Our meeting on 20th July consisted of 3 ‘mini talks’ expertly presented by Martin Butler – M1MRB. The first part of Martin’s presentation was an introduction to the ‘Natter Night’ regulars and the sort of activities they get up to. It seems that quite a variety of plans are ‘hatched’ at these sessions resulting in the following activities over the past year.
Hill top excursions to Reigate Hill – lousy weather is usually obligatory, particularly when taking part in a contest! The 6M WAB contest was particularly notable for Sandie Looker – M3XSL as she made her first contact outside the UK (to Hungary) on this occasion. Oaks Park is also a favourite operating location, with cold & wet weather thrown in!
One major activity for the group was JOTA. This included a radio talk for the scouts, some kit building, morse tuition and an opportunity to send greetings messages on VHF & HF. A further radio ‘play day’ has also taken place at the Banstead scout hall.
The second part of Martin’s illustrated talk was a brief report on the foundation course that was run at the 7th Banstead scout HQ in April. The course consisted of 2 days training, 1 week to study the course work, a revision session on the second Saturday morning with the exam itself in the afternoon. A group of youngsters and adults (12 in total) sat the exam. The net result was 5 band new M3s! We understand that a least one of the youngsters who only just failed the exam is hoping to try again in the future. Further foundation courses have been planned.
The final part of Martin’s presentation was on the subject of Multimeters, particularly the comparison of the characteristics and operating techniques of Analogue and Digital meters. Basic advise was given on purchasing a good quality analogue meter, particularly making sure that it has high sensitivity of 20K.Ohm per Volt or greater on DC voltage ranges. Anything less would be unsuitable for electronic testing. Extreme caution should be exercised when purchasing a cheap meter although it should be possible obtain a suitable instrument for as little as £15.00.
Anyone purchasing their first multimeter may find a digital one easier to use, particularly as they have a very high internal resistance (at least 1M.Ohm & often 10M.Ohm) and take negligible power from the circuit the are testing.
With an analogue meter it is often necessary to account for the internal resistance of the meter to calculate an accurate reading.
Martin described the various common sense precautions that are recommended when using mutimeters along with an explanation of the internal circuitry and the various techniques employed for testing, diodes, zener diodes, transistors, thyristors, coils, chokes, fuses, bulbs and batteries.
It seems that Martin is an avid collector of multimeters and he bought along a variety of his treasured instruments for everyone to study at the end of the meeting. He packed a lot into the meeting and it was greatly appreciated by those members who came along. Many thanks to him for an excellent presentation.
