[Elecraft] K3 Audio routing question

[W8JI Tom]

> I'm sorry but I completely disagree with you.  Apparently you have not 
> used diversity mode, or you haven't enjoyed it with an AB - BA (or AB- B) 
> Mix mode on.

I've been using stereo diversity and other forms of diversity receiving 
since around 1970 or so. After almost 40 years of using it, I can't imagine 
why anyone would want to mix one channel into both ears unless they didn't 
have the antenna spacing to actually produce true diversity. .

> The point behind diversity is NOT to have one antenna in one ear and 
> another in the other.. The purpose of Diversity is to enable the user to 
> hear a signal from TWO different sources (Main and Sub Receiver with 
> Horz/Vertical antennas) at the same time.

The phase continually rotates in the phase relationship from one antenna to 
another. The only exception to this is when the antenna are unable to 
provide diversity, and act like a single antenna. So if you have the proper 
configuartion to provide diversity, and you directly mix the signals, the 
result will always be something between no change at all to MORE fading and 
reduced S/N ratio. It will never be better without and equal or longer time 
being worse.

> If you've ever used Diversity on a weak signal, or on a station that is 
> phasing from Horz. to vertical polarization (as they do coming over the 
> ocean all the time), then you would know that the signal "SWIMS" from your 
> left ear to your right ear.  This effect is NOT desirable when the 
> frequency of the swimming becomes constant.  The effect in fact can cause 
> one to feel like they are on a rocking boat.

Your brain will probably get used to it, and eventually process it 
correctly.

> For this reason alone it is nice to be able to "add" the Sub (or Vertical 
> phase) to the Main (Horz. phase) thereby canceling out the swimming effect 
> on the listener.  This allows for easy reception and a single signal that 
> "fills" the ears with a constant audio even as the phase shifts from one 
> polarity to the other.
> In the AB - B mix mode the user can still ascertain which antenna the 
> signal is coming from because even though the both phases are filling both 
> ears, there is a slight "leaning" effect to the signal in the right ear 
> when phasing to the Sub receiver.

If you add A to B in one ear, that channel will have reduced S/N and 
increased fading at least 50% of the time or more. The other channel, being 
just B, will be unaffected.

> Diversity mode has NOTHING to do with being forced to listen to 2 signals 
> in one ear or the other.  In any case, if this is the effect you want, 
> feel free to keep the mixer off.  For others, like myself who may have a 
> beverage antenna and a vertical set up, we would like not to have to feel 
> like we're sitting on the high seas while listening to a signal.
> I completely understand why this other user in the group would request 
> this feature.  I was simply correcting Lyle that it was not available in 
> the diversity mode as he suggested that it was. (or so it read)
>
> Again, this Mix mode option IS available for Sub mode only, but it has not 
> been implemented in the Diversity mode yet.  I'm only asking that the 
> switch gets flipped to allow it to be turned on while in Diversity mode.

I have no opinion one way or another on programming requests, but I do know 
very well how diversity works and how the K3 works. The K3 has a stable 
phase relationship from channel to channel (main to sub) on any given 
frequency but the exact phase difference from main to sub changes as the 
frequency is varied. You can hear this if you mix both channels into mono 
and listen to background noise as you tune the VFO up and down the band. 
What you will hear is peaks and nulls in background noise as the phase 
rotates with the VFO setting. This is because you are changing the combined 
antenna array PATTERN as the VFO is moved up or down the band. If you 
directly mix two antennas with any significant spacing as processed through 
the main and sub into one channel, be it one ear or both ears, you 
absolutely will have a random changing antenna pattern as you tune the VFO. 
Since the K3 has no controlled way to vary channel to channel phase, we 
would have a random uncontrolled pattern null or nulls moving around in 
different directions as the VFO knob is rotated.

Changing phase from channel to channel in the receiver is exactly like 
mixing the two antennas together before they get to the rig and varying the 
phase delay on one antenna prior to RF mixing. So when we mix A and B at 
audio is like adding a noise canceller and mixing two channels with a random 
spin of the knob. No difference at all. None....and this is etched in stone. 
It is how phase meters like the old HP vector voltmeters work so it is a 
well-established process.

The second issue is the arriving signals will have significant phase shift 
from antenna to antenna that changes over time if the antennas are far 
enough apart or enough different in polarization (a Beverage is vertically 
polarized, as is a vertical antenna...so with a Beverage and  vertical we 
really have TWO verticals...not one vertical and one horizontal) and this 
adds a random phase variation that can add or subtract signals depending on 
the moment in time. If we really had two different polarization antennas, 
like one responding to horizontal polarization and the other to vertical, 
mixing would increase fading.

If that "feature" was added, it should be added with an ability to lock it 
out. I would want it permanently disabled here so operators would not 
accidentally turn it on. :-)

73 Tom