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High Current only on 20 Meters

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Leroy Buller

High Current only on 20 Meters

I have a K3 that seems to have a problem. I am getting HI CURRENT warning
only on 20 meters. The antenna is matched. 80, 40 and 15 do not have the
issue. The current meter on the power supply does show quite a bit of
current (20+ amps) on 20 meters but when I reduce power it stops giving me
the issue on 20 meters. When I reduce power on 20 meters, the high current
goes away around 65 watts.

Anyone have an idea what is going on? I do appreciated the help

Lee - K0WA
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k6mkf

Re: High Current only on 20 Meters

What 'pins' do you have? Nickel-platted or gold pins?

- 73 and good DX de Mike, K6MKF, NCDXC Secretary

> -----Original Message-----
> From: [hidden email] <[hidden email]>
> On Behalf Of Leroy Buller
> Sent: Wednesday, March 04, 2020 10:33
> To: Elecraft Reflector <[hidden email]>
> Subject: [Elecraft] High Current only on 20 Meters
>
> I have a K3 that seems to have a problem. I am getting HI CURRENT warning
> only on 20 meters. The antenna is matched. 80, 40 and 15 do not have the
> issue. The current meter on the power supply does show quite a bit of

current
> (20+ amps) on 20 meters but when I reduce power it stops giving me the
issue on

> 20 meters. When I reduce power on 20 meters, the high current goes away
> around 65 watts.
>
> Anyone have an idea what is going on? I do appreciated the help
>
> Lee - K0WA
> ______________________________________________________________
> 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

Message
> delivered to [hidden email]

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Leroy Buller

Re: High Current only on 20 Meters

Gold. They were replaced.

On Wed, Mar 4, 2020, 12:36 PM Mike Flowers <[hidden email]> wrote:

> What 'pins' do you have? Nickel-platted or gold pins?
>
> - 73 and good DX de Mike, K6MKF, NCDXC Secretary
>
> > -----Original Message-----
> > From: [hidden email] <[hidden email]
> >
> > On Behalf Of Leroy Buller
> > Sent: Wednesday, March 04, 2020 10:33
> > To: Elecraft Reflector <[hidden email]>
> > Subject: [Elecraft] High Current only on 20 Meters
> >
> > I have a K3 that seems to have a problem. I am getting HI CURRENT
> warning
> > only on 20 meters. The antenna is matched. 80, 40 and 15 do not have
> the
> > issue. The current meter on the power supply does show quite a bit of
> current
> > (20+ amps) on 20 meters but when I reduce power it stops giving me the
> issue on
> > 20 meters. When I reduce power on 20 meters, the high current goes away
> > around 65 watts.
> >
> > Anyone have an idea what is going on? I do appreciated the help
> >
> > Lee - K0WA
> > ______________________________________________________________
> > 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
> Message
> > delivered to [hidden email]
>
>

Don Wilhelm

Re: High Current only on 20 Meters

In reply to this post by Leroy Buller

Lee,

What is the voltage out of your power supply during transmit? View it
with the K3 ALT VFO B display. If it is below 12 volts, check your
power supply connections. If you are powering the K3 through a
RigRunner or other DC distribution system, eliminate it for the K3 and
connect directly to the power supply terminals.

The K3 will try to keep the power constant, so if the voltage is low,
the current must go up.

73,
Don W3FPR

On 3/4/2020 1:32 PM, Leroy Buller wrote:
> I have a K3 that seems to have a problem. I am getting HI CURRENT warning
> only on 20 meters. The antenna is matched. 80, 40 and 15 do not have the
> issue. The current meter on the power supply does show quite a bit of
> current (20+ amps) on 20 meters but when I reduce power it stops giving me
> the issue on 20 meters. When I reduce power on 20 meters, the high current
> goes away around 65 watts.
>
> Anyone have an idea what is going on? I do appreciated the help
>
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Leroy Buller

Re: High Current only on 20 Meters

Don. It goes to 12.9 volts on 20. On 40 it goes to 13.0. Current on 20
goes to 24 amps then gives me the message. No rig runner. 24 inch #10
wire to the k3

Lee

On Wed, Mar 4, 2020, 12:47 PM Don Wilhelm <[hidden email]> wrote:

> Lee,
>
> What is the voltage out of your power supply during transmit? View it
> with the K3 ALT VFO B display. If it is below 12 volts, check your
> power supply connections. If you are powering the K3 through a
> RigRunner or other DC distribution system, eliminate it for the K3 and
> connect directly to the power supply terminals.
>
> The K3 will try to keep the power constant, so if the voltage is low,
> the current must go up.
>
> 73,
> Don W3FPR
>
> On 3/4/2020 1:32 PM, Leroy Buller wrote:
> > I have a K3 that seems to have a problem. I am getting HI CURRENT
> warning
> > only on 20 meters. The antenna is matched. 80, 40 and 15 do not have
> the
> > issue. The current meter on the power supply does show quite a bit of
> > current (20+ amps) on 20 meters but when I reduce power it stops giving
> me
> > the issue on 20 meters. When I reduce power on 20 meters, the high
> current
> > goes away around 65 watts.
> >
> > Anyone have an idea what is going on? I do appreciated the help
> >
>

Don Wilhelm

Re: High Current only on 20 Meters

Lee,

That should be fine. Try doing the Transmit Gain Calibration on the K3
and if it persists afterwards, email [hidden email].

73,
Don W3FPR

On 3/4/2020 1:54 PM, Leroy Buller wrote:
> Don. It goes to 12.9 volts on 20. On 40 it goes to 13.0. Current on
> 20 goes to 24 amps then gives me the message. No rig runner. 24 inch
> #10 wire to the k3

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Leroy Buller

Re: High Current only on 20 Meters

I did a recalibration. Nada. Off to support

Lee

On Wed, Mar 4, 2020, 1:01 PM Don Wilhelm <[hidden email]> wrote:

> Lee,
>
> That should be fine. Try doing the Transmit Gain Calibration on the K3
> and if it persists afterwards, email [hidden email].
>
> 73,
> Don W3FPR
>
> On 3/4/2020 1:54 PM, Leroy Buller wrote:
> > Don. It goes to 12.9 volts on 20. On 40 it goes to 13.0. Current on
> > 20 goes to 24 amps then gives me the message. No rig runner. 24 inch
> > #10 wire to the k3
>
>

Bob McGraw - K4TAX

Re: High Current only on 20 Meters

In reply to this post by Leroy Buller

I would run a TX gain calibration using the K3 Utility and a 50 ohm dummy load. Then with an external power meter and dummy load, observe the power output on each band. Be sure the ATU is bypassed for this measurement. This would isolate the issue to the PA, ATU or low pass filter which is band dependent.

Bob, K4TAX

Sent from my iPhone

> On Mar 4, 2020, at 12:46 PM, Leroy Buller <[hidden email]> wrote:
>
> I have a K3 that seems to have a problem. I am getting HI CURRENT warning
> only on 20 meters. The antenna is matched. 80, 40 and 15 do not have the
> issue. The current meter on the power supply does show quite a bit of
> current (20+ amps) on 20 meters but when I reduce power it stops giving me
> the issue on 20 meters. When I reduce power on 20 meters, the high current
> goes away around 65 watts.
>
> Anyone have an idea what is going on? I do appreciated the help
>
> Lee - K0WA
> ______________________________________________________________
> 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
> Message delivered to [hidden email]
>

Leroy Buller

Re: High Current only on 20 Meters

Bob,

Yes I think you are right but I think the amps Hp and Lp are ok because it
just happens on 20 mtrs. I think there is something bad in the LPF or
ATU. I betting on the ATU. But not for sure. Emailed support
Lee

On Wed, Mar 4, 2020, 2:11 PM Bob McGraw K4TAX <[hidden email]> wrote:

> I would run a TX gain calibration using the K3 Utility and a 50 ohm dummy
> load. Then with an external power meter and dummy load, observe the power
> output on each band. Be sure the ATU is bypassed for this measurement.
> This would isolate the issue to the PA, ATU or low pass filter which is
> band dependent.
>
> Bob, K4TAX
>
>
> Sent from my iPhone
>
> > On Mar 4, 2020, at 12:46 PM, Leroy Buller <[hidden email]> wrote:
> >
> > I have a K3 that seems to have a problem. I am getting HI CURRENT
> warning
> > only on 20 meters. The antenna is matched. 80, 40 and 15 do not have
> the
> > issue. The current meter on the power supply does show quite a bit of
> > current (20+ amps) on 20 meters but when I reduce power it stops giving
> me
> > the issue on 20 meters. When I reduce power on 20 meters, the high
> current
> > goes away around 65 watts.
> >
> > Anyone have an idea what is going on? I do appreciated the help
> >
> > Lee - K0WA
> > ______________________________________________________________
> > 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
> > Message delivered to [hidden email]
> >
>
>
>

Mark Musick

Re: High Current only on 20 Meters

Hi Lee,

If the ATU is bypassed, it should have no effect.
I'm betting on a LPF issue.

