Qype User (.
Yelp
A great wee museum - well worth the visit. It has a fascinating display of old radio equipment, information, etc. The museum is manned by a friendly and knowledgeable bunch of volunteers who can regale you with tales from Orkney's recent past related to telecommunications.
A lot of the contents of the museum are related to Orkney's wartime history - don't miss out on finding out about it. Orkney (and Scapa Flow) played an important role in World War 2 and you'll find out more about it here.
The museum may not sound like it's going to be interesting, and may not look like much from the outside, but it is worth the visit, especially for historians.