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K3S Audio buzz on transmit, especially AM

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Nicklas Johnson

K3S Audio buzz on transmit, especially AM

I'm trying to track down a pretty obnoxious audio problem on AM, and to a
much lesser extent on SSB.

On transmit I get an audio buzz with the highest spikes on 350, 470, and
830 Hz.

At first I thought I had a ground loop hum, so I disconnected everything
from the K3s except the antenna and switched the power over to battery
only. It made no difference.

Other things that don't make any difference: lowering the mic/line input
level to 0, changing the mic input among front panel, rear panel, line-in,
changing frequency, changing output power all the way down to 0.1w, turning
off all the lights and shutting off any other nearby equipment in the room,
running into a dummy load with the receiver nearby.

Physically touching the case or grabbing the barrel of the front panel mic
connector actually does cause the buzz to get just a little softer.

I generally use solar/battery power, though my ground is bonded to my
utility ground.

Any other ideas? I'm running out of them.

Nick

--
*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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Grant Youngman-2

Re: K3S Audio buzz on transmit, especially AM

Microphone? Or anything in between the mic and the radio, if there is anything?

Grant NQ5T
K3 #2091 KX3 #8342

>
>
> Any other ideas? I'm running out of them.
>
> Nick
>
> --
> *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
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>
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Nicklas Johnson

Re: K3S Audio buzz on transmit, especially AM

That was my second thought, but then I disconnected everything, including
the microphone, and it made no difference.

Nick

On Thu, Apr 25, 2019, 8:20 PM Grant Youngman <[hidden email]> wrote:

> Microphone? Or anything in between the mic and the radio, if there is
> anything?
>
> Grant NQ5T
> K3 #2091 KX3 #8342
>
> >
> >
> > Any other ideas? I'm running out of them.
> >
> > Nick
> >
> > --
> > *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
> > Post: mailto:[hidden email]
> >
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: http://www.qsl.net/donate.html
>
>

Jim Brown-10

Re: K3S Audio buzz on transmit, especially AM

In reply to this post by Nicklas Johnson

On 4/25/2019 8:15 PM, Nicklas Johnson wrote:
> Physically touching the case or grabbing the barrel of the front panel mic
> connector actually does cause the buzz to get just a little softer.

I suspect either a bonding problem or a problem with the wiring of the mic.

> I generally use solar/battery power, though my ground is bonded to my
> utility ground.

I suggest that you carefully study either N0AX's recent ARRL book on
grounding and bonding, or the slides for talks I've given at Visalia and
Pacifion.

73, Jim K9YC

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Nicklas Johnson

Re: K3S Audio buzz on transmit, especially AM

Again, the problem persists with all inputs completely disconnected and the
mic gain set at 0. And running solely on a battery into a dummy load.

Nick

On Thu, Apr 25, 2019, 10:10 PM Jim Brown <[hidden email]> wrote:

> On 4/25/2019 8:15 PM, Nicklas Johnson wrote:
> > Physically touching the case or grabbing the barrel of the front panel
> mic
> > connector actually does cause the buzz to get just a little softer.
>
> I suspect either a bonding problem or a problem with the wiring of the mic.
>
> > I generally use solar/battery power, though my ground is bonded to my
> > utility ground.
>
> I suggest that you carefully study either N0AX's recent ARRL book on
> grounding and bonding, or the slides for talks I've given at Visalia and
> Pacifion.
>
> 73, Jim K9YC
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

Nicklas Johnson

Re: K3S Audio buzz on transmit, especially AM

This morning just for yuks, I also temporarily disconnected the ground from
the rig entirely while also connecting only to a dummy load, so there could
be no path to ground at all, let alone multiple paths. No change.

I guess the next things I'll probably try are a full factory reset, and
then perhaps popping it open to make sure nothing has come unseated. But
first I'll drop a line to Elecraft support too. I've seen a number of
people post about similar problems that either magically resolved
themselves or ended up being a fault on the audio board.