73,
Mark, WB9CIF

-----Original Message-----
From: [hidden email] <[hidden email]> On Behalf Of Leroy Buller
Sent: Wednesday, March 4, 2020 21:24
To: Bob McGraw K4TAX <[hidden email]>
Cc: Elecraft Reflector <[hidden email]>
Subject: Re: [Elecraft] High Current only on 20 Meters

Bob,

Yes I think you are right but I think the amps Hp and Lp are ok because it just happens on 20 mtrs. I think there is something bad in the LPF or ATU. I betting on the ATU. But not for sure. Emailed support Lee

On Wed, Mar 4, 2020, 2:11 PM Bob McGraw K4TAX <[hidden email]> wrote:

> I would run a TX gain calibration using the K3 Utility and a 50 ohm dummy
> load. Then with an external power meter and dummy load, observe the power
> output on each band. Be sure the ATU is bypassed for this measurement.
> This would isolate the issue to the PA, ATU or low pass filter which
> is band dependent.
>
> Bob, K4TAX
>
>
> Sent from my iPhone
>
> > On Mar 4, 2020, at 12:46 PM, Leroy Buller <[hidden email]> wrote:
> >
> > I have a K3 that seems to have a problem. I am getting HI CURRENT
> warning
> > only on 20 meters. The antenna is matched. 80, 40 and 15 do not
> > have
> the
> > issue. The current meter on the power supply does show quite a bit
> > of current (20+ amps) on 20 meters but when I reduce power it stops
> > giving
> me
> > the issue on 20 meters. When I reduce power on 20 meters, the high
> current
> > goes away around 65 watts.
> >
> > Anyone have an idea what is going on? I do appreciated the help
> >
> > Lee - K0WA
> > ______________________________________________________________
> > 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 Message delivered to
> > [hidden email]
> >
>
>
>

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Adrian-3

Re: High Current only on 20 Meters

In reply to this post by Leroy Buller

Use a 15v 30 amp power supply (adjust what you have from 14 to 15 v)
Your IMD also will improve.

Adrian ... vk4tux

On 5/3/20 4:54 am, Leroy Buller wrote:

> Don. It goes to 12.9 volts on 20. On 40 it goes to 13.0. Current on 20
> goes to 24 amps then gives me the message. No rig runner. 24 inch #10
> wire to the k3
>
> Lee
>
> On Wed, Mar 4, 2020, 12:47 PM Don Wilhelm <[hidden email]> wrote:
>
>> Lee,
>>
>> What is the voltage out of your power supply during transmit? View it
>> with the K3 ALT VFO B display. If it is below 12 volts, check your
>> power supply connections. If you are powering the K3 through a
>> RigRunner or other DC distribution system, eliminate it for the K3 and
>> connect directly to the power supply terminals.
>>
>> The K3 will try to keep the power constant, so if the voltage is low,
>> the current must go up.
>>
>> 73,
>> Don W3FPR
>>
>> On 3/4/2020 1:32 PM, Leroy Buller wrote:
>>> I have a K3 that seems to have a problem. I am getting HI CURRENT
>> warning
>>> only on 20 meters. The antenna is matched. 80, 40 and 15 do not have
>> the
>>> issue. The current meter on the power supply does show quite a bit of
>>> current (20+ amps) on 20 meters but when I reduce power it stops giving
>> me
>>> the issue on 20 meters. When I reduce power on 20 meters, the high
>> current
>>> goes away around 65 watts.
>>>
>>> Anyone have an idea what is going on? I do appreciated the help
>>>
> ______________________________________________________________
> 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
> Message delivered to [hidden email]
>

Adrian-3

Re: High Current only on 20 Meters

In reply to this post by Leroy Buller

I get the same on my KX3 on 12m , When using an antenna analyser the 12m
radiation resistance is lower (much less than 50 ohm),

with more reactance component than in the other bands, and when the ATU
corrects the reactance component of the load, the current

tends to be higher (multi-band antenna use with ATU). than the other
bands with more radiation resistance values.

