4M radar experiments (part1)

(PE1ITR 2020-12-14)
These are the first attempts of my 4m radar. The intention is to make a pulsed radar, just as I had made for 2m. But we are not there yet.

In the first attempts it is the setup of a bi-static radar. This consists of a transmitter with the antenna arrangement as shown in the pictures below. The remote receiver is located 18 km north east of the transmitter.

The transmitter transmits a 50w carrier at 70,310 MHz. The transmitter circuit follows the next path. The start is a Siglent SDG1050 frequency generator. The signal then multiplied by 2 by a mini circuit RK-3. Subsequently filtered and amplified with a PSA4-5043, 2N3866, BLY87A and MRF151.
The antenna is circularly polarized and points straight up. It is the same setup as the BRAMS 6m beacon.

The transmitter was on for 2 hours during the Gemini meteor shower. The first photo shows reflections of aircrafts taking off from Eindhoven Airport. The other two photos are meteor reflections showing the famous "C" shape.
The next step is to build a pin diode coax relay for 4m. The setup is then linearly polarized again. With circular polarization it becomes too complicated for me for now because in addition to switching from rx / tx, the polarization from LHCP also has to be switched to RHCP. After a backscatter reflection, the polarization reverses.

4m Antenna. 1.5m above ground.

The two dipoles.

Airplane reflections.

Meteor reflection with "C" shape.

Meteor reflection with "C" shape.

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