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K3 Hum on Audio...

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Phil Hystad-3

Re: K3 Hum on Audio...

No one mentioned the firmware level but I am not on any beta version. I am at MCU firmware level 4.39.

73, phil, K7PEH

On Jan 13, 2012, at 12:33 PM, NZ0T wrote:

> Phil, which firmware version are you using? I was using the beta 4.47 and
> I developed audio problems the other night, After I deleted 4.47 and went
> back to the latest production firmware all was fine. Sorry if this has
> already been discussed - I just read this thread.
>
> 73 Bill NZ0T
>
> On Fri, Jan 13, 2012 at 1:32 PM, Phil Hystad-3 [via Elecraft] <
> [hidden email]> wrote:
>
>> Ron,
>>
>> Well, I just had a quick SSB chat with Clyde (AA7WC) (pre Noon Time net on
>> 40 meters) and asked specifically for audio report with possible hum. His
>> report was no hum, clear good sounding audio, with S7 signal.
>>
>> So I am suspicious of my florescent lights in the garage although they are
>> on right now with no hum. I am thinking though that maybe there is
>> something intermittent with those lights. But, then again, the "something
>> loose in the mic cord" maybe be the cause too. But, I jiggled that cord
>> and connection and so on quite vigorously before when I had the hum and it
>> did not change the hum status. Then, when the hum disappeared, I did those
>> jiggle the cord and connector on the mic tests again and the hum DID NOT
>> come back.
>>
>> Wow, I can't believe I have spent the entire morning fooling around with
>> this. I even called into work and said that I was not coming in today just
>> to work on this problem. I don't really want to go outside anyway despite
>> that the temperature has now risen to a toasty 36 degrees.
>>
>> 73, phil, K7PEH
>>
>>
>> On Jan 13, 2012, at 11:23 AM, Ron D'Eau Claire wrote:
>>
>>> Good luck Phil. That last part really suggests something loose in the
>> mike
>>> cord as I suggested at first.
>>>
>>> Ron AC7AC
>>>
>>> -----Original Message-----
>>> Ron,
>>>
>>> OK, now it appears I was mistaken when I said that that the hum was in
>> both
>>> mics. I think I flubbed something up in my previous test due to the way
>>> that the macros are assigned to keys which led me to thinking that the
>> hum
>>> occurred in both mics. But, I learned something in this...
>>>
>>> One, don't try to use one of your macro assigned keys (in my case M2 and
>> M1)
>>> while in the menu because that merely reassigns the key to the new menu
>>> entry. I made this mistake several times this morning. But, when I
>>> discovered it and then reset my macro definitions, I rediscovered that
>> the
>>> HUM occurs in the front panel MH2 hand held mic only. I did this test
>>> several times to make sure I was not confusing things.
>>>
>>> I discovered something else that I did not know before. PTT is actuated
>> by
>>> any of the methods of PTT. So, when I thought I had the headphones
>> CM500
>>> mic enabled I used my foot switch for push to talk and since that worked
>> for
>>> some dumb reason I was thinking I had successfully switched from front
>> panel
>>> to rear panel. But, I had not. I also discovered that I could use the
>> hand
>>> mic (front panel) PTT switch even though my rear panel mic was being
>> used.
>>> Now, after I discovered this, I realize that it is obvious but something
>>> that lead to my confusion.
>>>
>>> So, the problem occurs on the FRONT PANEL mic only and not the rear
>> panel.
>>> And, the problem occurs when the K3 is in TOTAL isolation from all AC
>>> sources except for possibly me. I mean, I am holding the mic but then I
>>> don't think that is a cause of the hum because I tried it with a
>> insulated
>>> hand and it still caused the hum on the front panel mic.
>>>
>>> I doubt that this is caused by wall-outlet type AC because I have erased
>> all
>>> AC for some of my tests. And, besides, this problem seemed to occur
>> ....
>>>
>>> OK, while writing that last sentence something occurred to me. Another
>>> change I had made on Wednesday after I had my good audio reports on the
>> MH2
>>> front panel mic was that I set the configuration for the band specific
>> power
>>> levels to work with the KPA500. So, I just now went to test the mic and
>>> change that setting around but the hum is gone.
>>>
>>> I repeat, the hum is gone from the front panel mic. I now can't test
>> the
>>> band specific power menu setting because I have no problem.
>>>
>>> But, I have a suspicion as to the cause now and I am going to do some
>> other
>>> experiments.
>>>
>>> 73, phil
>>>
>>
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riese-k3djc

Re: K3 Hum on Audio...

In reply to this post by Phil Hystad-3

On Fri, 13 Jan 2012 12:26:47 -0800 Phil Hystad <[hidden email]> writes:

> bob,
>
> I am not sure if you understand my previous problems I was
> reporting. The hum has nothing to do with the mic plugged into the
> K3 or not (obvious if the mic is not plugged in, there is no
> problems). But, the hum comes with PTT transmit and not merely
> because the mic is plugged in.
>
> But, for some unusual reason, the hum is no longer there. But I
> fear it is waiting out there, maybe in the greenbelt behind our
> house, to make a sneak attack when I least expect it.
>

