[Elecraft] K3 Audio routing question

[Jim Brown]

On Tue, 6 Jul 2010 16:16:29 +0000, The Smiths wrote:

>Now, this has become an argument.

That happens when some of the people talking don't know what they're 
talking about. Tom (JI), Tom (RC), Paul, Joe, and Guy know what they're 
talking about. They not only have the experience, they understand the 
physics. There is more to this than some folks understand. I urge them 
to go back and study my most early in this thread. 

Pete asks, 

>Isn't the whole point of diversity reception in the K3
>that the receivers **are** synchronized to the same clock?

That puts them on VERY nearly the same frequency, but the RF inputs to 
the two RXs are from different antennas. Think about what W8JI has said, 
which is absolutely correct -- that is, to be effective in DIVERSITY 
mode, antennas must be widely separated. WHY?  Because MOST fading is 
the result of cancellations between a direct wave and a reflected wave 
arriving at some particular point. This is EXACTLY the same as picket-
fencing on VHF and UHF that we hear when we or the other station is 
mobile, or when there is a reflection from an airplane completing the 
path. When the signal peaks, the two delay between the two signals are 
some multiple of wavelengths so that they are precisely in phase AT THAT 
FREQUENCY. At some other frequency, they will be some degree of out of 
phase, and for some delay they will be 180 degrees out of phase. That 
fading is periodic, and is wavelength and frequency dependent. That's 
why it's fast at VHF/UHF, and MUCH slower on 160M -- indeed, that's what 
we're hearing when there's LONG, DEEP QSB on 160M. 

Diversity helps this by having two RXs listening to two antenna that are 
SPATIALLY separated from each other, so that when the null is at one 
antenna, the peak is more likely to be at the other (or, with less 
separation, the null is not so deep). But it is the TIME DIFFERENCE 
between these antennas, plus the delay in the feedlines of the two 
antennas, that produces the time offset between the two signals. And 
that time offset produces a phase difference that depends on the time 
and frequency. It is the relation of the time and frequency to phase 
shift that produces the ROTATION that several guys have talked about. 
That's the swimmy sound you hear in the headphones in diversity mode 
with widely separated antennas. 

73, Jim Brown K9YC