I wasn't sure whether to call
it a "Radio" or "Radar" altimeter. In WW2
radar, could have transmission frequencies below 30MHz, but nowadays
radar is confined to the microwave bands. This set probably uses
something between 100MHz and 300MHz?
This set uses a 6J6 transmitter
and a similar valve for receive, each in a tuned lines configuration
The set used a DC input which
powered the valve heaters and drove a rotary converter for its
HT and connected to a small circular display unit which gave
the aircraft's height.
waiting for better pictures...