THE TRANSMISSION GALLERY
|Photos by Bill Wright||Page last updated: 2017-09-20|
|Kinlochbervie's UHF TV transmissions are listed in many places as being vertically polarised. In fact the transmissions are horizontally polarised across a wide arc from the south to the north-east, with vertically polarised signals being transmitted to the south-east only. The HP transmissions are from the customary stacks of crossed log periodics. They cover most of the village and surrounding area. The VP transmissions are from a single stack of logs which looks along Loch Inchard to the tiny settlements on and near the shore.|
Why were both polarisations used? In such a remote location it seems unlikely that co-channel interference was an issue. There must surely have been four channels available for (virtually) omnidirectional VP use.
A lot of aerials in the coverage area are Group A, HP, and aligned on Eitshal. Possibly HP was used at Kinlochbervie so the locals didn't have to alter their aerials. This theory falls down rather seriously though when you remember that Kinlochbervie is Group B, and of course most of the Eitshal aerials aren't pointing towards it anyway.
Whatever the reason for the use of both polarizations, it seems to have confused the local aerial riggers (most of whom are also the viewers, since at such a remote spot DIY is often the only affordable option). In the area towards which the transmitter radiates HP signals, with just a bit of signal "off the back" of the VP logs, I saw vertical Group B aerials and also one vertical group A! Tellingly I didn't see a single HP group B, although there aren't many aerials to look at to be honest.
Perhaps someone with proper information will come along and tell all.
April 2016 and Derek Cornell has been in contact with an answer for Bill. He writes:
The Kinlochbervie relay station was the last one that I planned and site-tested before my retirement from BBC Spectrum Planning in March 2000 after 34 years at Kingswood Warren! I don't have access to the planning files and am desperately trying to remember why the dual polarisation. You are correct in assuming it wasn't on account of either incoming or outgoing c.c.i. More probably it was to achieve coverage in two areas that could not have been achieved with a cardioid tx antenna. Using the same polarisation for both arrays could have created some deep nulls in in between areas.
|Receive log periodic pointing at Eitshal|
|Horizontal transmit array|
|Vertical transmit array|
|Looking down across the harbour from the site|
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