Bob,
Your explanation to my questions make much more sense now that I worked another pass of the satellites. Today the two were sufficiently separated that I could see one lagging behind and thus higher up in frequency because of Doppler shift. Your explanation on why the same frequencies for the two birds is quite nice. Also the frequency offset difference for the PSK beacons as well as the different IDs work as well.
Bricsat was quite a bit weaker but that was probably because I was trying to track PSAT with my Arrow on a tripod. It was also a couple of Khz higher up. I also saw the difference in the two beacons so now I know how to tell which from which.
I did try transmitting PSK31 USB on 28.120 + 1Khz or so and listening through HDSDR on 435.350. I heard faint signals of other PSK signals but believe they were just some other terrestrial QSOs and not directed through the satellite. They were slipping down the DIgipan waterfall as they would be without correction. I was not doing correction either on 28Mhz but I was hoping, even on playback of the HDSDR I/Q recording, to find me but I never did. Going to try a different software configuration next weekend to try and hear myself live.
The best time to test PSK through these satellite transponders will be overnight passes when possible so as to avoid terrestrial stations from calling other terrestrials and confusing things. Will have to wait for times to shift for that.
73, Tom, N5HYP
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Message: 11 Date: Sun, 24 May 2015 10:56:55 -0400 From: Robert Bruninga [email protected] To: [email protected] Subject: Re: [amsat-bb] PSAT and Bricsat FM PSK on same frequencies Message-ID: [email protected] Content-Type: text/plain; charset=UTF-8
... how will this work with two FM satellites on the same frequency?
The idea is to serve users no matter which spacecraft is in view. And to not have the users have to always change frequencies and track different objects. Imagine a camper in the field. Just point your beam towards AOS generally and set +5 KHz tuing and when a satellite comes into view, you can use it.
Many things separate them: 1) Distance 2) Time 3) Doppler 4) Users antenna beamwidth
When they are 5 minutes apart, the beam headings will be over 90 degrees apart (10 to 15 dB separation), the Doppler will be typically 10 KHz (10-15 dB separation) for a total of 20-30 dB or more to prevent capture effect.
Since an orbit is 95 minutes long, and the satellites will drift, then 95% of the time, this condition of at least 5 minute separation, will be met.
PSAT PSK (W3ADO-5) was built over 3 years ago and is hardwired to power up by default (maximum chance it will work despite spacecraft packet link or other failures)
BRIC PSK (W3ADO-6) was built just last year and has independent control by Brno designers (can be off while sats are adjacent) It also powers up by default (again, for maximum availability in case of bus failure).
So I think the choice pretty much meets the goals of maximum availability to users and as independent of spacecraft failures as we could make them.
Hope that Helps. Bob, WB4aPR