There were two Powys Amateur radio Club 2m cavity resonators at a
commercial transmitter location south of Newtown in Mid wales. They did
have a tendency to drift off frequency, probably according to the
temperature, being located in an uninsulated, brick hut on the Welsh
hillside. The construction probably wasn't up to commercial standards
and the weather there was alway wintery, even in the height of summer.
The replacements, made by Dave, GW8GLO, have been made with large
coaxial cable donated to the club and sit on the back of a 19" rack rear
door. It leaves more space in the hut apart from anything else.
Hugh, M0DSZ
On 11/04/2016 22:07, Paul Nicholson wrote:
Takes me back to the 1970's when I was a student working for
Gerald David at Aerial Facilities in Chesham building these
things -
http://www.ingenia.org.uk/Ingenia/Articles/240
which worked incredibly well thanks to the ingenuity of some
people at Bradford Uni who designed the adjustable center
conductor of the cavity so that the overall temperature
coefficient of the 'barrel' as we called the cavities, was close
to zero. Bandwidths of a few kHz at VHF with insertion loss
of less than 1dB were normal.
Gerald was a wonderful larger than life character, I could
relate many stories about life at AFL in those days - not
least Gerald's specialised driving techniques applied to the
country lanes of Buckinghamshire. There were many jokes about
ensuring the barrels were empty and Friday lunchtimes at the
pub were generally devoted to that.
--
Paul Nicholson
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