Chelmsford Amateur Radio Society
G0MWT, GX0MWT, GB5HF, GB100MWT & GB100MZX

CARS Meetings: Jan - March 2025


January Meeting
7-Jan-2025, 7.30-9pm
Danbury Village Hall		 "Practical Skills Evening"
By CARS Members

On Tuesday January 7th at Danbury Village Hall, CARS held a practical skills evening that featured construction and HF radio operating

This was the second radio kit building occasion and was a popular and enjoyable session. The kits were a variety of synthesised FM receivers which worked really well.

This is the sort of activity that used to be undertaken on the former Intermediate training course. Whilst that syllabus no longer requires hands-on practical work, some recent trainees found it valuable. Whilst we do have a few more of the kits, we are looking at what other designs are available for a future session

Overall as we ran on a little while, the quiz that had been prepared by John M0JOC was held over for another time, though Andy G0IBN ran another great raffle

Keen Constructors in the Hawkins room - One of the FM Receiver kits

HF Operating - Raffle Prizes!

February Meeting
Tue 4-Feb-2025, 7.30-9:30pm
Danbury Village Hall		 "Radar-90 Anniversary Talk"
By Andy Tyler G1GKN

The February meeting had a great turnout to hear all about the 90th anniversary of the Daventry Experiment on the 26th February 1935, which quickly led to the Birth of British Radar and many related innovations.

The 360ft tower at Great Baddow (originally at Canewdon, until it was moved in 1956) was an early result of this work, as it formed part of the Chain Home radar system for the Battle of Britain.

RF Expert Andy G1GKN began with the early history and fear of air attack following WW1 and early attempts at aircraft detection. Following wild suggestions for a Sci-Fi death ray, Robert Watson-Watt suggested that the power was not available for that but should at least be able to detect enemy aircraft and provide useful early warning.

The test performed near Daventry used a pair of Dipoles arranged to null out the direct BBC broadcast signal - but as the flew by its body reflected and scattered the signal which could be reliably detected. From that basic demonstration the team set up at Orford Ness (and then Bawdsey) on the Suffolk coast to develop not only Chain Home in record time, but related systems for IFF, VHF radar and eventually microwave systems.

The Chain Home original system was on HF and locked to the 50Hz of the national grid with metal towers holding the transmit arrays and wooden towers for the receivers. The low frequencies confounded early German reconnaissance who were expecting a more conventional microwave radar system. Our thanks to Andy G1GKN The enjoyable evening was rounded off by Andy G0IBN who ran another great raffle.

See also: GB9OCH Special Event for the anniversary day on 26-Feb-2025

March Meeting
4-Mar-2025, 7.30-9:30pm
Danbury Village Hall		 "Practical Skills Evening"
by CARS Members

Our March 2025 meeting was the second session of our hands-on meeting theme. Following the popular FM radio kit evening in January, a broader set of kits was available:

SK-Sales: We also had many of the smaller items left by Tony G4YTG, which John M0JOC is coordinating - quite a few items left, so do enquire! Later on we concluded with the Quiz, which had been held over from last time and the raffle.

March Meeting: Morse Keyer and Radio kit construction

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