Chelmsford Amateur Radio Society

Past Club Meetings:   July to September 2008

September Meeting. Amateur Radio from Brownsea Island, GB100BI/S by Peter Best, G8BLS

Peter drove from his home town of Ipswich to be with us and picked up a collegue Ewan Fenn, G3RTF (ex) who worked for Marconi building large transmitters (500kWatt).   Peter is the Chairman of the Felixstowe & District Amateur Radio Society, FDARS & he is also heavily involved with Scouts.

He started by asking who was a Scout, from BT, ex Boys Brigade and who had been to Brownsea Island where just over a 100 years ago the first Scout camp was held. There were a few takers for each request.

Peter gave a quick potted history of his involvement with radio.

Peter Best, G8BLS
Peter showing how he was given a Crystal set by his Father in July 1953.
His comment was that is how he suspected many of the large audience started - right!
Photos by John, G8DET

Peter Best, G8BLS
Part of the large audience.

Peter Best, G8BLS
Photo of a group of GPO Telephone Engineers (Peter is front, left) on a Course at Bletchley Park in 1963.
This was before anyone knew what had happened there during WWII.

A large audience listened entranced as Peter told of the organisation which was needed to accommodate so many Scouts from over 160 Countries.   Because so many Scouts wanted to come to the event they were arranged into 3 parties. The 3 camps on BSI were, 1st one for UK Patrol Leaders, 2nd was for 2 Scouts from each of the above 160 countries (320 in total). These took part in the Sunrise Ceremony on the 1st of August, and the 3rd camp was the New Century camp and the members mostly came from outside of Scouting.

Peter said the challenge was to tell a story of an event that has lasted 100 years, has had a cast of countless millions, in one evening, and to mention radio as well.   It has been calculated that the Adults involved with the Jamboree put in 5.5 Million person hours, before, during and after the event. All voluntary!!! Most paid to be involved!

A BP ferry boat transported all the kit to the island but could not land - it had to ride the tide during a limited period and used its ramp to unload & load all the vehicles and stores.

A number of aerials were assembled - one with a large red LED lamp on it as the military used to fly helicopters low over the island at night - this lamp was demonstrated.

To demonstrate that alternative power sourses could be used a selection of Wind and Solar Power was produced, however most of the power actually came from a generator.

Peter Best, G8BLS
Peter shaving on BSI using Solar power to drive a 12 volt razor.

Peter Best, G8BLS
A One Person Horsepower - Peter said that as there were so many willing feet
it could be used to charge many batteries.   A "poor Motor" but it will charge a 12 volt battery at 10 Amps,
and more with a very enthusiastic jockey - quite a useful power source.

Peter Best, G8BLS
Peter told that to occupy the many Scouts all sorts of games were thought up including
making a wall using 40,000 Woggles.

Peter Best, G8BLS
Brian, G3CVI making the anouncement about Science & Discovery Day at
Sandford Mill on Sunday, 28th September.

Peter Best, G8BLS
Peter drawing the Raffle tickets for Chairman John.
Photo by John Yates

After the Break, Peter told of his involvement listening and looking at the International Space Station as it passed overhead in QSO with the Scouts at Hylands House.   Peter played the video of the event at Chelmsford - great.

Peter Best, G8BLS
Peter polishing the dust off BP's pate just before he left BSI in August 2007.

Thank you Peter for such an interesting and well presented evening.

August Meeting:-
Constructor's Competition
Organised by Carl, G3PEM

The advert for this evening's event stated:- "Yes it is soldering iron time already!

CARS gives away real money. £10, £7, £5, and £5 for 1st, 2nd, 3rd & First Time Winners Award, respectively. This is good money for your efforts.

Basically anything entered can win (don’t forget a house brick won in the 1980s) but there is a better chance if it is a) Safe; b)Connected with Radio; c)Electrical or Electronic or d) Interesting.

Each Entrant is requested to tell the audience something about the entry – if you prefer, a Committee Member will read out your spiel.

After the announcements, Chairman John, G8DET started the event off by showing a Jason FM Tuner assembled by Mr Vincett of Moor Hall Lane in Bicknacre in 1961.   It was the main set for the house for some 30 years.  

