Chelmsford Amateur Radio Society
G0MWT, GX0MWT, GB5HF, GB5SM, GB100MWT, G100RSGB & GB95-2MT

CARS Meetings: Jan - March 2019


Award for All


January Meeting
Tuesday 8th Jan 2019, 7:30-10pm
Oaklands Museum, Moulsham Street
"Sub-Surface Comms"
Peter Bridgeman G3SUY

The January meeting was unusually on the second Tuesday, January 8th to avoid New Year’s day. Despite the cool winter evening it was well attended to hear all about a real challenge for radio – underground systems.

Peter Bridgeman G3SUY gave a well-illustrated talk of his time in Plessey and their development trials of the ‘Figaro’ system for use by the emergency services in tunnels. Venues included the London underground, or some other railway and sewer installations as well as a government bunkers!

The development of Figaro in the 1970s ran in parallel to VLF cave rescue equipment such as the Molephone by Lancaster University and later the Heyphone by John Hey G3TDZ) which run at ~87kHz Unlike VLF caving (or current UHF approaches), Plessey had remarkable success with HF and loop antennas. The happy reason for this was a number of reasons as became apparent in early tests:

 
Factors for frequency selection/performance

So for Figaro the optimum frequency range was between 3 and 6 MHz. And the reason for the name?...

FIre Ground Apparatus for Radio Operations

 
Figaro Radio Equipment

The trials ended up in all sorts of locations including various London underground tunnels, Clapham Common Deep Shelter, the Wheel Jane and South Crofty mines and the Severn Railway tunnel. Some of the metallic lined tunnels did indeed act a waveguides where performance dropped down within yards.

Despite a great technical effort over two years of trials, the government would not pay for the development costs that would be spread and levied over the production models. In the end only two systems were ever purchased - one by the Home Office and the other by the London Fire Brigade.

However Figaro did see real action once – during the Feb-28th 1975 Moorgate disaster. It was later retired around 1986 and superseded by leaky feeder being installed in the London Underground tunnels.
- Our thanks to Peter G3SUY for a great piece of storytelling!!

Following the break the CARS Raffle was drawn. With Chairman Elliot 2E0JSE away, Bob G4MDB did the draw and also made a somewhat overdue presentation…


Bob G4MDB presenting John G8DET with his delayed certificate
for the Constructors Competition 3rd Place

Useful Link:

  • Figaro - Useful web page: www.dtels.org/html/sub_surface_radio.html



    February Meeting
    Tue 5-Feb-2019, 7.30-10pm
    Oaklands Museum, Moulsham Street
    "Data Modes for all Occasions"
    By David Cutts M0TAZ

    The February meeting proved to be a popular one for a well-presented talk on Data Modes by Dave Cutts M0TAZ. Dave operates most data modes, and enjoys RTTY contests:
    "I don't chase awards, but do enjoy keeping track of my LoTW digital and WAS count. I enjoy alternative data modes, so quite often can be found in ROS, JT65, JT8, JT9, MFSK or Olivia modes. Experimenting with 160m loaded vertical on JT65 over the winter."

    Dave first spent time explaining the basis of many of them including their tone structure and use of Forward Error Correction (FEC) – which is why they perform so well at lower power, or in poor propagation conditions.

     
    The talk gave a great insight into modes and sounds

    Of course datamodes are not new CW and ‘Hell’ have been around a long time (Hell dates back to ~1920. RTTY also has old origins, but recently we have had PSK and of course the newer WSJT suite (WSPR, JTxx, MSK, FT8 etc).

    In the past identifying them on air took a skilled ear but the variety of them (especially courtesy of the JT suite) makes that harder. Fortunately waterfall displays are increasingly common thanks to SDR transceivers. David also gave a useful summary of various datamode advantages and drawbacks. See the useful links below for a couple of handy websites.


    There are sound clips online useful for identifying modes

    CARS refreshments and raffle followed the talk. Our thanks to David - and we look forward to his return.


    Refreshments break - tea, coffee, biccies and cake!

    Useful Links:

  • Fldigi by W1HKJ: Files
  • Fldigi Modes: Digital Modes - Sight & Sound
  • George M1GEO: Modes



    March Meeting
    Tue 5-Mar-2019, 7.30-10pm
    Oaklands Museum, Moulsham Street
    "Offshore Radio"
    By Jim Salmon 2E0RMI

    Jim Salmon 2E0RMI will be giving a talk on ‘My Interest in Offshore Radio’. This will let Jim indulge in one of his passions and cover a wide variety of stations (not just Radio Caroline!)


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