come up with some general tips to make successful contacts on this bird more likely.
73, John Brier KG4AKV
https://twitter.com/k8yse/status/1476022600593809411 https://twitter.com/k8yse/status/1476047464796987400 https://twitter.com/dk3wn/status/1476276565285687312
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