In a recent email Ofcom has given guidance on the use of Regional Secondary Locators in the UK and Crown Dependencies with regard to Club callsigns
Clause 2(2) of the licence requires the licensee to use an RSL in the call sign to indicate where the station is currently operating. The available RSLs are then listed. Clause 2(2) applies to holders of the Full (Club) licence, as much as to individuals and club stations must therefore include an RSL in the transmitted call sign. However, Note (c) to the licence provides an alternative set of RSLs, which holders of a Full (Club) licence may use, if they wish. This alternative list includes an RSL for England (‘X’), which the list in Clause 2(2) does not. It means that a club station can identify itself as operating in England, while an individual Full or Foundation licensee cannot (for completeness, I should add that Intermediate licensees must also use an RSL, including ‘E’ when operating in England).
For example, an individual Full licensee with a main station address in Swansea but temporarily operating in Inverness, must use the RSL ‘M’ to signify operation in Scotland. Your illustrative call sign would therefore go from ‘GW3ABC’ (Wales) to ‘GM3ABC’ (Scotland). If the example given were a Swansea-based club station, the call sign would go from either ‘GW3ABC’ or ‘GC3ABC’ to either GM3ABC’ or ‘GS3ABC’.
In deciding which RSL to use, the licensee must ensure that the operation of the station complies with the overriding requirement set out in Clause 13(1)(a), that the station be clearly identifiable at all times. Having decided which RSL to use, the licensee must assess the risk of not being clearly identifiable, were the station suddenly to switch to an alternative RSL for the same part of the UK.
An element of confusion regarding this had originally arisen in 2013 following then Ofcom guidance on the matter. At that time Ofcom considered a GM4*** operate mobile from the Isle of Man would sign GM4***/M (still keeping their home RSL)