Continued ...
In 1965 a MOD was issued to introduce a solitary light weight Plessey PTR170 (ARI18197) Uhf radio in lieu of the existing 198x series Vhf radios. However this wasn't a UK fleet wide conversion and although the exact number of aircraft converted to Uhf remains unknown (including the split between RAF, RN and Army aircraft), a significant number of aircraft remained Vhf equipped retaining the 198x equipment. The 'Decision Criteria' for selecting airframes for conversion to Uhf remains unknown at this time.
Plessey PTR170 (AR118197)
With the installation of the PTR170 radios, associated Uhf Upper (Off Centre Port) and Lower (Off Centre Starboard) Blade aerials began to appear on the rear fuselage and the removal of the inverted ground plane Quarter Wave Rod aerial under the starboard wing. There is some evidence to suggest that a small number of airframes retained the obsolete Vhf aerial once converted to Uhf, then being removed at a later date, possibly due to a lack of available blanking plates.
The PTR170 control boxes were mounted on top of the front cockpit coaming.
In early 1976 a MOD was issued to introduce a Bendix RT221 Vhf 360/380 Channel radio. The DH Support IoM states that the
existing TR1936 was to be retained (this is an unexplained anomaly in the MOD history). It's unknown how many Vhf equipped Chipmunks received the Bendix RT221 MOD, however WK518 is known to have benefited from this modification but again this was a solitary Vhf installation.
Bendix RT221
In late 1976 a MOD was issued to introduce a solitary Marconi AD120 (WR800) Vhf 720 Channel radio in lieu of the existing TR198x series equipment.
Marconi AD120 (WR800)
In mid 1978 a MOD was issued to introduce a D403 (ARI23159) Stand-By Uhf radio to the Army Air Corps fleet. This MOD was for Uhf equipped airframes, but not all.
In early 1980 a MOD was issued to replace the RAF PTR170 (ARI18197) Uhf radios with PTR1751/PP (ARI23301) Uhf radios. The Army Air Corps implemented a similar replacement in early 1984 using the PTR1751/BB (ARI23291).
In mid 1985 the RAF converted their PTR1751/PP's to 25 Khz with the Army Air Corps doing the same conversion to their PTR1751/BB's in mid 1988.
Interestingly, according to the DH Services IoM, the RN in mid 1987, introduced the Marconi AD120 (WR800) Vhf 720 Channel radio in lieu of the PTR170 Uhf
and Stand-By Bendix RT221 Vhf radios (this is an unexplained anomaly in the MOD history).
In 1991 a Dittel ATR720B 720 Channel Vhf radio was installed in addition to a PTR1751 Uhf radio to all aircraft forming the then FSS (Flying Selection Squadron, renamed EFTS idc) fleet. This was some 15 airframes. The aerial installation was a Whip extending vertically from the tail cone to the rear of the rudder. The dual radio installation was a necessity given the intensity of flying training operations with the need to penetrate/operate above cloud/in IMC by EFTS.
Dittel ATR720B
The above summary now ties back to the Pilots Notes referenced by Kenparry ...
RAF: Choice of PTR170 Uhf; PTR1751PP (also Uhf); or a Marconi AD120 720 Channel Vhf.
Army: PTR1751BB, either alone or "with standby Uhf" D403 (ARI23159).
Also, in the text, additional info:
1. RAF aircraft could have a 720 Channel Vhf (likely to have been the Dittel ATR720B) plus the PTR1751; .
2. RN aircraft had a Bendix RT221 380-chan Vhf plus either a PTR170 Uhf or the Marconi AD120 720-chan Vhf;
3. The Army standby Uhf radio D403 (ARI23159).
I therefore stand corrected in saying "No RAF Chipmunks were fitted with both Vhf and Uhf radios (they were either Vhf or Uhf equipped)" ... the Dittel/Plessy 15 at EFTS being the exception
The RN also had a mix of comms kit
