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K3 RFI in transmitted audio

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Felipe Ceglia - PY1NB-2

K3 RFI in transmitted audio

Hi,

I frequently see some RFI talkback on transmitted audio on my K3,
which serial number is on 4000's batch.

When second rig is TX on 80m, I get the whole audio being coupled by the K3.

Is this a common issue? Any tips to solve?

73
--
Felipe Ceglia - PY1NB
-------------------------------------------------------------------------------------
PR1T team member /// Rio DX Group member /// Araucaria DX Group member
http://www.dxwatch.com /// http://reversebeacon.net ///
http://riodxgroup.dxwatch.com
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Jim Brown-10

Re: K3 RFI in transmitted audio

On Fri, 10 Sep 2010 21:35:49 -0300, Felipe Ceglia wrote:

>When second rig is TX on 80m, I get the whole audio being coupled by the K3.

Please give more detail about your problem. Are both radios transmitting at
the same time? Both K3s, or one a different radio? Is there a computer
feeding either radio? Where do you hear the RFI? Where do the radios get
their DC power? Exactly. What kind of power supply? Is the V- terminal
bonded to the chassis at the power supply?

>Is this a common issue?

It depends on the details of your problem.

>Any tips to solve?

It depends on the details of your problem. :) Once we hear more details, we
can give some ideas.

73, Jim K9YC

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Felipe Ceglia - PY1NB-2

Re: K3 RFI in transmitted audio

Hi Jim

Here is the setup:

rig A:
K3
heil proset on front panel
pc audio on rear plugs
cat plugged via microham microkeyer
nothing plugged on cw key jack (that minimized rfi a bit, it was
coming from microkeyer)
JRC 1kw amp

rig B
ft2000
cat cable to pc
icom pw1 amp

The antennas are all near the shack.

When rig B TX, depending on band, it gets into K3 TX audio.

2010/9/11 Jim Brown <[hidden email]>:

> On Fri, 10 Sep 2010 21:35:49 -0300, Felipe Ceglia wrote:
>
>>When second rig is TX on 80m, I get the whole audio being coupled by the K3.
>
> Please give more detail about your problem. Are both radios transmitting at
> the same time? Both K3s, or one a different radio? Is there a computer
> feeding either radio? Where do you hear the RFI? Where do the radios get
> their DC power? Exactly. What kind of power supply? Is the V- terminal
> bonded to the chassis at the power supply?
>
>>Is this a common issue?
>
> It depends on the details of your problem.
>
>>Any tips to solve?
>
> It depends on the details of your problem. :) Once we hear more details, we
> can give some ideas.
>
> 73, Jim K9YC
>
>
>
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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--
Felipe Ceglia - PY1NB
-------------------------------------------------------------------------------------
PR1T team member /// Rio DX Group member /// Araucaria DX Group member
http://www.dxwatch.com /// http://reversebeacon.net ///
http://riodxgroup.dxwatch.com
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Fred Atchley

Re: K3 RFI in transmitted audio

In reply to this post by Felipe Ceglia - PY1NB-2

Felipe

If you are using external speakers with built-in audio amps, they can cause
this problem. I solved the problem by turning the speaker amp volume down to
less than ¼, and turning up the K3 audio to compensate.

73, Fred, AE6IC, K3 2241, P3 100

" Do or Do-not. There is no 'Try'..." ~ Yoda

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Joe Subich, W4TV-4

Re: K3 RFI in transmitted audio

In reply to this post by Felipe Ceglia - PY1NB-2

> When rig B TX, depending on band, it gets into K3 TX audio.

Use standard audio decoupling techniques ... use separate power
supplies for each transceiver and the microKEYER. Do not use
Mic + Line with the K3, make sure that any external power supply
does not tie V- to chassis (and/or third pin on the power cable),
add decoupling (common mode) chokes to the power supply cables,
use common mode chokes on all antenna cables and don't transmit
on both radios at the same time.

73,

... Joe, W4TV

On 9/11/2010 9:37 AM, Felipe Ceglia wrote:

> Hi Jim
>
> Here is the setup:
>
> rig A:
> K3
> heil proset on front panel
> pc audio on rear plugs
> cat plugged via microham microkeyer
> nothing plugged on cw key jack (that minimized rfi a bit, it was
> coming from microkeyer)
> JRC 1kw amp
>
> rig B
> ft2000
> cat cable to pc
> icom pw1 amp
>
> The antennas are all near the shack.
>
> When rig B TX, depending on band, it gets into K3 TX audio.
>
>
> 2010/9/11 Jim Brown<[hidden email]>:
>> On Fri, 10 Sep 2010 21:35:49 -0300, Felipe Ceglia wrote:
>>
>>> When second rig is TX on 80m, I get the whole audio being coupled by the K3.
>>
>> Please give more detail about your problem. Are both radios transmitting at
>> the same time? Both K3s, or one a different radio? Is there a computer
>> feeding either radio? Where do you hear the RFI? Where do the radios get
>> their DC power? Exactly. What kind of power supply? Is the V- terminal
>> bonded to the chassis at the power supply?
>>
>>> Is this a common issue?
>>
>> It depends on the details of your problem.
>>
>>> Any tips to solve?
>>
>> It depends on the details of your problem. :) Once we hear more details, we
>> can give some ideas.
>>
>> 73, Jim K9YC
>>
>>
>>
>>
>>
>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>> Please help support this email list: http://www.qsl.net/donate.html
>>
>
>
>

