Really simple, really nice. I like the innovative way they achieved the RF quadrature: they did it by splitting and phase-shifting the RF signal, not the VFO signal. I also like Peter’s use of the AM broadcast signal to demonstrate the sideband suppression. Then, SSTV for icing on the cake.
The crew on the space station have been transmitting SSTV images. This morning I threw together a receiving system: I used my four element refrigerator tubing quad feeding the an RTL-SDR Dongle with HD-SDR software in the computer. For the SSTV decoding I downloaded a program from Japan: MMSSTV (very nice). To get the signal from HD-SDRto MMSSTV I just plugged a cheap little electret computer mic into the computer and taped it to the speaker.
At 0838 local today ISS flew almost directly over me. I aimed the quad south-west, and almost as soon as it was above the horizon very strong signals started pouring in. They produced the first picture (above).
ISS went silent as it passed over head. I swung the quad to the north-east hoping to catch another image as the station moved away. That is the second image (below). You can see that I was losing the signal about halfway through.
The distortion in the video image may be the result of me manually adjusting the receiver for Doppler shift.
Here is a little video of the action in the shack during the first half of the pass.
Here is the RTL-SDR Dongle Receiver in an Altoids Box:
Here is that the programs looked like on the screen — HDSDR on top, MMSS on the bottom:
Here is what the orbital pass looked like. ISS was East of New Zealand when I took this picture. ISS came up over the Eastern Pacific and Mexico before passing over N2CQR. This display comes from the excellent Heavens Above web site:
In celebration of Cosmonautics Day, Russian ARISS SSTV activity is planned for the second week of April.
Cosmonautics Day celebrates Yuri Gagarin’s famous flight on April 12, 1961 becoming the first human to reach space.
The SSTV event is planned for Saturday, April 11, beginning at 10:00 UTC and continuing until 21:00 UTC. All transmissions will use the high resolution SSTV mode PD180. Transmissions will be at 145.800 MHz. If similar to past events, 12 different photos will be sent through the weekend with 3 minute off periods between transmissions.
To receive the images in real time, all that’s required is a 2 meter radio receiver and a computer to convert the receiver’s audio to image form. The software to do this is available as freeware on the internet at sites such as http://hamsoft.ca/pages/mmsstv.php. Received images can be uploaded and viewed at the ARISS Image gallery found at http://www.spaceflightsoftware.com/ARISS_SSTV/index.php .
Please be advised that situational demands on crew time could result in postponement or cancellation of any ARISS activity. Please pay attention to the possibility of any change in scheduling.
So I was sitting in the shack yesterday morning, drinking coffee and listening to IGY by Donald Fagen on Pandora, when I heard what I thought was an alarm. I thought it might have been a smoke detector going off (always a real possibility in the N2CQR shack!). It took me a moment to realize that what I was hearing was the device pictured above. I’d left my 2 meter HT tuned to 145.950 MHz, and Arissat-1 was breaking squelch with SSTV tones. Very cool.
Later, I was thinking about this as I pedaled along on my bike. I remembered our recent discussion of Copthorne MacDonald, inventor of SSTV. Way to go Cop!
It is easy to join in the fun. Just tune you two meter gear to 145.950 and leave it there. You’ll soon be alarmed just as I was.
