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K3: Very distorted audio on transmit but only on 20m and only with the KPA500 on

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tomb18

K3: Very distorted audio on transmit but only on 20m and only with the KPA500 on

Ok,

So my audio is quite distorted as I can hear in my headphones with the monitor. But this only happens on 20m and only with the KPA500 in operate.
Sound like RF? or is something else going on?

Thanks
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Donehrlich@q.com

Re: K3: Very distorted audio on transmit but only on 20m and only with the KPA500 on

Almost certainly RF getting into the mic circuit. Try a different mic
.. or use the rear panel mic connector as a check. You probably have
high SWR into the antenna feedline (or coax) after the tuner on 20
meters and that is why you only see problem on 20M. High SWR on the
feedline (Note: your rig can be seeing low swr .. it is AFTER the tuner
where you have high SWR) results in high current or high voltage that
then couples into other shack wiring. Of course, the higher power from
the KPA500 pushes those voltages/currents to levels that are more likely
to cause problems. Been there, done that .. many times.

Don K7FJ

> Ok,
>
> So my audio is quite distorted as I can hear in my headphones with the monitor. But this only happens on 20m and only with the KPA500 in operate.
> Sound like RF? or is something else going on?
>
>
> Thanks
> ______________________________________________________________
> 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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tomb18

Re: K3: Very distorted audio on transmit but only on 20m and only with the KPA500 on

Ok, thanks, that's what I thought. A little more complicated since I have a MicroHam microkeyer II in the circuit but probably fixable.

73's Tom

On 3/11/14, "[hidden email]" <[hidden email]> wrote:

> Almost certainly RF getting into the mic circuit. Try a different mic .. or use the rear panel mic connector as a check. You probably have high SWR into the antenna feedline (or coax) after the tuner on 20 meters and that is why you only see problem on 20M. High SWR on the feedline (Note: your rig can be seeing low swr .. it is AFTER the tuner where you have high SWR) results in high current or high voltage that then couples into other shack wiring. Of course, the higher power from the KPA500 pushes those voltages/currents to levels that are more likely to cause problems. Been there, done that .. many times.
>
> Don K7FJ
>
>
> >Ok,
> >
> >So my audio is quite distorted as I can hear in my headphones with the monitor. But this only happens on 20m and only with the KPA500 in operate.
> >Sound like RF? or is something else going on?
> >
> >
> >Thanks
> >______________________________________________________________
> >Elecraft mailing list
> >Home: http://mailman.qth.net/mailman/listinfo/elecraft
> >Help: http://mailman.qth.net/mmfaq.htm
> >Post: mailto:[hidden email] <[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] <[hidden email]>
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>

Stewart@twinwood

Re: K3: Very distorted audio on transmit but only on 20m and only with the KPA500 on

Tom,
Check that your MKII has the capacitor modification that decouples the USB cable
shield. If not, RF on the cable can cause audio problems. Details are on the
MicroHam site.

73
Stewart G3RXQ

On Tue, 11 Mar 2014 17:58:00 -0400, [hidden email] wrote:
> Ok, thanks, that's what I thought. A little more complicated since I have a
MicroHam microkeyer II in the circuit but probably fixable.
>
> 73's Tom
>
> On 3/11/14, "[hidden email]" <[hidden email]> wrote:
>> Almost certainly RF getting into the mic circuit. Try a different mic .. or
use the rear panel mic connector as a check. You probably have high SWR into the
antenna feedline (or coax) after the tuner on 20 meters and that is why you only
see problem on 20M. High SWR on the feedline (Note: your rig can be seeing low
swr .. it is AFTER the tuner where you have high SWR) results in high current or
high voltage that then couples into other shack wiring. Of course, the higher
power from the KPA500 pushes those voltages/currents to levels that are more
likely to cause problems. Been there, done that .. many times.
>>
>> Don K7FJ
>>
>>
>> >Ok,
>> >
>> >So my audio is quite distorted as I can hear in my headphones with the
monitor. But this only happens on 20m and only with the KPA500 in operate.