Those evil north Koreans
Har

GL on your fixing the problem,,, been there done that

Bob K3DJC

73, phil

>
>
> On Jan 13, 2012, at 12:09 PM, [hidden email] wrote:
>
> > so you unplug the mike input to K3 the hum goes away
> > when you plug into the K3 mike input the hum is there ?
> > I would think you have a bad mike/cord/connecter
> >
> > Bob K3DJC
> >
> > On Fri, 13 Jan 2012 11:31:38 -0800 Phil Hystad <[hidden email]>
> writes:
> >> Ron,
> >>
> >> Well, I just had a quick SSB chat with Clyde (AA7WC) (pre Noon
> Time
> >> net on 40 meters) and asked specifically for audio report with
> >> possible hum. His report was no hum, clear good sounding audio,
>
> >> with S7 signal.
> >>
> >> So I am suspicious of my florescent lights in the garage although
>
> >> they are on right now with no hum. I am thinking though that
> maybe
> >> there is something intermittent with those lights. But, then
> again,
> >> the "something loose in the mic cord" maybe be the cause too.
> But,
> >> I jiggled that cord and connection and so on quite vigorously
> before
> >> when I had the hum and it did not change the hum status. Then,
> when
> >> the hum disappeared, I did those jiggle the cord and connector on
>
> >> the mic tests again and the hum DID NOT come back.
> >>
> >> Wow, I can't believe I have spent the entire morning fooling
> around
> >> with this. I even called into work and said that I was not
> coming
> >> in today just to work on this problem. I don't really want to go
>
> >> outside anyway despite that the temperature has now risen to a
> >> toasty 36 degrees.
> >>
> >> 73, phil, K7PEH
> >>
> >>
> >> On Jan 13, 2012, at 11:23 AM, Ron D'Eau Claire wrote:
> >>
> >>> Good luck Phil. That last part really suggests something loose
> in
> >> the mike
> >>> cord as I suggested at first.
> >>>
> >>> Ron AC7AC
> >>>
> >>> -----Original Message-----
> >>> Ron,
> >>>
> >>> OK, now it appears I was mistaken when I said that that the hum
>
> >> was in both
> >>> mics. I think I flubbed something up in my previous test due to
>
> >> the way
> >>> that the macros are assigned to keys which led me to thinking
> that
> >> the hum
> >>> occurred in both mics. But, I learned something in this...
> >>>
> >>> One, don't try to use one of your macro assigned keys (in my
> case
> >> M2 and M1)
> >>> while in the menu because that merely reassigns the key to the
> new
> >> menu
> >>> entry. I made this mistake several times this morning. But,
> when
> >> I
> >>> discovered it and then reset my macro definitions, I
> rediscovered
> >> that the
> >>> HUM occurs in the front panel MH2 hand held mic only. I did
> this
> >> test
> >>> several times to make sure I was not confusing things.
> >>>
> >>> I discovered something else that I did not know before. PTT is
>
> >> actuated by
> >>> any of the methods of PTT. So, when I thought I had the
> >> headphones CM500
> >>> mic enabled I used my foot switch for push to talk and since
> that
> >> worked for
> >>> some dumb reason I was thinking I had successfully switched from
>
> >> front panel
> >>> to rear panel. But, I had not. I also discovered that I could
>
> >> use the hand
> >>> mic (front panel) PTT switch even though my rear panel mic was
> >> being used.
> >>> Now, after I discovered this, I realize that it is obvious but
> >> something
> >>> that lead to my confusion.
> >>>
> >>> So, the problem occurs on the FRONT PANEL mic only and not the
> >> rear panel.
> >>> And, the problem occurs when the K3 is in TOTAL isolation from
> all
> >> AC
> >>> sources except for possibly me. I mean, I am holding the mic
> but
> >> then I
> >>> don't think that is a cause of the hum because I tried it with a
>
> >> insulated
> >>> hand and it still caused the hum on the front panel mic.
> >>>
> >>> I doubt that this is caused by wall-outlet type AC because I
> have
> >> erased all
> >>> AC for some of my tests. And, besides, this problem seemed to
> >> occur ....
> >>>
> >>> OK, while writing that last sentence something occurred to me.
>
> >> Another
> >>> change I had made on Wednesday after I had my good audio reports
>
> >> on the MH2
> >>> front panel mic was that I set the configuration for the band
> >> specific power
> >>> levels to work with the KPA500. So, I just now went to test the
>
> >> mic and
> >>> change that setting around but the hum is gone.
> >>>
> >>> I repeat, the hum is gone from the front panel mic. I now
> can't
> >> test the
> >>> band specific power menu setting because I have no problem.
> >>>
> >>> But, I have a suspicion as to the cause now and I am going to do
>
> >> some other
> >>> experiments.
> >>>
> >>> 73, phil
> >>>
> >>
> >> ______________________________________________________________
> >> 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
> >>
> >>
> >
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Jim Brown-10

Re: K3 Hum on Audio...

In reply to this post by Phil Hystad-3

On 1/13/2012 10:30 AM, Phil Hystad wrote:
> I disconnected EVERYTHING. Nothing on the back panel of the K3 at all except for a Li-nano-phosphate battery as my power source.

Was your antenna connected? If so, where is the coax shield connected
to ANYTHING -- the earth, other gear, at a tower, etc.? These are all
paths for AC leakage current, and your K3 can be in that path.

> All AC off at the breaker panel for this room. The only electrical equipment on was my K3 via the battery and my Macbook Pro laptop via its battery.
>
> Given those conditions, the hum was still there.
>
> Jim Brown suggested that I consider TXEQ to cut off the low frequencies, I did max cut for all frequencies up to 400 Hz. The hum did not start being attenuated until 400 Hz cut. But, max cut on 400 Hz did not attenuate it completely. I did not do higher frequencies.

Then what you have is BUZZ, NOT HUM. HUM would be affected ONLY by the
60 Hz frequency band. The coupling mechanisms are entirely different.
That's why it was my first question!

BUZZ is leakage current from the AC mains power, OR, as Ron suggested, a
flaky shield connection of the mic. BUZZ is almost never due to
magnetic coupling, so magnetic shielding doesn't matter. What DOES
matter is ELECTRIC shielding, which is what the cable shield provides.
And MAIN thing that matters is BONDING -- CHASSIS TO CHASSIS, and from
the combination of those chassis to the station ground, AND to the power
system ground.

Study http://audiosystemsgroup.com/HamInterfacing.pdf

73, Jim Brown K9YC
______________________________________________________________
Elecraft mailing list
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Phil Hystad-3

Re: K3 Hum on Audio...

Jim,

In answer to your first question below, that particular test NOTHING was connected other then the battery to provide power. That included the antenna.

I will read your paper -- maybe it will describe hum and buzz as to how they sound different. If you know of a good audio stream available on the web maybe I can listen to that. But, audio is definitely not a strong suit for me and this is the first time I have heard of a distinction in buzz and hum. I don't mean that I haven't heard of different kinds of hum or buzz, just that I didn't know that the terms had been so precisely defined.

However, the good news is that the problem no longer occurs (as I had mentioned in a previous post). Not sure of the cause though but I am heavily leaning towards some kind of loose connection or other electro-mechanical problem with the mic itself (or its connector to the K3). That seems to be the only source so far that can meet the requirements of all the tests that I did.

73, phil

On Jan 13, 2012, at 2:11 PM, Jim Brown wrote:

> On 1/13/2012 10:30 AM, Phil Hystad wrote:
>> I disconnected EVERYTHING. Nothing on the back panel of the K3 at all except for a Li-nano-phosphate battery as my power source.
>
> Was your antenna connected? If so, where is the coax shield connected
> to ANYTHING -- the earth, other gear, at a tower, etc.? These are all
> paths for AC leakage current, and your K3 can be in that path.
>
>> All AC off at the breaker panel for this room. The only electrical equipment on was my K3 via the battery and my Macbook Pro laptop via its battery.
>>
>> Given those conditions, the hum was still there.
>>
>> Jim Brown suggested that I consider TXEQ to cut off the low frequencies, I did max cut for all frequencies up to 400 Hz. The hum did not start being attenuated until 400 Hz cut. But, max cut on 400 Hz did not attenuate it completely. I did not do higher frequencies.
>
> Then what you have is BUZZ, NOT HUM. HUM would be affected ONLY by the
> 60 Hz frequency band. The coupling mechanisms are entirely different.
> That's why it was my first question!
>
> BUZZ is leakage current from the AC mains power, OR, as Ron suggested, a
> flaky shield connection of the mic. BUZZ is almost never due to
> magnetic coupling, so magnetic shielding doesn't matter. What DOES
> matter is ELECTRIC shielding, which is what the cable shield provides.
> And MAIN thing that matters is BONDING -- CHASSIS TO CHASSIS, and from
> the combination of those chassis to the station ground, AND to the power
> system ground.
>
> Study http://audiosystemsgroup.com/HamInterfacing.pdf
>
> 73, Jim Brown 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

Guy, K2AV

Re: K3 Hum on Audio...

