Re: [K3] Diversity Reception and Antenna Directivity

Posted by David Gilbert on Sep 16, 2010; 5:08pm
URL: http://elecraft.85.s1.nabble.com/K3-Diversity-Reception-and-Antenna-Directivity-tp5537531p5539433.html


Thanks for the reply, Alan.

That's interesting.  I didn't realize that the two receivers in the K3
had a random phase difference between them even when locked.  I noticed
differences in phase delay when I changed frequencies during my tests
with the two horizontal antennas on the tower, but I mostly attributed
that to different arrival angles for the different stations being
monitored, and different phase delay of the feed lines (expressed in
wavelengths) at the new frequencies.

However, that random phase difference between the two receivers could be
adjusted out by momentarily feeding the same antenna into both receivers
at each new frequency.  That routing could be accomplished within the K3
if there was a quick and easy way to control whether or not the sub
receiver was switched to the AUX RF antenna when diversity mode is
active.  If that routing option took the form of a command, the whole
process could be done in software (either external or internal to the
K3) each time the frequency was changed ... albeit of course with some
settling delay while the phase difference was determined and adjusted out.

73,
Dave   AB7E




On 9/16/2010 8:42 AM, Alan Bloom wrote:
> Yes, I think that would work fine. There are two issues that I can
> think of: While the main and sub receivers are phase-coherent, the
> actual phase difference between them is random. I believe that if you
> change frequency it is not guaranteed that the phase difference will
> be the same. So every time you change frequency you may have to
> re-adjust the phase delay to get the antenna to "point" in the right
> direction.

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