>> >Sound like RF? or is something else going on?
>> >
>> >
>> >Thanks
>> >______________________________________________________________
>> >Elecraft mailing list
>> >Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> >Help: http://mailman.qth.net/mmfaq.htm
>> >Post: mailto:[hidden email] <[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] <[hidden email]>
>>
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>> Please help support this email list: http://www.qsl.net/donate.html
>>
>>
> ______________________________________________________________
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Joe Subich, W4TV-4

Re: K3: Very distorted audio on transmit but only on 20m and only with the KPA500 on

The capacitor modification applied to fewer than 200 units shipped more
than six years ago. It was identified early and most of the initial
production run were modified by the factory or distributors before they
ever reached an end-user.

73,

... Joe, W4TV

On 3/11/2014 6:21 PM, Stewart wrote:

> Tom,
> Check that your MKII has the capacitor modification that decouples the USB cable
> shield. If not, RF on the cable can cause audio problems. Details are on the
> MicroHam site.
>
> 73
> Stewart G3RXQ
>
> On Tue, 11 Mar 2014 17:58:00 -0400, [hidden email] wrote:
>> Ok, thanks, that's what I thought. A little more complicated since I have a
> MicroHam microkeyer II in the circuit but probably fixable.
>>
>> 73's Tom
>>
>> On 3/11/14, "[hidden email]" <[hidden email]> wrote:
>>> Almost certainly RF getting into the mic circuit. Try a different mic .. or
> use the rear panel mic connector as a check. You probably have high SWR into the
> antenna feedline (or coax) after the tuner on 20 meters and that is why you only
> see problem on 20M. High SWR on the feedline (Note: your rig can be seeing low
> swr .. it is AFTER the tuner where you have high SWR) results in high current or
> high voltage that then couples into other shack wiring. Of course, the higher
> power from the KPA500 pushes those voltages/currents to levels that are more
> likely to cause problems. Been there, done that .. many times.
>>>
>>> Don K7FJ
>>>
>>>
>>>> Ok,
>>>>
>>>> So my audio is quite distorted as I can hear in my headphones with the
> monitor. But this only happens on 20m and only with the KPA500 in operate.
>>>> Sound like RF? or is something else going on?
>>>>
>>>>
>>>> Thanks
>>>> ______________________________________________________________
>>>> Elecraft mailing list
>>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>>> Help: http://mailman.qth.net/mmfaq.htm
>>>> Post: mailto:[hidden email] <[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] <[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]
>
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Joe Subich, W4TV-4

Re: K3: Very distorted audio on transmit but only on 20m and only with the KPA500 on

In reply to this post by tomb18

VSWR is not an issue - the issue is imbalance in the antenna system.
The problem is well known as the "common mode RFI" issue due to a lack
of effective decoupling of the antenna and feedline.

A *much more common* issue is users who fail to follow instructions and
connect microKEYER II (or any other accessory that handles microphone
audio) to the same power supply as the transceiver. With "modern" rigs
which use 12V finals, the peak power supply current can be greater than
25 amps. When the transceiver uses light cable for power (anything
less than #10 wire) and "friction" connectors like Molex or Power Pole,
the voltage drop in the power supply return can be significant. That
drop causes some current to flow through the accessory and "pump" the
ground reference to the accessory. With just 0.2 Ohms in the connector
and ground return, that means at least 0.5V *in series* with the audio
input!

If you are using any device that handles microphone audio, either power
it from the K3's +12V accessory jack or use a *separate* isolated power
supply.