Nick

On Thu, 25 Apr 2019 at 23:27, Nicklas Johnson <[hidden email]> wrote:

> Again, the problem persists with all inputs completely disconnected and
> the mic gain set at 0. And running solely on a battery into a dummy load.
>
> Nick
>
> On Thu, Apr 25, 2019, 10:10 PM Jim Brown <[hidden email]>
> wrote:
>
>> On 4/25/2019 8:15 PM, Nicklas Johnson wrote:
>> > Physically touching the case or grabbing the barrel of the front panel
>> mic
>> > connector actually does cause the buzz to get just a little softer.
>>
>> I suspect either a bonding problem or a problem with the wiring of the
>> mic.
>>
>> > I generally use solar/battery power, though my ground is bonded to my
>> > utility ground.
>>
>> I suggest that you carefully study either N0AX's recent ARRL book on
>> grounding and bonding, or the slides for talks I've given at Visalia and
>> Pacifion.
>>
>> 73, Jim K9YC
>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>
>

--
*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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Bob McGraw - K4TAX

Re: K3S Audio buzz on transmit, especially AM

I did listen and look at my K3S on my SDR receiver in AM mode. I do find
there is a small amount of hum on the carrier. Then switching to LSB, I
do not find the hum present.

You may want to check the settings of your TX EQ. If you have any low
frequency boost, that will contribute to the level of the hum. My
operating values are: 50 Hz = -16 dB , 100 Hz = -16 dB , 200 Hz = -16 dB
, 400 Hz = -6 dB, everything above that is set to 0 dB or flat. The
mike is a Shure SM-58.

In AM mode the hum is noted at 120 Hz, 240 Hz, and 360 Hz, all multiples
of the 60 Hz line. At the same time, the hum level of the individual
frequencies, worst case, is some 40 dB below 100% modulation. Some are
50 dB below 100% modulation with the worst case being 120 Hz.    In
working several AM stations over the past year or so, I've not had any
comments regarding hum on the carrier.    These tests were done with MIC
level set to 0 and COM level set to 0.   Everything else normal and
connected to the radio. Different power levels, mike level and comp
level made no difference in the amplitude of the hum components.

73

Bob, K4TAX

On 4/26/2019 10:43 AM, Nicklas Johnson wrote:

> This morning just for yuks, I also temporarily disconnected the ground from
> the rig entirely while also connecting only to a dummy load, so there could
> be no path to ground at all, let alone multiple paths. No change.
>
> I guess the next things I'll probably try are a full factory reset, and
> then perhaps popping it open to make sure nothing has come unseated. But
> first I'll drop a line to Elecraft support too. I've seen a number of
> people post about similar problems that either magically resolved
> themselves or ended up being a fault on the audio board.
>
> Nick
>
>
> On Thu, 25 Apr 2019 at 23:27, Nicklas Johnson <[hidden email]> wrote:
>
>> Again, the problem persists with all inputs completely disconnected and
>> the mic gain set at 0. And running solely on a battery into a dummy load.
>>
>> Nick
>>
>> On Thu, Apr 25, 2019, 10:10 PM Jim Brown <[hidden email]>
>> wrote:
>>
>>> On 4/25/2019 8:15 PM, Nicklas Johnson wrote:
>>>> Physically touching the case or grabbing the barrel of the front panel
>>> mic
>>>> connector actually does cause the buzz to get just a little softer.
>>> I suspect either a bonding problem or a problem with the wiring of the
>>> mic.
>>>
>>>> I generally use solar/battery power, though my ground is bonded to my
>>>> utility ground.
>>> I suggest that you carefully study either N0AX's recent ARRL book on
>>> grounding and bonding, or the slides for talks I've given at Visalia and
>>> Pacifion.
>>>
>>> 73, Jim K9YC
>>>
>>> ______________________________________________________________
>>> Elecraft mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>> Help: http://mailman.qth.net/mmfaq.htm
>>> Post: mailto:[hidden email]
>>>
>>> This list hosted by: http://www.qsl.net
>>> Please help support this email list: http://www.qsl.net/donate.html
>>>

K8TE

Re: K3S Audio buzz on transmit, especially AM

In reply to this post by Nicklas Johnson

The word that struck my attention is "solar" and the possibility of that
controller causing noise. When you were connected to just the battery and
dummy load, was the battery disconnected from the solar system? And, at
what level was the buzz relative to a full power carrier?

Every transmitter has some noise on its signal. Specifications and FCC
rules in some cases call for a specific ratio. I can't imagine a factory
reset solving a problem like this. Be certain you have saved your
configuration first. Solving issues like this is not magic, but sometimes a
mystery.

