Orkney Image Library

Octagon brick structure always make me think of a RAF DF tower but can't see enough of this to see if it is one.

This is one in Caithness

canmore.rcahms.gov.uk/en/site/314258/contribution/lybster/

They originally had a wooden tower inside , rather like a windmill without the sails.

This similar but not very standard
canmore.rcahms.gov.uk/en/site/142172/contribution/corse+hill/FNL7065320649/

But gives an idea of the size.

We have a similar structure in Birsay on Eefie Hill and after some research this was found to be a VHF radio, direction finding/tracking station. Inside the octagonal brick wall in the one in Birsay was a wooden building about 8 - 10m high and the same shape with wooden supports over the top of the wall. The Air Ministry kept an interest in the building until 1959. I will post a computer image of what we think it was like when in use

I think the one on Eefie Hill gets a mention in one of the books on their airfields on Orkney. I will check when I get hom. I did look on Google Earth but could not see anything.

The other type of DF station to watch out for is the type used by the RN, RSS and others. There was just a small building (often a wooden hut) with four masts around it. I don't have any listed on Orkney but the RN used some ex GPO sites of which there is little information. This is one I found on Tiree.

www.flickr.com/photos/doffcocker/sets/72157627691877906/with/6156291961/

It shows well on Google Earth.

This type seem quite rare

www.flickr.com/photos/doffcocker/sets/72157628704884757/with/6630738823/

Also the "bird table" is a distinctive feature of that type of site and was used for calibration.

Another distinctive feature is a circular feature, quite a number visible on the postwar aerial photographs in Caithness.

Rarest of all and sure none on Orkney is the underground water tank type.

Martin & Tommy's comments confirm what we thought.
inside this brick structure is a concrete kerb with iron supports, and it looks like external concrete mast anchors have been grubbed up from around the building and dumped inside it.
I must look at Sky Over Scapa. I wonder if there are "official" records anywhere for the sites. We would also be very interested in the original plans for the Chain Home radar buildings & associated camps...

There is a sketch of one of this type of towers here

http://www.monktonwyldcourt.co.uk/About_the_Court/page54/assets/DHallMedHutHistory%20copy.pdf

I have some lists of DF and intercept sites that were given to me but they do not seem to be complete and positions are not very accurate. There are none shown on Orkney but it is clear the RAF had some.

Don't know about plans, you can search the National Archives catalogue but I don't think all were kept. The other place that could have some is the RAF Air Defence Museum. The Tiree archive were given plans of the Chain Home and ROTOR site there when a local building company closed down and cleared out their cupboards.

For anyone with a serious interest in early radar and particularly the development and building of the Chain Home defences the book to get is Building Radar by Colin Dobson and published by Methuen in 2010. Radio stations are unfortunately not included!