03 November 2019

First check with CDM324 couples

As I did on 10 GHz back in Spring 2017, I checked the frequency difference between my 3x CDM324 modules. Currently I have no means to measure a frequency at 24 GHz, so I trust that they are in the ballpark.

Test setup is as follows:
  • put two radars in front of each other at 20-40 cm distance
  • power them up and pick the IF output of one CDM324
  • feed the IF output signal to an
    • oscilloscope
    • frequency counter
    • spectrum analyzer
Samples 1-2 were visible on the 'scope and the counter, about 25-30 MHz apart.

Samples 1-3 were not detected on the first two instruments, but the SA put them about 70 MHz apart.

With the couple 2-3 I should be able to understand how they are spread around 24.125 GHz :-)

This result also confirms that there is no low pass filter on the IF output of these things, so they can be used with an external "receiver" to demod WBFM.