73, Bill, K8TE

--
Sent from: http://elecraft.365791.n2.nabble.com/
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Don Wilhelm

Re: K3S Audio buzz on transmit, especially AM

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
[hidden email] - 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

On 4/26/2019 5:36 PM, K8TE wrote:

> The word that struck my attention is "solar" and the possibility of that
> controller causing noise. When you were connected to just the battery and
> dummy load, was the battery disconnected from the solar system? And, at
> what level was the buzz relative to a full power carrier?
>
> Every transmitter has some noise on its signal. Specifications and FCC
> rules in some cases call for a specific ratio. I can't imagine a factory
> reset solving a problem like this. Be certain you have saved your
> configuration first. Solving issues like this is not magic, but sometimes a
> mystery.
>

Jim Brown-10

Re: K3S Audio buzz on transmit, especially AM

In reply to this post by K8TE

I think you may have hit on it, Bill. Say it's a pulse-regulated
controller on the battery is on the soft side. BTW -- most solar charge
controllers put out a lot of RF noise. The only good pulsing
controllers I've found are the MPPT controllers made by Genasun.
https://sunforgellc.com/genasun/#gen_product_row

Another question to help diagnose the problem if it's the battery --
what's the DC voltage at the battery in RX mode? In TX mode? What does
the K3 internal voltmeter read for RX and TX?

73, Jim K9YC

73, On 4/26/2019 2:36 PM, K8TE wrote:
> The word that struck my attention is "solar" and the possibility of that
> controller causing noise. When you were connected to just the battery and
> dummy load, was the battery disconnected from the solar system?

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donovanf

Re: K3S Audio buzz on transmit, especially AM

In reply to this post by Don Wilhelm

I had this same problem years ago before purchasing my first K3.
It turned out to magnetic field coupling between my HyGain
T2X control box and an audio transformer in the transceiver.

As Don suggested, be sure all power supplies including computers,
UPSs and lamps are turned off during the test.

If this doesn't work, take to K3S to a friends QTH and repeat the test

73
Frank
W3LPL

----- Original Message -----

From: "Don Wilhelm" <[hidden email]>
To: [hidden email]
Sent: Friday, April 26, 2019 9:51:15 PM
Subject: Re: [Elecraft] K3S Audio buzz on transmit, especially AM

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
[hidden email] - 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

On 4/26/2019 5:36 PM, K8TE wrote:

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Jim Brown-10

Re: K3S Audio buzz on transmit, especially AM

That makes sense too. The transformers are unshielded, so are sitting
ducks for strong nearby magnetic fields. K6XX ran into this early on
running RTTY from a big amp PSU very close to a K3. The coupling was so
strong that it went into regeneration!

73, Jim K9YC

On 4/26/2019 3:16 PM, [hidden email] wrote:
> I had this same problem years ago before purchasing my first K3.
> It turned out to magnetic field coupling between my HyGain
> T2X control box and an audio transformer in the transceiver.

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Nicklas Johnson

Re: K3S Audio buzz on transmit, especially AM

In reply to this post by K8TE

I did in fact wonder the same thing myself-- whether the solar controller
could be injecting some noise or just making some noise, so when I did the
battery test, I disconnected the battery from the controller and ran
directly from the battery to the rig.

I couldn't tell you a dB level of the buzz without having some more
accurate equipment to measure it, but it's very noticeable relative to my
voice when testing. It was enough to make me think I had either RF
feedback or a ground loop giving me grief.

There could be something to be learned from the predominant frequencies
present in the buzz... they're more or less 120Hz apart, but they start at
a weird place-- 350 isn't a multiple of 60 or 120, but that particular spur
and the 470 and 830 Hz spurs are all pretty exact, though of course it's
not impossible that there's some FFT error in determining those frequencies
and they're actually 360, 480, and 840.

Curious, though, is that running on a battery, there's nothing to inject a
60Hz or 120Hz noise directly, especially not once I disconnected the rig
ground from the ground rod outside. Which makes me wonder if the buzz is
just something in the house that's mixing with the carrier and
re-radiating. For my next trick, this weekend I think I'll take everything
outside on a picnic table, away from house wiring, etc., and see if that
changes anything, or I might start with just the receiver outdoors and away
from house wiring, and then move on to both if needed.

Nick

On Fri, 26 Apr 2019 at 14:37, K8TE <[hidden email]> wrote:

Nicklas Johnson

Re: K3S Audio buzz on transmit, especially AM

In reply to this post by Don Wilhelm

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 <[hidden email]> 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
> [hidden email] - 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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Bob McGraw - K4TAX

Re: K3S Audio buzz on transmit, especially AM

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 <[hidden email]> 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 <[hidden email]> 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
>> [hidden email] - 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.
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

Nicklas Johnson

Re: K3S Audio buzz on transmit, especially AM

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 <[hidden email]> 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 <[hidden email]> 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 <[hidden email]>
> 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
> >> [hidden email] - 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.
> > ______________________________________________________________
> > Elecraft mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/elecraft
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:[hidden email]
> >
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: http://www.qsl.net/donate.html
> >
>
>

