More SSTV from the ISS

Like many others around the globe I spent yesterday attempting to receive and decode the SSTV transmissions being broadcast from the International Space Station by the Russian Cosmonauts.

The SSTV activity had been due to last three days starting on Saturday but commencement was delayed by the NASA space walk.

Receiving the signal and decoding is relatively straightforward due to relatively high power used (around 25W) however getting a perfect image is a challenge and dependant on a number of factors.

  • The timing of the overhead pass. Due to the time taken to transmit the image and the three minute delay between each image it is possible to only be in reception range for the end of one image and the start of the next. 
  • The ISS is moving quickly and so the transmission suffers noticeable Doppler shift. FM is more immune to the effect but for optimal performance adjustment of the tuned frequency is required especially on high elevation passes (more information).
  • The ISS moves position, both in direction and elevation as it moves across the sky and will show up the peaks and troughs in a static antennas radiation pattern. This leads to bands of noise when the signal level falls. The use of a rotatable (and if possible tiltable) antenna (or even an handheld one) is the dirigour mode of operating satellites (and the ISS) for serious enthusiasts. 
  • Noise and local interference will also obviously affect the image.
Mission Control

I opted a two pronged approach, the Yaesu FT857D connected to my rotatable four element YAGI which is mounted horizontally for SSB and the old TRIO/KENWOOD TR9000 was connected to the X50 dual-band collinear mounted vertically.

I had two copies of the MMSSTV program running on separate laptops The TR9000 was left running largely unattended tuned to 145.800MHz, while the FT857D was tweaked to the optimum frequency while the YAGI antenna was rotated to the correct azimuth during the pass.

All adjustments were done manually and I use the Orbitron program for prediction and under the Rotor/Radio tab the frequency and azimuth are shown and updated during the pass (as can be seen in the screen show below)

I missed the first low elevation at 11:07UTC, but was able to monitor and decode images on all the remaining passes during the day, with some excellent results, the images show the full images decodes on both radio set ups as a comparison.

FT857D – Yagi

TR9000 – Collinear

FT857D – Yagi

TR9000 – Collinear

FT857D – Yagi

TR9000 – Collinear

FT857D – Yagi

TR9000 – Collinear

FT857D – Yagi

TR9000 – Collinear

I was especially pleased when one of my best images was featured on the Amsat-UK and the Southgate Amateur Radio News websites.

What was slightly worrying and it also happened during the last SSTV activities were some operators transmitting on the downlink frequency even during a pass, what sounded like someone keying up was responsible for the single noise line on another perfect image. I even received an unexpected SSTV image, complete with a call sign while the system was waiting for the next pass. I won’t publish it here as everyone makes mistakes.

The experiments are continuing today but I am in work so will just leave an automated set up running on the collinear.

Judging by the messages on social media these SSTV activities seem to have captured the imagination of a lot of operators and several members of my local club South Kesteven Amateur Radio Society (SKARS) had their first go with some excellent results and are hooked! The images can seen on the SKARS Facebook page

Long may the activities continue, hopefully started to transmit some live images from space.

Freeband SSTV Reception with RTL-SDR

Over the last few days there has been a lot of activity on some of the normally quiet amateur and ‘CB’ bands due to some Sporadic-E propagation yesterday the 50MHz (6 metre band) was a mass of SSB signals as operators chased some DX contacts.

I set up a WSPR receiver using my FUNCube Dongle and got a few contacts on 6 meters over a couple of hours.

The 27 MHz (11 metre band) was also very active, while I know it can be an active band I normally don’t receive much here due to location but last night I was getting lots of SSB transmissions by the ‘DX Freebanders‘ and I even caught a couple of SSTV transmissions.

I didn’t get many clear pictures not because the signals or audio was weak but mainly because one transmission would be broadcast over another before it had finished, causing noise, or worse stopping the decode and getting a truncated image..

Tonight conditions were similar but instead of the FUNCube Dongle+ I tried the RTL-SDR dongle with the R820T tuner chip which can tune down to the 27MHz frequencies and I managed to get some decent if again noisy and sometimes truncated images.

I used the SDRSharp/SDR# program and the free MMSSTV decoder, here are some more of posts concerning SSTV. I made a quick video showing the decode process.

Digital SSTV Decoding

I’ve decoded analogue SSTV transmissions before (check out some earlier posts) using the MMSSTV program, but another form of picture transmission is referred to as Digital SSTV.. It isn’t technically slow scan the the SSTV part has stuck because it sends images. In very basic terms it is file transfer using DRM “Digital Radio Mondiale” encoding.

The advantage over analogue SSTV is the use of error correction, with the error correction you can get a perfect image.

This afternoon while the snow was falling outside I had got SDR# with the FCDP+ running and noticed that there was some activitiy on 14.233 Mhz and fired up the EasyPal software and decoded a few images, and made a small video showing one image being received.

As you will observe in the video Easypal actually decoded the image before the end of the transmission because it didn’t need the extra data to error correct because of the very strong clear signal.
 
