r/amateursatellites

İ am New to this. So... İs this supose to funny? İ dont get it?

This is from sdr-rtl blog v3 and antennas. And someone

Also why is there static things. İs my device broken or something?

Hey all, got my first Meteor M2-3 image last night (night pass so just IR). Pretty stoked it worked at all, but I lost a big chunk of the pass.

Setup: RTL-SDR Blog dipole kit as a V (53 cm, 120°, flat, pointed south) on a chair in the garden, Wideband LNA V2 between the antenna and the Airspy R2, Airspy at 2.5 MSPS, SatDump.
Pass went up to 59 degrees. I had a good lock between about 30 and 45 degrees on the way up, then it dropped out completely near the top and only came back for a few seconds on the way down. The live output was empty too, I only got images after running the .cadu through offline processing.

Is the dropout at high elevation the known M2-3 antenna thing, or is it my setup? And is a QFH worth building, or should I get a filtered LNA first?

Thanks!

437.625 MHz FM SSTV

I had so much fun receiving these. But it was a lot of work, since I captured every pass during the time and tried to decode every transmission.

Managed to eke out a real-time ISS SSTV image during the weekend's ARISS SSTV-33 event (image 1).

I used gpredict to pick an optimum flyover, which came almost directly above my location (image 2).

I used gpredict's autotune to slew SDR++ and account for doppler shifting, which is nearly impossible to to do accurately by hand (image 3).

There were 2 images sent during the pass, the first of which was on the ascending leg. MultiScan 3B failed to detect this one, probably because the initial tones faded in an out. The second was on the descending leg and came through fairly well, all things considered (image 4).

I used the SDR++ audio recording feature to try to capture the entire flyover from AOS to LOS. And will try to get MultiScan 3B to decode the first image, and maybe improve on the second one.

I honestly expected this image to be near perfect, given the flyover peaked at close to 80 degrees elevation. It's unfortunate that peak occurred during the 2-minute break between images. But that's life.

Equipment used:

• Receiver: RTL-SDR v3.
• Antenna: Standard TV antenna on the roof aimed roughly 30 degrees (towards DC) - not real optimum, has a few null spots, but works real well in general for other satellites.
• Software: SDR++ v1.3.0, gpredict v2.6.1-9399, MultiScan 3B v1.9.1
• Location: Remington, Virginia | FM18bn

Reception notes:

• RTL-SDR was set for 250 kHz sample rate, Direct sampling disabled, Gain 49.6 dB, no other options (including AGCs) set.
• SDR++ Radio was set for NBFM, 12500 kHz bandwidth, no other options (although some have had success setting the IF Noise Reduction to Narrow Band).
• gpredict was set for ISS Mode U - SSTV - Robot 36, which is nominally tuned for 437,550 kHz. Device was set to SDRpp, with a 10ms cycle rate, then engaged with Track and Lock depressed.
• MultiScn 3B was set for Robot, 36s Color, H. Sync engaged, Normal bandpass, 800 Hz BB. Saving the image is a trip, because all images are saved to an 'Rx memory' that is buried within the app bundle's Resources folder. It has to be dug out of there and copied because of recent macOS sandboxing rules prohibit it from accessing other disk storage areas. It should request access but this is an old app and doesn't know how to do that. Lol

After getting some nice LRPT images I decided to build myself an antenna to receive HRPT images from METEOR M2-3 and M2-4. I went for a direct helical antenna design: while less performant than a dish+antenna, it's much more portable. Also, my goal was to learn how to build it and do everything by myself.

My first design is made out of a rigid copper wire H07V-U 2.5mm², 13 turns around a 50mm PVC pipe connected to an SMA, with a reflector of 17cm. I'm directly connected to a Nooelec Sawbird GOES+, then an RTL-SDR V4, then a shielded 2m USB 2. I'm holding the reflector from the inside with a suction cup.

I've made a first reception try from by balcony in a dense city, thus in a really non ideal environnement. The first picture of the post is the image I've got.

The problems start here: I then decided to add an impedance matching stripe. I used a VNA that showed me nice results. However, I completely stopped receiving anything. I even went to an open field to test it, no sync. At the middle of the pass, at 80° elevation, I just completely bent the stripe out to "remove" it, and it directly synced for the rest of the pass until a 10° elevation.

Do you have any idea of why this happened? I'm going to see what's going on with the bent stripe on the VNA, but I may just completely remove it. Also, I'm open to any suggestions for improvements (for example, I'm thinking of reducing the number of turns to 12 or even 11). Thank you!

437.550MHz FM, Robot 36C, 1/4 wave groundplane antenna.