After some emails asking me how I got started in Ham Radio, I thought I would put a post up relating my story.

I was a product of the boom in CB Radio in the UK. I had always had a lurking interest in communications, my dad worked for British Telecom (nationalised telephone company which was privatised in 1984) (or the GPO (General Post Office) as it was known when he started in the 1960’s) as a telephone engineer for 32 years before he retired, so to me, the concept of people communicating with each other by electrical means wasn’t a new one.

About 1979 I first came across CB Radio. At this time, CB was illegal in the UK, and most of the equipment available was just the US FCC 40 channel AM stuff, as introduced in 1977. There was some 23 channel gear, and some people had the Sideband equipment as well.

As I have already said in the “About G6RBM” page, after hearing 2 guys in the US talking to each other whilst I was sat on my drive at home, I was hooked. I wanted to get on to this, but I had a major problem……

In those days, the radio communications regulatory body was the “Home Office”, and it used a piece of statutory legislation called “The Wireless & Telegraphy Act 1949” to determine who could use a transmitter and who couldn’t. Every piece of transmitting equipment had to conform to technical standards and work on frequencies that were available. Unfortunately, the FCC channels section of 26-27MHz was already allocated to commercial paging including hospitals, and the first whiff of interference on this from CB radio’s led to the media branding CB radio enthusiasts as lower down the food chain than child molesters……

So, the airwaves were “controlled” in the UK by the Home Office. At that time, all radio interference was investigated by the radio section of the Post Office Telecommunications section of the Home Office…… which was who my dad worked for as a telephone engineer.

Bummer!!!

So my CBing activities were restricted to using other people’s sets.

This didn’t dampen my enthusiasm any, in fact it strengthened my resolution to get on the air. I read every CB magazine I could lay my hands on, and soon got to hear about these “Radio Hams” who could sit an exam, legally buy/build a radio set, and get on the air to talk to each other. This situation continued for maybe a year or so

So, around mid 1981, I noticed that just around the corner from my house was a guy who sat in his car talking on a radio with what looked like a PMR magmount antenna on his roof, every Thursday night. So I made a few inquiries, and found out that it was a guy who ran a TV/Radio repair shop in the local town, and that he visited his daughter/grandchildren who lived in the adjacent house.

So, one Thursday night I plucked up the courage to knock on his car window and ask him about what he was doing. To my surprise he spent the next 2 hours telling me all about amateur radio, “A” licenses and “B” licenses, HF, 2 metres, VHF/UHF…..  I had to go, I had school next day!!!

He pointed me in the direction of “How To Become A Radio Amateur”, a free book from the Home Office, which told you all about the RAE (Radio Amateurs Exam) and Morse tests (12WPM was mandatory in those days if you wanted access to frequencies below 144MHz), and onto the next step which was to read the “Radio Amateurs Examination Manual”. So I bought a copy of that when I next went into my nearest city (the local town bookshops didn’t stock it and couldn’t find it!!!), and I read it till the pages fell out of it.

After scouring the local papers, I found that one of the schools just outside the local city was running an RAE night class starting in the September, with the intention of sitting the following June’s RAE. So, I enrolled, and got a lift there and back with one of my neighbours who also wanted to pass the RAE.

I enrolled for the December 1981 exam, and to my shock, passed it. Then came the wait till the next year to be 14 to hold a license, and a remarkable number of “cock-ups” by the Home Office and City & Guild’s (who ran the exams at this time), and I finally got my license through in early November 1982.

The guy sat in the car was Mr Ted Higton G8OVV, unfortunately a silent key now, but I will be forever grateful to him for the nights he spent explaining the various amplifier circuits to me, and for generally tolerating an annoying teenager whose endless questions must have driven him mad. Thank you.

Alan G6RBM.

As seen previously, there are many different ways of transmitting information via voice on a radio transmission. This article is concerned with the more complex component of an Amplitude Modulated transmitter, called SSB or single sideband. This mode is most commonly used for HF communications and is very popular with radio amateurs wishing to talk long distances (DX)

SSB (Single Sideband)

Single Sideband was developed in the 1920’s, following a patent registered in 1915, but didn’t really make an impression on the amateur communications arena until the 1950’s. This was mainly due to the level of technology catching up with the requirements to implement the mode.

Single Sideband is 1/3 of a modulated AM signal envelope. When audio is applied to a radio transmission, there are 3 components to the resultant signal. These are: the carrier, which contains no information but is the reference for the signal, and the upper and lower sidebands, which contain the same information as each other.

So, if we were to remove the carrier (which contains no information) and one sideband (seeing as the sidebands are identical), we could have a transmitter that uses considerably less power to produce the same output power, or for the same input power, could have up to 3 times the final transmitted output power.

This is a very simplistic view on SSB. In reality, it is relatively complex to create a single sideband transmission. There are two reasonably common methods of creating an SSB signal, with this first method being the most common. The simplest method is to feed the audio signal and the oscillator into a “balanced modulator” (enhanced mixer) which is configured to remove the carrier part of the signal. The resultant “double sideband” signal is then fed through a crystal filter with a very narrow (approx 2.4Khz @ 6db) bandwidth and very steep skirt response to remove the unwanted sideband.

Generally (although not exclusively) there is only 1 filter, and the frequency of the generated signal is shifted up or down to allow the filter to remove the unwanted sideband. Certain high grade transmitter manufacturers have included 2 filters, but these transmitters often have the facility to switch between variations of the SSB mode, such as: SSB with no carrier (the most common), DSB (double side band) with no carrier (quite popular on the HF Amateur Radio bands, SSB with reduced carrier (used by some HF stations to allow easier reception by having a percentage of carrier in the signal as reference) and DSB with reduced carrier.

The second, and possibly less common method of SSB generation is to use 90degree phase separation modulators. These use a network of amplifiers and capacitive/resistive filters to alter the phases of the audio information component and the generated carrier until the carrier and the unwanted sideband have cancelled each other out and the only component left is the wanted sideband. In years gone by, this method wasn’t popular due to the high component count, and the inability to get cheap close tolerance capacitors to create the filtering networks. However, with the advancement of digital signal processing (DSP) electronics, this method is finding more popularity due to the reduced cost of implementation. Common forms of this type of modulator are the Hartley and Weaver modulators.

Reception and recovery is also more difficult than for an AM signal. Because there is no carrier for the receiver to reference against to recover the audio, a carrier insertion method has to be employed. This is usually called a BFO or Beat Frequency Oscillator, and inserts the carrier normally at the second IF (intermediate frequency) in a super-heterodyne receiver, which is often at 455khz. On most communication receivers, there is a control known as “clarifier” or “fine tune”. This moves the received signal around the 455khz BFO and allows the detector to “de-modulate” the audio by making it more intelligible. After the carrier reinsertion, the detection process follows the same path as the AM detection. This method is known a synchronous detection and is highly reliant on oscillator stability.

There are other methods to de-modulate an SSB signal. One way used by high grade communications receivers is the envelope detection method. As above, this method is now starting to become more popular following the advancement of DSP