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Communication
We continue flying and remember to report when we pass Borup.
Roskilde O-TZ passes Borup 1500 ft.
Contacting Copenhagen Information
O-TZ Roger Squawk 7000
Squawk 7000 O-TZ (seven THOUSAND)
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4.10.3 Transponder use and phraseology
In order to ensure protection from enemy aircraft, radar systems were
developed during World War II.
4.10.3.1 Radar
The system is based on the reflection of radio waves when they encounter an
impenetrable mass.
The reflected beams are picked up on the radar screen.
The radar screen would show something in the given direction and a certain
distance from the radar reflecting the radiation.
It was impossible to tell whether it was a friend or enemy. This was known as
the "primary" radar signal.
By sending back response pulses when affected by radar pulses, it could be
determined whether it was “friend or foe.”
That was the idea laying behind development of the “Transponder”.
Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 404
