[Elecraft] K3S Audio buzz on transmit, especially AM

Frank Krozel kg9hfrank at gmail.com
Fri Apr 26 22:48:50 EDT 2019 

Try switching to a linear supply?




Sincerely,  Frank Krozel t: 1-630-924-1600 frank at electronicinstrument.com
BSEE,   AASEET,   FCC Lic.# PG-18-19178,   KG9H
Electronic Instrument Associates - Central, Inc. ...since 1971
w: www.electronicinstrument.com  d/l our linecard at http://www.electronicinstrument.com/lc.pdf  


> On Apr 26, 2019, at 9:46 PM, Nicklas Johnson <nick at n6ol.us> wrote:
> 
> Before I forget, thank you to everyone who has responded thusfar with ideas
> and suggestions.  This one is a real head-scratcher, and I appreciate
> everyone bouncing ideas around with me.
> 
> If the problem is in fact originating with power line neutral distortion,
> what, if anything could I actually do about it, beyond what I've already
> done in running on battery power?  I can't really move my 'shack' in this
> case.
> 
> I did find the "squeaky wheel" at least.  It was the end of one of the
> aluminum straps of an antenna mast chimney mount brushing against a copper
> ground wire in the wind.  A pair of tin snips solved that problem.  This
> bit was kind of fascinating-- if I held a copper wire against the aluminum
> strap, and position the antenna of the KX3 nearby, I could receive some
> broadcast AM station on the 51.123 MHz carrier I was transmitting from
> inside the house (it's pretty close to a multiple of 810kHz, so if I had to
> guess, it was likely KGO I was getting).
> 
> I also found the noise gets a hell of a lot louder near the back gutter of
> the house (which runs parallel to the power lines that run through the back
> yard), though this could just be because the antenna of my KX3 was coupling
> to it.
> 
> Yet to be determined is whether the noise is a local thing only affecting
> reception (e.g., some kind of passive intermod), or if in fact it becomes
> part of the signal I'm sending up to the ionosphere.  To really figure that
> one out, I probably will need to make an actual distant AM contact and ask
> someone to tell me how it sounds... this may be no small feat with the way
> the sun is behaving lately, but I'll keep trying.
> 
>   Nick
> 
>> On Fri, 26 Apr 2019 at 19:18, Bob McGraw K4TAX <rmcgraw at blomand.net> wrote:
>> 
>> I think Jim's concern, expressed earlier, about power line neutral
>> distortion components is valid. And it may be originating in "the big green
>> transformer" in the yard.
>> 
>> Bob, K4TAX
>> 
>> 
>> Sent from my iPhone
>> 
>>> On Apr 26, 2019, at 8:53 PM, Nicklas Johnson <nick at n6ol.us> wrote:
>>> 
>>> Sorry for the additional email, but this is particularly interesting: it
>>> occurred to me that I'd never tried the reverse setup, so I put the KX3
>> in
>>> transmit mode and 0.1W on AM in another room, and set the K3S on receive.
>>> And sure enough, the K3S immediately started picking up S40 of buzzing
>>> noise.  However if I tune the K3S to an AM broadcast station or WWV, no
>>> buzz. So either both the K3S and KX3 are being affected on transmit in
>> the
>>> same way (which seems implausible but not impossible), or possibly
>>> something else is going on at my QTH.
>>> 
>>> On the P3, I definitely see the noise when the KX3 is transmitting from
>> the
>>> other room.
>>> 
>>> Now I wish I had a scope so I could see what the AM carrier generated by
>>> the KX3 and K3S looks like so I could tell if this is something that's
>>> happening inside the transmitter, or something that is happening because
>> of
>>> some outside influence mixing powerline noise with the AM carrier.  The
>>> important thing to me is that the carrier I'm putting out there is
>> clean...
>>> if there's some local mixing that happens that means I can't listen to my
>>> own transmission without a buzz, I can live with that.
