[1000mp] tip: switching in extra band filters for reception

[Tom Rauch]

> I've been using this setup for several years. Someone posted this on
> the reflector a few years ago. I had an ANC-4 but my W1FB homebrew
> "QRN squasher" seems to me to be superior. The 12 volt power from the
> MP such low power that it is almost useless. Don't know why Yaesu
> didn't make this a bit heftier. 73, Tom K5IID

I'm a bit surprised that the QRN Squasher seems to work better than 
the ANC-4. Either the QRN Squasher you have has changed from the 
original article, something else is going on other than phase 
cancellation, or you are pretty lucky with noise direction and 
antenna phase.

A necessary part of properly working noise cancellation is the 
ability to rotate the relative phase difference between the main 
antenna and noise antenna through all 360 degrees of phase angle, and 
to keep the noise levels exactly matched between the two antennas.

I looked at the design of the QRN Squasher and it had no system to 
rotate phase more than a few degrees. The "phase control" (as 
originally designed) can not change phase more than a few degrees, 
other than a 180-degree flip when the control crosses center. Gain 
would change like crazy with phase setting.

It measures that way on a test bench also. I measured a maximum phase 
rotation on the order of 5 degrees from end-to-end on the phase 
control (other than the sharp 180-degree flip at the middle of the 
control setting).

The ANC-4 could adjust phase almost 300 degrees total. The only bad 
thing was gain varied all over the place with phase adjustment, and 
phase did not rotate through all 360 degrees.

Maybe you are just using the "phasing unit" as a gain control? Or has 
the QRN Squasher design been significantly changed?   73, Tom W8JI
W8JI@contesting.com