In reply to this post by Jim Brown-10

Let's call it buzz. If it was AC power hum the main components would be
60, 120 and 180 Hz. Cutting 400 Hz and below would have made it
significantly better. When the K3 is running on batteries without ANY
mikes and other connections, it has NO way to produce 60/120/180 Hz related
to AC house voltage. (I am PRESUMING that your batteries did not have a
charger running on them, or long leads. Anything connected to the charger
is connected to the K3.) It DOES have misc low level processing artifacts
that are normally so far down as to be covered up by the normal noise
levels of anything coming in on audio inputs at routine levels.

That said, what you have sounds more like gain gone to maximum looking for
input when power level has never been defined, or has had all prior data
wiped. Especially if compression is set to max, you will now have many
dB's of amplification in force as the rig attempts to provide 100 watts of
output with no power level or mic gain defined.

Once you set yourself to something less than wide open on all bands and
modes and inputs, and your compression to a realistic level that matches
your voice and microphones, it will no longer be running "open gain" and
amplifying internal circuit noise (always present in ANY electronic gear)
to audible levels.

73, Guy.

On Fri, Jan 13, 2012 at 5:11 PM, Jim Brown <[hidden email]>wrote:

> On 1/13/2012 10:30 AM, Phil Hystad wrote:
> > I disconnected EVERYTHING. Nothing on the back panel of the K3 at all
> except for a Li-nano-phosphate battery as my power source.
>
> Was your antenna connected? If so, where is the coax shield connected
> to ANYTHING -- the earth, other gear, at a tower, etc.? These are all
> paths for AC leakage current, and your K3 can be in that path.
>
> > All AC off at the breaker panel for this room. The only electrical
> equipment on was my K3 via the battery and my Macbook Pro laptop via its
> battery.
> >
> > Given those conditions, the hum was still there.
> >
> > Jim Brown suggested that I consider TXEQ to cut off the low frequencies,
> I did max cut for all frequencies up to 400 Hz. The hum did not start
> being attenuated until 400 Hz cut. But, max cut on 400 Hz did not
> attenuate it completely. I did not do higher frequencies.
>
> Then what you have is BUZZ, NOT HUM. HUM would be affected ONLY by the
> 60 Hz frequency band. The coupling mechanisms are entirely different.
> That's why it was my first question!
>
> BUZZ is leakage current from the AC mains power, OR, as Ron suggested, a
> flaky shield connection of the mic. BUZZ is almost never due to
> magnetic coupling, so magnetic shielding doesn't matter. What DOES
> matter is ELECTRIC shielding, which is what the cable shield provides.
> And MAIN thing that matters is BONDING -- CHASSIS TO CHASSIS, and from
> the combination of those chassis to the station ground, AND to the power
> system ground.
>
> Study http://audiosystemsgroup.com/HamInterfacing.pdf
>
> 73, Jim Brown 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
>

Phil Hystad-3

Re: K3 Hum on Audio...

Guy,

Thanks for the comments. Later on I might experiment to see if I can purposely reproduce the buzz by methods you mention.

Yes, my test condition was using ABSOLUTELY no AC and no nearby AC or AC artifacts. No charger on the battery but then again I had AC switched off at the breaker panel during those tests. The leads on the batter were about 4 inches long. The battery by the way was a 4S1P configuration (4 individual cells) producing 1.38 volts of A123 Systems Lithium Nano-Phosphate battery available for lots of money from Buddipole. I like them so much, I am planning on buying more.

phil

On Jan 13, 2012, at 2:34 PM, Guy Olinger K2AV wrote:

> Let's call it buzz. If it was AC power hum the main components would be
> 60, 120 and 180 Hz. Cutting 400 Hz and below would have made it
> significantly better. When the K3 is running on batteries without ANY
> mikes and other connections, it has NO way to produce 60/120/180 Hz related
> to AC house voltage. (I am PRESUMING that your batteries did not have a
> charger running on them, or long leads. Anything connected to the charger
> is connected to the K3.) It DOES have misc low level processing artifacts
> that are normally so far down as to be covered up by the normal noise
> levels of anything coming in on audio inputs at routine levels.
>
> That said, what you have sounds more like gain gone to maximum looking for
> input when power level has never been defined, or has had all prior data
> wiped. Especially if compression is set to max, you will now have many
> dB's of amplification in force as the rig attempts to provide 100 watts of
> output with no power level or mic gain defined.
>
> Once you set yourself to something less than wide open on all bands and
> modes and inputs, and your compression to a realistic level that matches
> your voice and microphones, it will no longer be running "open gain" and
> amplifying internal circuit noise (always present in ANY electronic gear)
> to audible levels.
>
> 73, Guy.
>
> On Fri, Jan 13, 2012 at 5:11 PM, Jim Brown <[hidden email]>wrote:
>
>> On 1/13/2012 10:30 AM, Phil Hystad wrote:
>>> I disconnected EVERYTHING. Nothing on the back panel of the K3 at all
>> except for a Li-nano-phosphate battery as my power source.
>>
>> Was your antenna connected? If so, where is the coax shield connected
>> to ANYTHING -- the earth, other gear, at a tower, etc.? These are all
>> paths for AC leakage current, and your K3 can be in that path.
>>
>>> All AC off at the breaker panel for this room. The only electrical
>> equipment on was my K3 via the battery and my Macbook Pro laptop via its
>> battery.
>>>
>>> Given those conditions, the hum was still there.
>>>
>>> Jim Brown suggested that I consider TXEQ to cut off the low frequencies,
>> I did max cut for all frequencies up to 400 Hz. The hum did not start
>> being attenuated until 400 Hz cut. But, max cut on 400 Hz did not
>> attenuate it completely. I did not do higher frequencies.
>>
>> Then what you have is BUZZ, NOT HUM. HUM would be affected ONLY by the
>> 60 Hz frequency band. The coupling mechanisms are entirely different.
>> That's why it was my first question!
>>
>> BUZZ is leakage current from the AC mains power, OR, as Ron suggested, a
>> flaky shield connection of the mic. BUZZ is almost never due to
>> magnetic coupling, so magnetic shielding doesn't matter. What DOES
>> matter is ELECTRIC shielding, which is what the cable shield provides.
>> And MAIN thing that matters is BONDING -- CHASSIS TO CHASSIS, and from
>> the combination of those chassis to the station ground, AND to the power
>> system ground.
>>
>> Study http://audiosystemsgroup.com/HamInterfacing.pdf
>>
>> 73, Jim Brown 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
>>
> ______________________________________________________________
> 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

Phil Hystad-3

Re: K3 Hum on Audio...

