Exploring 13cm

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Having tried to receive some stations during the 13cm UKAC Contests, it is now time to try transmitting. First of all I needed to register my interest in 13cm with OFCOM as the band is shared. Mark M0UFC has kindly loaned me the Bolton Wireless Club’s ‘Phoenix Transverter’ which gives an output of around 400mw. This along with a 16db gain Patch Antenna gives me the ability to work stations on 13cms.

My first contact was with Ross G6GVI on the other side of town, we successfully exchanged reports. My antenna is not in an ideal place, but was the best I could do without running a long length of Mini 8 to the garden. I now need to get a length of RG213 or similar for the next contest. In the contest I worked two stations G6GVI and Dave G4JLG/P who is on Winter Hill. Very pleased for my first attempt at this new band!

The Bolton Wireless Club ‘Phoenix Transceiver’.

Patch Antenna on a pole at side of house.

My first ever 13cm QSO

High Altitude Balloon Tracking

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Following an interesting talk by Ross G6GVI about tracking High Altitude Balloons at The Bolton Wireless Club I decided to give it a go.

High Altitude Balloons are Helium Weather Balloons that carry a payload into the edge of space. These are usually projects associated with schools and colleges linked with STEM. Telemetry is transmitted on the 70cms band with very low power, about 10mw, which can be received and tracked using software. Today there were two balloon launches around Oswestry in the Midlands, the first one is called ‘Hi-impact’ and the second one ‘Spacecamp’. I could copy both balloons on 70cm, the Hi-Impact was using 50 Baud RTTY and Spacecamp using 300 Baud RTTY. Using the dedicated software package DL-FLDIGI I was able to decode the 50 Baud RTTY with no problem, but could not decode the 300 Baud. When the packets are received the software automatically sends the data to HABHUB which shows on the tracking map that my signals have been received. All clever stuff!

Screenshot showing the DL-FLDIGI software receiving and decoding the Hi-impact balloon. In the background is the HABHUB tracking and mapping of the two balloons.

Perseid Pings

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A bit of Radio Astronomy here…

Here are some of the meteor reflections from the GRAVES transmitter on 143.050Mhz last night during the Perseids Meteor Shower. The peaks can be heard as tuneful ‘pings’ when a meteorite enters the atmosphere. The pings are displayed using ‘SpectrumLab’ software. I am using my Yaesu FT857D along with a 5 element yagi set to 143.049Mhz and USB.

R109 Receiver Renovation

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Back in 1969 I bought an R109A receiver from a shop in Bolton that sold lots of ex-government radios. It was Arthur G3JJM that told me about it and he went to buy it for me at the knock-down price of 30 shillings.
The R109 covers 1.8Mhz – 3.9Mhz and 3.9Mhz – 8.5Mhz, I used it as my first receiver and listened on Topband and 80m every night. It was powered by two 6v motorbike batteries that I kept under my bench.

Here I am back in 1969 with my original R109A receiver.

I gave the R109A away after I got a Hallicrafters SX24 receiver. Since then I have never seen an R109A anywhere, I always wanted to acquire one as a renovation project, but they are very rare and although lots of searching over the years I have never come across one…until now!
This started with a conversation on 23cm with Dave G4JLG and Ross G6GVI. I was talking about the renovation of the Eddystone S750 when Dave mentioned that he had an old receiver in his shed that had been there untouched for over 40 years. He had no idea what it was except that it was square in shape. I suggested that it could be a CR100 or maybe an R109 as these were the only ones I could think of. Dave then went down to his shed to have a look, he came back and announced that it was in fact an R109. I nearly fell off my chair!
The next day Dave sent me some photos.

The front panel, almost unrecognisable. Note the yellow ‘T’ this identifies the receiver as a Tropical Version.

The inside of the R109…immaculate!

The outside was a mess and almost unrecognisable with the caked on dirt, however, this receiver is the R109T, which is the tropical version used during the war. When he opened it up the inside was immaculate as it was hermetically sealed, amazing! All the valves and wiring were as new, but there was no vibrator in the PSU. Dave managed to find a couple of old vibrators for me to try. He also sent me a manual and some notes on the R109.

Dave kindly let me have the receiver to be renovated, I couldn’t wait to try it out and bring back all those old memories!

Here I am 50 years on with the R109T ready for renovation.

Now where do I start with this receiver?

Well first of all I need a 6v battery!  A trip to a local motorbike spares shop got me 4AH battery very cheap. That will do fine for testing the receiver.

I removed the front panel from the main receiver ready for cleaning. This took a whole afternoon of scrubbing with warm water, detergent and toothbrush. The muck came off fairly easy and the more stubborn dirt was removed with some Sodium Bicarbonate. I didn’t use any harsh cleaner at all. When it was finished the front panel looked like new, even the decals were intact. The dial, fixtures and identification plate were removed and cleaned separately.