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Jim Brown-10

Re: K3 RFI in transmitted audio

In reply to this post by Felipe Ceglia - PY1NB-2

On Sat, 11 Sep 2010 13:37:49 +0000, Felipe Ceglia wrote:

>Here is the setup:

>rig A:
>K3
>heil proset on front panel
>pc audio on rear plugs
>cat plugged via microham microkeyer
>nothing plugged on cw key jack (that minimized rfi a bit, it was
>coming from microkeyer)
>JRC 1kw amp

>rig B
>ft2000
>cat cable to pc
>icom pw1 amp

>The antennas are all near the shack.

>When rig B TX, depending on band, it gets into K3 TX audio.

You still didn't tell us about DC power for these rigs and the other equipment.
That can be VERY important for problems like these. Note W4TV's advice on this.

Based on limited information, I suspect a pin 1 problem in the computer, but
I'm not ready to rule out the power supply, and strongly urge you to follow
Joe's advice. If RF is getting into the computer, the solution is a multi-turn
choke on the audio cable between PC and the K3, and another on the serial
cable. I think you said 80M was the primary band. That will take a lot of
turns. See my RFI tutorial. http://audiosystemsgroup.com/RFI-Ham.pdf

So I repeat my question about power -- EXACTLY how are you powering each rig
and each piece of equipment connected to these rigs? I don't know the FT2000.
Does the FT2000 run on 14Vdc, or does it plug directly into mains power?

73, Jim Brown K9YC

>2010/9/11 Jim Brown <[hidden email]>:
>> On Fri, 10 Sep 2010 21:35:49 -0300, Felipe Ceglia wrote:
>>
>>>When second rig is TX on 80m, I get the whole audio being coupled by the K3.
>>
>> Please give more detail about your problem. Are both radios transmitting at
>> the same time? Both K3s, or one a different radio? Is there a computer
>> feeding either radio? Where do you hear the RFI? Where do the radios get
>> their DC power? Exactly. What kind of power supply? Is the V- terminal
>> bonded to the chassis at the power supply?
>>
>>>Is this a common issue?
>>

Felipe Ceglia - PY1NB-2

Re: K3 RFI in transmitted audio

In reply to this post by Joe Subich, W4TV-4

2010/9/11 Felipe Ceglia <[hidden email]>:

> well...
>
> FT2000 is fed by its own internal PS.
>
> K3 is being fed by an alinco DM330 PS, and I have wounded a choke on a
> flyback toroid on the K3 red/black PS wire. (I havent actually checked
> its characteristics on VNA)
>
> microham is being fed from K3 12v port.
>
> I use no external speaker, but a heil headset
>
> the RFI gets into TX audio, blurring it a bit.
>
> I cant stop TX 2 rigs at once, as we are running WAE contest, and we
> are alowed to do so.
>
> Probably computer tied to k3 has pin 1 problem, as I am using its
> onboard soundcard. I will replace it later with a pci soundcard with
> pin1 fixed.
>
> Thanks for your help & attention,
>
> Felipe - PY1NB
>
> 2010/9/11 Joe Subich, W4TV <[hidden email]>:
>>
>> > When rig B TX, depending on band, it gets into K3 TX audio.
>>
>> Use standard audio decoupling techniques ... use separate power
>> supplies for each transceiver and the microKEYER. Do not use
>> Mic + Line with the K3, make sure that any external power supply
>> does not tie V- to chassis (and/or third pin on the power cable),
>> add decoupling (common mode) chokes to the power supply cables,
>> use common mode chokes on all antenna cables and don't transmit
>> on both radios at the same time.
>>
>> 73,
>>
>> ... Joe, W4TV
>>
>>
>> On 9/11/2010 9:37 AM, Felipe Ceglia wrote:
>>> Hi Jim
>>>
>>> Here is the setup:
>>>
>>> rig A:
>>> K3
>>> heil proset on front panel
>>> pc audio on rear plugs
>>> cat plugged via microham microkeyer
>>> nothing plugged on cw key jack (that minimized rfi a bit, it was
>>> coming from microkeyer)
>>> JRC 1kw amp
>>>
>>> rig B
>>> ft2000
>>> cat cable to pc
>>> icom pw1 amp
>>>
>>> The antennas are all near the shack.
>>>
>>> When rig B TX, depending on band, it gets into K3 TX audio.
>>>
>>>
>>> 2010/9/11 Jim Brown<[hidden email]>:
>>>> On Fri, 10 Sep 2010 21:35:49 -0300, Felipe Ceglia wrote:
>>>>
>>>>> When second rig is TX on 80m, I get the whole audio being coupled by the K3.
>>>>
>>>> Please give more detail about your problem. Are both radios transmitting at
>>>> the same time? Both K3s, or one a different radio? Is there a computer
>>>> feeding either radio? Where do you hear the RFI? Where do the radios get
>>>> their DC power? Exactly. What kind of power supply? Is the V- terminal
>>>> bonded to the chassis at the power supply?
>>>>
>>>>> Is this a common issue?
>>>>
>>>> It depends on the details of your problem.
>>>>
>>>>> Any tips to solve?
>>>>
>>>> It depends on the details of your problem. :) Once we hear more details, we
>>>> can give some ideas.
>>>>
>>>> 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
>>
>
>
>
> --
> Felipe Ceglia - PY1NB
> -------------------------------------------------------------------------------------
> PR1T team member /// Rio DX Group member /// Araucaria DX Group member
> http://www.dxwatch.com /// http://reversebeacon.net ///
> http://riodxgroup.dxwatch.com
>