Please multiply the voltage by 10 in the sentence below where I am describing the battery. I think I rushed to quickly to drop in that decimal point.

And, thanks for all the help and comments from others. I always learn a lot in these trials.

phil

On Jan 13, 2012, at 2:41 PM, Phil Hystad wrote:

> Guy,
>
> Thanks for the comments. Later on I might experiment to see if I can purposely reproduce the buzz by methods you mention.
>
> Yes, my test condition was using ABSOLUTELY no AC and no nearby AC or AC artifacts. No charger on the battery but then again I had AC switched off at the breaker panel during those tests. The leads on the batter were about 4 inches long. The battery by the way was a 4S1P configuration (4 individual cells) producing 1.38 volts of A123 Systems Lithium Nano-Phosphate battery available for lots of money from Buddipole. I like them so much, I am planning on buying more.
>
> phil
>
>
> On Jan 13, 2012, at 2:34 PM, Guy Olinger K2AV wrote:
>
>> Let's call it buzz. If it was AC power hum the main components would be
>> 60, 120 and 180 Hz. Cutting 400 Hz and below would have made it
>> significantly better. When the K3 is running on batteries without ANY
>> mikes and other connections, it has NO way to produce 60/120/180 Hz related
>> to AC house voltage. (I am PRESUMING that your batteries did not have a
>> charger running on them, or long leads. Anything connected to the charger
>> is connected to the K3.) It DOES have misc low level processing artifacts
>> that are normally so far down as to be covered up by the normal noise
>> levels of anything coming in on audio inputs at routine levels.
>>
>> That said, what you have sounds more like gain gone to maximum looking for
>> input when power level has never been defined, or has had all prior data
>> wiped. Especially if compression is set to max, you will now have many
>> dB's of amplification in force as the rig attempts to provide 100 watts of
>> output with no power level or mic gain defined.
>>
>> Once you set yourself to something less than wide open on all bands and
>> modes and inputs, and your compression to a realistic level that matches
>> your voice and microphones, it will no longer be running "open gain" and
>> amplifying internal circuit noise (always present in ANY electronic gear)
>> to audible levels.
>>
>> 73, Guy.
>>
>> On Fri, Jan 13, 2012 at 5:11 PM, Jim Brown <[hidden email]>wrote:
>>
>>> On 1/13/2012 10:30 AM, Phil Hystad wrote:
>>>> I disconnected EVERYTHING. Nothing on the back panel of the K3 at all
>>> except for a Li-nano-phosphate battery as my power source.
>>>
>>> Was your antenna connected? If so, where is the coax shield connected
>>> to ANYTHING -- the earth, other gear, at a tower, etc.? These are all
>>> paths for AC leakage current, and your K3 can be in that path.
>>>
>>>> All AC off at the breaker panel for this room. The only electrical
>>> equipment on was my K3 via the battery and my Macbook Pro laptop via its
>>> battery.
>>>>
>>>> Given those conditions, the hum was still there.
>>>>
>>>> Jim Brown suggested that I consider TXEQ to cut off the low frequencies,
>>> I did max cut for all frequencies up to 400 Hz. The hum did not start
>>> being attenuated until 400 Hz cut. But, max cut on 400 Hz did not
>>> attenuate it completely. I did not do higher frequencies.
>>>
>>> Then what you have is BUZZ, NOT HUM. HUM would be affected ONLY by the
>>> 60 Hz frequency band. The coupling mechanisms are entirely different.
>>> That's why it was my first question!
>>>
>>> BUZZ is leakage current from the AC mains power, OR, as Ron suggested, a
>>> flaky shield connection of the mic. BUZZ is almost never due to
>>> magnetic coupling, so magnetic shielding doesn't matter. What DOES
>>> matter is ELECTRIC shielding, which is what the cable shield provides.
>>> And MAIN thing that matters is BONDING -- CHASSIS TO CHASSIS, and from
>>> the combination of those chassis to the station ground, AND to the power
>>> system ground.
>>>
>>> Study http://audiosystemsgroup.com/HamInterfacing.pdf
>>>
>>> 73, Jim Brown 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
>>>
>> ______________________________________________________________
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>> Post: mailto:[hidden email]
>>
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>
> ______________________________________________________________
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>
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N2TK

Re: K3 Hum on Audio...

In reply to this post by Phil Hystad-3

Make sure the LIN IN is not turned up. Early on I had a problem with hum in
my audio, especially if an amp was close to the K3. For some reason my LIN
IN was at max. Turned it down and hum went away.
73,
N2TK, Tony

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Phil Hystad
Sent: Friday, January 13, 2012 12:54 PM
To: [hidden email]
Cc: [hidden email]
Subject: Re: [Elecraft] K3 Hum on Audio...

Jim,

Well, I would call it mostly a buzz. Also, the only near magnetic field of
the KPA500 power transformer is off, I mean powered off and unplugged, so
that does not seem to be the problem.

I just ran another test with everything disconnected, including ground and
coax. With the K3 in TEST mode, key-down on the mic still produces the hum.
I double checked the grounds. I did this because if I were to touch
anything metal on the k3, the metal part of the PL259 or the ground strap,
the hum is damped quite a bit to almost insignificant. It seems that if my
rig were already well grounded this would not happen so I am curious if this
is something I would normally expect.

I will experiment with the TXEQ but this is a real puzzle I would like to
solve, not merely erase it.

73, phil

On Jan 13, 2012, at 9:37 AM, Jim Brown wrote:

> On 1/13/2012 9:20 AM, Phil Hystad wrote:
>> Unfortunately, it is in both mics but not as strong in the Yamaha CM500
mic as in the MH2 but it is present.

>
> Clarification question. Is it HUM (pure 60 Hz), or BUZZ (mostly
> harmonics of 60 Hz)? If it's HUM, I would suspect magnetic field
> coupling into the audio, either from a big power transformer (like the
> one in a power amp or a big linear power supply) or from a AC power
> wiring fault called a double-bonded neutral.
>
> The K3 has unshielded audio transformers at all the audio inputs and
> outputs, and an unshielded transformer is a sitting duck for magnetic
> fields.
>
> The good news is that the K3 has excellent audio equalization (TXEQ)
> that allows us to remove that 60 Hz hum by filtering. The lower audio
> frequencies in the human voice make NO useful contribution to speech
> intelligibility, but they do waste transmit power. So it is ALWAYS a
> good thing to set the TXEQ for maximum cut of the lowest two bands,
> and at least some cut of the third band. This is true with virtually
> ALL mics and ALL voices. AND it will reduce that hum enough that you
> may no longer hear it.
>
> There are several solutions to magnetic field coupling. 1) Rotate the
> noise source or the victim circuit to put the fields at right angles
> to the victim. 2) Move the noise source further from the victim. 3)
> If the hum field is produced by that AC power wiring error, fix the
> error to eliminate the field.
>
> 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

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Post: mailto:[hidden email]

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K6LMP

Re: K3 Hum on Audio...

