Radio Astronomy

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This month’s Sky at Night program was all about meteorites and how to find and detect them especially during the Perseids meteor shower. In the program was a section that showed some Radio Astronomy which detected incoming meteorites. This involved listening to a powerful VHF radio station out of range normally, in this case France (GRAVES) . When a meteorite enters the atmosphere it leaves an ionised trail which reflects radio waves back down to the ground. This is heard as a ‘ping’ and can be viewed on a computer. Impressive, but I thought it looked complicated.

Then the following night I went to a meeting of the Bolton Wireless Club and Ross (G6GVI) told me how he had re-created the set up on Sky at Night by using a piece of software called ‘SpectrumLab’ and a receiver tuned to 143.050Mhz to monitor the GRAVES VHF station in Dijon, France.  I decided to have a go myself with some amazing results! I used my Yaesu FT857D tuned to 143.049Mhz and set to USB with just my collinear as an antenna.

The first image shows a larger ‘ping’ along with some smaller ones recorded over about half an hour just after midnight shortly after the Perseids peak.

The second image is captured over a longer period, from around midnight to 8:00am, it shows lts of small pings along with some quite big ones. Remember that these are taken after the Perseids maximum, but still a lot of activity.

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Easy Topband Transmitter by G3OGR

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At last…I managed to find the original article in Short Wave Magazine!

In 1970 just before I got my Amateur Radio licence I built my very first transmitter for Topband. The circuit came from Short Wave Magazine and was produced by F.G. Rayer G3OGR. My first attempt was built on an aluminium chassis and my Dad made me a front panel out of mild steel. At the time Neil, G3ZPL had built the same circuit and it worked great! The circuit consisted of an EF91 valve in the VFO and another in the buffer. The Power Amplifier (PA) was a 5763 valve which could run about 15 watt input.
I have never been able to trace the original article, I remember that it was in SWM and had a green cover with TRIO on the top. I even wrote to SWM to see if they could trace it in a back issue, the guy managed to find a ‘similar’ circuit by G3OGR, but it was not the original with all the construction details. There is a nice website  http://www.americanradiohistory.com/Short_Wave_UK.htm which has scanned copies of  the archives of many of the old radio magazines. I managed to find the magazine that I was looking for…. April 1970!  http://www.americanradiohistory.com/Archive-Short-Wave-UK/70s/SWM-1970-04.pdf   (You have to scroll down a bit to find the beginning of the magazine)

 

After spending weeks of painstaking drilling, filing and soldering I finally got the transmitter to work, but it had a problem. The VFO seemed to react with the PA. When I tuned the transmitter to the antenna the VFO would pick up spurious signals and shift up the band! Although I had an OA2 stabiliser valve this did not solve the problem. Maybe this was caused by the power supply dropping in voltage when the PA was taking more power.
Later I borrowed my transmitter to George G3ZQS and his antenna got hit by lightning which welded together the vains on the tuning capacitor! Not to mention the Power Supply which ‘blew-up’ – one of the smoothing capacitors exploded leaving a permanent dint in the roof!
When I got my licence I rebuilt the transmitter with a screened VFO in a separate aluminium box, and an aluminium front panel, this worked really well and was completely stable. The modulator used an ECC83 which had a high gain, I seem to remember using an ECC82 which had a lower gain, but same valve pin configueration.
F.G. Rayer produced loads of circuits and designs for transmitters and receievers in the 1960’s and 70’s. Almost every month had a design from this guy in Practical Wireless, Short Wave Magazine or Radio Communication. Most were variations of a theme and at the time he was the Enid Blyton of radio. I have to admire Francis G. Rayer, his designs were always well written and easy to follow. I recently found out that he also wrote science fiction books!
Thank you G3OGR!

Topband 1963Mhz net

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Listening to the 1963 net on my Sangean Radio in the garden this morning!

The 1963 net is on Topband at 11.00am where some Radio Amateurs from Bolton use AM. It is a pleasure to listen to using the Sangean Radio, the sound quality is superb and is sensitive enough to hear all the stations using it’s own telescopic whip. Reminds of the days back in 1967 when I used to listen to the Sunday afternoon Topband net using my Roamer 7.

