National HRO Renovation Project

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My Autumn project this year has been the renovation of an old HRO receiver that I picked up on ebay. This is another receiver that I have always wanted to have. Many years ago when I was still at school I was given one, along with power supply and coils. I carried it home with my friend on the bus all the way from Bury. I never got to use the receiver because I gave it to my friend as he didn’t have a receiver of his own.

Now I have one of my own with a full set of coils to renovate and have pride of place in my shack.

The HRO and coils were in a poor state having been stored for many years, covered in rust and full of dead spiders! However, the inside and underneath was untouched and in its original state. Ideal for a renovation project.

I didn’t even think about powering up this baby yet, first some cosmetic work was needed, it needed a good cleaning and some of the rust removed. I removed the case and front panel and set about cleaning with a wire brush and metal polish. Taking the covers off the valves were quite tricky as they are a tight fit and it is tempting to twist the cover which would also twist the class on the valve causing the glass to separate from the base. This had already happened with one valve in the past.
After a good clean I decided to paint the chassis and cover up the rust patches. I have lots of small tins of Humbrol model paint that I use for model making and realised that the HRO chassis colour is actually Pru-Blue and I have that colour. Painting needed a lot of patience with a small paint brush, but the results are amazing, I am very pleased with the results.

The next step involves a rebuild under the chassis by replacing all the wax capacitors and old resistors. I managed to get all the capacitors (10n and 100n, 650v) on ebay and got all the 2 watt resistors from Modern Radio in Bolton. Identifying all the components was fairly straightforward from the original HRO manual, to make things easier I took photos of the underside of the chassis and labelled all the components. Rebuilding was an enjoyable experience, I had to call on my soldering skills to change all the components while keeping everything neat.
The layout and wiring of the HRO receiver is easy to follow and everything is done logically. A pleasure to work on!

At the same time I also worked on the plug in coil units. They need stripping right down and cleaning, some were in a poor state. After cleaning the coil units the paint work needed some renovating. At first I was going to re-paint the fronts of the units, but I found an easy way, I used a cheap permanent marker pen. This really worked well! The graphs on the front of the coil units needed a bit of TLC, they were originally covered by Perspex, but had all perished. As I removed the metal frames I had to be careful not to disturb the paper graphs. Some were stuck to the metalwork, so I had to carefully peel them off without ripping them. I managed to find copies of the graphs on the internet, so I printed off the bandspread graphs to put in the second metal frames.
The coil units came in the original HRO wooden storage rack, after cleaning I painted it black with matt spray paint.

Now the moment of truth…will it work?
I had not built a power supply yet, but I already had a Codar AT5 power supply that I built previously which should be fine to power up the HRO.

At switch-on the filaments glowed nicely and after warm up a loud hum started to appear from the speaker, but nothing else. This is where I had to call my fault finding skills.
I managed to trace the fault down to the 6B7 Detector/AGC/Audio Valve. After a hunt on eBay I found a new valve cheap and ordered it. When it arrived I changed the valve and switched on.

It works!

All the controls were working fine, but there was a problem with the S Meter. To solve that problem I found an old article in Short Wave Magazine which suggested a modification. I carried this out and the S Meter worked fine. The original S meter had a horrible yellow face and the numbers had worn off, so I made a new one.

Finally, it was time paint the case and front panel then build a power supply for the HRO. I needed a suitable Mains Transformer, Smoothing Choke and Smoothing Capacitor. First of all I measured the current being drawn from the AT5 power supply, this was about 50ma. So I searched on ebay to find something suitable. I managed to get all the components at a reasonable price. I also needed a case for the PSU. On a visit to the rally at Rochdale I found an old CB PSU which was an ideal size. I stripped it down, gave it a coat of black paint and began building the HRO PSU into the case.

This has been a wonderful project, I now have a fully working HRO Receiver and set of coils that has pride of place in my shack!





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Received a nice award certificate today to celebrate receiving SSTV signals from the International Space Station on 29th October 2018. Managed to receive two images on the same pass at 10.28am using my colinear and Yaesu FT857D on 145.800Mhz.

Here are the two images received using MMSSTV Software to decode.


G7FEK Antenna

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Just completed building a G7FEK antenna. Seems to work fine after a little bit of tweeking of the two counterpoise / radials.(Used 65ft and 33ft) Now have good SWR on both 80m and 40m without a tuner. I am now comparing signals on 80m and 40m with the random Longwire that I already have up.  Listening on 80m and 40m tonight with the G7FEK. First contact with FT8 on 80m was TF3GB in Iceland (was only just detectable on the Longwire) Went on 40m and was amazed at the number of stations across the Atlantic in both North and South America. Have not managed to work any yet because I am only running low power at the moment. Switching between the G7FEK and Longwire I can’t even detect any stations Trans-Atlantic stations. It’s working well.