Thank you, Tony!

I had developed a maddening audio hum suddenly, and couldn't find the cause. The curious thing was that it was WORSE when no mike was plugged into the jack on the back panel.

Based on your email, I checked the menu settings. Sure enough, MIC + LINE: ON. Switched to OFF and the hum totally disappeared. You don't need to adjust the LIN volume; just cut it off entirely.

Lew K6LMP

On Jan 14, 2012, at 9:02 AM, N2TK, Tony wrote:

> Make sure the LIN IN is not turned up. Early on I had a problem with hum in
> my audio, especially if an amp was close to the K3. For some reason my LIN
> IN was at max. Turned it down and hum went away.
> 73,
> N2TK, Tony
>
> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Phil Hystad
> Sent: Friday, January 13, 2012 12:54 PM
> To: [hidden email]
> Cc: [hidden email]
> Subject: Re: [Elecraft] K3 Hum on Audio...
>
> Jim,
>
> Well, I would call it mostly a buzz. Also, the only near magnetic field of
> the KPA500 power transformer is off, I mean powered off and unplugged, so
> that does not seem to be the problem.
>
> I just ran another test with everything disconnected, including ground and
> coax. With the K3 in TEST mode, key-down on the mic still produces the hum.
> I double checked the grounds. I did this because if I were to touch
> anything metal on the k3, the metal part of the PL259 or the ground strap,
> the hum is damped quite a bit to almost insignificant. It seems that if my
> rig were already well grounded this would not happen so I am curious if this
> is something I would normally expect.
>
> I will experiment with the TXEQ but this is a real puzzle I would like to
> solve, not merely erase it.
>
> 73, phil
>
>
> On Jan 13, 2012, at 9:37 AM, Jim Brown wrote:
>
>> On 1/13/2012 9:20 AM, Phil Hystad wrote:
>>> Unfortunately, it is in both mics but not as strong in the Yamaha CM500
> mic as in the MH2 but it is present.
>>
>> Clarification question. Is it HUM (pure 60 Hz), or BUZZ (mostly
>> harmonics of 60 Hz)? If it's HUM, I would suspect magnetic field
>> coupling into the audio, either from a big power transformer (like the
>> one in a power amp or a big linear power supply) or from a AC power
>> wiring fault called a double-bonded neutral.
>>
>> The K3 has unshielded audio transformers at all the audio inputs and
>> outputs, and an unshielded transformer is a sitting duck for magnetic
>> fields.
>>
>> The good news is that the K3 has excellent audio equalization (TXEQ)
>> that allows us to remove that 60 Hz hum by filtering. The lower audio
>> frequencies in the human voice make NO useful contribution to speech
>> intelligibility, but they do waste transmit power. So it is ALWAYS a
>> good thing to set the TXEQ for maximum cut of the lowest two bands,
>> and at least some cut of the third band. This is true with virtually
>> ALL mics and ALL voices. AND it will reduce that hum enough that you
>> may no longer hear it.
>>
>> There are several solutions to magnetic field coupling. 1) Rotate the
>> noise source or the victim circuit to put the fields at right angles
>> to the victim. 2) Move the noise source further from the victim. 3)
>> If the hum field is produced by that AC power wiring error, fix the
>> error to eliminate the field.
>>
>> 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
>
> ______________________________________________________________
> 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
>
> ______________________________________________________________
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> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
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>
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Dick Williams-2

Re: K3 Hum on Audio...

In reply to this post by Phil Hystad-3

This is a "common" problem when a amplifer is placed next to the left side of the K3 (especially if the transformer in the amp is on the rigt side - like the Alpha amps).

The problem is caused because the K3 line in has a isolation transformer conveniently located on the left side. Place a power transformer next to it, and all hell breaks loose (something to do with the magnetic lines of force interacting).

It took me a few hours of contemplating and experimenting to figure this out. If someone has come up with a easy "fix", please let me know. I tried buying a steel plate (alum will definitely not work) at Home Depot and placed that between the K3 and amp; it did nothing to fix the problem (or even help). One sure fire fix is to turn off the amp!

Dick K8ZTT

--- [hidden email] wrote:

From: Lew Phelps K6LMP <[hidden email]>
To: "[hidden email] List" <[hidden email]>
Subject: Re: [Elecraft] K3 Hum on Audio...
Date: Thu, 02 Feb 2012 10:24:07 -0800

Thank you, Tony!

I had developed a maddening audio hum suddenly, and couldn't find the cause. The curious thing was that it was WORSE when no mike was plugged into the jack on the back panel.

Based on your email, I checked the menu settings. Sure enough, MIC + LINE: ON. Switched to OFF and the hum totally disappeared. You don't need to adjust the LIN volume; just cut it off entirely.

Lew K6LMP

On Jan 14, 2012, at 9:02 AM, N2TK, Tony wrote:

Guy, K2AV

Re: K3 Hum on Audio...

This is an endemic "uncurable" problem. By uncurable, I mean there is
no reasonable way to shield or "cure" it. There is nothing WRONG with
either the amp or the K3. It has the same issues as an over/under
refrigerator-stove combination. They just don't belong together, and
a carefully laid out kitchen design would never have things arranged
that way.

Redo your station layout. And while you're redesigning, figure out
how to NOT run your RF connections past your computer, or your RF
connections anywhere in parallel with the computer connections to any
of your radio gear.

We used to have this problem with amps next to CRT monitors causing a
very irritating constant wiggle in the display. LED flat monitors
fixed that. But isolation transformers and amplifier primary power
transformers are going to be with us for the long haul.,

Good luck and 73, Guy.

