Archive for category: SSTV

Some continuing short bits on SSTV….

March 16, 2014 | Amateur Radio, Raspberry Pi, SSTV | By: Mark VandeWettering

Nothing too exciting going on, but minor bits of code and play have been done, so I thought I’d update. First of all, there is a program for decoding SSTV on the Pi, called QSSTV. I don’t have a proper sound setup on the Pi yet, so I couldn’t test it live on the air, […]

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Analyzing an SSTV recording…

March 12, 2014 | SSTV | By: Mark VandeWettering

Inspired by this webpage, I decided to write a simple zero-crossing analyzer, just like his. The code turns out to be remarkably simple, and would allow me to reverse engineer modes that aren’t adequately documented. I called this program “analyze”: The code is dead simple. It loads the sound file into memory and then figures […]

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A brief introduction into color spaces, as used in SSTV…

March 11, 2014 | SSTV | By: Mark VandeWettering

Rob (AK6L) was interested in my recent experiments in slow scan television, but didn’t know much about color spaces. It’s an interesting topic on many fronts, and I thought I’d write a brief post about it here to explain it to those who may not be familiar. Consider this nice 320×240 test image of Wall-E […]

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Additional Experiments with SSTV, with some ideas….

March 9, 2014 | Amateur Radio, Raspberry Pi, SSTV | By: Mark VandeWettering

Previously, I had written an encoder for the Robot 36 SSTV mode. I chose this for a simple reason: it appears to be the most common mode used in downlinks from satellites, such as the ARISSat-1. It’s not a bad choice, and presents reasonable quality in just 36 seconds. Today, I decided that I should […]

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SSTV travels through the Ether! A minor success!

March 8, 2014 | Amateur Radio, Raspberry Pi, SSTV | By: Mark VandeWettering

So, this morning I played around a bit more with my Raspberry Pi code to try to see if I could make an SSTV beacon. The idea was to use two existing bits of code, raspistill and my own SSTV encoder (robot36), and glue them together with a small bit of Python. The code uses […]

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Apologies to Ken and Eric re: SSTV Challenge…

September 29, 2011 | Amateur Radio, SSTV | By: Mark VandeWettering

My face is red. I had claimed yesterday that nobody had tried to decode my SSTV challenge, when in fact both Ken and Eric decoded it. Eric was the first, who sent me this decode: It’s a bit noisy, because he just played the sound file on his laptop and decoded it on a PC […]

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An impractical classic SSTV decoder…

September 28, 2011 | Amateur Radio, SSTV | By: Mark VandeWettering

A few days ago, I posted a .WAV file for a classic 8s SSTV image and asked if anyone could decode it. Nobody replied (I wasn’t surprised) so I set about writing my own demodulator. Since I’m inherently lazy, here was my idea: generate the complex signal using my previously debugged Hilbert transform code. Then, […]

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Classic Black and White SSTV timings?

September 26, 2011 | Amateur Radio, SSTV | By: Mark VandeWettering

I was trying to determine the exact timings for the classic “8 second” black and white SSTV mode. Copthorne MacDonald suggests 15 lines per second, to make 120 lines in 8 seconds. The vertical sync pulse has a duration of 30ms, and the horizontal sync pulse duration is just 5ms. The sync frequency is 1200Hz, […]

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“Classic” Black & White SSTV…

September 25, 2011 | Amateur Radio, SSTV | By: Mark VandeWettering

I haven’t had much time for actual experimentation, but I have spent some time researching and some more time thinking about how to properly implement and test analog SSTV modulators and demodulators. I haven’t made much actual progress, but I thought I’d document some of the information that I’ve discovered and my current thoughts. First […]

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Experiments with SSTV in the presence of noise…

September 20, 2011 | Amateur Radio, SSTV | By: Mark VandeWettering

Last night while watching television, I decided to code up an SSTV modulator for the most popular US mode, which is reportedly Scottie 1. I had done most of the heavy lifting when I created a Robot36 encoder a few years ago, so I mostly cribbed the meat out of that code, and modified it […]

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