I have now added a loading coil for 160m Topband and it is working well. I built the loading coil of 30 turns on 4 inch pipe with taps so that I could find the best setting for low SWR. The SWR peaks at 1.9Mhz with 16 turns. I have found that the G7FEK works best for local groundwave contacts on 160m, gives about 2 S points more on receive when compared to my existing longwire. The longwire seems better with more distant stations. Not sure about DX stations yet.

Morse Code with G3ZQS

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Yesterday afternoon I listened to an interesting conversation about Morse on the Bolton Wireless Club Network Radio.

It made me think about how I learned Morse Code. I was taught by George (Geo) G3ZQS back in 1970. He produced some tutorial ‘tapes’ that you could learn to read the morse alphabet from scratch. George’s method was to group letters together, the first ones that I learned were A, W and J (di dah, di dah dah, di dah dah dah)
The tape would introduce the letters, then send them mixed up so that you could recognise them. After that you move to the set of letters in this case N, D, B
(dah dit, dah di dit, dah di di dit)
Again on the tape, learn the letters then listen to them mixed up.
The next step was to try to receive both groups of letters together before learning the next group (Which I think was E, I, S and H)
George always emphasised that we listen to the rhythm and not the dots and dashes. Some letters you can remember from the rhythm like Q (dah, dah, di, dah God Save the Queen) and F (di, di dah dit Filling Station)

I found this method very effective (for me) You just take your time and if you want to, try to practice sending the letters that you have learned.

Sadly George is now silent key, but he founded FISTS which promotes the use of CW throughout the world.
I have been trying to trace one of his tapes, but without success. It would be great to get hold of a copy to maybe produce a digital version.

Many of these tapes were in circulation around the Bolton and Blackburn areas back in the 1970’s.


Topband Beacon

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A bit of nostalgia here…the Topband Beacon! (or Bells)

Back in the 1970’s when Topband AM was the flavour of the day there was a beacon on 1.900Mhz. During the day it was a simple two tone beat, but at night it came alive making Topband very tuneful. Back in the 70’s the beacon was an ideal place to tune up your AM transmitter. I used to monitor 1.900Mhz when I was in the shack for stations that tuned up, then I would call them.

Here is an old recording that I found on the internet played to a video of my R1155 receiver…. ahhh… memories!

Steam Radio

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Today I listened out for the special event station  GB0ELR at the East Lancashire Railway at Bury. They were operating on 40m, 20m and 15m.  A message from Facebook told me that the station was operating FT8 on 20m during the afternoon, so I set up my FT8 to find them. Although GB0ELR is only about 4 miles away I found it difficult to find them through the very strong FT8 stations on 20m. After putting out a call I managed to link up with the station.  It was a rainy afternoon, so I decided to go down to East Lancs Railway and deliver a QSL directly to the station.  I love going to the station to see the steam trains and today the Flying Scotsman was running along with the City of Wells Loco.

Here is Mo M0TXK operating GB0ELR from the hut next to Flying Scotsman on the platform. I used the opportunity to talk with Jack G8HIK and Chris G4HYG on the Bolton Wireless Club on Network Radio.

Here is the Flying Scotsman departing to Rawtenstall today.

Topband with an R1155 Receiver

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Latest news on the R1155 Receiver project…

The R1155 is working fine on all bands, but unfortunately my version of the receiver doesn’t cover Topband (1.8Mhz – 2.0Mhz). I believe that one of the later versions of the receiver had Trawler Band, but these are quite rare to find.  So to be able to listen on Topband with my receiver it requires a converter, in this case to convert 1.8Mhz – 2.00Mhz to the Medium Wave band. The R1155 covers 600Khz – 1500Khz, so I decided to use 800Khz – 1000Khz as the converted Topband Frequency.

I found that the simplest circuit to use for this purpose is to use an NE602N chip, this is a double balanced mixer that can convert almost any input frequency to an output frequency using the correct crystal oscillator. In my case, I want to convert 1.9Mhz on the input to 900Khz  on the output. To do this I need a 1MHz crystal for the oscillator and choose the correct values of capacitors in the oscillator circuit.


L1 is a TOKO equivalent coil that can be purchased from http://www.spectrumcomms.co.uk/  I used the 45uH coil for 1.9Mhz.  I found that C1 needs to be around 220pf to tune the coil. X1 is a 1Mhz crystal and C3 is 100pf, C4 is 1000pf. I built the circuit on a small printed circuit board, which was very easy to make.

The circuit works really well, very stable and gives an output that suits the input of the receiver. I was able to tune Topband on the Medium wave frequencies and listen to stations on AM, SSB and CW.
Really pleased with the results!
On the board I left room for an extra coil on the input, but the circuit works fine with just a single coil and seems very selective.

I added a switch so that I could switch between Topband and Medium Wave. I also used the switch to mount the board inside the R1155 Receiver. The 6v for the board is powered by rectifying the 6.3v heater voltage, doing this meant that I didn’t need R1 in the circuit.


The converter working fine on the Sunday morning 1963Khz AM Net with G3EGC, G0CTO and M3RNX.