On Fri, Feb 3, 2012 at 3:21 PM, <[hidden email]> wrote:

> This is a "common" problem when a amplifer is placed next to the left side of the K3 (especially if the transformer in the amp is on the rigt side - like the Alpha amps).
>
> The problem is caused because the K3 line in has a isolation transformer conveniently located on the left side. Place a power transformer next to it, and all hell breaks loose (something to do with the magnetic lines of force interacting).
>
> It took me a few hours of contemplating and experimenting to figure this out. If someone has come up with a easy "fix", please let me know. I tried buying a steel plate (alum will definitely not work) at Home Depot and placed that between the K3 and amp; it did nothing to fix the problem (or even help). One sure fire fix is to turn off the amp!
>
> Dick K8ZTT
>
>
>
>
> --- [hidden email] wrote:
>
> From: Lew Phelps K6LMP <[hidden email]>
> To: "[hidden email] List" <[hidden email]>
> Subject: Re: [Elecraft] K3 Hum on Audio...
> Date: Thu, 02 Feb 2012 10:24:07 -0800
>
> Thank you, Tony!
>
> I had developed a maddening audio hum suddenly, and couldn't find the cause. The curious thing was that it was WORSE when no mike was plugged into the jack on the back panel.
>
> Based on your email, I checked the menu settings. Sure enough, MIC + LINE: ON. Switched to OFF and the hum totally disappeared. You don't need to adjust the LIN volume; just cut it off entirely.
>
> Lew K6LMP
>
>
> On Jan 14, 2012, at 9:02 AM, N2TK, Tony wrote:
>
>> Make sure the LIN IN is not turned up. Early on I had a problem with hum in
>> my audio, especially if an amp was close to the K3. For some reason my LIN
>> IN was at max. Turned it down and hum went away.
>> 73,
>> N2TK, Tony
>>
>> -----Original Message-----
>> From: [hidden email]
>> [mailto:[hidden email]] On Behalf Of Phil Hystad
>> Sent: Friday, January 13, 2012 12:54 PM
>> To: [hidden email]
>> Cc: [hidden email]
>> Subject: Re: [Elecraft] K3 Hum on Audio...
>>
>> Jim,
>>
>> Well, I would call it mostly a buzz. Also, the only near magnetic field of
>> the KPA500 power transformer is off, I mean powered off and unplugged, so
>> that does not seem to be the problem.
>>
>> I just ran another test with everything disconnected, including ground and
>> coax. With the K3 in TEST mode, key-down on the mic still produces the hum.
>> I double checked the grounds. I did this because if I were to touch
>> anything metal on the k3, the metal part of the PL259 or the ground strap,
>> the hum is damped quite a bit to almost insignificant. It seems that if my
>> rig were already well grounded this would not happen so I am curious if this
>> is something I would normally expect.
>>
>> I will experiment with the TXEQ but this is a real puzzle I would like to
>> solve, not merely erase it.
>>
>> 73, phil
>>
>>
>> On Jan 13, 2012, at 9:37 AM, Jim Brown wrote:
>>
>>> On 1/13/2012 9:20 AM, Phil Hystad wrote:
>>>> Unfortunately, it is in both mics but not as strong in the Yamaha CM500
>> mic as in the MH2 but it is present.
>>>
>>> Clarification question. Is it HUM (pure 60 Hz), or BUZZ (mostly
>>> harmonics of 60 Hz)? If it's HUM, I would suspect magnetic field
>>> coupling into the audio, either from a big power transformer (like the
>>> one in a power amp or a big linear power supply) or from a AC power
>>> wiring fault called a double-bonded neutral.
>>>
>>> The K3 has unshielded audio transformers at all the audio inputs and
>>> outputs, and an unshielded transformer is a sitting duck for magnetic
>>> fields.
>>>
>>> The good news is that the K3 has excellent audio equalization (TXEQ)
>>> that allows us to remove that 60 Hz hum by filtering. The lower audio
>>> frequencies in the human voice make NO useful contribution to speech
>>> intelligibility, but they do waste transmit power. So it is ALWAYS a
>>> good thing to set the TXEQ for maximum cut of the lowest two bands,
>>> and at least some cut of the third band. This is true with virtually
>>> ALL mics and ALL voices. AND it will reduce that hum enough that you
>>> may no longer hear it.
>>>
>>> There are several solutions to magnetic field coupling. 1) Rotate the
>>> noise source or the victim circuit to put the fields at right angles
>>> to the victim. 2) Move the noise source further from the victim. 3)
>>> If the hum field is produced by that AC power wiring error, fix the
>>> error to eliminate the field.
>>>
>>> 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
>>
>> ______________________________________________________________
>> 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
>>
>> ______________________________________________________________
>> 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
>
> ______________________________________________________________
> 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
>
>
> ______________________________________________________________
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> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
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Alan Bloom

Re: K3 Hum on Audio...

In reply to this post by Dick Williams-2

One trick I have used in the past is to put a copper strap around the
transformer. It acts as a shorted turn for the radiated fields,
reducing their amplitude. You could try that both on the power
transformer and on the audio transformer in the K3. Of course, the
strap needs to be soldered so it makes a continuous loop.

Alan N1AL

On Fri, 2012-02-03 at 12:21 -0800, [hidden email] wrote:

> This is a "common" problem when a amplifer is placed next to the left
> side of the K3 (especially if the transformer in the amp is on the
> rigt side - like the Alpha amps).
>
> The problem is caused because the K3 line in has a isolation
> transformer conveniently located on the left side. Place a power
> transformer next to it, and all hell breaks loose (something to do
> with the magnetic lines of force interacting).
>
> It took me a few hours of contemplating and experimenting to figure
> this out. If someone has come up with a easy "fix", please let me
> know. I tried buying a steel plate (alum will definitely not work) at
> Home Depot and placed that between the K3 and amp; it did nothing to
> fix the problem (or even help). One sure fire fix is to turn off the
> amp!
>
> Dick K8ZTT
>
>
>
>
> --- [hidden email] wrote:
>
> From: Lew Phelps K6LMP <[hidden email]>
> To: "[hidden email] List" <[hidden email]>
> Subject: Re: [Elecraft] K3 Hum on Audio...
> Date: Thu, 02 Feb 2012 10:24:07 -0800
>
> Thank you, Tony!
>
> I had developed a maddening audio hum suddenly, and couldn't find the cause. The curious thing was that it was WORSE when no mike was plugged into the jack on the back panel.
>
> Based on your email, I checked the menu settings. Sure enough, MIC + LINE: ON. Switched to OFF and the hum totally disappeared. You don't need to adjust the LIN volume; just cut it off entirely.
>
> Lew K6LMP
>
>
> On Jan 14, 2012, at 9:02 AM, N2TK, Tony wrote:
>
> > Make sure the LIN IN is not turned up. Early on I had a problem with hum in
> > my audio, especially if an amp was close to the K3. For some reason my LIN
> > IN was at max. Turned it down and hum went away.
> > 73,
> > N2TK, Tony
> >
> > -----Original Message-----
> > From: [hidden email]
> > [mailto:[hidden email]] On Behalf Of Phil Hystad
> > Sent: Friday, January 13, 2012 12:54 PM
> > To: [hidden email]
> > Cc: [hidden email]
> > Subject: Re: [Elecraft] K3 Hum on Audio...
> >
> > Jim,
> >
> > Well, I would call it mostly a buzz. Also, the only near magnetic field of
> > the KPA500 power transformer is off, I mean powered off and unplugged, so
> > that does not seem to be the problem.
> >
> > I just ran another test with everything disconnected, including ground and
> > coax. With the K3 in TEST mode, key-down on the mic still produces the hum.
> > I double checked the grounds. I did this because if I were to touch
> > anything metal on the k3, the metal part of the PL259 or the ground strap,
> > the hum is damped quite a bit to almost insignificant. It seems that if my
> > rig were already well grounded this would not happen so I am curious if this
> > is something I would normally expect.
> >
> > I will experiment with the TXEQ but this is a real puzzle I would like to
> > solve, not merely erase it.
> >
> > 73, phil
> >
> >
> > On Jan 13, 2012, at 9:37 AM, Jim Brown wrote:
> >
> >> On 1/13/2012 9:20 AM, Phil Hystad wrote:
> >>> Unfortunately, it is in both mics but not as strong in the Yamaha CM500
> > mic as in the MH2 but it is present.
> >>
> >> Clarification question. Is it HUM (pure 60 Hz), or BUZZ (mostly
> >> harmonics of 60 Hz)? If it's HUM, I would suspect magnetic field
> >> coupling into the audio, either from a big power transformer (like the
> >> one in a power amp or a big linear power supply) or from a AC power
> >> wiring fault called a double-bonded neutral.
> >>
> >> The K3 has unshielded audio transformers at all the audio inputs and
> >> outputs, and an unshielded transformer is a sitting duck for magnetic
> >> fields.
> >>
> >> The good news is that the K3 has excellent audio equalization (TXEQ)
> >> that allows us to remove that 60 Hz hum by filtering. The lower audio
> >> frequencies in the human voice make NO useful contribution to speech
> >> intelligibility, but they do waste transmit power. So it is ALWAYS a
> >> good thing to set the TXEQ for maximum cut of the lowest two bands,
> >> and at least some cut of the third band. This is true with virtually
> >> ALL mics and ALL voices. AND it will reduce that hum enough that you
> >> may no longer hear it.
> >>
> >> There are several solutions to magnetic field coupling. 1) Rotate the
> >> noise source or the victim circuit to put the fields at right angles
> >> to the victim. 2) Move the noise source further from the victim. 3)
> >> If the hum field is produced by that AC power wiring error, fix the
> >> error to eliminate the field.
> >>
> >> 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
> >
> > ______________________________________________________________
> > 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
> >
> > ______________________________________________________________
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> > Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> > Post: mailto:[hidden email]
> >
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>
> ______________________________________________________________
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>
> ______________________________________________________________
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Jim Brown-10