Bob McGraw - K4TAX

Re: K3S Audio buzz on transmit, especially AM

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 <[hidden email]> 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 <[hidden email]> 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 <[hidden email]> 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 <[hidden email]>
>> 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
>>>> [hidden email] - 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.
>>> ______________________________________________________________
>>> Elecraft mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>> Help: http://mailman.qth.net/mmfaq.htm
>>> Post: mailto:[hidden email]
>>>
>>> This list hosted by: http://www.qsl.net
>>> Please help support this email list: http://www.qsl.net/donate.html
>>>
>>
>>
>
> --
> *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
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

Jim Brown-10

Re: K3S Audio buzz on transmit, especially AM

In reply to this post by Nicklas Johnson

A pro audio colleague, Neil Muncy, now deceased, specialized in chasing
down hum and buzz in home studios. One mechanism he ran into several
times was "triplen" harmonic current on the incoming neutral or ground,
and I worked with him on one of them. These harmonic currents are the
result of distortion of the current waveform on power lines,which in
turn is caused by current in anything with a capacitor input power
supply drawing most of the current at positive and negative peaks of
the AC cycle. Most power lines outside our home are some form of
3-phase, and in these systems, any harmonic divisible by 3 ADDS in the
neutral rather than cancelling. The most prominent components are 180
Hz, 360 Hz, 540 Hz, 720 Hz, and so on, and they are heard as "buzz"
rather than hum.

Few of us have 3-phase power in our homes, but a power distribution
system called "high leg Delta" or "wild leg" is VERY widely used in
neighborhoods where the customers are a mix residential and light
industrial. This system is a Delta, but with one leg of the Delta
center-tapped. The 3-phase customers are fed from the Delta, and
single-phase customers from the center-tapped transformer. Single phase
customers get phase-phase-neutral. The 3-phase customers get no neutral,
but they generate lots of triplen harmonics that go to ground via the
neutral bond in single-phase homes. My home in the Santa Cruz
Mountains, is fed single-phase power (120-0-120) by high-leg Delta.

Depending on lots of factors, that triplen current can get pretty large,
and the magnetic field can couple into any magnetic loop, into any
unshielded transformer, and into magnetic guitar pickups! That's where
Neil came in. How strong the pickup is depends on the routing of the
neutral and ground wire carrying that triplen current. Another colleague
working on the design of audio for a major TV studio in NYC found very
high triplen currents in a vertical riser in the high rise building
housing the studio, right next to the main mix console. MAJOR problem --
it got into almost all the gear and low level mic wiring in the room!

As to the accuracy of your FFT frequencies -- FFT's are computed in
"bins" with their width dependent on the FFT parameters for any given
measurement/display width. If bins are fairly wide, the frequencies
you're reading could easily be triplen harmonics.

73, Jim K9YC

On 4/26/2019 3:38 PM, Nicklas Johnson wrote:
> they're more or less 120Hz apart, but they start at
> a weird place-- 350 isn't a multiple of 60 or 120, but that particular spur
> and the 470 and 830 Hz spurs are all pretty exact, though of course it's
> not impossible that there's some FFT error in determining those frequencies
> and they're actually 360, 480, and 840.

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Jim Brown-10

Re: K3S Audio buzz on transmit, especially AM

In reply to this post by Bob McGraw - K4TAX

On 4/26/2019 5:28 PM, Bob McGraw K4TAX wrote:
> I suggest -16 dB on the first 3 bands.

My standard recommendation for ham radio is to start with max cut of 50,
100, and 200 Hz bands, 6 dB of cut of the 400 Hz band, and get signal
reports. Do this in TXEQ. What sounds "right" will depend on your voice
and your mic, so take this as a starting point.

73, Jim K9YC

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Nicklas Johnson

Re: K3S Audio buzz on transmit, especially AM

In reply to this post by Bob McGraw - K4TAX

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 <[hidden email]> 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 <[hidden email]> 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 <[hidden email]>
> 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 <[hidden email]> 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 <[hidden email]>
> >> 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
> >>>> [hidden email] - 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.
> >>> ______________________________________________________________
> >>> Elecraft mailing list
> >>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> >>> Help: http://mailman.qth.net/mmfaq.htm
> >>> Post: mailto:[hidden email]
> >>>
> >>> This list hosted by: http://www.qsl.net
> >>> Please help support this email list: http://www.qsl.net/donate.html
> >>>
> >>
> >>
> >
> > --
> > *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
> > Post: mailto:[hidden email]
> >
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: http://www.qsl.net/donate.html
> >
>
>
>