Constructors Competition
Chairman John showing the Jason tuner made by Mr Vincett of Moor Hall Dane, Danbury in 1960.
Photo by John Yates, G1UZD

Switching it on produced a distorted sound due to flat batteries of John’s audio amplifier but Colin, G0TRM, our Sound Maestro soon patched it into the PA and sweet sounds filled the room.

Next on the podium was John Yates, G1UZD who explained that while working in Finland his switched-mode power supply for his laptop produced so much RF interference he had to replace it with a home designed, home constructed 20 Amp PSU of conventional build.  

Constructors Competition
John Yates, G1UZD.
Photos by John, G8DET

Constructors Competition
A very large cooling fin had to be fitted soon after construction for continuous rating.   An ex-Marconi brass box housed it and the finished diagram was beautifully drawn up using Microsoft Word – a nice piece of useful equipment.

Patrick, M0XAP showed a remote tuning unit as he has a 20m dipole and a long wire for Top Band.   His IC775 manages Top Band, but O/P on 80m problematic and 40m more so.

Constructors Competition
Patrick, M0XAP

The idea was to make an Aerial Tuner that would solve those 2 problems but without switching, relying on a remotely-operated variable capacitor.   This was done by trial and error; the coil was wound on a heavy cardboard curtain roll fixed by Ronseal wood hardener.   A suitable tapping point was selected and soldered.
Constructors Competition
The 'Como' electric motor had a built-in 512:1 reduction and was connected by plastic bevel gears to the capacitor.   There was a 'straight through' relay which bypassed the secondary in order to work Top Band.   The results on 80m locally are excellent, with better reports on 40m as well.   Total cost about £40.00

Philip Lewis (who has just past his Foundation Course – Congratulations) said that he had nipped home & brought back an Audio Amplifier he was involved with the design and construction some 20 years ago.  

Constructors Competition
The Power Amp.
It was a Current Dumping design working at 60 Volts with up to 1 Watt in Class “A”, rest Class “AB”.   It has been tested at 0.001% distortion.   It had a “running meter” which recorded 7640 hours – a lot of usage.   It was constructed from ex-computer pieces – cost very little to build and sounded excellent.

The Late Anthony, M1FDE ran an Echolink system from his garden shed and an Ofcom requirement is that on receipt of an appropriate telephone call it has to be shut down – how?

Constructors Competition
The Late Anthony Martin, M1FDE.
Anthony passed away 6 weeks later.

Constructors Competition

Anthony explained that by obtaining a surplus Key Fob and Receive unit from a scrap car he has modified it to respond to a single key press from his kitchen – to stop it being switched on again he has produced a series of key presses only known to himself.  
Constructors Competition
A beautiful piece of micro-soldering and design.   It works on 433.92MHz with an output of 10mW and a range of 30 metres.

Ron Keefe, G4SIS held up a lovely shinning variable Butterfly Capacitor.   It was used to tune his single Loop Aerial in the loft and could have many thousands of Volts across it, hence the wide spacing.  

Constructors Competition
Ron Keefe, G4SIS.
Each blade was cut out of a sheet of 1.5mm Aluminium sheet – took 3 months in hours to do!  
Constructors Competition
It measured about 240pF and had to be completely de-burred or it may flash-over when in use.   “Too good to use – put it on the Mantelpiece” was a comment from the floor.

Norman Awcock, G8GWP produced a One Valve Reaction Medium Wave Radio from a WWII design using a 6J7 valve.  

Constructors Competition
Norman Awcock, G8GWP.
This was supplied from a 30v PSU with 6v for the Heaters.   The Audio Amplifier used only 12v HT!   He had used Litz wire (from Geoff, G7KLV who had given him encouragement).

Geoff, G7KLV started his presentation with the words “Well you have stolen my pitch.   I am going to show a very similar set-up”.   It transpired both Amateurs had produced the same One Valve Receiver from two different sources – both published by Mr Camm of Practical Wireless fame.   Geoff had used an ECH81 and 12v HT.

Constructors Competition
Geoff, G7KLV.

Richard Beck, M3YLB had built a nice kit Morse Oscillator with two sockets so that he could “send” to his mate who could then “reply” to improve their Morse speed.

