[Elecraft] K3 Audio routing question

Joe Subich, W4TV lists at subich.com
Mon Jul 5 23:25:57 EDT 2010 


 > I'm not sure how your rig works, but with mine, when I have phase
 > shifting between the two antennas I don't have Phase shifting in my
 > audio Left and right.  In that I mean, if I look at the spectrum
 > analyzer/o'scope I do not see the signal coming out of my head phones
 > phasing from positive voltage to a negative voltage in the inverse
 > between the two headphone outputs.

When you have phase shifting between the antennas, the relative
audio phase between the two audio signals most certainly changes.

You can't see the phasing with an oscilloscope because you don't
have stable single tone signals to compare.  The best chance of
seeing the changing phase relationship between the two signals is
to use a Lissijous display with one receiver driving the vertical
amplifier and the other driving the horizontal amplifier.  You
quickly see the display morph from long narrow lines to wide
ellipses to short narrow lines and small ellipses as the relative
phase and signal levels between the receivers changes.

If you mix those two signals, the audio level will change from
zero when the two signals are the same level but out of phase
to +6dB when the two signals are in phase and at the same level.
Most of the time the mixed signal level will average around
the relative volume level with very strange frequency response
as the relative phase shifts with frequency within the passband.

 > There is no "magic audio" or Voltage that is swinging in a negative
 > polarity in my headphones from an antenna that is not receiving an
 > opposite polarity  signal.

You obviously do not understand the nature of time varying multi-
path signals.  The whole point is that the effective path length
to each receive antenna changes constantly.  At 14,000,000 Hz, the
transmission path (height of the ionosphere) for one of the two
receive antennas needs to change only 16 feet (5 meters) - or
put another way, the signal reaching one antenna needs to be
delayed only about 3 nanoseconds relative to the other antenna,
for a mixed signal to go from maximum volume (in phase) to nothing
at all (out of phase).

If you have separate speakers or earphones the apparent location
of the signal will move around the room but unless the signal
to BOTH receivers goes to zero, it won't disappear.  With mixing,
a signal that would be "everywhere" in the stereo field would
disappear completely while signals that would be directly "between
the ears" would be at maximum loudness.

