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Sometimes Data Can Be Eye-catching


Gary
 Gary
(@gary)
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image

Caught this on the waterfall last night as JY1SAT and CAS-4A satellites were passing overhead at the same time and occupying the same frequency. 

The wide signal between about 145.833 MHz and 145.8425 MHz is the 4.8K Baud telemetry data from CAS-4A.

The bright data signal from about 145.8365 MHz and 145.8375 MHz is the 1200 BPSK telemetry from JY1SAT.

And over to the right at about 145.8565 MHz is the CW beacon from CAS-4A.

Of course, the slant in the signals is due to the Doppler shift.

There is a sort of beauty in it that maybe only RF nerds can appreciate, hi.

 

Gary, WB5PJB

Castle Rock

 


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Jeff Karpinski
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Outstanding capture!


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kx3dx
(@kx3dx)
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Joined: 3 years ago
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Gary - what antenna are you using for these satellite passes?  Back in the 80's I was using a small 3 element yagi without elevation control for the 2m uplink and a full wave horizontal loop 10 feet off the ground for the 10M down-link.  For the old RS10/11/12/13 birds.  RS15 was fun but had problems soon after it was placed into service.

I'm making some ISS APRS "repeats" with just 4w and a small gain stick on the roof.  I was wondering if a dual band turnstile would work for 2m/440 for some of the overhead passes.  I don't know that I want to get back into full blown antenna setup just yet.

My SDRplay is sitting here idle.....hmmm.  Do you have a pre-amp on yours?

Dave - kx3dx, Larkspur


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Gary
 Gary
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@kx3dx Hi, Dave. Due to being in an HOA, and space limitations, I have to compromise on antennas. I recently purchased a Qudrafilar Helix antenna (QFHA) from antennas.us for both 2 meters and 70 cm satellite reception. The 2 meter model is the UC-1464-531 ( https://www.antennas.us/uc-1464-531-vhf-qfh-amateur-satellite-antenna.html ). If you go to that link, you will see a photo of my QFHA that I sent them while it got initiated right away with our snowfall last week. So far, I have been very pleased with the QFHA antenna. It performs better than the eggbeater antenna that I also have for satellite work, and has a much smaller footprint. Omni antennas like QFHAs and Eggbeaters certainly aren't going to match circular polarized Yagis on an AZ-EL rotator, but they definitely cost less and take up little real estate. The QFHA from antennas.us is encased in a PVC radome and painted black. It is well-built and can probably go on top of a roof without raising the ire of HOA cops. The 70 cm version of the QFHA is very small and could definitely be placed on a roof and no one would be the wiser.

Right now, my preamps are on the eggbeater antennas in my attic, so the QFHA antennas are running barebones to the RSPduo SDR receiver. I have mainly been doing 2 meters lately, and the QFHA is doing so well without a preamp that I am not sure a preamp is going to help all that much. The eggbeaters, being in the attic, are at a disadvantage due to losses incurred by the roof, so they need the preamps more so than the QFHAs. But, I did have the eggbeaters outside previously, so that is what I base my performance comparison on between the two antenna styles. 

If you have space for Yagis and if you can rotate them with a relatively cheap TV rotator in the azimuth, then aiming them at 45 degrees fixed elevation, or thereabouts, can perform quite well. Of course, you have to keep manually turning the rotator during passes. A RS-232 controlled rotator is ideal, but the prices go up quite a bit with that control feature.

If serious voice contacts are your goal, then the Yagis are ideal. If casual voice contacts and decoding telemetry is your goal, then the QFHA antenna can be a good option for a lot less $$$ and a lot less space required.

Yes, it is good to see the ISS APRS back in operation. That is always fun to digipeat through during passes. I hope the equipment keeps working for a long time on the ISS this time around.

73,

Gary, WB5PJB


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kx3dx
(@kx3dx)
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Joined: 3 years ago
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Gary, thanks for your reply - antenna.us has a lot of offerings for some very good prices!  I'm in a little bit of a holding pattern right now - I am becoming semi-retired - just working on the details of off-loading my projects and mentoring the kids to take over.  But very soon I should be a part time employee and have more time for fun.

A home brew turnstile or egg-beater will be my first step.  My home brew turnstile worked well 30 years ago.  My little SDRplay box sits unused so that will be the 2m receive - my FT-817 will be the up-link.  I guess I'll pickup a FT-991a if this all pans out for me.

Dave kx3dx


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