Re: K3 Hum on Audio...

In reply to this post by Guy, K2AV

On 2/3/2012 12:43 PM, Guy Olinger K2AV wrote:
> This is an endemic "uncurable" problem.

Maybe not. One mechanism I suspect, based on the symptom that it
happens with the Line Input turned up, is magnetic coupling into the
unshielded audio transformer on the Line Input. That coupling is nearly
always pure 60 Hz, without harmonics, and is a well known problem.. In
data modes, the Line Input is rolled off sharply at some frequency like
200 Hz or so, which knocks the hum down by something like 18dB.. I
recommend doing that for SSB too, because the lower octaves carry no
intelligibility but can waste a lot of TX power.

The separation that matters this this case is the generator of the
magnetic field, usually the power transformer for a big power amp, but
it can also be caused by wiring errors in the power wiring in a home. It
can help a lot to rotate the amp to put its field at right angles to the
magnetic receiver (the audio transformer in the K3), and also to move it
further away from the K3.

As to RFI with lines running past a computer -- I had that issue in
Chicago, where I used a long wire antenna on 80 and 160, and it locked
up the serial connection. The culprit there was the K2 serial cable,
which used PARALLEL wires inside a shield. I replaced it with TWISTED
PAIRS without a shield, with one pair for each circuit used between the
computer and the rig, with the return for each pair going to the chassis
on each end, and the problem went away. With the original cable, it
locked up at 12 watts. With the twisted pair, I could run full power
from my Titan 425.

73, Jim K9YC
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Guy, K2AV

Re: K3 Hum on Audio...

Hi Jim,

For a price and/or sufficient work and enough expertise, it might be
possible to shield anything. There is that mu-metal stuff. But mostly
that level of induction from something pulling that much current into
microphone level devices is a really really hard cure, hence
"uncurable" in quotes. For equipment that is sold at ham-affordable
prices, and where most people do not have the problem, and it is a
layout choice, the level of shielding would seem a good commercial
choice by manufacturers.

Again, if one considers all these issues when one is CHOOSING one's
station layout, you really do not have to kick all those dogs and put
yourself in the position in the first place.

I WOULD expect YOU to be able to cobble something to make it work in
spite of a station layout that kicks the dogs. :>) But for the rest
of us for which that is endless experimenting and not necessarily
knowing WHICH detail of the fix we messed up when we tried it, not
kicking the dogs at all, when we don't have to, is a very profitable
direction.

73, Guy

On Fri, Feb 3, 2012 at 11:27 PM, Jim Brown <[hidden email]> wrote:

> On 2/3/2012 12:43 PM, Guy Olinger K2AV wrote:
>> This is an endemic "uncurable" problem.
>
> Maybe not. One mechanism I suspect, based on the symptom that it
> happens with the Line Input turned up, is magnetic coupling into the
> unshielded audio transformer on the Line Input. That coupling is nearly
> always pure 60 Hz, without harmonics, and is a well known problem.. In
> data modes, the Line Input is rolled off sharply at some frequency like
> 200 Hz or so, which knocks the hum down by something like 18dB.. I
> recommend doing that for SSB too, because the lower octaves carry no
> intelligibility but can waste a lot of TX power.
>
> The separation that matters this this case is the generator of the
> magnetic field, usually the power transformer for a big power amp, but
> it can also be caused by wiring errors in the power wiring in a home. It
> can help a lot to rotate the amp to put its field at right angles to the
> magnetic receiver (the audio transformer in the K3), and also to move it
> further away from the K3.
>
> As to RFI with lines running past a computer -- I had that issue in
> Chicago, where I used a long wire antenna on 80 and 160, and it locked
> up the serial connection. The culprit there was the K2 serial cable,
> which used PARALLEL wires inside a shield. I replaced it with TWISTED
> PAIRS without a shield, with one pair for each circuit used between the
> computer and the rig, with the return for each pair going to the chassis
> on each end, and the problem went away. With the original cable, it
> locked up at 12 watts. With the twisted pair, I could run full power
> from my Titan 425.
>
> 73, Jim K9YC
> ______________________________________________________________
> Elecraft mailing list
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> Please help support this email list: http://www.qsl.net/donate.html

Jim Brown-10

Re: K3 Hum on Audio...

On 2/3/2012 9:25 PM, Guy Olinger K2AV wrote:
> There is that mu-metal stuff. But mostly
> that level of induction from something pulling that much current into
> microphone level devices is a really really hard cure, hence
> "uncurable" in quotes.

From the symptoms, it was coming into the LINE INPUT -- he said the
Line Input was cranked up and he turned it down or off and cured the
problem.

