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THE TRANSMISSION GALLERY

Photos by David Neale and Dan Glover Page last updated: 2016-12-31
Rough Common Kent
NGR: TR124597 Maps: Google  Bing (Ord Surv) Site Height: 74m      Structure Height:
Digital TV:
BBC Radio:
 
Ind. National Radio:
Ind. Local Radio: KMFM: 106.0 
Digital Radio:
Comments:

July 2008, updated December 2016

This BT tower was built in the 1980s, not far from the (now demolished) Canterbury Band I TV relay.

The local station for Canterbury originally launched in 1997 as 106 CTFM but was acquired by the KMFM group and re-launched in October 2000. The original transmitter site was the water tower at TR133592 (about one mile south east) and the station moved to Rough Common in February 2002.

We previously understood that KMFM used the folded dipole shown in David's photos, with maximum coverage to the south west. A quick visit at the end of December 2016 produced an unexpected result: the expected vertical dipole has been joined by another, slant polarised, and they are mounted on a different part of the tower. Ofcom data continues to show vertical polarisation only however there have been variations at some other KMFM sites over the past few years.

This is not the only oddity, see final photos.








Above: the dipole (and another end-fed antenna) seem to have been mounted above the feeder support/ladder.

Below: as seen in December 2016 - two dipoles now mounted on an extension above one leg of the tower.


At one time the tower would have carried large dishes on this face (and on the opposite side) connecting Westley Heights with another BT site near Dover as part of a cross-channel telephony link. Each of the tower sections is 4.6 m, here producing a structure just over 55 m tall. It's just possible to see that the tubular "legs" are thicker for the bottom three sections - there may be a further transition from "medium" to "light" modules towards the top.

In any case the structure is more than adequate to support one or two Band II dipoles...


This is a more robust mounting than before. The tower is aligned approximately 45 degrees from north and the support pole is above the western "leg" of the structure.

The dipole on the right hand side is on the north/east face and assumed to be for some other purpose, although it looks to be the right sort of length for Band II and is close to the position of the dipole in David Neale's photos from 2008. So, which direction does the (new) KMFM array favour?


We're now slightly to the north east of the tower. The "left leg" is the southern corner and the dipoles are definitely carried on an extension above the western corner of the structure. The dipoles seem to be oriented further to the north, with the null from the metalwork somewhere vaguely between west and south west.

This is all a bit of a mystery since the Ofcom detailed parameters show a restriction of around 4 or 5 dB (the sort of pattern given by a side-mounted dipole) to the east. Also the antenna height is given as 56 m but that would be only just above the main structure.

It would appear there has been some change to KMFM's licence for this site but the details haven't yet percolated through to the Ofcom parameters?


Difficult to be certain, but it appears the vertical and slant dipoles are part of the same array, connected to one main feeder.

Canterbury VHF

BT Sites: Rough Common

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