>>> 
>>> One kind of curious thing is that there's also a superimposed "squeaky
>>> wheel" sound at random intervals detectable when the KX3 is transmitting
>> an
>>> AM carrier, and not otherwise, and also not when listening to WWV or AM
>>> broadcast, which vaguely seems to correlate with how windy it is at any
>>> given moment.  Could all of this be a "rusty bolt" effect from something
>> in
>>> the vicinity?
>>> 
>>>  Nick
>>> 
>>> 
>>> 
>>>> On Fri, 26 Apr 2019 at 18:11, Nicklas Johnson <nick at n6ol.us> wrote:
>>>> 
>>>> A few more data points:
>>>> 
>>>> Changing TX EQ, including cutting the first 4 bands all the way down to
>>>> -16 had no effect on the received signal.
>>>> 
>>>> Plugging in some headphones, turning the TX Monitor up all the way, I
>>>> don't detect the hum in the TX monitor signal either in TX test mode,
>>>> transmitting into a dummy load, or even transmitting into the antenna
>> with
>>>> very low power.  If I turn up the Line In level, I just hear expected
>> white
>>>> noise on the TX monitor.  So at least as far along the path as the TX
>>>> monitor, there's no hum or buzz introduced.
>>>> 
>>>> Switching the receiver (a KX3) to USB mode and using one leg of a
>>>> buddistick as an antenna so I can walk around, the noise received around
>>>> the house and outside is around S4 when transmitting about 100mW into
>> the
>>>> antenna, though it varies some as I walk around.
>>>> 
>>>> I do have a set of power lines running through my back yard, and where I
>>>> live in San Mateo, you're always near somebody's wiring for something,
>>>> unfortunately... my neighbor's south wall is possibly as far as 8 feet
>> away
>>>> from my north wall, etc.
>>>> 
>>>> It looks like two phases running along the top, then a transformer to
>> two
>>>> phases and a neutral along the bottom, to which people's houses are
>>>> connected.
>>>> 
>>>> We also have underground utilities on our street, including a big green
>>>> transformer that sits in the corner of our front lawn.
>>>> 
>>>> I think the next test will be to take the K3S and the KX3 some distance
>>>> away from all of these things and see if the hum goes away, and if it
>> does,
>>>> then figure out what thing the K3S needs to get away from in particular.
>>>> If it's the powerlines in my back yard or the transformer in my front
>> yard,
>>>> then that'll be a difficult problem.
>>>> 
>>>>  Nick
>>>> 
>>>> 
>>>> 
>>>> On Fri, 26 Apr 2019 at 17:28, Bob McGraw K4TAX <rmcgraw at blomand.net>
>>>> wrote:
>>>> 
>>>>> Yes but the EQ is in the digital path.  The EQ should be done there,
>>>>> preferably after the MIC input.   The AM BW does not attenuate the end
>> like
>>>>> the SSB filter.
>>>>> 
>>>>> I suggest -16 dB on the first 3 bands.
>>>>> 
>>>>> Bob, K4TAX
>>>>> 
>>>>> 
>>>>> Sent from my iPhone
>>>>> 
>>>>>> On Apr 26, 2019, at 6:38 PM, Nicklas Johnson <nick at n6ol.us> wrote:
>>>>>> 
>>>>>> Flat, except I turned the first one down a few notches, which doesn't
>>>>>> really do much in my case because both the microphone and mixer that I
>>>>> use
>>>>>> (when they're actually connected) roll off below 150 and 80 Hz
>>>>>> respectively.  It had previously been suggested to me that rolling off
>>>>> low
>>>>>> frequency cruft is a good idea for AM and SSB.
>>>>>> 
>>>>>> Nick
>>>>>> 
>>>>>>> On Fri, 26 Apr 2019 at 15:57, Bob McGraw K4TAX <rmcgraw at blomand.net>
>>>>> wrote:
>>>>>>> 
>>>>>>> I recall commenting earlier.  What TX EQ values are being used for
>> AM.
>>>>> ?
