T-21,
I believe that you are confusing Rebecca IV with something else.
I never saw it installed in any a/c that did not have a Navigator. Its use was far too operator intensive and heads down for a pilot to use.
Rebecca Mk VII, also called DME, was fitted to Hunters and other a/c without navigators, and worked on the same frequencies, in conjunction with the same Eureka beacons.
You can see the Rx aerials on either side of the BBMF Lancaster. They are half wave dipoles with one director, or 'H' aerials approximately 50cm high.
Last edited by ian16th; 1st Apr 2013 at 10:35.