Topband: Polarity and Phase

[Tom Rauch]

I'm going to make one last comment on this because although I'm pretty busy
this is really a fascinating thing for me also, and very difficult to
understand!

> >having constantly varying phase in the antennas. At any instant of time
the
> >signals might be in phase, in quadrature, or out-of-phase.
>
> If the receivers are tuned to different frequencies, the resulting
> audio signals are of different frequencies, and phase has no meaning!

Well, I don't mean they are THAT far off frequency. I just mean the phase
relationship is not stable because the oscillators are less than a few Hz
off frequency. The result is a slow whoosh whoosh in background noise and
the same thing on tones of signals. This is why I stress the oscillators
MUST be exactly locked even in stereo for maximum effect.

K9DX John questioned this, so I retested. I just double checked and it all
behaves exactly as I say.
(I generally remember things like this correctly, but don't mind rechecking.
Especially
since I use this for DFing signals, hi hi.)

 I just ran a test signal into my TX antenna, and put both phase locked
receivers on NW receive antennas spaced 1500 feet apart. I paralleled the
audio with equal volume.

1.) I nulled the audio with an IF phase delay adjustment.

 2.) I inverted the audio for a peak.

 3.) I then added a 180 shift transformer in one antenna lead and it went
 right back to a null.

 4.) I reversed the audio line on one receiver and it is back to a peak.

 5.) I renulled it.

 6.) I changed to another TX antenna 500ft to the side

 7.) It came back out of the null.

 8.) I can't null my background noise because it comes from all directions.
 It always stays the same level regardless of phase.

 9.) I can very easily peak and null audio from signals with the IF delay.

10.) It does not remove all audio on SSB because I can't match AGC and group
delay tracking in filters close enough for a perfect null as input frequency
changes, but I can get severe audio distortion. It sounds just like nasty
selective fading.

73 Tom