73,

... Joe, W4TV

On 3/11/2014 5:58 PM, [hidden email] wrote:

> Ok, thanks, that's what I thought. A little more complicated since I have a MicroHam microkeyer II in the circuit but probably fixable.
>
> 73's Tom
>
> On 3/11/14, "[hidden email]" <[hidden email]> wrote:
>> Almost certainly RF getting into the mic circuit. Try a different mic .. or use the rear panel mic connector as a check. You probably have high SWR into the antenna feedline (or coax) after the tuner on 20 meters and that is why you only see problem on 20M. High SWR on the feedline (Note: your rig can be seeing low swr .. it is AFTER the tuner where you have high SWR) results in high current or high voltage that then couples into other shack wiring. Of course, the higher power from the KPA500 pushes those voltages/currents to levels that are more likely to cause problems. Been there, done that .. many times.
>>
>> Don K7FJ
>>
>>
>>> Ok,
>>>
>>> So my audio is quite distorted as I can hear in my headphones with the monitor. But this only happens on 20m and only with the KPA500 in operate.
>>> Sound like RF? or is something else going on?
>>>
>>>
>>> Thanks
>>> ______________________________________________________________
>>> Elecraft mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>> Help: http://mailman.qth.net/mmfaq.htm
>>> Post: mailto:[hidden email] <[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] <[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
>

tomb18

Re: K3: Very distorted audio on transmit but only on 20m and only with the KPA500 on

Hi,

Thanks for all the replies.
My Microham is a relatively recent unit.
I also have a separate power supply for the MicroHam.

Is having the Microham directly on top of the KAT500 Tuner with the microphone cable almost touching the RF out a potential issue? If so, this might be an easy fix for now.

Thanks

On 3/11/14, "Joe Subich, W4TV" <[hidden email]> wrote:

>
> VSWR is not an issue - the issue is imbalance in the antenna system.
> The problem is well known as the "common mode RFI" issue due to a lack
> of effective decoupling of the antenna and feedline.
>
> A *much more common* issue is users who fail to follow instructions and
> connect microKEYER II (or any other accessory that handles microphone
> audio) to the same power supply as the transceiver. With "modern" rigs
> which use 12V finals, the peak power supply current can be greater than
> 25 amps. When the transceiver uses light cable for power (anything
> less than #10 wire) and "friction" connectors like Molex or Power Pole,
> the voltage drop in the power supply return can be significant. That
> drop causes some current to flow through the accessory and "pump" the
> ground reference to the accessory. With just 0.2 Ohms in the connector
> and ground return, that means at least 0.5V *in series* with the audio
> input!
>
> If you are using any device that handles microphone audio, either power
> it from the K3's +12V accessory jack or use a *separate* isolated power
> supply.
>
> 73,
>
> ... Joe, W4TV
>
>
> On 3/11/2014 5:58 PM, [hidden email] wrote:
> >Ok, thanks, that's what I thought. A little more complicated since I have a MicroHam microkeyer II in the circuit but probably fixable.
> >
> >73's Tom
> >
> >On 3/11/14, "[hidden email]" <[hidden email]> wrote:
> >>Almost certainly RF getting into the mic circuit. Try a different mic .. or use the rear panel mic connector as a check. You probably have high SWR into the antenna feedline (or coax) after the tuner on 20 meters and that is why you only see problem on 20M. High SWR on the feedline (Note: your rig can be seeing low swr .. it is AFTER the tuner where you have high SWR) results in high current or high voltage that then couples into other shack wiring. Of course, the higher power from the KPA500 pushes those voltages/currents to levels that are more likely to cause problems. Been there, done that .. many times.
> >>
> >>Don K7FJ
> >>
> >>
> >>>Ok,
> >>>
> >>>So my audio is quite distorted as I can hear in my headphones with the monitor. But this only happens on 20m and only with the KPA500 in operate.
> >>>Sound like RF? or is something else going on?
> >>>
> >>>
> >>>Thanks
> >>>______________________________________________________________
> >>>Elecraft mailing list
> >>>Home: http://mailman.qth.net/mailman/listinfo/elecraft
> >>>Help: http://mailman.qth.net/mmfaq.htm
> >>>Post: mailto:[hidden email] <[hidden email]> <[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] <[hidden email]> <[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] <[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] <[hidden email]>
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>

Joe Subich, W4TV-4

Re: K3: Very distorted audio on transmit but only on 20m and only with the KPA500 on

> Is having the Microham directly on top of the KAT500 Tuner with the
> microphone cable almost touching the RF out a potential issue? If so,
> this might be an easy fix for now.

