What is SSDV? No, it is not a typo!

This week, every amateur radio satellite enthusiast is busy decoding and posting SSTV (Slow Scan TV) images from International Space Station. Now what is SSDV? SSDV is the abbreviation for Slow Scan Digital TV, in contrast to SSTV which is analog and has been there for a long time. It has been mentioned that SSDV is a packetised digital form of SSTV. I heard of SSDV first when I read about the recently launched ASRTU-1 amateur radio satellite, which has a UHF SSDV in addition to the V/U transponder and 10GHz high resolution image downlink onboard. UBSEDS24 Balloon with SSDV launched from Bristol, UK sometime back had recorded nice SSDV images of the clouds from above.


Lunar-OSCAR-94 which went into lunar orbit had transmitted SSDV images back to radio amateurs on Earth. WSJT JT4G was used for messages and transmissions were on 435.400 and 436.400 MHz. Transmitting power was about 2W, using VHF/UHF SDR transceivers. It was the world's smallest spacecraft to enter lunar orbit independently and radio amateurs had tracked its progress as it travelled towards the Moon and successfully entered lunar orbit.

JY1Sat was another satellite capable of downlinking images in SSDV format. This image format was developed by MI0VIM, for use in High Altitude Balloons. The satellite was named in honour of King Hussein of Jordan who was a radio amateur with callsign JY1 (SK). JY1Sat had an inverting linear transponder working in U/V mode as well. According to EA4GPZ, SSDV images from JY1Sat can also be decoded using gr-satellites, an open source program. Detailed instructions are available on the webpage, which I could not grasp much due to unfamiliarity with the program! He has also posted a partial image decoded from the audio recorded by K4KDR. Alternate option is to decode with FUNcube dashboard software, which is a closed-source program.

Comments

Post a Comment

Popular posts from this blog

What is LMR SDR?

Image
See also (new post):   Standalone Versions of LMR SDR!  I have been hearing about LMR SDR during discussions among homebrewers for the past few days on 40m. Thought of learning a bit about it and my web searches told me that some of the persons behind the development of LMR SDR are YE3CIF, UT3MK and F5NPV. F5NPV has given detailed descriptions about homebrewing LMR SDR on his webpage, including videos. Even though I did look at the pages of YE3CIF and UT3MK, they seem to be in regional languages. I could not find the expansion of LMR on those pages, though I presume that it would stand for land mobile radio. LMR cables which many of us use were initially designed for land mobile radio. SDR stands for Software Defined Radio like my FT-710, which uses software to do many of the functions done by hardware in the conventional superheterodyne radio receiver . It is interesting to note that LMR SDR covers from 160m to 10m band, that is the whole amateur radio HF bands. There are a...
Read more

Have you heard of zBITX?

Image
 Well, I had not heard till I read the program schedule of LARC-7 today. Most of you would be familiar with uBITX which has gone up to version 6. Some of you would be aware of sBITX, which is quite an advance over uBITX. Almost daily I am meeting a new uBITX user on the band, most of them using additional linear amplifiers. That made me join the BITX group on groups.io , where I am getting messages from uBITX and sBITX users from all sides of the globe. Still I was not aware of zBITX and that made me look around and came across two references. One was the video of a talk by VU2ESE at QRP ARCI . Another was an email in the BITX groups.io which was citing the former. zBITX is a new transceiver from VU2ESE based on Raspberry Pi Zero for 20W, having CW skimmer and FT8 modes in addition to the regular SSB mode and waterfall display which the sBITX also has. zBITX is quite small, just 3" x 3" x 1.5" in size. It is a Raspberry Pi Zero based 20 W software defined radio which h...
Read more

Homebrewing a Slim Jim Antenna

Image
 Slim Jim antenna, as the name implies, has a very slim design and hence very little wind loading. JIM stands for "J Integrated Matching" as it uses a J type matching stub. Slim Jim antenna was described by Fred Judd, G2BCX in 1978. The antenna has a lower takeoff angle and hence reported to have better performance than 5/8 wavelength ground plane antenna. People have made it using half inch copper pipe, ladder line and many other options! Approximate gain in the horizontal plane has been mentioned as around 2  dBi. Slim Jim antenna should be insulated from the antenna mast with a 'free space' of at least quarter wavelength. Antenna itself can be supported on a PVC pipe. Though it can be made for any band, it is quite popular as a 2m VHF antenna which can be made easily with good performance. It is almost like a vertical asymmetric folded dipole with a gap between the half wave and quarter wave regions. The exact feed points on the long and short parts of the antenna ...
Read more