Guy, K2AV

Re: K3 RFI in transmitted audio

Hi Felipe,

>> microham is being fed from K3 12v port.
>>

This is not a good idea. Repeating W4TV's warning with a different
choice of words....

The 12V at the K3 will vary up and down according to the audio current
draw, at an audio rate. This variation in the 12V will now modulate
anything else that uses it including audio circuits in the uHam gear.
Depending on the characteristics this could cause the transmission
from one rig to appear in the other. Even without uHam or other
utility low level audio boxes, the same thing can happen with the two
rigs if they share the same power supply. It would likely be a muddled
sounding audio crosstalk, but based upon the degree of DC filtering in
a rig or device, could be quite loud.

Always run a separate small power supply to feed uHam devices and low
level audio station utility gizmo's. Always use separate DC power
supplies for SSB transceivers operated concurrently: one supply per
transceiver.

You can get away with mixed supply leads on CW, but NOT on SSB.

73, Guy.
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Joe Subich, W4TV-4

Re: K3 RFI in transmitted audio

> This is not a good idea. Repeating W4TV's warning with a different
> choice of words....

Actually, using +13.8V *from the transceiver* is not a major issue
since there is no current return via the microHAM interface (or any
other accessory device).

The big problem is with using the same supply as the transceiver
and connecting at the power supply end of the transceiver power
cable because a portion of the transceiver return current flows
through the microHAM interface (or other accessory device). That
return current modulates the V- line of the accessory and puts
the voltage drop on the accessory V- line in series with the
microphone audio! The variable voltage on the accessory V- is
often in the 10 to 50 mV range - equivalent to the level of many
microphones!

The problem with the K3 +12V jack is the two series diodes and the
power switch FET between the +13.8V input and the switched power
output. The voltage drop is rather significant and can be quite
variable under load ....

> Always use separate DC power supplies for SSB transceivers operated
> concurrently: one supply per transceiver.

This is good advice ... and always bond the chassis of each piece
of equipment to the common ground point and not "chassis to chassis."

73,

... Joe, W4TV

On 9/11/2010 3:02 PM, Guy Olinger K2AV wrote:

> Hi Felipe,
>
>>> microham is being fed from K3 12v port.
>>>
>
> This is not a good idea. Repeating W4TV's warning with a different
> choice of words....
>
> The 12V at the K3 will vary up and down according to the audio current
> draw, at an audio rate. This variation in the 12V will now modulate
> anything else that uses it including audio circuits in the uHam gear.
> Depending on the characteristics this could cause the transmission
> from one rig to appear in the other. Even without uHam or other
> utility low level audio boxes, the same thing can happen with the two
> rigs if they share the same power supply. It would likely be a muddled
> sounding audio crosstalk, but based upon the degree of DC filtering in
> a rig or device, could be quite loud.
>
> Always run a separate small power supply to feed uHam devices and low
> level audio station utility gizmo's. Always use separate DC power
> supplies for SSB transceivers operated concurrently: one supply per
> transceiver.
>
> You can get away with mixed supply leads on CW, but NOT on SSB.
>
> 73, Guy.
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
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> Please help support this email list: http://www.qsl.net/donate.html
>

Don Wilhelm-4

Re: K3 RFI in transmitted audio

Joe,

Let me rephrase your point and add a bit more.
Any accessories that are used during transmit would best be powered by a
supply different than the transceiver power supply. Strange modulation
of the V- line to the accessory can result, especially with SSB
transmission, but possible with other modes as well.
If the accessory is only used during receive, it can use the same supply
as the transceiver because the current draw of the transceiver is
constant during receive.