No, not if your antenna system is properly designed and there is no
common mode current on the outside of the feedline. If you do have a
common mode issue, arrangement of equipment may make minor differences
as the effective line length changes but rearranging equipment is not
going to *fix* an antenna system issue.

Old timers will recognize common mode as "getting bit by the mic" or
getting a "tickle" when touching metal portions of the key <G>. That
was an extreme level of common mode RF (several volts). Just a volt
or two can seriously upset modern solid state equipment or impact low
level microphone audio (a dynamic mic has a level generally less than
20 mV).

73,

... Joe, W4TV

On 3/11/2014 7:07 PM, [hidden email] wrote:

> Hi,
>
> Thanks for all the replies.
> My Microham is a relatively recent unit.
> I also have a separate power supply for the MicroHam.
>
>
> Is having the Microham directly on top of the KAT500 Tuner with the microphone cable almost touching the RF out a potential issue? If so, this might be an easy fix for now.
>
>
> Thanks
>
>
> On 3/11/14, "Joe Subich, W4TV" <[hidden email]> wrote:
>>
>> VSWR is not an issue - the issue is imbalance in the antenna system.
>> The problem is well known as the "common mode RFI" issue due to a lack
>> of effective decoupling of the antenna and feedline.
>>
>> A *much more common* issue is users who fail to follow instructions and
>> connect microKEYER II (or any other accessory that handles microphone
>> audio) to the same power supply as the transceiver. With "modern" rigs
>> which use 12V finals, the peak power supply current can be greater than
>> 25 amps. When the transceiver uses light cable for power (anything
>> less than #10 wire) and "friction" connectors like Molex or Power Pole,
>> the voltage drop in the power supply return can be significant. That
>> drop causes some current to flow through the accessory and "pump" the
>> ground reference to the accessory. With just 0.2 Ohms in the connector
>> and ground return, that means at least 0.5V *in series* with the audio
>> input!
>>
>> If you are using any device that handles microphone audio, either power
>> it from the K3's +12V accessory jack or use a *separate* isolated power
>> supply.
>>
>> 73,
>>
>> ... Joe, W4TV
>>
>>
>> On 3/11/2014 5:58 PM, [hidden email] wrote:
>>> Ok, thanks, that's what I thought. A little more complicated since I have a MicroHam microkeyer II in the circuit but probably fixable.
>>>
>>> 73's Tom
>>>
>>> On 3/11/14, "[hidden email]" <[hidden email]> wrote:
>>>> Almost certainly RF getting into the mic circuit. Try a different mic .. or use the rear panel mic connector as a check. You probably have high SWR into the antenna feedline (or coax) after the tuner on 20 meters and that is why you only see problem on 20M. High SWR on the feedline (Note: your rig can be seeing low swr .. it is AFTER the tuner where you have high SWR) results in high current or high voltage that then couples into other shack wiring. Of course, the higher power from the KPA500 pushes those voltages/currents to levels that are more likely to cause problems. Been there, done that .. many times.
>>>>
>>>> Don K7FJ
>>>>
>>>>
>>>>> Ok,
>>>>>
>>>>> So my audio is quite distorted as I can hear in my headphones with the monitor. But this only happens on 20m and only with the KPA500 in operate.
>>>>> Sound like RF? or is something else going on?
>>>>>
>>>>>
>>>>> Thanks
>>>>> ______________________________________________________________
>>>>> Elecraft mailing list
>>>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>>>> Help: http://mailman.qth.net/mmfaq.htm
>>>>> Post: mailto:[hidden email] <[hidden email]> <[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] <[hidden email]> <[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] <[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] <[hidden email]>
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>
>>
>

tomb18

Re: K3: Very distorted audio on transmit but only on 20m and only with the KPA500 on

Ok,Will do some investigation here then.
Thanks for all the replies. I'll look into this tomorrow with my usual tricks and see if this makes a difference.
For the moment though, I'm enjoying 10m!