The finished front panel, written in pen on the yellow T is a callsign and name – G3RVR Dennis. Dave G4JLG thinks that this is where the R109 originated many years ago and was given to him.

The PSU is somewhat novel as it uses a vibrator unit in order to produce the HT voltage, also the valve heaters are directly fed from the 6v DC battery that powers the receiver. The PSU is a separate unit that can be powered on its own for testing. Close inspection of the capacitors showed that most of the electrolytics were either bubbled or leaking, so replacing these was my first job. The R109 is very well built, but unfortunately a lot of the decoupling capacitors are not easy to get to. Some are inside the IF cans that are welded to the chassis and others are hidden. I decided that I would replace all the decoupling capacitors that were accessible. It is the same with the resistors, I thought that I would leave them for the time being.

The R109 chassis with the SPU on the left and RF unit on the right.

The next job was the vibrator. I tested the PSU with both of the old vibrators that Dave gave me, but neither of them worked. Solid state vibrators are available from the 19 set group, but they are quite expensive. I did some research and reading about how mechanical vibrators work as well as finding out about the pin-out connections of the vibrators that I have. Taking the vibrators to pieces proved quite tricky, but I managed to remove the cans with a bit of brute force and ignorance! Removing the inside was quite easy and both in good condition. Using my multimeter it was obvious that the contacts of the vibrating bit needed a good cleaning. I spent around an hour carefully cleaning the contacts on one of the vibrators and then tested the unit….it works!
I put it into the PSU and switched on and monitored the HT voltage, then to my astonishment the receiver burst into life! Connecting an antenna brought in stations on both bands. All the controls are working and the BFO is also working, but very weak. The HT voltage is about 150v which is correct according to the manual.
This brings back memories of my original R109, I spent quite a long time trying to improve the receiver by aligning the RF and IF stages. I also added an S meter as well.

The receiver worked fine, but I noticed that the battery was only lasting for about 15 minutes before the HT voltage and LT started to drop. The receiver then began to shut down although the vibrator kept on going. Measuring the current drain on the battery told that it was drawing too much current. After a while the receiver stopped working altogether. After some fault finding in the PSU I realised that a 0.1uf capacitor across the secondary winding of the HT transformer had gone short circuit. After replacing, the receiver worked perfectly, now only drawing less than 2A from the battery.

A bit of touching up with the paint on the front panel, repainting the handles and painting the case green finished off the R109T.

The completed R109T receiver in all its glory.

13cm Crossband Contact

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Had an interesting X-Band contact on Tuesday night with Ross G6GVI. I set up the 13cm converter and antenna in my garden and we arranged a X-Band QSO between 13cm and Topband. I transmitted on Topband and Ross transmitted on 13cm. Copied Ross at about S7 on 13cm. Later, I listened to the UKAC contest and heard some stations. This is my first encounter with 13cm, maybe I will have a go at building a transmitter.

Here is a photo of the 13cm set up in my garden.

Practical Wireless QRP Contest

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Some photos from Sunday’s contest with the Bolton Wireless Club at Horrocks Wood. An enjoyable day, 75 contacts and it didn’t rain!

Eddystone S750 Renovation

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For my next renovation project I would like to have a go at an Eddystone receiver. These classic receivers were produced in Birmingham just after the war and they produced many different models. The early models used a mains transformer for the PSU, but later ones were AC/DC which meant that they did not have an isolating mains transformer and used a mains dropper like the old TV sets. These models are dangerous as the chassis is not earthed and is liable to become live. After some careful research I decided that the best model for renovation would be the S640, S680 or S750. I particularly like the S750 because of the classis Eddystone 898 style of dial.

After a while I came across a very sad looking S750 on E-Bay that needed a lot of TLC, but for £50 I thought it would make an ideal project. I managed to secure it and was delivered in a huge box!

Cosmetically, it was in a bad way. The receiver had been stored for a long time, the finger plate, selectivity knob and drive coupling were missing and the paintwork was very poor. Inside, the chassis and valves were all in good condition and underneath the original components were intact, but the soldering of some of the wires needed some attention. The drive mechanism was very dirty and not working correctly. This was going to be challenging project!

So where do start? Well, first of all removing the case and front panel so that I can see clearly the work involved. There are lots of information about restoring Eddystone receivers on the Eddystone Users Group and forum. Some great stuff written by Gerry O’Hara, which takes you through the renovation of an S750. At this stage I had no intention of powering up the receiver. Instead I checked the resistances of the mains transformer and choke, everything seems fine.

The front panel includes the 898 style drive mechanism, which of course will need a lot of work later. I decided to put this to one side and concentrate on the main chassis first.

The chassis was caked with dirt and nicotine and quite smelly, a good clean was necessary. Using a wire brush, isopropyl alcohol and metal polish I set about cleaning above the chassis.

