UK Broadcast Transmission

THE TRANSMISSION GALLERY

Hemdean Berkshire NGR: SU710762 Maps: Google  Bing (Ord Surv)   Site Height: 67.5m       Structure Height: 45m Digital TV: BBC A: 33   D3&4: 36   BBC B: 48   National Radio: Radio 1: 99.4   Radio 2: 89.8   Radio 3: 92.0   Radio 4: 94.2   Classic FM: 101.8   Local Radio: Digital Radio: BBC National: 12B   Berkshire & North Hants: 12D   Digital One: 11D   Comments: Hemdean is a TV relay of Hannington. Pre-B700 allocations: 52/46/48.

Show historic services
Updated April 2006

Hemdean was originally a BBC landlord site which started out as a UHF TV relay transmitting from a 17m wooden pole in October 1979. Transmissions were vertically polarised only and were intended to serve about 1200 people. Channel 4 was added on 26-Sep-1986. The wooden pole was replaced by the current 45m tower in 1994 for the addition of BBC national FM radio, which entered service in December that year. At the same time a horizontally polarised component was added to UHF TV, to extend coverage to areas of new housing. Transmitter power is split equally between the two antenna systems. The nominal ERPs for the analogue service were 32W (VP) and 8W (HP). For DSO the ERPs are the same - 7 dB higher than the standard conversion.

Mike Smith's photos (above and below) were taken before the addition of DAB

According to the published data the the tv relay transmits 32W ERP vertically and 8W horizontally, so there are two sets of tx aerials for the tv service. The above photo shows the vertical tv logs as well as the dipole aerials used to transmit the radio services.

The vertically polarised 4 element band II yagi, on the left, is the Classic FM RBL aerial, pointing towards Oxford.

The DAB Tx aerials shared by all 3 muliplexes. Service dates: Berks & N.Hants 31-Jul-2004; Digital One 15-Nov-2006; BBC National 29-Oct-2009.

Twin horizontally polarised 4 element yagis pointing towards Wrotham for the BBC FM radio RBL.

2 vertical dipoles used for Tx of all 5 FM radio services. The radiation pattern has deep nulls to the north - but this is probably due to side-mounting on a large structure.

The HP transmit logs...

...and the receive log, quite low on the tower.

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