73's Tom

On 3/11/14, "Joe Subich, W4TV" <[hidden email]> wrote:

>
> > Is having the Microham directly on top of the KAT500 Tuner with the
> > microphone cable almost touching the RF out a potential issue? If so,
> > this might be an easy fix for now.
>
> No, not if your antenna system is properly designed and there is no
> common mode current on the outside of the feedline. If you do have a
> common mode issue, arrangement of equipment may make minor differences
> as the effective line length changes but rearranging equipment is not
> going to *fix* an antenna system issue.
>
> Old timers will recognize common mode as "getting bit by the mic" or
> getting a "tickle" when touching metal portions of the key <G>. That
> was an extreme level of common mode RF (several volts). Just a volt
> or two can seriously upset modern solid state equipment or impact low
> level microphone audio (a dynamic mic has a level generally less than
> 20 mV).
>
> 73,
>
> ... Joe, W4TV
>
>
> On 3/11/2014 7:07 PM, [hidden email] wrote:
> >Hi,
> >
> >Thanks for all the replies.
> >My Microham is a relatively recent unit.
> >I also have a separate power supply for the MicroHam.
> >
> >
> >Is having the Microham directly on top of the KAT500 Tuner with the microphone cable almost touching the RF out a potential issue? If so, this might be an easy fix for now.
> >
> >
> >Thanks
> >
> >
> >On 3/11/14, "Joe Subich, W4TV" <[hidden email]> wrote:
> >>
> >>VSWR is not an issue - the issue is imbalance in the antenna system.
> >>The problem is well known as the "common mode RFI" issue due to a lack
> >>of effective decoupling of the antenna and feedline.
> >>
> >>A *much more common* issue is users who fail to follow instructions and
> >>connect microKEYER II (or any other accessory that handles microphone
> >>audio) to the same power supply as the transceiver. With "modern" rigs
> >>which use 12V finals, the peak power supply current can be greater than
> >>25 amps. When the transceiver uses light cable for power (anything
> >>less than #10 wire) and "friction" connectors like Molex or Power Pole,
> >>the voltage drop in the power supply return can be significant. That
> >>drop causes some current to flow through the accessory and "pump" the
> >>ground reference to the accessory. With just 0.2 Ohms in the connector
> >>and ground return, that means at least 0.5V *in series* with the audio
> >>input!
> >>
> >>If you are using any device that handles microphone audio, either power
> >>it from the K3's +12V accessory jack or use a *separate* isolated power
> >>supply.
> >>
> >>73,
> >>
> >> ... Joe, W4TV
> >>
> >>
> >>On 3/11/2014 5:58 PM, [hidden email] wrote:
> >>>Ok, thanks, that's what I thought. A little more complicated since I have a MicroHam microkeyer II in the circuit but probably fixable.
> >>>
> >>>73's Tom
> >>>
> >>>On 3/11/14, "[hidden email]" <[hidden email]> wrote:
> >>>>Almost certainly RF getting into the mic circuit. Try a different mic .. or use the rear panel mic connector as a check. You probably have high SWR into the antenna feedline (or coax) after the tuner on 20 meters and that is why you only see problem on 20M. High SWR on the feedline (Note: your rig can be seeing low swr .. it is AFTER the tuner where you have high SWR) results in high current or high voltage that then couples into other shack wiring. Of course, the higher power from the KPA500 pushes those voltages/currents to levels that are more likely to cause problems. Been there, done that .. many times.
> >>>>
> >>>>Don K7FJ
> >>>>
> >>>>
> >>>>>Ok,
> >>>>>
> >>>>>So my audio is quite distorted as I can hear in my headphones with the monitor. But this only happens on 20m and only with the KPA500 in operate.
> >>>>>Sound like RF? or is something else going on?
> >>>>>
> >>>>>
> >>>>>Thanks
> >>>>>______________________________________________________________
> >>>>>Elecraft mailing list
> >>>>>Home: http://mailman.qth.net/mailman/listinfo/elecraft
> >>>>>Help: http://mailman.qth.net/mmfaq.htm
> >>>>>Post: mailto:[hidden email] <[hidden email]> <[hidden email]> <[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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> >>>>
> >>>>This list hosted by: http://www.qsl.net
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> >>>>
> >>>______________________________________________________________
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> >>>
> >>>This list hosted by: http://www.qsl.net
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>

David Gilbert

Re: RF burns ... was K3: Very distorted audio on transmit

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

Old timer here ...