Do you have an antenna analyser ?

You are just on the edge. adj your power supply to 15v, and all will be
well.

Adrian ... vk4tux

On 5/3/20 7:24 am, Leroy Buller wrote:

> Bob,
>
> Yes I think you are right but I think the amps Hp and Lp are ok because it
> just happens on 20 mtrs. I think there is something bad in the LPF or
> ATU. I betting on the ATU. But not for sure. Emailed support
> Lee
>
> On Wed, Mar 4, 2020, 2:11 PM Bob McGraw K4TAX <[hidden email]> wrote:
>
>> I would run a TX gain calibration using the K3 Utility and a 50 ohm dummy
>> load. Then with an external power meter and dummy load, observe the power
>> output on each band. Be sure the ATU is bypassed for this measurement.
>> This would isolate the issue to the PA, ATU or low pass filter which is
>> band dependent.
>>
>> Bob, K4TAX
>>
>>
>> Sent from my iPhone
>>
>>> On Mar 4, 2020, at 12:46 PM, Leroy Buller <[hidden email]> wrote:
>>>
>>> I have a K3 that seems to have a problem. I am getting HI CURRENT
>> warning
>>> only on 20 meters. The antenna is matched. 80, 40 and 15 do not have
>> the
>>> issue. The current meter on the power supply does show quite a bit of
>>> current (20+ amps) on 20 meters but when I reduce power it stops giving
>> me
>>> the issue on 20 meters. When I reduce power on 20 meters, the high
>> current
>>> goes away around 65 watts.
>>>
>>> Anyone have an idea what is going on? I do appreciated the help
>>>
>>> Lee - K0WA
>>> ______________________________________________________________
>>> 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
>>> Message delivered to [hidden email]
>>>
>>
>>
> ______________________________________________________________
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> Message delivered to [hidden email]

Jim Brown-10

Re: High Current only on 20 Meters

On 3/4/2020 2:56 PM, Adrian wrote:
> I get the same on my KX3 on 12m , When using an antenna analyser the 12m
> radiation resistance is lower (much less than 50 ohm),
> with more reactance component than in the other bands, and when the ATU
> corrects the reactance component of the load, the current
> tends to be higher (multi-band antenna use with ATU). than the other
> bands with more radiation resistance values.

I suspect an understanding gap here. What you're describing implies a
severe mismatch AT THE ANTENNA. A mismatched load (the antenna) is
transformed by the transmission line to an entirely different impedance
at every point along the line. The mismatch establishes standing waves
on the line, and SWR is one measurement of that, BUT -- loss in the line
causes SWR to gradually get smaller along the line, reaching its lowest
value at the transmitter.

Computing programs like SimSmith and AC6LA's Excel spreadsheets can take
measured data from analyzers that are capable of producing suitable
files, and, if you know the cable's characteristics, can transform a
measurement made in the shack to the impedance of the antenna itself.

Radiation resistance has meaning ONLY at the antenna feedpoint, and it's
a characteristic of the antenna itself. It represents power that is
radiated by the antenna. IF we could connect the analzyer at the
feedpoint, we would measure its feedpoint impedance, Rs +jXs, but Rs is
NOT necessarily the radiation resistance.

A study of texts like the ARRL Antenna Book (or equivalent in VK-land)
are in order. There's a bit of a tutorial in slide show form on my
website that might get you started on understanding on the transmission
line part of it. http://k9yc.com/PacificonSmithChart.pdf The Smith
Chart is a graphical means of understanding (and computing) what happens
on a transmission line.

73, Jim K9YC
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Adrian-3

Re: High Current only on 20 Meters

Jim, I understand what you have said, and it is what I am familiar with.
My feedline is only 12 feet from kx3 to the lower corner feedpoint on my 80m FW delta loop outside the window, which has a male bnc termination.
I can work on it with a step ladder, it is only 16ft of the ground. The antenna high apex is at 70 ft in a tree out the front.

I measured my band impedance at the antenna itself which is direct fed with coax and using a good coax choke balun.
It varied from 1.3:1 at 80m to 3:1 at 20m and 1.4:1 at 6m, with other bands within those points.