73,
Don W3FPR

On 9/11/2010 8:06 PM, Joe Subich, W4TV wrote:

> > This is not a good idea. Repeating W4TV's warning with a different
> > choice of words....
>
> Actually, using +13.8V *from the transceiver* is not a major issue
> since there is no current return via the microHAM interface (or any
> other accessory device).
>
> The big problem is with using the same supply as the transceiver
> and connecting at the power supply end of the transceiver power
> cable because a portion of the transceiver return current flows
> through the microHAM interface (or other accessory device). That
> return current modulates the V- line of the accessory and puts
> the voltage drop on the accessory V- line in series with the
> microphone audio! The variable voltage on the accessory V- is
> often in the 10 to 50 mV range - equivalent to the level of many
> microphones!
>
> The problem with the K3 +12V jack is the two series diodes and the
> power switch FET between the +13.8V input and the switched power
> output. The voltage drop is rather significant and can be quite
> variable under load ....
>
> > Always use separate DC power supplies for SSB transceivers operated
> > concurrently: one supply per transceiver.
>
> This is good advice ... and always bond the chassis of each piece
> of equipment to the common ground point and not "chassis to chassis."
>
> 73,
>

Jim Brown-10

Re: K3 RFI in transmitted audio

In reply to this post by Joe Subich, W4TV-4

On Sat, 11 Sep 2010 20:06:50 -0400, Joe Subich, W4TV wrote:

>This is good advice ... and always bond the chassis of each piece
>of equipment to the common ground point and not "chassis to chassis."

This is the only advice that I disagree with. Low impedance bonding
chassis to chassis of equipment that mave an unbalanced signal
connection between them is a VERY GOOD THING, because it can
effectively short out any voltage that may be present between them
(like the IR drop being discussed here).

Don said:

>Strange modulation of the V- line to the accessory can result,
>especially with SSB transmission,

Nothing strange about it, it's simple Ohm's Law. :) You have DC
current on the V- lead that reaches a peak value of at least 20A, so
there is voltage drop on that lead as predicted by Ohm's Law. That
voltage drop becomes a problem if it appears between equipment that
has unbalanced connections, like a computer sound card and a rig, or
between an outboard audio interface and a rig. That's why an interface
device SHOULD be powered from the end of the power cable nearest to
the rig, which is the basis of Joe's advice.

W8JI was the first guy I know of who brought this problem to our
attention. That IR drop from current that varies with SSB modulation
from about 1A to about 20A will sound very much SSB audio in an AM
detector, and just like RF in the audio. So you THINK you have RFI,
but what you really have is simple IR drop. That's why I've asked
about power and bonding in this discussion.

Another part of this equation is whether V- is bonded to the chassis
in the power supply. In general, it should NOT be bonded. Most power
supplies are built so that they are either NOT bonded, or have a
single bond that can easily and safely be removed. The linear Astrons
are an example -- the entire V- bus floats all the way through the
supply, but is bonded near the V- terminal. This can very easily and
safely be cut.

Now, getting back to Felipe's RFI problem. If, as I suspect, it's a
pin 1 problem in the computer sound card, the ferrite choke could fix
that problem. But if it's the DC power problem, removing the V- bond
in the Alinco power supply (if there is one) would be a likely
solution. I think the DC power problem is unlikely in this situation,
because, as I understand it, it's the FT2000 RF that is getting into
the K3 audio, and it's running on it's own internal supply.

73, Jim K9YC

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Joe Subich, W4TV-4

Re: K3 RFI in transmitted audio

>> This is good advice ... and always bond the chassis of each piece
>> of equipment to the common ground point and not "chassis to chassis."
>
> This is the only advice that I disagree with. Low impedance bonding
> chassis to chassis of equipment that mave an unbalanced signal
> connection between them is a VERY GOOD THING, because it can
> effectively short out any voltage that may be present between them
> (like the IR drop being discussed here).

Bonding unit to unit ENCOURAGES common mode currents to flow through
all of the units in series. Bonding to a single LOW IMPEDANCE ground
moves the common mode and RF currents to the ground and *NOT* the
other equipment.

The purpose of grounding/bonding is to eliminate common mode currents
and tie everything to a common reference. "Daisy chain" bonding,
particularly when done with a few small gauge wires can encourage
common mode problems - particularly where there are issues in the
transceiver V- connection.

73,

... Joe, W4TV

On 9/12/2010 12:34 PM, Jim Brown wrote:

> On Sat, 11 Sep 2010 20:06:50 -0400, Joe Subich, W4TV wrote:
>
>> This is good advice ... and always bond the chassis of each piece
>> of equipment to the common ground point and not "chassis to chassis."
>
> This is the only advice that I disagree with. Low impedance bonding
> chassis to chassis of equipment that mave an unbalanced signal
> connection between them is a VERY GOOD THING, because it can
> effectively short out any voltage that may be present between them
> (like the IR drop being discussed here).
>
> Don said:
>
>> Strange modulation of the V- line to the accessory can result,
>> especially with SSB transmission,
>
> Nothing strange about it, it's simple Ohm's Law. :) You have DC
> current on the V- lead that reaches a peak value of at least 20A, so
> there is voltage drop on that lead as predicted by Ohm's Law. That
> voltage drop becomes a problem if it appears between equipment that
> has unbalanced connections, like a computer sound card and a rig, or
> between an outboard audio interface and a rig. That's why an interface
> device SHOULD be powered from the end of the power cable nearest to
> the rig, which is the basis of Joe's advice.
>
> W8JI was the first guy I know of who brought this problem to our
> attention. That IR drop from current that varies with SSB modulation
> from about 1A to about 20A will sound very much SSB audio in an AM
> detector, and just like RF in the audio. So you THINK you have RFI,
> but what you really have is simple IR drop. That's why I've asked
> about power and bonding in this discussion.
>
> Another part of this equation is whether V- is bonded to the chassis
> in the power supply. In general, it should NOT be bonded. Most power
> supplies are built so that they are either NOT bonded, or have a
> single bond that can easily and safely be removed. The linear Astrons
> are an example -- the entire V- bus floats all the way through the
> supply, but is bonded near the V- terminal. This can very easily and
> safely be cut.
>
> Now, getting back to Felipe's RFI problem. If, as I suspect, it's a
> pin 1 problem in the computer sound card, the ferrite choke could fix
> that problem. But if it's the DC power problem, removing the V- bond
> in the Alinco power supply (if there is one) would be a likely
> solution. I think the DC power problem is unlikely in this situation,
> because, as I understand it, it's the FT2000 RF that is getting into
> the K3 audio, and it's running on it's own internal supply.
>
> 73, Jim K9YC
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

Don Wilhelm-4

Re: K3 RFI in transmitted audio

In reply to this post by Jim Brown-10

Jim,

Sorry about my phrasing, I did not mean to imply that it was strange
that the varying V- current would cause modulation, it can and it will.

What I intended to say was that the modulation itself might appear
"strange", and may not be recognized as mmodulation at all.

73,
Don W3FPR

On 9/12/2010 12:34 PM, Jim Brown wrote:
>
> Don said:
>
>> Strange modulation of the V- line to the accessory can result,
>> especially with SSB transmission,
> Nothing strange about it, it's simple Ohm's Law. :) You have DC
> current on the V- lead that reaches a peak value of at least 20A, so
> there is voltage drop on that lead as predicted by Ohm's Law.
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Jim Brown-10

Re: K3 RFI in transmitted audio

In reply to this post by Joe Subich, W4TV-4

On Sun, 12 Sep 2010 15:08:34 -0400, Joe Subich, W4TV wrote:

>Bonding unit to unit ENCOURAGES common mode currents to flow
through
>all of the units in series. Bonding to a single LOW IMPEDANCE
ground
>moves the common mode and RF currents to the ground and *NOT* the
>other equipment.

This is a common misconception that results from muddy thinking. It
is the big lie, repeated over and over again until somehow everyone
believes it. DC and low frequency currents follow Ohm's Law -- that
is, the path with the lowest DC resistance.

First, the issue here is AUDIO AND DC, NOT RF, and it is the
injection of AUDIO noise into unbalanced connections.

Let's say that you bond all equipment to your MAGIC SINGLE POINT,
and it takes 3 ft of wire to get there. If two pieces of equipment
are only three inches apart and you bond directly between them,
CHASSIS to CHASSIS, the wire might be only 6 inches long. Assuming
the same size wire, the path through that MAGIC SINGLE POINT has 12
times the resistance as compared to the direct path. That's 22dB
MORE NOISE (20 log of the voltage, and the voltage is proportional
to the resistance) that any circulating current would add to an
unbalanced connection between that equipment.

Second, the bonding together of equipment at RF is for LIGHTNING
SAFETY protection. It is NOT part of a solution to RFI or RF noise.
What matters is that everything be maintained as close to the same
potential as possible, and that is achieved by LOW INDUCTANCE bonds,
and by bonding EVERYTHING together.

Providing a low resistance bond between interconnected equipment
also puts a band-aid on low frequency pin 1 problems, because most
current that flows between equipment takes the lower resistance
chassis-to-chassis bonding path rather than the higher resistance
path via cable shields and onto the signal return bus.

For those who haven't heard, a "pin 1 problem" is the connection of
a cable shield to internal wiring of equipment rather than to the
chassis. The only proper connection of a cable shield is the
CHASSSIS. When noise current flows on a signal return trace, it gets
added to the signal chain at one or more points, where it appears as
noise (hum, buzz, or that modulation of the V- rail), and if it's
RF, it will be detected by the first semiconductor junction it
encounters. Pin 1 problems are the primary causes of hum, buzz, and
RFI in virtually ALL systems. When you see a connector whose shell
is insulated from the chassis, or where a mic shield goes to "audio
ground," it's a "pin 1 problem." It's CALLED a pin 1 problem because
this issue was first clearly described and understood in the pro
audio world, where the shield contact of an XLR connector is pin 1.

73, Jim Brown K9YC

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Jorge Diez - CX6VM

Re: K3 RFI in transmitted audio

In reply to this post by Don Wilhelm-4

I experimented a problem during WAE contest this weekend.

I was working OK till this afternoon. When I transmit, N1MM freeze, and I
need to rebbot my computer.