I remember once building a DDRR antenna (before I learned what a joke
that idea was) for 20m on the floor on my apartment using just wire for
both the ring and the "ground plane". It was essentially a vertical 10
inches or so of wire with a quarter wave parallel wire transmission line
configured in a circle to "match" it to my SB-101 barefoot. I somehow
managed to make some stateside CW contacts with it, but I had to wear
thick gloves to avoid the severe RF burns (as in black holes deep into
my fingers) from the hand key. Needless to say it only lasted one evening.

73,
Dave AB7E

On 3/11/2014 4:24 PM, Joe Subich, W4TV wrote:

Don Wilhelm-4

Re: K3: Very distorted audio on transmit but only on 20m and only with the KPA500 on

In reply to this post by tomb18

Yes, that condition *does* sound like RF-in-the-Shack - on only some
bands and only at higher powers is the clue to that conclusion.
Refer to the RFI document by K9YC
(http://audiosystemsgroup.com/RFI-Ham.pdf) and construct the common mode
current chokes that he details. One should be at the antenna feedpoint,
and possibly another may be required at the shack entry point (on all
feedlines).

You may get by putting clamp-on ferrites on your mic cable, but the best
solution is to keep the RF out of the shack with the addition of
effective common mode chokes in your antenna system.

73,
Don W3FPR

On 3/11/2014 4:39 PM, [hidden email] wrote:

tomb18

Re: K3: Very distorted audio on transmit but only on 20m and only with the KPA500 on

Hi,

It was some time ago I read that article. I bought about 40 of the big ferrites and I have made one of the chokes near the antenna feed point. I guess another is needed in the shack entry. I used to have them ine th shack just before the equipment but I guess a better place is right outside. It was too much of a pain in the shack.
Will try this out tomorrow.
73’s
On Mar 12, 2014, at 12:09 AM, Don Wilhelm <[hidden email]> wrote:

> Yes, that condition *does* sound like RF-in-the-Shack - on only some bands and only at higher powers is the clue to that conclusion.
> Refer to the RFI document by K9YC (http://audiosystemsgroup.com/RFI-Ham.pdf) and construct the common mode current chokes that he details. One should be at the antenna feedpoint, and possibly another may be required at the shack entry point (on all feedlines).
>
> You may get by putting clamp-on ferrites on your mic cable, but the best solution is to keep the RF out of the shack with the addition of effective common mode chokes in your antenna system.
>
> 73,
> Don W3FPR
>
> On 3/11/2014 4:39 PM, [hidden email] wrote:
>> Ok,
>>
>> So my audio is quite distorted as I can hear in my headphones with the monitor. But this only happens on 20m and only with the KPA500 in operate.
>> Sound like RF? or is something else going on?
>>
>>
>> Thanks
>> ______________________________________________________________
>> 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
>>
>

Joe Subich, W4TV-4

Re: K3: Very distorted audio on transmit but only on 20m and only with the KPA500 on

In reply to this post by Don Wilhelm-4

> Yes, that condition *does* sound like RF-in-the-Shack - on only some
> bands and only at higher powers is the clue to that conclusion.

The key to understand this is to remember that the common mode RF
creates a standing wave on the outside of the coax as if it was a
random length radial which may be open circuited, short circuited or
terminated in a complex impedance. Due to the "random radial" effect,
the standing wave has RF voltage peaks and troughs. If a peak happens
to occur on a sensitive piece of equipment, e.g., the mic preamp in
an audio processor or transceiver, you will most certainly have "RF
feedback" on that band. However, if the voltage trough happens to
occur on the equipment you will never notice the common mode RFI.

