Unknown RT- 7 / APN-1 - Frequency-Modulated Altimeter

For sale: Military RT- 7 / APN-1 - Frequency-Modulated Altimeter 



Please ask a shipping quote for the exact shipping costs.

This FM-modulated radio altimeter was designed by RCA and became operative in 1943, during

WWII. It is described in Volume II, ‘Radar Aids to Navigation’, of the MIT Radiation Lab. Series,

1947. Basically the transmitter frequency sweeps continuously between 420 and 400 MHz.

Depending upon the selected range, 400 or 4.000 feet, sweep rate can be 40 or 4 MHz per second.

Due to the delay introduced by the path from the transmitting antenna to ground and back to the

receiving antenna, the altitude information is obtained directly comparing the frequency difference between the transmitter and the receiver.

27v DC

See pictures for more details.


Untested due to not having the right equipment, therefore sold for parts or in not working condition.



Dimensions (LxWxH): 46x20x18cm

Weight: 6,8Kg



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-Shipping in the EU up to 30 KG (max)

-Shipping outside of the EU up to 20 KG (max)



Please note: ‘’Whenever an item exceeds the weight noted above. Please ask for a shipping quote before making a purchase. The shipping costs are estimated in our shop because we do not know the shipping address.