Inspection of the Power Supply unit made me realise that it was a rats nest of wires that needed removing or replacing. The smoothing capacitors were bubbled and needed replacing. The smoothing choke was not original and had been poorly fitted above the chassis, likewise the audio output transformer. I decided that a complete rebuild of the Power Supply unit was needed.
I drew lots of diagrams and took many photos of the wiring before removing the PSU from the rest of the receiver. I was then able to work on the unit by itself. A lot of the wiring was to the octal sockets on the rear panel which is no longer necessary, so I could remove most of it, which I did. The octal rectifier valve had been changed for an unknown four pin rectifier valve. I removed this and used a couple of IN4007 for the rectifiers instead. A new smoothing block and new capacitors and resistors used to replace the existing ones. I also replaced the wiring sticking to the original colours. Testing the Power Supply gave me 300v HT and 150v regulated along with two 6.3v heater supplies.
While rebuilding the PSU the underside of the chassis was cleaned.

Now it is time to move on to the RF / IF and audio stages. The RF unit is in good condition, the components are very difficult to get to, so I will leave this alone unless there are any faults that emerge when it is tested. The IF and audio unit can be separated from the rest of the chassis (like the PSU) this needs most of the resistors and capacitors replacing. It was quite easy to work on and most of the decoupling capacitors were bolted onto the chassis. They just needed unbolting and then replacing with up to date components.

Once this was completed I could assemble the whole chassis back together again and re-fit the front panel ready for testing.
I Powered up the receiver while monitoring the HT voltage, after a while I heard a faint hum from the speaker, but nothing else. After some investigating I realised that I had made a wrong connection to one of the switches. When I repaired the connection, the receiver sprang into life!
All the switches and controls appeared to work apart from the BFO. I was able to listen on 80m, but couldn’t resolve the SSB stations. Note that the drive mechanism was not working, I tuned in stations by moving the arm on tuning gang.
One thing that I did notice was that audio was quite low and also when I switched on it took a long time before coming on. I checked the heater voltages, there are two 6.3v windings on the transformer, one gives around 3A and the other, which only supplies the noise limiter valve, is only rated at 300ma. The main heater voltage was down to 4v, but the other was fine. It turned out that the two 6.3v windings were connected the wrong way. This was wired like this when I got it. Swopping the windings over cured the problem, now I have lots of audio and the valves warm up quickly.

I now moved on to looking at the cosmetic problems and drive. I became aware from the Eddystone User Group that some components are still available for these receivers from Ian Nutt, who has a stock of parts. My first step was to message Ian to see if he had any spare parts to replace the ones missing from my receiver. I needed a finger plate, drive coupling spring, selectivity knob and also two drive chord spools. Ian managed to find some of the parts, particularly the spools, which would have been difficult to replace. Ian didn’t have a finger plate, so I solved this by using a template from Gerry O’Hara to have an aluminium sign made by a printing company called ‘Helloprint’. This was not perfect, but acceptable.

The drive mechanism is quite a challenge, stripping down the front dial and drive chord is a bit scary! Never the less I managed to complete it, replacing the chord spools and also the drive chord, which was too thick. I bought some 7 strand, steel Pike wire from a fishing shop. This was used in the original receivers. The drive mechanism itself was thoroughly cleaned and polished. I lubricated the bearings with machine oil so that it would run smoothly. The drive is pleasure to use!

Connecting the drive to the tuning gang needed some thought, the spring that holds the ratio arm to the spindle is still missing. I managed to fabricate a new one from some steel wire. Again, not perfect, but acceptable.

I painted the front panel and case with VHT Wrinkle paint, it worked quite well and I now have a nice wrinkled finish. Before re-assembling the front panel I replaced all the original switches with new ones.

The receiver is now working fine apart from the BFO and a problem with Band 1, which doesn’t seem to be working. First I had a look at the BFO module and stripped it down, it appears to be working, but may not be on the correct frequency which should be 85Khz. Checking the frequency on an oscilloscope confirmed that the BFO is working, but why can I not hear a beat?
Well, this turns out that the S750 has a terrific amount of RF and IF gain, so having the gain controls turned up completely swamps the very low level BFO injection. Gerry O’Hara explained to me that the correct use of the receiver is to keep the RF and IF gains turned well down and the Volume Control turned up. The volume is adjusted using the RF and IF gain controls when listening to SSB or CW. This solved the problem!

Next, why is Band 1 not working?

Investigating with my oscilloscope revealed that the mixer oscillator on this band was not working. Further investigation tells me that the coupling winding on the oscillator coil is open circuit. I decided to strip down the coil assembly, but the faulty winding was buried under wax. I made my own coupling coil of 4 turns and fitted it to the assembly, it works perfectly!
I finished by aligning the RF and IF stages as best I could.

Now I have a wonderful, fully restored Eddystone S750 in true BBC Repair Shop manner!