>>>>>>> 
>>>>>>> Bob, K4TAX
>>>>>>> 
>>>>>>> 
>>>>>>> Sent from my iPhone
>>>>>>> 
>>>>>>>> On Apr 26, 2019, at 5:48 PM, Nicklas Johnson <nick at n6ol.us> wrote:
>>>>>>>> 
>>>>>>>> My desk in this case sits adjacent a wall, and there's only a shower
>>>>> on
>>>>>>> the
>>>>>>>> other side of that wall.  I did turn off everything in the vicinity
>> of
>>>>>>> the
>>>>>>>> desk and all the lights in the room (I've in fact heard a very
>> similar
>>>>>>> hum
>>>>>>>> from the switching power supply for my mixer, and my first thought
>>>>> was it
>>>>>>>> was this that was being picked up), but I didn't turn off the
>>>>> computer on
>>>>>>>> the other side of the room.  In this case it will be easier to move
>>>>> the
>>>>>>> rig
>>>>>>>> outdoors with a battery than it will be to turn that computer off
>> for
>>>>> the
>>>>>>>> moment.  It would have to be an impressively/obnoxiously strong
>>>>> magnetic
>>>>>>>> field from that side of the room to influence the transformers
>> inside
>>>>> the
>>>>>>>> rig 8 feet away, but it's worth trying and simple enough to rule it
>>>>> out.
>>>>>>>> 
>>>>>>>> Nick
>>>>>>>> 
>>>>>>>>> On Fri, 26 Apr 2019 at 14:51, Don Wilhelm <donwilh at embarqmail.com>
>>>>>>> wrote:
>>>>>>>>> 
>>>>>>>>> In addition to operating from a battery isolated from the solar
>>>>> system,
>>>>>>>>> I would recommend that you do a quick test - remove all cables from
>>>>> the
>>>>>>>>> K3S except the power cable and a coax to a dummy load.  Power down
>>>>> all
>>>>>>>>> power supplies in your station, including any desk lamps.
>>>>>>>>> Go into Transmit by tapping the XMIT button.
>>>>>>>>> Is the hum still present?  If not, then start connecting things to
>>>>> your
>>>>>>>>> K3S one at a time, doing the same test after each thing connected.
>>>>>>>>> 
>>>>>>>>> Of course, if the hum is present with nothing connected, contact
>>>>>>>>> support at elecraft.com - but I cannot imagine a hum with harmonics
>> of
>>>>> 60
>>>>>>>>> Hz being induced if you take away all the 60 Hz operated sources in
>>>>> the
>>>>>>>>> area.
>>>>>>>>> 
>>>>>>>>> 73,
>>>>>>>>> Don W3FPR
>>>>>>>>> 
>>>>>>>>> --
>>>>>>>> *N6OL*
>>>>>>>> Saying something doesn't make it true.  Belief in something doesn't
>>>>> make
>>>>>>> it
>>>>>>>> real. And if you have to lie to support a position, that position is
>>>>> not
>>>>>>>> worth supporting.
>>>>>>>> ______________________________________________________________
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>>>>>>>> 
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>>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>> 
>>>>>> --
>>>>>> *N6OL*
>>>>>> Saying something doesn't make it true.  Belief in something doesn't
>>>>> make it
>>>>>> real. And if you have to lie to support a position, that position is
>> not
>>>>>> worth supporting.
>>>>>> ______________________________________________________________
>>>>>> Elecraft mailing list
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>>>>>> Help: http://mailman.qth.net/mmfaq.htm
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>>>>>> 
>>>>>> This list hosted by: http://www.qsl.net
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>>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>> 
>>>> --
>>>> *N6OL*
>>>> Saying something doesn't make it true.  Belief in something doesn't make
>>>> it real. And if you have to lie to support a position, that position is
>> not
>>>> worth supporting.
>>>> 
>>> 
>>> 
>>> --
>>> *N6OL*
>>> Saying something doesn't make it true.  Belief in something doesn't make
>> it
>>> real. And if you have to lie to support a position, that position is not
>>> worth supporting.
>>> ______________________________________________________________
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>>> 
>> 
>> 
>> 
> 
> -- 
> *N6OL*
> Saying something doesn't make it true.  Belief in something doesn't make it
> real. And if you have to lie to support a position, that position is not
> worth supporting.
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
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