Jørn,
Interesting.
Gebhard Aders in his book uses these lowercase letter designations (Appendix 10). I wonder where he derived them from? What does Fritz Trenkle have to say on this in his book (not in my library unfortunately)? Presumably both gentlemen consulted official sources in their research. Nevertheless, perhaps the first three versions of the SN2 (i.e. a,b,c) did not use these designations, but it does appear that the “d” suffix was used - at least on the aircraft themselves.
Photographs reveal that in most cases features of the radar type was indicated on the fin of Ju88G-6s and Bf110G-4s (or also the nose of the He219). It was occasionally painted in black, but more often in white where it tended to be obscured by reflection or camouflage paint. Sometimes one sees simply a Roman numeral (IV, V, VI) with no other letters, other times with one or both letters in uppercase.
For example, I would interpret VD/R or V/DR in the following manner:
- V = SN2 frequency range 5 (V)
- D = SN2 “D” version (with slanted dipoles)
- R = Rückwärts (rearward-looking attachment)
In addition to this use for the FuG 220 Lichtenstein SN2, such nomenclature was used on aircraft with the FuG 218 Neptun VR, and FuG 240 Berlin N 1a. It is interesting that the FuG 240 Berlin N 1a used a lower case letter as a designation per official documents.
Hopefully some information can be presented here to add clarity to determining if such designations were used officially or not.
Best,
David