I tried many things, change USB port of the USB interface, switch off amp,
etc.

When I wanted to check the RS232 in the back of the K3 I noticed that the
ground was disconnected (I removed recently the K3 from this position, and
seems I forgot to connect it again).

After I connect the ground to the K3 all started working properly right
again..!

That´s why a good ground is necessary!...

73,
Jorge
CX6VM/CW5W

-----Mensaje original-----
De: [hidden email]
[mailto:[hidden email]] En nombre de Don Wilhelm
Enviado el: Domingo, 12 de Septiembre de 2010 05:38 p.m.
Para: Jim Brown
CC: [hidden email]
Asunto: Re: [Elecraft] K3 RFI in transmitted audio

Jim,

Sorry about my phrasing, I did not mean to imply that it was strange
that the varying V- current would cause modulation, it can and it will.

What I intended to say was that the modulation itself might appear
"strange", and may not be recognized as mmodulation at all.

73,
Don W3FPR

On 9/12/2010 12:34 PM, Jim Brown wrote:
>
> Don said:
>
>> Strange modulation of the V- line to the accessory can result,
>> especially with SSB transmission,
> Nothing strange about it, it's simple Ohm's Law. :) You have DC
> current on the V- lead that reaches a peak value of at least 20A, so
> there is voltage drop on that lead as predicted by Ohm's Law.
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Joe Subich, W4TV-4

Re: K3 RFI in transmitted audio

In reply to this post by Jim Brown-10

> This is a common misconception that results from muddy thinking. It
> is the big lie, repeated over and over again until somehow everyone
> believes it. DC and low frequency currents follow Ohm's Law -- that
> is, the path with the lowest DC resistance.

And the proper low impedance ground fits that requirement but the
common point must be proper - not just a couple of ground rods.

> Let's say that you bond all equipment to your MAGIC SINGLE POINT,
> and it takes 3 ft of wire to get there. If two pieces of equipment
> are only three inches apart and you bond directly between them,
> CHASSIS to CHASSIS, the wire might be only 6 inches long.

That's fine with two pieces of equipment that are physically close
to each other. However, if one has several pieces stretched along
a long bench with a power supply at one end, bonding box to box
could conceivably cause common mode currents to flow through all
of the boxes causing who knows what kind of abnormal operation -
and pin 1 problems!

> Providing a low resistance bond between interconnected equipment
> also puts a band-aid on low frequency pin 1 problems, because most
> current that flows between equipment takes the lower resistance
> chassis-to-chassis bonding path rather than the higher resistance
> path via cable shields and onto the signal return bus.

But that's only a band aid. Address the issues by properly connecting
the cable shields to the chassis and bonding the the signal returns
to the circuit common properly (e.g. removing things like RF chokes
between signal returns and the chassis).

73,

... Joe, W4TV

On 9/12/2010 4:52 PM, Jim Brown wrote:

> On Sun, 12 Sep 2010 15:08:34 -0400, Joe Subich, W4TV wrote:
>
>> Bonding unit to unit ENCOURAGES common mode currents to flow
> through
>> all of the units in series. Bonding to a single LOW IMPEDANCE
> ground
>> moves the common mode and RF currents to the ground and *NOT* the
>> other equipment.
>
> This is a common misconception that results from muddy thinking. It
> is the big lie, repeated over and over again until somehow everyone
> believes it. DC and low frequency currents follow Ohm's Law -- that
> is, the path with the lowest DC resistance.
>
> First, the issue here is AUDIO AND DC, NOT RF, and it is the
> injection of AUDIO noise into unbalanced connections.
>
> Let's say that you bond all equipment to your MAGIC SINGLE POINT,
> and it takes 3 ft of wire to get there. If two pieces of equipment
> are only three inches apart and you bond directly between them,
> CHASSIS to CHASSIS, the wire might be only 6 inches long. Assuming
> the same size wire, the path through that MAGIC SINGLE POINT has 12
> times the resistance as compared to the direct path. That's 22dB
> MORE NOISE (20 log of the voltage, and the voltage is proportional
> to the resistance) that any circulating current would add to an
> unbalanced connection between that equipment.
>
> Second, the bonding together of equipment at RF is for LIGHTNING
> SAFETY protection. It is NOT part of a solution to RFI or RF noise.
> What matters is that everything be maintained as close to the same
> potential as possible, and that is achieved by LOW INDUCTANCE bonds,
> and by bonding EVERYTHING together.
>
> Providing a low resistance bond between interconnected equipment
> also puts a band-aid on low frequency pin 1 problems, because most
> current that flows between equipment takes the lower resistance
> chassis-to-chassis bonding path rather than the higher resistance
> path via cable shields and onto the signal return bus.
>
> For those who haven't heard, a "pin 1 problem" is the connection of
> a cable shield to internal wiring of equipment rather than to the
> chassis. The only proper connection of a cable shield is the
> CHASSSIS. When noise current flows on a signal return trace, it gets
> added to the signal chain at one or more points, where it appears as
> noise (hum, buzz, or that modulation of the V- rail), and if it's
> RF, it will be detected by the first semiconductor junction it
> encounters. Pin 1 problems are the primary causes of hum, buzz, and
> RFI in virtually ALL systems. When you see a connector whose shell
> is insulated from the chassis, or where a mic shield goes to "audio
> ground," it's a "pin 1 problem." It's CALLED a pin 1 problem because
> this issue was first clearly described and understood in the pro
> audio world, where the shield contact of an XLR connector is pin 1.
>
> 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
>

