[Elecraft] K3 Audio routing question

[Jim Brown]

On Mon, 05 Jul 2010 15:53:39 -0700, Lyle Johnson wrote:

>Perhaps the person who wishes to hear both receivers in diversity mode 
>is partially or fully deaf in one ear, so he or she needs the ability to 
>listen to both receivers in the same audio transducer.

SNIP

>I don't know if there will be side effects you'd rather not hear when 
>you do this, nor how often you'll have to send this string if you remain 
>in DIVRSTY mode.

The problem is that there ARE SERIOUS DESTRUCTIVE SIDE EFFECTS from 
mixing the audio from the two receivers in diversity mode because the two 
receivers are not in phase with each other!  That is, they are listening 
to antennas that are PHYSICALLY SEPARATED, and thus are receiving the 
signal at different times. AND they may also be hearing a direct and 
reflected signal. 

BTW -- an important definition. Inverting the signal by reversing wires 
changes the POLARITY, not the phase. Phase is a continuously valued 
function that can have any value between -infinity degrees and +infinity 
degrees. The phase difference between two signals that differ in TIME is 
proportional to their time offset. 

When signals are precisely in phase AND in polarity with each other, they 
can be summed together in the same channel and they will add. When 
signals are precisely in phase and OUT of polarity, they will cancel. And 
when signals are out of phase and IN polarity with each other, they can 
add or cancel each other to varying degrees depending on the phase 
relationship AT EACH FREQUENCY!  The result of such a summation produces 
a frequency response that looks like the teeth of a comb -- that is, 
peaks and dips of addition and cancellation. In the pro audio world, it 
is called comb filtering, or phasing, or flanging, depending on how the 
delays are generated and used. 

Bottom line -- it is a REALLY BAD IDEA to sum the output of both 
receivers into the same channel!  It is a REALLY GOOD IDEA to put one RX 
in one ear and the other RX in the other, allowing the brain to combine 
them. 

73, Jim Brown K9YC