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.

This is the second part of the FeedLines article, and deals with lower freqencies and the use of open wire feeder.

The impedance for openwire feeder varies with construction, but is generally in the order of 450ohms. Openwire can be manufactured in the hobby environment quite easily by stretching out 2 lengths of wire (hard drawn single strand copper is the best, but any will do) parallel to each other, then placing spreaders between them at regular intervals.

The distance between the wires is dependant on the output power of the transmitter used, the higher the power, the wider the spacing. This is to prevent “flash over” on high voltage peaks on the line.

For lower output transmitters, 300ohm ribbon cable (often sold with Band II FM tuners as the antenna) is also usable. If using this, it should be noted that the output power should not be allowed to exceed 150watts, or flashover in the clear dielectric between the conductors could occur. This feeder is not recommended without some form of treatment for outdoor use, as water will collect on the dielectric when it rains increasing the risk of flashover.

Another variation on this theme is the “slotted ribbon line”. This is a “half way house” between 300ohm ribbon cable and full open wire feeder. Its impedance can be anywhere between 300 – 450 ohms, and due to its construction, is easier to deal with than full openwire feeder. The slots in the dielectric mean that it is not as susceptible to the effects of dampas ribbon feeder, however, the dielectric between conductors can harden an snap allowing the conductors to close up. This causes an impedance hump in the line and in extreme circumstances, flashover on transmitter voltage peaks. If this feeder is to be used, then it must be inspected regularly to ensure that it is in good mechanical order.

For any of the above open wire type of feeders to be used, it is imperative that matching units are used to match the impedance of the transmitter to the feeder. Most modern low power transmitters are in the order of 50ohms impedance, so direct connection to a frequency resonant dipole via openwire feeder will immediately result in an SWR of 6:1 or greater, which some valve PA’s will tolerate for a modest period of time, but can be considered to be suicide for a transistor PA. The design and use of “baluns” (balanced to unbalanced) and ATU’s (Antenna Tuning Units) is beyond the scope of this article, but both are required for the above.

Finally, for signals in the VLF (9 – 30Khz), LF(30 -300Khz) and MF (300KHz -3Mhz), any of the above systems used for HF signals can be used. The constraints about the construction of openwire feeder are even more important, due to the inability to erect efficient antenna systems (a half wave dipole or doublet antenna at 198Khz (BBC Radio 4 Long Wave frequency) is 758m long or nearly 1/2mile!!!) means that the transmitters are usually far higher output power. Also, the matching units for such antennas are substantially larger, again to reduce the possibilities of flash over during transmitter voltage peaks.

This concludes my brief look at feedlines. There is loads of information available both in books and on the internet regarding this subject. Although not the most exciting aspect of radio work, get this part wrong and you will lose that important output power, and in a transciever envirionment, this  loss is also there on recieve. So, that really large 17element 2metre beam you have just erected doesn’t work as well as joe’s 4 element quad down the road?? Did you use the right feeder and install it properly…..? Think on…!!

See you soon,

Alan.