First WFM on 10 GHz (HB100 radar)

The transmitter of this test.

After fiddling for a while with the modulator circuit by DJ7OO, I managed to transmit audio using Wide-FM through a HB-100 radar module. The single-tone beacon was already working (with a NE555), even though I should try to widen its resulting RF bandwidth (which means increasing the amplitude).

The ability to increase the receiver's bandwidth on an SDR automatically compensates for the short-term frequency instability of the HB-100. At least for "operations" within indoor conditions, that are pretty much static.

The test setup was as follows. RX: RTL-SDR dongle receiving the IF output of a stock HB-100 module. TX: retuned HB-100 driven by my own version of DJ7OO modulator (LM317). No external antenna aids, no real line-of-sight but a loose zig-zag in the house for a total of about 10 metres. There was also a slight polarisation mismatch.

My WFM signal at about 10.452 GHz, as received on another HB-100 radar sensor.

In the conditions described above the signal is about 30 dB peak above noise. I think the peak could be higher if LOS could be established over the same distance. But now it is really time to test it over a longer distance!