When I say radiation resistance I include the small copper resistance also, which is negligible on this heavy copper wire delta loop.
My observation is that the band with the lowest real resistance at the feedpoint is the band that draws most current on my kx3 ,
which did have the atu engaged, again feedline loss is very low, since it is so short, and quality LMR240 bnc terminated both ends.

So I do understand your correct explanation Jim, and it was good revision, however I should have explained my setup better to
remove any assumptions on your part. The antenna works very well, and I have been working USA, Europe and Asia this week with it on most bands with FT8.

Adrian... vk4tux

My observation

-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On Behalf Of Jim Brown
Sent: Thursday, 5 March 2020 1:54 PM
To: [hidden email]
Subject: Re: [Elecraft] High Current only on 20 Meters

On 3/4/2020 2:56 PM, Adrian wrote:
> I get the same on my KX3 on 12m , When using an antenna analyser the
> 12m radiation resistance is lower (much less than 50 ohm), with more
> reactance component than in the other bands, and when the ATU
> corrects the reactance component of the load, the current tends to be
> higher (multi-band antenna use with ATU). than the other bands with
> more radiation resistance values.

I suspect an understanding gap here. What you're describing implies a severe mismatch AT THE ANTENNA. A mismatched load (the antenna) is transformed by the transmission line to an entirely different impedance at every point along the line. The mismatch establishes standing waves on the line, and SWR is one measurement of that, BUT -- loss in the line causes SWR to gradually get smaller along the line, reaching its lowest value at the transmitter.

Computing programs like SimSmith and AC6LA's Excel spreadsheets can take measured data from analyzers that are capable of producing suitable files, and, if you know the cable's characteristics, can transform a measurement made in the shack to the impedance of the antenna itself.

Radiation resistance has meaning ONLY at the antenna feedpoint, and it's a characteristic of the antenna itself. It represents power that is radiated by the antenna. IF we could connect the analzyer at the feedpoint, we would measure its feedpoint impedance, Rs +jXs, but Rs is NOT necessarily the radiation resistance.

A study of texts like the ARRL Antenna Book (or equivalent in VK-land) are in order. There's a bit of a tutorial in slide show form on my website that might get you started on understanding on the transmission line part of it. http://k9yc.com/PacificonSmithChart.pdf The Smith Chart is a graphical means of understanding (and computing) what happens on a transmission line.

73, Jim K9YC
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Jim Brown-10

Re: High Current only on 20 Meters

On 3/4/2020 8:15 PM, Adrian wrote:
> When I say radiation resistance I include the small copper resistance also, which is negligible on this heavy copper wire delta loop.

An important part of my post was about using the right words to describe
physical reality. Radiation resistance is a characteristic of an
antenna, and can be used to compute antenna efficiency. That's NOT what
you're measuring. You are measuring feedpoint impedance (assuming you
can connect at the feedpoint AND that your measurement setup doesn't
change the impedance).

So please call it what it is -- the feedpoint impedance, which your
analzyer probably reports as Rs + j Xs). :)

73, Jim K9YC

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Adrian-3

Re: High Current only on 20 Meters

Jim, yes in you example ' Rs + j Xs)' I was referring to Rs, which I though
was the antenna resistance, and jXs the capacitive or Inductive reactance,
of which does not
consume any power, but effects the power factor (phase shift) acting on the
real antenna resistance. Which part did I misquote or misunderstand Jim, or
is Rs not the antenna resistance
under the conditions of measurement. ?

Adrian ... vk4tux

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Jim Brown
Sent: Thursday, 5 March 2020 2:32 PM
To: [hidden email]
Subject: Re: [Elecraft] High Current only on 20 Meters

On 3/4/2020 8:15 PM, Adrian wrote:
> When I say radiation resistance I include the small copper resistance
also, which is negligible on this heavy copper wire delta loop.

An important part of my post was about using the right words to describe
physical reality. Radiation resistance is a characteristic of an antenna,
and can be used to compute antenna efficiency. That's NOT what you're
measuring. You are measuring feedpoint impedance (assuming you can connect
at the feedpoint AND that your measurement setup doesn't change the
impedance).

So please call it what it is -- the feedpoint impedance, which your analzyer
probably reports as Rs + j Xs). :)

73, Jim K9YC

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Jim Brown-10

Re: High Current only on 20 Meters

Adrian,

Power factor is a quantity associated with mains power (and similar
power distribution systems). In the old days (when I went through EE),
it was, indeed, related to the phase angle.

