It Comes and it Goes

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Harry Leeming G3LLL discusses intermittent faults, the price of gear and other topics that take his fancy!

 

 

Harry Leeming G3LLL discusses intermittent faults, the price of gear and other topics that take his fancy!

 

You arrive at the health centre looking fit and tell the doctor that you are fine at the moment but that occasionally, when you get out of bed in the morning, you are somewhat dizzy and that have a bump on your head to prove it. What does the doctor do?

Intermittent faults are always a bit of a puzzle and all the doctor can do is to ask loads of questions, such as how much you drank the night before, make a few tests and then rely on his experience. (It’s not that much different for a ‘rig doctor’ except that if we get really stuck, we are allowed to put it in a box and send it back to its maker!)

Peter was a member of FOC (The First Class CW Operators Club). He was very proud of his proficiency in the mode and of the quality of his signal. Of late, however, he had been getting some adverse reports and had been told that sometimes his transmissions were T7 plus chirp (a perfect note would be T9). He started asking for critical reports. Most of the time he got T9 and then just after he started to think that there was nothing wrong, it would be back to T7.

He set up a receiver to monitor his transmissions and, sure enough, very occasionally he would hear the dreaded T7 note. When the trouble was occurring, he found that he could clean the note up to some extent if he dropped the power to around 5W. In desperation he brought his rig into my shop and sat there while I grilled him.

 

The Consultation

Had he noticed any particular pattern to the trouble, was it affected by the room temperature, or time of day? “Well”, he said, “It doesn’t seem to make sense, because the room is centrally heated, but it seems worse if the weather is very cold, especially around meal times.”

My mind jumped back to a receiver that had been brought in years earlier, when Coronation Street was essential viewing in the North of England. This had the complaint that it was occasionally extremely distorted in the SSB and CW modes but would never show any fault when I tested it. In that case it was eventually realised that the distortion was worse in cold weather, especially around 8pm when people switched on their kettles after the Soap had finished and the mains voltage dropped slightly. A fault in the PSU was found to be making it oversensitive to mains voltage variations.

Thinking of this I got Peter to leave his rig with me and when I had a bit of time I fed it from a variable voltage transformer, Fig. 1, and monitored the CW note on a receiver while I turned the mains input down. At anything above 225V the note was perfect but as I reduced the voltage more, the note became worse and the rig moved slightly off frequency.

As older readers will remember, the mains supply in the UK was at one time 240V ±6% while on the Continent 220V was the standard. Some years ago, as I’ve mentioned before, we ‘harmonised’ our mains supply with the rest of the EEC by means of bureaucratic fudge. Nothing changed but now the UK mains supply voltage must be 230V within +10% to −6%, thereby allowing the European 220V system to stay at 220V and the UK to stay at 240V! This does, unfortunately, mean that our mains supply can now fall as low as 216V or go as high as 253V without being out of specification. However, some equipment may not respond well to such large variations.

To understand what was happening, have a look at Fig. 2. This shows a simple voltage stabiliser arrangement used to feed a variable frequency oscillator (VFO) with 8.5V from a 12V supply. With any voltage stabiliser, the output voltage must always be considerably less than the input voltage so consider what will happen if the mains falls to 216V. 216 is 230 minus 6% but it is actually 10% less than 240 and, hence, if the rig’s mains transformer is set at 240, the nominal non-stabilised 12V rail will fall by 10% to something just over 10V. This is only slightly higher than the required output and it is quite possible that it will be insufficient to enable the regulator to hold the output up to 8.5V. Obviously, if Peter’s mains voltage was permanently somewhat on the low side, his simplest move would have been to reset the rig’s mains transformer to the 225V setting, but was it?

 

The Prescription

I got Peter to take his rig back and to check his mains voltage at different times over the next week. He reported that it was usually around 235V but that it did fall to just below 220V at the times he was having the T7 reports. At the other extreme, he had noted that if he could not sleep and tried to work a little DX in the early hours, it could be just over 250V. He explained that he was located in an isolated farmhouse way out in the country. This no doubt explained the wide variations in voltage.

I suggested he brought his rig back and I would see if I could do anything to make it less fussy about the mains voltage.

The VFO was fed from a voltage stabiliser similar to that in Fig. 2 and this time I monitored the VFO supply as I turned the supply voltage down with my transformer. Sure enough, the VFO supply rail dropped if I fed the rig with much less than 225V and then dropped even more if I then keyed the rig up at full power. I wondered just how much voltage the VFO needed and I experimentally turned the potentiometer on the regulator until the output voltage fell by 10%. This did not seem to make much difference on transmit or receive but it increased the difference between the input and output voltage of the regulator, gave it more ‘head room’ and improved the stability. I could then reduce the mains voltage to the official 216V limit before the problems started.

I checked the rig over, reset the clarifier pot, and let Peter have it back. He did not have any more complaints. I have had similar problems brought to me by other customers, when running HF rigs from their cars ‘static mobile’, but that’s another story.

 

Is Amateur Radio Getting too Expensive?

When radio amateurs in my age bracket look at some of the latest HF rigs and see the prices of £1K plus plus, we get quite a shock but, in practice, electronics is actually getting much cheaper. In 1952 when I entered the TV trade in Accrington, Lancashire, a 12in black-and-white TV cost £60 and yet a qualified City and Guilds TV engineer only earned £11 a week (which is one of the reasons why many folk rented their TV sets in the early days). Now you can have a much larger, colour TV for less than one week’s wage and TV rental companies are long gone.

