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?
waiting for better pictures...
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.