Chelmsford Amateur Radio Society

CARS Meetings April - June 2019

Award for All

April Meeting
Tue 2-Apr-2019, 7.30-10pm
Oaklands Museum, Moulsham Street
"A Canal Journey"
Vic Rogers G6BHE

For the April meeting we had a double feature. For the main session before the break Vic Rogers G6BHE recounted his hard work and experiences on ‘A Canal Journey’ up the Grand Union Canal. This entailed travelling from Harefield to Leicester - 118 miles, 128 locks, 8 swing bridges and 4 tunnels, single handed in 7 days! For anyone who has been on a canal – all those locks etc can be quite an effort!

Vic's boat and giving the talk

After the break, the raffle was drawn and there was a short Q&A ‘Brains Trust’ session, with questions including the latest position on plans for IMD. Our thanks to Vic who is also the South Essex District Rep for RSGB. So whether it’s boating or radio – he is always pleased to hear enquiries!

Vic gettting his speakers mug from Colin G0TRM

May Meeting
Tue 7-May-2019, 7.30-10pm
Oaklands Museum, Moulsham Street
Broadcast TV Development
Andy Fremont

For May, we were pleased to host Andy Fremont who is involved with the TV collection at Sandford Mill and took us on a brief tour of Broadcast TV development.

This started with the 'Nipkow disc' , originally developed for scanning photos and used by Logie Baird for his mechanically scanned system, which by 1948 had been overtaken by the Image Orthicon camera tube and the Marconi-EMI system. Early cameras were pretty heavy and a Marconi one from that era features in teh BBC Sport Personality of the Year Trophy

Camera tube development did progress with the Orthicon being key in the early days. The Orthicon saw us through to the start of the 60’s when the Plumbicon appeared. The introduction of colour (and 625 lines) added to the complexity for setup calibration and yo the PAL signal that had to fit it all in (to which NICAM Stereo and Teletext were later embedded as well).

Andy explaining how the orthicon became the key tube for many cameras

Andy's background in Marconi Comms Broadcast Division provided for a highly informative talk on some of the key developments

Some of the earlier Marconi camera models with rotating turret lenses

Transistor technology was introduced in newer camera models. Another change was Variable Zoom lenses eventually replaced the rotating turret fixed lenses. Marconi also did other broadcast equipment inc the B3410 telecine, which lasted until Digital started to appear. However competition from other manufacturers eventually took its toll and resulted in the closure of the Marconi Comms Broadcast Division.

The Mk5 Camera - transistorised with zoom lens - and the Marconi Telecine at Sandford Mill

Andy receiving his speakers mug from Elliot 2E0JSE, CARS Chair (Photo by Colin G0TRM)

June Meeting
Tue 4-Jun-2019, 7.30-10pm
Oaklands Museum, Moulsham Street
Beam Building
Dave Cutts M0TAZ

Dave Cutts M0TAZ who gave us the Datamodes talk in February, returned to CARS for something different - DIY Antennas. Dave gave a presentation and some small hardware demos on Beam Building.

Whilst full size HF beams did not fit in the room or his garden, Dave enjoys field day work and was keen to try something that wasn’t possible at home.

He started with a 14 MHz Quad as it was easy to transport and low noise floor. Based on roach poles and a central plate (see pics).

Dave's next project was a rather substantial 4-element Yagi on 21 MHz, as well as a 3-element on 18 MHz – quite a handful. As discussed with the audience – some attention to detail is needed to get the right tube sizes that telescope snugly inside each other.

Dave with one of his modest size Yagi’s – and some tubing detail

3D Printed insulators and DIY brackets

David’s approach for lightweight portable designs for field work did not need permanent guy ropes and heavy duty all-weather construction – so it was a little different – but the results on air were pretty good. Dave has given a few links below for the design info. Our thanks again for a well presented and entertaining talk!

Bob G4MDB with Chairman Elliot 2E0JSE drawing the raffle (Photo: John G8DET)

Useful Links:

  • YU7EF antenna page:
  • DK7ZB antenna website:
  • Dave M0TAZ beam building:

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