Constructors Competition
Morse Sender
He had obtained from W&S a beaten-up Morse key which he had stripped down, mounted on a new base, polished up and reassembled to look better than new.

At the Refreshment Break, Carl, G3PEM counted the Voting Forms to produce the results.

Unfortunately, Gary Broad, G6AXE had placed his entry by Harry, G5HF’s kit on the back table and so did not get voted for – sorry about that.

Constructors Competition
Garry Broad holding his Amateur Radio Car Unit.

It was a nicely made unit to mount in a Vauxhall Astra to hold a Mobile Tx with 10 Watts of Audio and a link to the 25Watt Linear mounted in the boot.   Replying to a question from the floor, Gary did say that there was a possibility he had blown up the car electronics while testing the unit.

CARS now famous Raffle with lots of very useful goodies was drawn.  

Constructors Competition
Raffle Table & "strong arm Raffle Salesman" Geoff.
Geoff, G7KLV provided the mobile strong arm sales patter while Colin purchased many of the goodies assisted by CARS Members and Peter Graves, G0KSJ manned the table – thanks to all.

After the Raffle was drawn, CARS President Harry, G5HF presented the prizes to the Constructors Competition.

Constructors Competition
1st Ron Keefe, G4SIS for his Capacitor.

Constructors Competition
2nd The Late Anthony Martin, M1FDE - Remote Unit.
Constructors Competition
3rd Richard Beck, M3YLB - Morse Key/Sender.
Constructors Competition
First Time Winner: John Yates with his PSU.
Congratulations to all.

Harry, G5HF then showed us how to make an Electrolytic Rectifier.   These were used during the 1920s and 1930 to rectify up to 1,000 Volts but Harry will limit his to only 180 Volts!

Constructors Competition
President Harry, G5HF

Constructors Competition
Harry started by giving us the background to early Amateur Radio Transmitters.   After the First World War mains transformers could be quite cheaply be purchased but Rectifiers at over 1,000 Volts were so expensive & difficult to obtain only Governments could afford them.   However by using one electrode of Aluminium & another of Lead suspended in a solution of Ammonia Phosphate and water a Diode is produced.   If DC is presented to this “plant” with the polarity one way a Capacitor is formed and the other way, current passes.

Harry demonstrated this with a 45 Volt system.   It appears that 1 Amp is possible at over 10,000 Volts (more comforting in the Winter), it produces heat to warm your feet but slightly more disconcerting it glows a yellow hue as you key the transmitter.

Harry concluded his talk by showing a battery which cost nothing to run.   It was a cell of dissimilar metals in a glass container of water and powered a Liquid Crystal Clock (which was keeping perfect time).  

Constructors Competition
Unfortunately, Harry said it sometimes stops – the water has
evaporated – but a sort trip to a tap soon has it going again.

Thank you Harry for a brilliant end to a very “Constructive” evening.

John G8DET

We will run the Constructors Competition again next year - look out for it in our 2008 Programme.

July Meeting:-
7.30pm, Tuesday 1st July
Solar Observing
By Peter Meadows, 2E0ZBU

Martyn, G1EFL, CARS Vice Chairman took control of the meeting as John, G8DET was on holiday.

Solar activity has a significant impact on radio propagation through the state of the Earth's ionosphere.   In general the more solar activity, the greater the density of the ionosphere which gives rise to better HF propagation and the availability of higher frequencies for long distance communications.

This talk described how sunspot activity can be safely observed using modest sized telescopes with special filters as well as the more dynamic solar features of solar flares and prominences using more specialised hydrogen alpha telescopes.   A selection of observations made by the speaker over the last solar cycle and from other solar observers was then shown.   After describing the characteristics of solar cycles, the present solar minimum and the start of the new cycle was discussed.

This leads one to ask the question "Where has the latest Solar Cycle gone?".

Finally there was a short summary of the activities of the Radio Astronomy Group of the British Astronomical Association: -

Peter 2E0ZBU is the Solar Editor for ‘The Astronomer’ magazine: -

His Solar Observing website can be seen at: - Thank you Peter for an enlightening presentation.

CARS famous Raffle produced lots of very useful goodies - Geoff, G7KLV sold plenty of tickets to the large audience.

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©Copyright CARS 2008
Last revised:- 20th September to add the August Meeting.