Difference between revisions of "Saffron Green"
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Latest revision as of 04:51, 30 September 2013
Saffron Green is a 4 mast directional MF array near Barnet in North London which superceded Lots Road, a temporary site established earlier to allow Capital and LBC to get on air by their deadline in 1973. Saffron Green was constructed in 1975 to allow the station to radiate high powers towards London on 1548kHz and 1152kHz whilst radiating virtually no power at all towards Birmingham and Liverpool where the frequencies are used by other ILR stations.
Roger Piper writes :
The original Capital installation at Saffron Green consisted of four 10kW linear amplifiers, Marconi if I remember correctly, one on standby and three in use to give the 27.5kW needed to achieve the licensed erp of 100kW maximum. Initially the transmitter failed to produce the expected power output. IBA staff traced this to the coaxial cables from the drive unit to the individual amplifiers each having been routed most conveniently so they were not equal lengths.
With the coordinated frequency changes in 1978 Saffron Green Capital's MF transmitter had to be changed from 1546kHz to 1548kHz. At first all seemed well, but driving around away from the main lobe there seemed to be audio distortion not there before the change. Apparently the initial changes had resulted in the directivity of the antenna array being frequency dependant across the 9kHz wide channel, resulting in incorrect sidebands to carrier relative levels. A complaint to the IBA resulted in an acceptable change.
I asked Ray Hills, former IBA Assistant Director of Engineering, what he remembered about the problems of finding a permanent London MF site and have the following reply which may be of interest.
"At that time I was not responsible for service planning and site finding so I don't know the details. As far as I recall, Brookmans Park was ruled out because of the high powers being used there and because, unlike TV, radio site sharing was not mandated by Government. I don't think we shared any radio sites with the BBC. Even the VHF ones were on existing IBA masts (or new sites of course). The incinerator site was, I believe, somewhere near Heathrow.
I don't know how we achieved the Saffron Green site but it is not beyond possibility that some pressure was applied at a high level."
As mentioned in the mb21 Transmission Gallery, on the evening of 1-Jul-1985 a serious fire occurred at Saffron Green. Originating in the transformers of a reserve transmitter for LBC, the fire spread and affected other parts of the building, and resulted in the loss of the AM service from Capital Radio. IBA maintenance staff worked throughout the night and had restored both services by 6.00am the following morning. The extensive damage to the building meant that transportable radio transmitters had to be brought to the site and special measures taken against chemical hazards. Permanent replacements for the LBC transmitters were due to be installed in April 1986.
See also :