UK Microwave Group Round Table meeting

Sunday 13th September 2009

Hut 18, Tilgate Recreational Centre, Tilgate Forest, Crawley, West Sussex

The doors will open at 10-00 am for a nominal start time at 10-30
am. The planned format will be for a bring and buy / natter session
in the morning with the display of home-brew microwave gear running in
parallel until lunchtime with the lectures starting at around 2-00
pm.

Immediately after lunch the results of the UK uW Group constructional
competition will be then be announced followed the first talk and
demonstration:

The Goubau single wire RF transmission line revisited.

Speaker : Prof. Mike Underhill, G3LHZ

The Goubeau single wire transmission line technique is often seen as something of an historical curiosity with limited practical application but Mike hopes as ever, to bring some new thoughts on the subject. He also poses the question “Does the Goubeau line actually help to explain how antennas actually work?”

The Type 85 Multi-Megawatt Air Defence Radar – A Cold War Monster!

Speaker : Derek Atter, G3GRO

So you think that you have problems getting your 10 watt TX output on 10Ghz up to the top of your 40ft mast ?. Think of the problems facing the design team of the Type 85 air defence radar when circa 1959 at the start of the cold war, they were asked to design a new high power air defence radar to combat the potential threat posed by possible mass airborne attack by Eastern Bloc aircraft with multiple wide-band jammers against the UK East Coast Bloodhound missile sites and Vulcan bomber airfields.

The required power budget of the radar ran something like – “ Take 12 off frequency-agile “S-band” klystron transmitter each of 6MW peak, 20kW mean, located on the ground floor of a two story hardened building and feed a 60ft by 25ft rotating stacked beam parabolic antenna on the roof with 12 separate beams covering a 500Mhz bandwidth. At the same time, feed 12 associated receiver channels down to the receiver racks on the floor below without blowing the balanced mixer diodes. Throw in a few technical “frills” such as a switchable circular polarisation system capable of handling a maximum of around 250kw average RF power without melting! etc. etc.“

Dr Who and the attack of the Klystrons "Take me to your leader"
(It is actually a picture of one of the twelve 6 megawatt transmitter valves in the Type 85 super power air defence radar from the cold war era when it was being de-commissioned)