14 April 2022

75 metres on 24 GHz

Finally! A proper Spring day and 90 minutes free to spare! I took my 24 GHz experimental setup to a park and checked how far I can receive my own beacon.

The previous successful test was on about 12 metres distance.

The experiment uses only radar modules, both on the TX and the RX end. This means that the receive mixer is the one inside the radar module (CDM-324 in this case).

The frequency difference between the chosen modules was about 54 MHz and the modulation was WBFM through Vcc on the TX side.

The transmitter was arranged on a tripod and I walked away keeping the receiver both oriented and tuned to the right frequency. Since both modules were not thermally isolated, they followed the breeze. Fortunately the sky was cloudy and I was close enough that the "wind" affected both modules so they changed their frequency in the same direction, keeping the delta_F quite constant (+/- 1 MHz).

The Kenwood scanner could pick up the signal at about 75 metres. If someone had been at the transmitter changing its direction, probably I could have achieved few tens of metres more.

Now, if I add 30 dB gain ... can the distance increase of the same amount, which is 1000x?

First things first: add thermal insulation. Then get a second experimenter to help estimate the right radiation patterns of those patch antennas.


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