There's no trouble with active antennas, in fact they're handier because you can
get exactly the location you want when you construct your phased array of two.

What's most likely is that you're nowhere near the right gain to make the signal
you want to cancel the same strength in both antennas, and so you get no indication
of a null direction.

The ANC-4 has linear gain pots, which unfortunately means that the phase control
also changes the gain (strong at the ends, weak in the middle), which makes
searches for the null harder than it has to be.

A technique called successive overrelaxation is the most successful in searching
for a null.

Say, step the phase, and at each step minimize the S-meter with the gain, but going
a little past the minimum each time (choose a direction for this and stick to it).

Go back to the best phase, and repeat with smaller steps. Hairline changes will
be necessary at the end.

And finally notice that there's a phase button, and searching with the opposite
phase might surprise you. Having the wrong hi-lo frequency setting also changes
things, giving you less than a complete phase control.

Successive overrelaxation works when the search controls aren't orthogonal, which is
what most of the time happens.

--
Ron Hardin


On the internet, nobody knows you're a jerk.