Description

NOTE: We are in development of a new filter / preamp combination, described here: http://wb6cxc.com/?p=417. If all goes well, this new design will be available soon. But if you don’t need a preamp, or can’t wait, the current filter board remains an excellent performer:

This is the filter described here:

https://turnislandsystems.com/filters-filters-and-more-filters/

and here:

https://turnislandsystems.com/test-results-shelving-low-pass-filter/

It’s a 30 MHz four section elliptic low-pass filter, combined with a bypassable two-section shelfing filter. The low-pass filter serves as an anti-aliasing filter for a SDR, especially one that is clocked at 66 MHz or so. The shelfing filter will provide moderate attenuation at the lower frequencies, where powerful signals can cause overload. Each of the two shelfing filters can be bypassed or enabled, using the provided jumper clips.

The filter is available in the in-line plug/jack configuration, or in a two-jack arrangement (which fits nicely in a small die-cast aluminum box for extra shielding.)

And these filters really work!  Here’s a report from one of the first to try it with the KiwiSDR and the RX888:
“The LPF is *great* at suppressing aliases!” – Phil Karn

See the User’s Guide for more details