Jim Brown-10

Re: K3 RFI in transmitted audio

On Mon, 13 Sep 2010 01:26:43 -0400, Joe Subich, W4TV wrote:

> > Let's say that you bond all equipment to your MAGIC SINGLE POINT,
> > and it takes 3 ft of wire to get there. If two pieces of equipment
> > are only three inches apart and you bond directly between them,
> > CHASSIS to CHASSIS, the wire might be only 6 inches long.

>That's fine with two pieces of equipment that are physically close
>to each other. However, if one has several pieces stretched along
>a long bench with a power supply at one end, bonding box to box
>could conceivably cause common mode currents to flow through all
>of the boxes causing who knows what kind of abnormal operation -
>and pin 1 problems!

By definition, a common mode current is one that flows on all
conductors of a SIGNAL cable, usually as a result of a potential
difference between the equipment at either end, or as a result of
antenna action. The bonding I've described tends to strongly reduce
common mode current to very small values, both by diverting it away
from signal cables, and by reducing the potential between one chassis
and another to a very small value. Further, I cannot conceive of ANY
current THROUGH equipment if what is being bonded is the CHASSIS of
one piece of equipment to the CHASSIS of another!

> > Providing a low resistance bond between interconnected equipment
> > also puts a band-aid on low frequency pin 1 problems, because most
> > current that flows between equipment takes the lower resistance
> > chassis-to-chassis bonding path rather than the higher resistance
> > path via cable shields and onto the signal return bus.

>But that's only a band aid. Address the issues by properly
connecting
>the cable shields to the chassis and bonding the the signal returns
>to the circuit common properly (e.g. removing things like RF chokes
>between signal returns and the chassis).

Often what you suggest is not possible, Joe, because of the way
equipment is built. As a manufacturer, I'm sure you've run into this
with your own products. Remember how pin 1 problems are typically
created -- connectors are mounted to a PC board, the board is stuffed
into a box, and the connector never touches the chassis. Instead,
shield current must wander around the PC board to get to the chassis,
which is required by NEC to be bonded to ground. Sometimes it's
possible to bond those connectors (I managed to do that with some Ten
Tec gear and a Time Wave DSP unit), but most equipment is built so
that you cannot fix pin 1 problems without doing major surgery to the
gear.

There is another fundamental principle at work here -- the engineers
who design a given piece of equipment and do the manufacturing
engineering to put it in production must verify that the equipment is
stable in all possible configurations. One of the things that can
strongly affect that is internal bonding of signal commons (what some
folks mistakenly call "grounding"). When you CHANGE that by fixing a
pin 1 problem, you had best be prepared to go through that stability
checkout. Again, a can of worms best left un-opened.

Pin 1 problems should be fixed at the DESIGN and MFG stage. When
encountered in the field, the best approach is a well thought-out
band-aid. Either choke the current, break the path of the current, or
divert the current. Ferrite chokes kill the current by inserting a
high common mode impedance in series, bonding diverts the current away
from the pin 1 problem, and opening the shield of BALANCED wiring at
one end breaks the path. None of those measures have are likely to
affect stability of the equipment, they're all simple, and
inexpensive. BTW -- these are not only my own judgements, but also
those of the VERY sharp engineering minds who have written AES EMC
Standards.

73, Jim Brown K9YC

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Don Wilhelm-4

Re: K3 RFI in transmitted audio

In reply to this post by Joe Subich, W4TV-4

Joe,

For elimination of DC and AF problems, no ground is required. The real
requirement is that all equipment be at the same potential. Connecting
the chassis of all equipment together with heavy gauge wire or strapping
material will provide that low resistance path. Potential differences
of a few millivolts matter here. As Jim has pointed out, divorcing the
power supply V- from the power supply chassis (and AC supply neutral) is
often needed to solve hum and modulation of the V- line.

If we were discussing RF, then your single point ground connected to a
low impedance ground for RF would be correct - keep the path to RF
Ground the same distance for each piece of equipment. will achieve what
is needed for lightning protection.

In difficult situations, both may be necessary. DC and audio grounding
requirements are different from RF grounding requirements.

