VHF Radio and IFF
In May and June of 1940 a small batch of Spitfire Is was fitted with a new VHF (Very High Frequency) transmitter/receiver, the TR1133. They were also equipped with the wide-bladed Rotol constant speed propellers later fitted to the Castle Bromwich built Spitfire Mk IIs. These aircraft, which seemed to be mostly in the N30– and N31– serial range, were issued to 54 and 66 Squadrons
The new equipment with its shorter wavelengths did not require the aerial wire from the mast to the fin and the mast housed the antenna. The triangular prong was removed from the mast. After some months of delay, from September 1940 front-line Spitfires were re-equipped with the new radios as a matter of priority and by the end of 1940 most aircraft had the mast without the wire and prong, although most retained the redundant anchor point on top of the rudder. It is more than likely that the various Maintenance Units (Mu)s would have have been responsible for fitting the new equipment to factory fresh Spitfires.
Also in late September and early October Spitfires started being fitted with Mk. I IFF equipment. This equipment received a signal transmitted from ground radar equipment and retransmitted it, creating a distinctive bright blip on the radar screen. The receiver and transmitter wires emerged from small insulators just in front of and slightly above the red centre spot of the fuselage roundels on both sides. The wires were anchored to the tailplane tips.
A late Spitfire Ia of 19 Sqn in September 1940. The lack of a triangular prong indicates TR1133 VHF radio equipment. Although there is now no wire the anchor point is still present on top of the rudder. IFF has yet to be fitted.
When modelling a Battle of Britain era Spitfire Mk. I four combinations are possible:
- Early rod mast, HF TR 9 radio with wire to the rudder.
- Tapered mast with triangular prong, TR 9 radio with wire from fuselage to mast and from mast to rudder.
- Tapered mast without triangular prong, VHF TR 1133 radio, no wire although the rudder post may still be fitted.
- Ditto 3; IFF fitted wires running from fuselage roundel to leading edge of tailplane tips. An insulator in the form off a small dot is visible just forward of upper part of the red centre spot.
By the end of 1940 most front-line Spitfires would have been fitted with VHF and IFF. As per usual changes could take a few months to filter through from the factory and photos of factory fresh Spitfire IIs still show the mast fitted with the triangular prong well into 1941. By the end of 1941 the plain tapered mast was universally fitted. The attachments points for the prong were still visible on the back of the mast.
The wire IFF antenna and VHF radio can be clearly seen on this Spitfire Mk. Vb. The insulator for the IFF wire to the tailplane can be seen on the red part of the fuselage roundel. The attachments points for the long obsolete triangular prong can be seen on the rear of the mast.
This mast remained standard until the Two Stage Griffon engined Mk XVI appeared in early 1944. The mast was replaced by a whip aerial mounted further aft on the fuselage spine.
In early 1943 a new IFF, the Mk III started being fitted to all front-line fighters. On the Spitfire the fuselage to tailplane wires were replaced by a single rod aerial mounted under the starboard wing.
IFF Mk III mast can be seen under starboard wing of these Spitfires Mk. IX, early 1945.
[Library and Archives Canada]
At about the same time the updated TR 1143 radio sets started replacing the TR 1133s, although no external changes were visible.
Later in 1943 some Spitfires started being fitted with “Rebecca” Mk II beam approach equipment. This responded to “Lorenz” ground signals transmitted by “BABS” beacons, allowing pilots to line up on runways and airstrips in conditions of poor visibility. Spitfires with this equipment had a small, semi-circular blister out of the back of which projected a short antenna. This was fitted underneath the fuselage, in line with the rear wing fillet. Some of the first Spitfires so equipped were Mk XIIs.
A Spitfire PR Mk XIX with a “Rebecca” Beam-approach aerial under the fuselage.
This equipment did not appear to be universally available, although it seemed to be more common on aircraft of the Second Tactical Air Force.
Spitfires which were supplied second hand to Portugal (Mk I and Vb), the Soviet Union (Mk Vb) and Turkey (Mk Vb) were retrofitted with the old TR 9 radios and masts with triangular prongs.
– Price, Alfred. Late Marque Spitfire Aces 1942 – 1945. Oxford, UK: Osprey Publishing, 1995.
– Price, Alfred. Spitfire Mark I/II Aces 1939-41. London: Osprey Aerospace, 1996.
– Hooton, Ted. Spitfire Camouflage 1938-1940. Scale Aircraft Modelling: Volume 5 No. 2, November 1982.
– Pope, Stephen. Across the Ether: RAF radio and radar equipment of the Second World War, Part One. Aeroplane Monthly: Volume 23 No. 5, May 1995.
– Pope, Stephen. Across the Ether: RAF radio and radar equipment of the Second World War, Part Two. Aeroplane Monthly: Volume 23 No. 6, June 1995.
– Website: http://www.qsl.net/pe1ngz/airforce/airforce-raf/raf-eureka-rebecca.html