David, G8UOD reports that the Saturday visit to Mullard Radio Astronomy Observatory went very well. We were given a brief history of the site from the war through to becoming a site for antennas to monitor the skies.
We were shown the museum, which is quite small, but had some interesting items from the early days, including part of the German radar equipment, which was initially used with some modifications.
We were shown several of the arrays, including the one mile and half mile antennas and the 4C array made of conventional structured antennas, only lots of them.
The last time we visited the site was back in 2003 and the long array of dishes on the old railway line have now been clustered as the technology now available enables the University to do the same job as the old. We visited the millimetre antennas which were being built the last time we visited.
Peter was a very good host and we all enjoyed ourselves, although some would have liked a bit more info on what the information received was used for, but Peter pointed out that he was an engineer and the academics at the university would have to be the ones to give that information.
The tour started about 11.00 and ended at 14.15. I thanked Peter on behalf of the club. All in all an enjoyable experience.
On the evening of the UK referendum, four members turned out for the Summer 2m DF hunt. Although it had rained during the day, the evening looked to be better. This year the ‘Fox’ was Paul, G1GSN who started transmissions at 20:00 but couldn’t be heard very well. After a few more tries the transmissions improved and the hunters were off. Of course, the winner would be the person who drove the shortest route to the fox and not the first to arrive.
Martin, M6SCI assisted by Ian, G3ORG found the fox after having driven only 4 miles! The final tally showed that David, G8UOD had driven 5 miles and Derek, M0DLM had driven 6.
It appears the initial problem with the transmissions was caused by the dense and very wet foliage where Paul had parked up opposite the Southill school.
The group retired to the Brewery Tap for discussions and a drink.
A General Discussion took place, mainly about the future of the club’s participation in 48 hour contests. David kept a ‘pro and ‘con’ tally on a white board. It did seem as though the ‘cons’ had won the evening, although the entire membership was not in attendance.
Don, G4LOO started his presentation by making certain every one knew the dates of the contest: 2 – 3 July. We then looked over last year’s results to analyze the data band by band to highlight errors. Don also showed our position in relation to others who entered the same sections. He then went on to outline our entry for this year. The equipment needed for each band was listed and discussed. Last but not least, the rota was passed for members to sign up as operators, selecting their time and band choice.
A good turn out heard Brian explain the need for a WW2 system to achieve greater accuracy in the Anti-aircraft systems. The equipment needed to track a moving aircraft was complicated by the typical shell time of ten to twenty seconds and the need to predict the movement of the target.
By 1940 various systems such as photo sensors, electrostatic or magnetic field sensors were tried buy found wanting. Fortunately, Three British men, Butement, Shire and Thomson of The Air Defence Experimental Establishment suggested a CW oscillator in the shell with a circuit that would measure the Doppler effect of a reflected signal from the target and trigger the explosive shell.
However, Britain did not have the resources to produce the fuze in sufficient numbers and the decision was taken to send the design to the USA as part of the ‘Tizard Mission’ since the USA had the industrial resources to exploit the military potential of the British research.
The system was used with very little modification and in combination with the SCR 584 ten centimetre tracking radar was considered the most important development in WW2 after the Atom Bomb.