Chelmsford Amateur Radio Society

CARS Meetings: July - September 2021

July Meeting
Tue 6-Jul-2021, 7.30-9pm
Online by Zoom
"Taking Toy Computers Seriously"
Damian Bevan G4WPO

Damian Bevan G4WPO who gave us the fascinating Alan Turing talk last year returns to talk about ‘Taking Toy Computers Seriously’.

Back in the 1980s many may recall we started with Sinclair et al which led to the BBC Micro which were ‘toys’ but very educational. Coding and understanding is now back in education fashion.

The teaching of Computer Science is vitally important and the current generation of school students are being taught ‘coding’. As modern computers are far more complex, the core concepts can be more easily taught with simplified models that can either be emulators of old ones, or new models that include Microbits, Arduinos and Raspberry Pi’s.

Back in the 1930s before electronics, computers were the people who operated mechanical tabulators. Katherine Johnson was one such, made famous for here pioneering work for Nasa in the film ‘Hidden Figures’. Pioneering names include: Charles Babbage, Ada Lovelace, and later Alan Turing.

Computing Pioneers: Charles Babbage, Ada Lovelace and Alan Turing

The original drivers included star, planet and tide tables for navigation, company accounts and pensions annuity tables. WW2 then pushed this to solve German codes.

After the war Turing came up with the concept of a general purpose programmable machine.

In practice the most popular practical architecture was by Von Neumann who developed a scheme in 1945 based on Control & Arithmetic units, memory storage and Input/Output.

Two emulations of such basic concepts that you can find on the internet are the Little Man Computer (LMC) and ARM-Lite assembly language emulator intended for A-Level syllabus.

Online Emulation of an ARM processor for the Game of Life

Computer Languages disguise low level machine code and assembler, to enable easier higher-level coding. In education popular ones are now:-

A useful learning resource for the latter is .

Other handy tools that Damian highlighted included CompilerExplorer on (mainly for C++) and for lots of other languages. These web based tools save having to install them for simple dabbling. A more entertaining example was Pico-8 for classic style game writing/sharing.

Finally Damian covered two of the most popular hardware models - the BBC Micro-bit and Raspberry Pi. The former is more of a simple microcontroller, whereas the Pi has now matured to have plenty of memory ports and graphics to be fully Linux capable.

Summarising, toy computers are valuable for ‘learning through playing’. However some have real ‘grown-up’ coding languages and uses. Indeed, many millions of Pi’s are now sold every year – a real success.

August Meeting
Tue 3-Aug-2021, 7.30-9pm
Online by Zoom
"Short Talks"
Murray G6JYB & Paul G4PVM

For August we had Two Short Talks:-

These two short talks by CARS members Murray & Paul illustrated where your wavelengths come from, down thru to your licence and then onto activities on the air, inc some forthcoming notable events

In just three slides, Murray explained how amateur radio allocations arise from the ITU Radio Regulations Treaty (dating back to the 1912 Titanic disaster) which are updated at World Radio Conferences. They then trickle down via CEPT and Ofcom into licence conditions and operating guidance. The latter include the band plans that RSGB/IARU maintain. Nothing can be taken for granted and it involves a lot of international effort as well as home-work.

Past IARU successes have included the WARC Bands, 136kHz, 472kHz, 5MHz, 7.2MHz and 50 MHz, but there are plenty of threats too! Remember - Without frequencies – there is no amateur radio.

The 'House of Amateur Radio' and its foundations (courtesy RSGB)

Paul started his talk by outlining the nature of the IARU Championship event which is held annually on the 2nd weekend in July:-

The RSGB HQ station is GR2HQ. For 2020, covid restrictions saw this operated by home-based operators. In the event, Germany had the leading HQ station, with GR2HQ coming 9th. For the 2021 summer effort a complex set up for GR2HQ involved 12 operators on various sites (inc M6T and Gilwell Park) with networked logging using Win-Test and coordination by Discord. Confirmed results are awaited, but provisionally 7th position is likely.

The M6T Saxmundham station – part of the GR2HQ team effort

Finally, Paul had a few AoB reminders for CARS events/history:-

CARS NFD History:

Future Special Event Stations: CARS QSL Archive - more entries welcome - see

  • Click for: Paul G4PVM - IARU HF Contest Slides

    September Meeting
    Tue 7-Sep-2021, 7.30-9pm
    Online by Zoom
    "Direction Finding for Fun"
    Roy Emeny G4JAC

    On Tuesday September 7th it was time for another CARS Zoom talk and the chosen topic this month was direction finding; and who better to tell us about it was Roy Emeny G4JAC and his talk entitled Direction Finding for Fun. As we heard from Roy throughout his talk, the accent was certainly on Fun.

    The Essex area has quite a track record in this activity and judging by Roy's long term enthusiasm he has played a big part in that track record and continues to do so, together with the help some keen Amateur Radio DF devotees.

    Roy explained to us the ins and outs of a DF hunt. That means using a special receiver to find the position of sometimes quite well hidden low power transmitters spread over a given area of countryside. Much skill and scheming goes into choosing locations for the individual hidden transmitters. Much skill is also required by competitors in hunting for the hidden transmitters. Before an event much advanced careful planning by the organizers is essential to ensure success. Up to ten transmitters are usually employed in a DF hunt, each set up with a different RF frequency and programmed to operate in a given time slot and with variable transmit on/off times.

    DF events take different formats, such as transmitters must be found in a given order or random order, time limits in place for time taken to find each transmitter and overall time taken. ARDF occurs on 160m, 80m and 2m with categories for every level and age group. The RSGB have promoted 80m DF as a radio sport with international links and competitors.

    Roy encouraged us to try a DF hunt and said that much help was available for beginners in the form of help on the day or / even in the construction and operation of the special receivers built for the job.

    Our thanks again to Roy for his very informative talk to CARS.

    Write-up by Colin G0TRM

    Easy, medium and hard transmissions vs 10min cycle - see

    For Forthcoming local DF events - see

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