I started selling amateur radio equipment in the early 1970s. Back then few second-hand HF SSB rigs were available and a new ‘economy’ SSB rig such as the Yaesu FT-200 (AM/SSB/CW, 100W on SSB, 80 through 10m) cost around £180, about four weeks’ wages then. More upmarket ones cost £250-300 and even a crystal-controlled 2m handheld would set you back a week’s earnings. Today you can get a very good second-hand HF rig for less than a week’s average wage and new upmarket rigs can cost less than a month’s salary. Some Chinese handhelds come almost in the spare change category. (House prices are another story. My dad paid £97 for our end of terrace ‘two-up two-down’ country cottage in 1948!)

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Cheek Sometimes Gets Free Publicity

Brenda’s Grandmother Holding was born in 1880 and because she had to start work aged 12, she received no secondary education, but she was not one to be pushed around by anyone. She often said in her broad Lancashire dialect “Cheek licks edication” (that’s how she pronounced it, and presumably spelt it) and it is surprising where a little cheek will get you.

How much do you think it would cost to have a full-page colour promotion on the front page of Hi-Fi News, showing not only that you sold hi-fi but were well equipped to repair it? £1000, £2000, nothing?

In the early 1970s, we gathered together quite an interesting looking range of our mainly Heathkit test equipment and set it up in the workshop. A member of the photographic side of the business took a picture of it, along with myself and my chief engineer Derek Fielding, suitably armed with test prods and soldering irons. I had intended it to be used in the shop window but then, mustering a little of Grandmother Holding’s Lancashire cheek, I sent a copy off to John Crabbe, the editor of Hi-Fi News. He wrote back enthusiastically, explained that they had been stuck for something to fill the front page in the next issue, and that they would be happy to use it. In the next issue, there we were in full colour on the front of all the copies of Hi-Fi News on display in WH Smith and elsewhere, with full acknowledgment to our shop inside.

Photos, interesting stories, articles, readers’ letters and so on are the lifeblood of magazines and newspapers and (don’t tell PW’s advertising manager I said so) with a little imagination you can get quite a large amount of publicity for your fledgling business, club or charity without having to pay for it! You can even get paid for writing articles that effectively publicise your business. Remember, though, it should not be all one way because it makes good commercial sense to focus your paid-for advertising in publications where your name is known.

 

Radio Amateurs Sometimes Lead the Way

One of the reasons amateur radio is tolerated, and in some cases encouraged, by governments is that it leads to an interest in electronics. Experiments carried out by individuals cost the country nothing but have, in some cases, led to them achieving ‘the impossible’, the classic example being Marconi.

Marconi had an Italian father and an English mother and part of his education was at Bedford in the UK (where, incidentally, I lived until the age of two). He made no claim to being a scientist. In fact, if he had been, he would probably have realised that what he was trying to do was ‘impossible’. In his late teens, when at his parents’ villa in Italy, he tinkered about with radio waves, with a view to using them for communication, without really knowing what he was doing, and was in many ways the first radio amateur. He was using a spark transmitter, which, in modern terms, produced bursts of interference. Most experimenters had simply connected a couple of short rods to the spark gap to act as radiators so the bursts of signal were centred on the resonant frequencies of these. It was in the 1890s that Marconi made a discovery that revolutionised radio. He added an antenna and an earth connection to the transmitter and receiver.

Adding an antenna and earth did more than increase the efficiency of radiation, it lowered the resonant frequency of his spark transmitter and receiver so that instead of transmitting his bursts of ‘interference’ at UHF, he was then radiating on what is now the Medium or Long Wave bands. The longer the antenna, the lower the frequency, and the range shot up.

He could not interest the Italian government in his discoveries so his mother sent him back to the UK, where he found backers who realised the potential of radio communication.

 

Shortwave Radio

Following on from Marconi’s transatlantic experiments a few years later, it was thought that for long distance communications, you needed to use the longest possible wavelengths, and that waves shorter than 200m were not of much use, hence they were allocated to home radio experimenters and hobbyists. According to my copy of the 1947 ARRL Handbook, the official attitude was, “Let them have the wavelengths shorter than 200m, they’ll never get out of their back yards with that”. It was radio amateurs who, left to experiment, then discovered long distance shortwave communication.

 

Speech Processing

Trying to ‘copy’ announcements in noisy railway stations was even more difficult in the 1950s than it is now. At that time nearly all the announcers were women, for the simple reason that their voices were clearer. Using male announcers, particularly any with deep voices, often resulted in muffled incoherent sound. Today many of the announcers are male and yet with a well-designed public address (PA) system, they are not usually any more difficult to understand than the lady announcers. What’s the difference?

The better PA systems now use speech processing along with microphones and loudspeakers with a controlled frequency response. In these the frequencies in the voice that are used by the brain to recognise words are emphasised. It seems possible that just a little of the expertise that amateur radio operators have gained, and published, after doing a great deal of experimenting to clarify male speech on noisy shortwave channels has spilled over into the public address field.

Keep experimenting, you don’t know what you will discover. 73 for now, Harry.

 

 

This article was featured in the August 2018 issue of Practical Wireless