Recently, we found need for a 10 MHz band pass filter in order to clean up a reference input port that was suffering from noise injection. Some quick googling yielded fellow amateur radio operator SV1AFN’s store, where he sells a custom developed filter at a very reasonable price.

There is little information about these filters outside of SV1AFN’s site, and they work well – so we figured that it would be nice to provide some measurements and a short write-up. This way, maybe more people can support the good work SV1AFN does.

Pass band (S21) of 10 MHz band pass filter from 0 to 350 MHz.

Since we bought three filters, we also had the opportunity to check for batch differences between the samples we had gotten. In short there were little to no difference between the samples, which the photos of their pass bands from 5 to 15 MHz (seen below) illustrate. The measurements are within the repeatability network analyzer, so things are pretty closely tuned.

  • Filter 1
  • Filter 2
  • Filter 3

Mechanically, the construction is reasonable. The filter PCB is slotted into an extruded aluminium enclosure, which is capped off using a small PCB at each end of the enclosure. These PCBs could have been a bit thicker to reduce strain when tightening the SMA connector. However, as long as care is taken when tightening the SMA, this is not a problem.

Finally, the match on both filter ports is very good, showing better than 20 dB return loss across all samples.

Overall, the filter performs well, is cheap, got delivered quickly and looks nice.