These were the two nice pictures I decoded today from OE3AWA based in Austria

Interestingly the only other previous D-SSTV image I have received was at the end of December last year, from the same operator!

Some SSTV Pictures

Over the last few days have been trying out the technology preview of SDR-Radio Version 2 with the FUNCube Dongle Pro PLUS and it seems excellent. While monitoring the bands I stumbled across some SSTV broadcasts on 14.230MHz, I haven’t decoded any for a while so left it running for a few hours and these are some of the better images.

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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Rainy Sunday, Damp Monday SSTV

With the total washout at the weekend with very heavy rain on Sunday I was able to spend a decent amount of time monitoring. I recently brought a dry-cell adapter for the Alinco DJ-X10 receiver (EDH-16) allowing me to power it using normal AA Ni-MH batteries as the rechargeable battery pack it came with doesn’t hold its charge any more.

So as the rain hammered on the window I decided to decode some SSTV images on the amateur bands. I connected up the discone and the computer tuned to 14.230Mhz USB and fired up MMSSTV. Some of the better decoded images I’ve got over the last couple of days are included below.

I did have an attempt at decoding some digital SSTV using EasyPAL but despite some strong signals couldn’t quite get a full sync, but I think that was down to the conditions and the relatively poor rejection of the DJ-X10. With no ATU the out of band signals and nearby signals from what I suspect are high power operators were just too much for it, as the following sound file demonstrates.

Swamped SSTV by nerdsville

ARISSat-1 Morse beacon

This weekend there are a couple of excellent daytime flybys of ARISSat-1 predicted, passing very high in the sky.  Up till now I have been concentrating on the FM transmission on 145.950MHz which carries the voice messages, voice telemetry and the SSTV. The other signals from the satellite use SSB and CW modulation.

So this morning I left the loft discone and my Realistic PRO2006 with MMSSTV in the spare bedroom waiting for the pass while I took the borrowed Alinco DJ-X10, which has SSB capability, outside and using the Yagi antenna I built up last weekend had a go at getting some of the CW beacon on 145.919MHz

I got a decent signal as you can hear below, and using CWGet managed to decode some of the telemetry and the identification, but the high noise and doppler effect did cause some problems.

Arissat1 cw beacon by nerdsville

While I was doing this the SSTV system caught a lovely image

Can not wait till tomorrow for two almost overhead passes in the morning and then time to watch the Grand Prix!

SSTV on PMR446

Following on from my experiments in receiving slow-scan television (SSTV) from the ARISSat-1 satellite I was intrigued by the prospect of actually transmitting and receiving some images myself.

Being unlicensed the only legal equipment I can used is PMR446 these are low power (500mW) handheld transceivers with very limited range. I have several some older models kicking about from when I built a eQSO internet PMR446 gateway.

The SSTV image is transmitted by frequency modulation using a varying audio tone to indicate different brightnesses. The software I have been using to decode SSTV is MMSSTV by JE3HHT (Makoto Mori) It can also be used to transmit SSTV images by connecting the audio output of the PC to the transmitter audio in. It allows editing and customisation of the images and the encoding format to use.

Obviously I couldn’t carry a PC around so instead I generated some images and recorded the generated sound to a WAV audio file and then used an old cheap MP3 player (which supported WAV files) connected to one of the Audiovox PMRS-838 handsets, configured to operate in VOX mode.

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The plan was to drive around to a number of local high spots and with the transceiver on the dashboard of the card output a series of images and see if they could be received and decoded back at base! – Each image taking around 2 minutes to transmit.

The base receiver was my Alinco DJ-X3 connected to the loft based discone. I had to use the DJ-X3 because it supports to 6.25kHz narrow band channel step required by the PMR446 channel allocations.

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Well the first set of results today have been pretty good, I went to three sites to transmit from and using the terrain profiler on HeyWhatsThat.com I could calculated any obstacles in the line of site..The base is on the left hand side, the transmission point on the right of the diagrams below.

Site 1, was 0.9 miles from home  This site is just across on the other side of the Trent Valley with no significant buildings in the transmission path.

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as you can see the five images all came across very well, just a slight sync error on one.

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Site 2, was 1.2 miles from home and is one of the local high spots. Unfortunately there is a housing estate on the top of the hill. It is possible to go by foot on some footpaths to get into some fields with a clear vantage point across the town and down the Trent Valley towards Nottingham. However today these were from the car parked up near to the edge of the estate. I just sent two images – and they are a lot nosier.

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Site 3, was 3.2 miles from home and is on a slight high spot across on the other side of the Trent Valley. I parked up in a layby and transmitted three images and really wasn’t expecting much. So was very pleasantly surprised by the high quality of the received images, as you can see there isn’t any geographical obstruction but there is a very big new power station at Staythorpe in the line of transmission which I expected to cause some issues. Some of the lines of noise on the images I suspect were caused when large lorries and vans were passing by on the road momentarily blocking the transmission path as it is quite a busy road.

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From these encouraging results definitely some more experiments to be done on this, and some tests further afield!