AliExpress 0-30 MHz low pass filters - tested
These are test results of a couple of low pass filters designated as 0 - 30 MHz and inexpensively available on AliExpress.
There are apparently at least two types - one is labelled 30M on the back and the other has a Rev 1 silk screened on it. The latter appears to be the better performer.
For testing I used a Red Pitaya StemLab 14 and set one of the outputs to sweep 0 - 50 Mhz. I set one of the FFT channels to look at 0 - 63 Mhz. I connected the generator output directly to the filter and connected a 30 dB 50 Ohm attenuator between the filter and the Red Pitaya input to simulate a 50 ohm dummy load. There is probably still some mismatch at the filter input, but I only had the one attenuator. Probably need to build another .....
Anyway, here are the results with the simple test method above.
Win W5JAG