GB17YOTA link with the ISS

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This week YOTA (Youngsters on the air) has been a focus for the RSGB with special event stations operating with GB17YOTA.  Today ARISS had set up a link with Astronaut: Paolo Nespoli IZØJPA on the International Space Station with 145.800Mhz downlink. In the past I had some success listening to the downlinks when Tim Peake did the links with schools.
The ISS pass scheduled was at 19.45pm and I watched the live feed from ISS. Unfortunately, it was not successful, it seems that the little handheld that they used in the ISS was not not working, although the TV feed from the ISS was fine. A bit of  disappointment for the youngsters, but ARISS managed to schedule another attempt on the next pass. Paulo moved into the Columbas part of the ISS where they had another transceiver, this time 25w output. As I watched the live feed I listened on 145.800Mhz on my Yaesu FT857D and also my Baofeng handheld. This time it worked a treat! I was copying the ISS at over S9 at times, very strong with my FT857D and colinear. Fantastic…I recorded the link:

GB5RC Radio Caroline 2017

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I have been looking forward to this event this year as it marks 50 years since the Marine Offences Act came into force and Radio Caroline defied the law and Radio Caroline and the pirate stations became illegal. Radio Caroline carried on broadcasting as long as it could.
The special event station operated from the Radio Caroline ship ‘Ross Revenge’ using the callsign GB5RC. Last year I worked the station on 80m.  I really wanted to work the station this year!

Gosh!  What a pile up there was when GB5RC appeared on 80m, I tried using my FT101E and 200w, but not a chance with the poor longwire antenna that I use. Then on the Saturday night 80m was full of contest stations, so GB5RC moved to the very top of 80m. I was copying at 20 over 9 and there was only a few stations calling, so I tried again….yes!  I managed to work GB5RC with Pete M1BRR operating, thanks Pete for pulling me out of the noise!

Summer of Love 50 years!

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Today I was walking around Bolton when I came across a hairdressers shop with some old mementos in the window. At the front was an old Elizabethan reel to reel tape recorder with the BSR deck. This was almost the same as the one that my Dad bought us back in 1967!
I know what I was doing 50 years ago during the 6 week school holidays in 1967…I was using a tape recorder for the very first time. Every Sunday my friend and I would set up his own tape recorder to record Alan Freeman on the ‘Light Program’ on 1500 metres long wave. We would put a microphone in front of the speaker of a transistor radio and record the top twenty songs.  This was all in the Summer of Love in 1967. Some classic songs!

We got our tape recorder about November 1967 in time for Christmas, I can still remember the clunky BSR deck and the green ‘magic light’ that you used to set the audio levels on record. I used the tape recorder for years after, still recording the top twenty every Sunday. I also used it with the morse practice tapes that George G3ZQS made to get me through my morse test and get my Amateur radio licence.

Raspberry Pi SDR with gqrx 2.6 software

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Latest project with my Raspberry Pi…an SDR receiver using a cheap RTL SDR Dongle!

I have to admit that I found this project somewhat frustrating at first. I was using a Raspberry Pi 2 and tried a couple of SDR software packages. The first was gqrx 2.6 which I downloaded and installed without any problems. Unfortunately, when I tried to run it I was confronted with various errors. Occasionally it started up with a waterfall for a few seconds and then crashed, also there was no sound. I put this down to the fact that the RPi 2 was not up to the job, so ordered a new RPi 3.
The second piece of software was qtcsdr. apparently this should work on a RPi 2. When I downloaded and installed the software I had endless problems starting up the application. Typing ‘qtcsdr’ gave a message ‘is a directory’, changing the directory to cd qtcsdr then typing ‘qtcsdr’ to start it up gave a message ‘no such file or directory’.  At this point I spent a long time trying to find an executable file without any success. I decided to re-install…got the same again! When I reached the point of giving up I downloaded qtcsdr one last time. This time it worked! The executable file could be seen and started up by typing ‘qtcsdr’.

So far so good…next problem was same as previous with gqrx, crashed after a few seconds!

Now I awaited the new RPi 3. When it arrived I downloaded and installed both pieces of software. When I ran them I had similar problems of the software crashing after a few seconds. Strange!

Meanwhile, I had fitted a new 5″ touch screen onto the RPi 2 which works great, so I thought I might try the SDR software again. Guess what?  They both worked perfectly. Strange again!
I can only assume that the monitor may have something to do with it. I have been using a normal VGA monitor with a VGA to HDMI converter for the RPi. With the small 5″ HDMI monitor it runs straight from the RPi without any converter. Could this be the problem?  looks like it…maybe adding too much load on the CPU.

Quite impressed with gqrx, much better than qtcsdr.  One thing to be aware of, you have to set the ‘mode’ when you start it up otherwise it defaults to ‘no mode’, also make sure that you set the squelch to -150 or you won’t hear any audio.