Yes, mu-metal shielding cures the problem, but that's a lot more
expensive than what's in the radio. The real issue is that transformers
are the wrong solution. All that is needed is simple chassis-to-chassis
bonding between the equipment being interconnected. This sort of design
error is what happens when you assign digital guys to design audio
circuits. :)

73, Jim Brown K9YC
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Eric Buggee; VK3AX

Re: K3 Hum on Audio...

In reply to this post by Alan Bloom

Hi List Mates;
For those who may not be aware regarding the
copper strap around the transformer
(as Alan N1AL says) it acts as a shorted turn to external "H" fields
make sure that the copper strap goes around the OUTSIDE of the windings
as well as the core and NOT thru the window of the core where the
windings go otherwise you will introduce a dead short circuit to the
magnetic flux in the core which will short out the primary & blow the
mains fuse(s).

Another approach is to make up a magnetic shield of about 4 or 6 sheets
of 0.020" (0.5mm) thick transformer core lamination steel; each sheet
cut to about 6" (152.4 mm) square - or- the same size as the side panel
of the linear am side panel tape them together and fit them inside the
amp adjacent to the core of the power transformer- in particurlar if the
gap between the two halves of the "C" cores is facing toward the side of
the linear amp.

The sheets of transformer core steel will shunt the stray (leaking)
magnetic field emanating from the two faces of the "C) cores. Will work
the same for the junctions of the "E's & I's of a conventional E&I built
transformer (although there is more stray magnetic field from
transformers of E&I construction.
Lowest stray magnetic leakage is from transformers using toroidal core
construction.

Hope this information is of use.

Eric VK3AX. K34250.

On 2/4/2012 7:51 AM, Alan Bloom wrote:

> One trick I have used in the past is to put a copper strap around the
> transformer. It acts as a shorted turn for the radiated fields,
> reducing their amplitude. You could try that both on the power
> transformer and on the audio transformer in the K3. Of course, the
> strap needs to be soldered so it makes a continuous loop.
>
> Alan N1AL
>
>
> On Fri, 2012-02-03 at 12:21 -0800, [hidden email] wrote:
>> This is a "common" problem when a amplifer is placed next to the left
>> side of the K3 (especially if the transformer in the amp is on the
>> rigt side - like the Alpha amps).
>>
>> The problem is caused because the K3 line in has a isolation
>> transformer conveniently located on the left side. Place a power
>> transformer next to it, and all hell breaks loose (something to do
>> with the magnetic lines of force interacting).
>>
>> It took me a few hours of contemplating and experimenting to figure
>> this out. If someone has come up with a easy "fix", please let me
>> know. I tried buying a steel plate (alum will definitely not work) at
>> Home Depot and placed that between the K3 and amp; it did nothing to
>> fix the problem (or even help). One sure fire fix is to turn off the
>> amp!
>>
>> Dick K8ZTT
>>
>>
>>
>>
>> --- [hidden email] wrote:
>>
>> From: Lew Phelps K6LMP<[hidden email]>
>> To: "[hidden email] List"<[hidden email]>
>> Subject: Re: [Elecraft] K3 Hum on Audio...
>> Date: Thu, 02 Feb 2012 10:24:07 -0800
>>
>> Thank you, Tony!
>>
>> I had developed a maddening audio hum suddenly, and couldn't find the cause. The curious thing was that it was WORSE when no mike was plugged into the jack on the back panel.
>>
>> Based on your email, I checked the menu settings. Sure enough, MIC + LINE: ON. Switched to OFF and the hum totally disappeared. You don't need to adjust the LIN volume; just cut it off entirely.
>>
>> Lew K6LMP
>>
>>
>> On Jan 14, 2012, at 9:02 AM, N2TK, Tony wrote:
>>
>>> Make sure the LIN IN is not turned up. Early on I had a problem with hum in
>>> my audio, especially if an amp was close to the K3. For some reason my LIN
>>> IN was at max. Turned it down and hum went away.
>>> 73,
>>> N2TK, Tony
>>>
>>> -----Original Message-----
>>> From: [hidden email]
>>> [mailto:[hidden email]] On Behalf Of Phil Hystad
>>> Sent: Friday, January 13, 2012 12:54 PM
>>> To: [hidden email]
>>> Cc: [hidden email]
>>> Subject: Re: [Elecraft] K3 Hum on Audio...
>>>
>>> Jim,
>>>
>>> Well, I would call it mostly a buzz. Also, the only near magnetic field of
>>> the KPA500 power transformer is off, I mean powered off and unplugged, so
>>> that does not seem to be the problem.
>>>
>>> I just ran another test with everything disconnected, including ground and
>>> coax. With the K3 in TEST mode, key-down on the mic still produces the hum.
>>> I double checked the grounds. I did this because if I were to touch
>>> anything metal on the k3, the metal part of the PL259 or the ground strap,
>>> the hum is damped quite a bit to almost insignificant. It seems that if my
>>> rig were already well grounded this would not happen so I am curious if this
>>> is something I would normally expect.
>>>
>>> I will experiment with the TXEQ but this is a real puzzle I would like to
>>> solve, not merely erase it.
>>>
>>> 73, phil
>>>
>>>
>>> On Jan 13, 2012, at 9:37 AM, Jim Brown wrote:
>>>
>>>> On 1/13/2012 9:20 AM, Phil Hystad wrote:
>>>>> Unfortunately, it is in both mics but not as strong in the Yamaha CM500
>>> mic as in the MH2 but it is present.
>>>> Clarification question. Is it HUM (pure 60 Hz), or BUZZ (mostly
>>>> harmonics of 60 Hz)? If it's HUM, I would suspect magnetic field
>>>> coupling into the audio, either from a big power transformer (like the
>>>> one in a power amp or a big linear power supply) or from a AC power
>>>> wiring fault called a double-bonded neutral.
>>>>
>>>> The K3 has unshielded audio transformers at all the audio inputs and
>>>> outputs, and an unshielded transformer is a sitting duck for magnetic
>>>> fields.
>>>>
>>>> The good news is that the K3 has excellent audio equalization (TXEQ)
>>>> that allows us to remove that 60 Hz hum by filtering. The lower audio
>>>> frequencies in the human voice make NO useful contribution to speech
>>>> intelligibility, but they do waste transmit power. So it is ALWAYS a
>>>> good thing to set the TXEQ for maximum cut of the lowest two bands,
>>>> and at least some cut of the third band. This is true with virtually
>>>> ALL mics and ALL voices. AND it will reduce that hum enough that you
>>>> may no longer hear it.
>>>>
>>>> There are several solutions to magnetic field coupling. 1) Rotate the
>>>> noise source or the victim circuit to put the fields at right angles
>>>> to the victim. 2) Move the noise source further from the victim. 3)
>>>> If the hum field is produced by that AC power wiring error, fix the
>>>> error to eliminate the field.
>>>>
>>>> 73, Jim K9YC
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>>> ______________________________________________________________
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>
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