ISS SSTV on 437.55 MHz @ 1511UT
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