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THE TRANSMISSION GALLERY

BEN DORRERY

Photos by Bill Wright Page last updated: 2020-05-02

Moray Firth Radio and Caithness FM broadcast from Ben Dorrery on a timeshare basis, on 102.5MHz.
[Ed]. From November 2019, they are now separate services.




















Caithness FM, a community station, has a studio in mainland Scotland's northernmost town, Thurso. In the studio car park is a mast made from two 20ft steel scaffold tubes very strongly guyed with concrete anchors that look almost big enough for Holme Moss. This is a very windy area. The mast holds a Group A TV aerial (which really needs to be replaced with a wideband one now DSO has happened!), the RBL link aerial, a VHF FM vertical dipole, and a six element VHF FM aerial - one of those DIY specials with the elements very close together. I recently removed one of these aerials from the roof of another radio station, the station manager having become deeply unimpressed with its performance. This example is not pointing the same way as the RBL aerial, presumably having been blown off beam. Maybe the dipole lower down the mast is in use for station monitoring. There's also a shrouded SHF yagi, also looking towards Dorrery.

The 50MHz RBL link seems to have caused problems, because up at Ben Dorrery mast there are two RBL receiver aerials, one a dipole on the main mast and the other a yagi on a ground mounted mast which is fixed and guyed with plastic rope. The yagi is one of those that can have the element lengths and matching stub adjusted to suit different frequencies. These aerials are not very strongly made, and I doubt if this one will survive intact for long at such a windswept location. However, given the horrendous price of a multi-element yagi when bought from the likes of Jaybeam it's no surprise when a low budget station tries a cheaper alternative.

The RBL link path is probably obstructed by the Hill of Lieurary, which is roughly at the midpoint.
Transmission from Dorrery is via two slant polarised folded dipoles on the north side of the structure.
Perhaps someone from Caithness FM will contact mb21 and put me right if what I've said here is wrong.









Ben Dorrery index

This site is now included in the Update List for the following reason:
Tx aerial replaced by two dipoles on a cantilever at the top of the main tower. 50 MHz link replaced with 5 GHz.

Please let us know if you think there is another reason photos should be updated.
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