Similar issues occur with computers - if the "radial" happens to
include the computer as it will with a computer connected to and
controlling a transceiver and the voltage peak occurs on the serial
or USB cable, you may lose control of the transmitter in transmit.
If the voltage peak happens to occur on a wired keyboard, the keyboard
may "go crazy" or lock up in transmit - the same thing can happen with
a wired mouse.

The worst effect can be physical damage to electronic devices if the RF
voltage gets excessive. If the peak RV voltage exceeds the operating
voltage of the solid state devices (5V for typical USB ports, 3.3V for
low power devices), that negative swings of the RF can cause permanent
reverse voltage breakdown in the solid state devices just as if one had
connected the power supply backward - fortunately the currents are
small and the pulse durations are limited but common mode RF has been
known to damage hardware so it should not be ignored.

73,

... Joe, W4TV

On 3/12/2014 12:09 AM, Don Wilhelm wrote:

> Yes, that condition *does* sound like RF-in-the-Shack - on only some
> bands and only at higher powers is the clue to that conclusion.
> Refer to the RFI document by K9YC
> (http://audiosystemsgroup.com/RFI-Ham.pdf) and construct the common mode
> current chokes that he details. One should be at the antenna feedpoint,
> and possibly another may be required at the shack entry point (on all
> feedlines).
>
> You may get by putting clamp-on ferrites on your mic cable, but the best
> solution is to keep the RF out of the shack with the addition of
> effective common mode chokes in your antenna system.
>
> 73,
> Don W3FPR
>
> On 3/11/2014 4:39 PM, [hidden email] wrote:
>> Ok,
>>
>> So my audio is quite distorted as I can hear in my headphones with the
>> monitor. But this only happens on 20m and only with the KPA500 in
>> operate.
>> Sound like RF? or is something else going on?
>>
>>
>> Thanks
>> ______________________________________________________________
>> 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
>

tomb18

Re: K3: Very distorted audio on transmit but only on 20m and only with the KPA500 on

In reply to this post by tomb18

Looks like im going to have to wait until the snow on the roof is gone. Cant budge the cable at all. And on top of that we're geting 10 more inches tonight.
Thatnks for all the responses
Tom

-------- Original message --------
From: Ian White <[hidden email]>
Date: 12/03/2014 03:59 (GMT-05:00)
To: [hidden email],"'Joe Subich, W4TV'" <[hidden email]>,[hidden email]
Subject: RE: [Elecraft] K3: Very distorted audio on transmit but only on 20m and only with the KPA500 on

>
>Is having the Microham directly on top of the KAT500 Tuner with the
>microphone cable almost touching the RF out a potential issue? If so,
this
>might be an easy fix for now.
>

It shouldn't be an issue... but the closer those two cables are
together, the more you are relying on both cables being fully shielded
and solidly connected to the metal cases of the KAT500 and the Microham.

Poor shield connections on PL259s are a very common source of RFI
problems, and they often grow worse over time. So check all of your
PL259s very carefully - not just at the equipment site but also further
down the line.

73 from Ian GM3SEK

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Post: mailto:[hidden email]

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OE5CSP-Chris

Re: K3: Very distorted audio on transmit but only on 20m and only with the KPA500 on

In reply to this post by tomb18

Hi,

Maybe rf is getting into the microphone.I had exactly the same problems here!!
There is a wonderful article in the latest issue of German´s FUNKAMATEUR.
I´m using the Heil MH2 microphone and I had always problems on 40m with rf getting into the microphone.
The modification is very easy:
Solder a ground strap (I used a "ground strap" for desoldering), to the ground connection of the microphone and connect it to the metal housing of the microphone connector.
This solved all my problems.
You can find the whole story in the December issue on page 1280.Hope that helps.

73,Chris-OE5CSP