73,
Don W3FPR

On 9/13/2010 1:26 AM, Joe Subich, W4TV wrote:
> > This is a common misconception that results from muddy thinking. It
> > is the big lie, repeated over and over again until somehow everyone
> > believes it. DC and low frequency currents follow Ohm's Law -- that
> > is, the path with the lowest DC resistance.
>
> And the proper low impedance ground fits that requirement but the
> common point must be proper - not just a couple of ground rods.
>
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Jim Brown-10

Re: K3 RFI in transmitted audio

On Mon, 13 Sep 2010 09:40:00 -0400, Don Wilhelm wrote:

>If we were discussing RF, then your single point ground connected to a
>low impedance ground for RF would be correct - keep the path to RF
>Ground the same distance for each piece of equipment. will achieve
what
>is needed for lightning protection.

I disagree with that concept as well. The notion that a separate wire
is required for each piece of gear to a point that is often at a fair
distance from a closely arranged collection of gear in a typical ham
shack when that gear is already well bonded together does not make
sense. How, for example, do we insure that each wire is the same
length, follows the same or a similar path, and thus has the same
inductance?

There is NO CONFLICT between bonding all equipment chassis together by
the shortest practical path, as I've outlined, and making one or more
bonds between that equipment and the earth electrode system (ground
rods).

Indeed, both IEEE Standards on Grounding and most building codes either
recommend or require multiple paths to ground for lightning protection.
A large part of the thinking behind that is that the inductance is
reduced by having multiple wires in parallel.

As hams, we tend to think of our antennas as the only source of
lightning ingress to our homes, but that is FAR from reality. It's like
looking at the circus elephant through a tiny hole in the tent. EVERY
CONDUCTOR that enters the house, and every conductor INSIDE the house,
is a receiver for energy from lightning. That's why IEEE Standards and
nearly all building codes call for ALL non-powered metal to be bonded
together, and to one or more earth connections, and for all earth
connections to be bonded togther.

One other thought on this. In thinking about how all this fuzzy
thinking about so-called single point grounding came about, one source
of it might be equipment with a pin 1 problem. If, for example, the
bonds to the equipment are improperly made to some point OTHER THAN THE
CHASSIS, then yes, lightning current WOULD go through equipment if it
was daisy-chained. But that's not a GROUNDING problem, it's an
EQUIPMENT problem, and it's IMPROPER bonding.

The good news is that I don't recall ever seeing ANTENNA connections in
ham gear with pin 1 problems (except, perhaps, for an occasional RX
antenna). It's only the audio and control wiring, and an occasional IF
output.

73, Jim Brown K9YC

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Eric Swartz - WA6HHQ

Re: K3 RFI in transmitted audio [End of thread]

Administrator

Jim, Don and Joe,

To keep list traffic reasonable, let's take this recurring discussion
off list to direct email for now. Once you have all agreed please feel
free post the results to the list.

Also, there is a lot of past info on this topic that is searchable in
the list archives.

Also, please keep all discussions civil on, or off, list.

73,
Eric WA6HHQ
Elecraft List Moderator
-----

On 9/13/2010 9:08 AM, Jim Brown wrote:

> On Mon, 13 Sep 2010 09:40:00 -0400, Don Wilhelm wrote:
>
>> If we were discussing RF, then your single point ground connected to a
>> low impedance ground for RF would be correct - keep the path to RF
>> Ground the same distance for each piece of equipment. will achieve
> what
>> is needed for lightning protection.
> I disagree with that concept as well. The notion that a separate wire
> is required for each piece of gear to a point that is often at a fair
> distance from a closely arranged collection of gear in a typical ham
> shack when that gear is already well bonded together does not make
> sense. How, for example, do we insure that each wire is the same
> length, follows the same or a similar path, and thus has the same
> inductance?
>
> There is NO CONFLICT between bonding all equipment chassis together by
> the shortest practical path, as I've outlined, and making one or more
> bonds between that equipment and the earth electrode system (ground
> rods).
>
> Indeed, both IEEE Standards on Grounding and most building codes either
> recommend or require multiple paths to ground for lightning protection.
> A large part of the thinking behind that is that the inductance is
> reduced by having multiple wires in parallel.
>
> As hams, we tend to think of our antennas as the only source of
> lightning ingress to our homes, but that is FAR from reality. It's like
> looking at the circus elephant through a tiny hole in the tent. EVERY
> CONDUCTOR that enters the house, and every conductor INSIDE the house,
> is a receiver for energy from lightning. That's why IEEE Standards and
> nearly all building codes call for ALL non-powered metal to be bonded
> together, and to one or more earth connections, and for all earth
> connections to be bonded togther.
>
> One other thought on this. In thinking about how all this fuzzy
> thinking about so-called single point grounding came about, one source
> of it might be equipment with a pin 1 problem. If, for example, the
> bonds to the equipment are improperly made to some point OTHER THAN THE
> CHASSIS, then yes, lightning current WOULD go through equipment if it
> was daisy-chained. But that's not a GROUNDING problem, it's an
> EQUIPMENT problem, and it's IMPROPER bonding.
>
> The good news is that I don't recall ever seeing ANTENNA connections in
> ham gear with pin 1 problems (except, perhaps, for an occasional RX
> antenna). It's only the audio and control wiring, and an occasional IF
> output.
>
> 73, Jim Brown K9YC
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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