73,

    ... Joe, W4TV


On 7/5/2010 9:33 PM, The Smiths wrote:
>
>
> I'm not sure how your rig works, but with mine, when I have phase
> shifting between the two antennas I don't have Phase shifting in my
> audio Left and right.  In that I mean, if I look at the spectrum
> analyzer/o'scope I do not see the signal coming out of my head phones
> phasing from positive voltage to a negative voltage in the inverse
> between the two headphone outputs. Unlike AC where when one side
> swings negative, if you were to add the inverse you would cancle out
> the entire signal, this is not the case with the diversity reception.
> The phase is in the antenna reception.. Not the audio that we listen
> to.  When my vertical is picking up a vertical phased signal it is
> very possible that my Horizontal antenna is not receiving any signal
> at all.. Therefore if I have Mix on so that the sub is placed in the
> Main's headphone I do not cancel out the audio in the both ears.
> There is no "magic audio" or Voltage that is swinging in a negative
> polarity in my headphones from an antenna that is not receiving an
> opposite polarity  signal.  If that were the case than I would just
> build an audio phase reverser and listen to my horizontal antenna as
> the signal phased into a vertical polarity.  I would never need
> diversity reception in the first place.  I could just flip the phase
> of the audio input to the receiver when I stopped hearing the signal
> on my horizontal antenna assuming it was now phased in the vertical
> field.
>
> If you use Lyle's Utility based Mixer mode for Diversity (IE. Enter
> the code he gave you here on the reflector) you will hear that it
> keeps the signal stable as it travels from one antenna to the other.
> It doesn't cause the audio in both my headsets to cancel itself out.
> I've used it before (both with Lyle's code, and with another rig) and
> have NEVER had the canceling affect. I would urge you to at least try
> it and see for yourself.
>
> Now, if this defies all principals of electronics and audio, then so
> be it.. but I can tell you with certainty that mixing the two antenna
> phases in one headset makes for BOTH signals to be heard at the same
> time. So once again, I completely disagree with your reasoning not to
> implement it.  Sorry, but we'll just have to agree to disagree..
>
> The code already exists, as you have already seen by the fact that
> Lyle has already writing it, and given you the knowledge how to turn
> it on.  The only missing key here is Wayne, or Eric's adding it to
> the Config menu.
>
>
>
>> Date: Mon, 5 Jul 2010 20:29:55 -0400 From: lists at subich.com To:
>> notforchat at hotmail.com CC: elecraft at mailman.qth.net Subject: Re:
>> [Elecraft] K3 Audio routing question
>>
>>
>>> 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'm sorry, you're wrong. If you MIX the two audio sources instead
>> of hearing them "swim" from ear to ear, you will hear them FADE out
>> completely as the phase differences cause them to cancel. "Swim" is
>> the mind's interpretation of the difference in phase and amplitude
>> between the PATH taken by the two signals.
>>
>> What you accomplish by mixing is to undo all the benefits of
>> diversity. You have simply moved the point of phase cancellation
>> from the single antenna to the single headphone. You have gone to
>> the great expense of building/buying/installing a second antenna
>> and buying/installing a second, identical receiver so you can
>> simply combine two non-coherent audio sources instead of two
>> non-coherent RF sources.
>>
>> The only way one can "mix" the feeds from a diversity receive
>> system is to provide a voting/switching system that evaluates the
>> signal to noise ratio (in FM it's called "quieting") and selects
>> the "better" signal - not mixes the two.
>>
>>> 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.
>>
>> Mixing is appropriate when one has two completely different
>> signals. It is NOT appropriate when one has the same signal with a
>> randomly varying phase and amplitude difference. With two
>> independent signals there is no cancellation.
>>
>> Again, enabling L - MIX - R in diversity is to waste programming
>> resources on something that is not only useless but will actually
>> result in decreased performance.
>>
>> 73,
>>
>> ... Joe, W4TV
>>
>> On 7/5/2010 7:34 PM, The Smiths wrote:
>>>
>>> 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. 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.
>>>
>>> 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. 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.
>>>
>>>
>>> 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.
>>>
>>>
>>>
>>>
>>>
>>>> Date: Mon, 5 Jul 2010 17:43:29 -0400 From: lists at subich.com
>>>> To: elecraft at mailman.qth.net Subject: Re: [Elecraft] K3 Audio
>>>> routing question
>>>>
>>>>
>>>>> As you know, this is NOT working in the Diversity mode as
>>>>> this person wants to use it. It is ONLY available with SUB
>>>>> mode at the time. Perhaps you can Stress to Wayne that he
>>>>> should finally make it available for use when in
>>>>> Diversity...
>>>>
>>>> Making L-Mix-R function in diversity mode defeats the purpose
>>>> of diversity mode. Placing EITHER receiver in both ears during
>>>> diversity essentially disables diversity.
>>>>
>>>> I hate to be the one to say "don't waste the programming time"
>>>> but this is another of those "enhancements" that is a complete
>>>> waste of programmer time and does not make *ANY* practical
>>>> sense.
>>>>
>>>> 73,
>>>>
>>>> ... Joe, W4TV
>>>>
>>>>
>>>> On 7/5/2010 4:41 PM, The Smiths wrote:
>>>>>
>>>>> Lyle,
>>>>>
>>>>> As you know, this is NOT working in the Diversity mode as
>>>>> this person wants to use it. It is ONLY available with SUB
>>>>> mode at the time. Perhaps you can Stress to Wayne that he
>>>>> should finally make it available for use when in
>>>>> Diversity...
>>>>>
>>>>>> Date: Mon, 5 Jul 2010 13:15:53 -0700 From:
>>>>>> kk7p at wavecable.com To: g0afh at g0afh.com CC:
>>>>>> Elecraft at mailman.qth.net Subject: Re: [Elecraft] K3 Audio
>>>>>> routing question
>>>>>>
>>>>>>
>>>>>>> Is there a way to get the audio from the sub receiver
>>>>>>> into both ears without external switching?
>>>>>>
>>>>>> Yes. See the firmware release notes and CONFIG:L-MIX-R
>>>>>>
>>>>>> 73,
>>>>>>
>>>>>> Lyle KK7P
>>>>
>>>> ______________________________________________________________
>>>> Elecraft mailing list Home:
>>>> http://mailman.qth.net/mailman/listinfo/elecraft Help:
>>>> http://mailman.qth.net/mmfaq.htm Post:
>>>> mailto:Elecraft at mailman.qth.net
>>>>
>>>> This list hosted by: http://www.qsl.net Please help support
>>>> this email list: http://www.qsl.net/donate.html
>>> _________________________________________________________________
>>>
>>>
The New Busy is not the too busy. Combine all your e-mail accounts
>>> with Hotmail.
>>> http://www.windowslive.com/campaign/thenewbusy?tile=multiaccount&ocid=PID28326::T:WLMTAGL:ON:WL:en-US:WM_HMP:042010_4
>
>>>
> _________________________________________________________________ The
> New Busy is not the too busy. Combine all your e-mail accounts with
> Hotmail.
> http://www.windowslive.com/campaign/thenewbusy?tile=multiaccount&ocid=PID28326::T:WLMTAGL:ON:WL:en-US:WM_HMP:042010_4

More information about the Elecraft mailing list