its fairly effective against single phased sources (like powerline buzz and other stationary noise sources). It is the unamplified version and does introduce a little signal loss. However, for what it is, it works good enough that I can do weak signal work on 80m.

Now,as for what it is:
the mfj antenna noise cancellation device is basically a diversity antenna matrix. It takes signals from both the primary antenna and a secondary (noise) antenna. It then mixes (or phases) those inputs such that (when properly adjusted) the noise disappears while leaving the signals you want intact. This technology predates DSP technology and is still very useful. In fact, in combination with DSP technology, noise can almost entirely be eliminated.

DE n7zzt Eric

On Oct 15, 2015, at 2:01 PM, Mike Keithley wrote:

> How effective is the MFJ-1025 noise canceler? What is it?
> 
> Thanks.