With RF systems, it's the load that the antenna presents to the
feedline, and it's different at every frequency. It's primary
significance is how it looks to the feedline, which in turn affects loss
in the line and, after being transformed by the line, whether the
transmitter can put power into it. The function of an antenna tuner is
to transform whatever that impedance is to something the 1) makes the
output stage "happy", and 2) that the output stage can supply power to
without stress on the output stage that could cause destructive failure.

When "happy" has been achieved, the transmitter is delivering power to
the line, but if the match between antenna and line is poor, not much of
that power may get to the antenna, but be turned into heat in the
transmission line.

Remember I said that VSWR in a system is set by the load (the antenna)
and is decreased by the loss in the line. If the line is long enough and
mismatch is great enough, the VSWR eventually ends up a 1:1. I've used
this example as an extreme case: a 1,000 ft spool of RG58 with a 10K ohm
load would look like a perfect 50 ohm load to a transmitter at 28 MHz,
the SWR would read 1:1 at the transmitter end of the line, and loss in
the feedline would be huge.

73, Jim K9YC

On 3/4/2020 9:57 PM, Adrian wrote:

> Jim, yes in you example ' Rs + j Xs)' I was referring to Rs, which I though
> was the antenna resistance, and jXs the capacitive or Inductive reactance,
> of which does not
> consume any power, but effects the power factor (phase shift) acting on the
> real antenna resistance. Which part did I misquote or misunderstand Jim, or
> is Rs not the antenna resistance
> under the conditions of measurement. ?
>
> Adrian ... vk4tux
>
> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Jim Brown
> Sent: Thursday, 5 March 2020 2:32 PM
> To: [hidden email]
> Subject: Re: [Elecraft] High Current only on 20 Meters
>
> On 3/4/2020 8:15 PM, Adrian wrote:
>> When I say radiation resistance I include the small copper resistance
> also, which is negligible on this heavy copper wire delta loop.
>
> An important part of my post was about using the right words to describe
> physical reality. Radiation resistance is a characteristic of an antenna,
> and can be used to compute antenna efficiency. That's NOT what you're
> measuring. You are measuring feedpoint impedance (assuming you can connect
> at the feedpoint AND that your measurement setup doesn't change the
> impedance).
>
> So please call it what it is -- the feedpoint impedance, which your analzyer
> probably reports as Rs + j Xs). :)
>
> 73, Jim K9YC
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html Message
> delivered to [hidden email]
>

Jim Brown-10

Power Factor

On 3/4/2020 10:15 PM, Jim Brown wrote:
> Power factor is a quantity associated with mains power (and similar
> power distribution systems). In the old days (when I went through EE),
> it was, indeed, related to the phase angle.

I meant to add that power factor now includes the triplen harmonics
resulting from non-sinusoidal current with power systems that are mostly
electronic loads. Current flows mostly in short peaks at the positive
and negative peaks of the mains waveform to charge the filter capacitors
in the power supply; as a result, the voltage waveform is rounded off
and the current is rich in harmonics of the mains frequency, 50 or 60 Hz.

Nearly all power distribution uses 3-phase wiring, and "triplen"
harmonics (those whose number is divisible by 3) add in the neutral, no
matter how well balanced the load between phases. This turned into a
major problem roughly 50 years ago, when a very high fraction of current
in these systems was delivered to electronic loads, everything from
fluorescent lights to computers to anything with an AC to DC power
supply. The most dangerous side effect is that triplen currents in the
neutral of 3-phase systems can be almost twice the current in the
phases, which can cause destructive failures in older systems, where the
neutral used conductors and hardware rated for half the current in the
phases! The movie "The Flaming Inferno" is based on the true story of a
massive fire in a high rise that was started by that neutral current,
spread through the building in vertical "riser" spaces, and that was
fueled by the insulation on the cables themselves! Sometime in the last
century, a major TV station almost went off the air because excessive
heating of their power distribution was close to catching on fire! I
attended an SBE (Society of Broadcast Engineers) meeting led by the
consultant who worked with the station engineers on the problem.

MAJOR changes were made to standards for mains wiring after this event,
including the rating of transformers and neutral hardware to handle the
peak currents and the harmonic content, conduit requirements for the
wiring, and requirements for insulation on the wiring that does not
contribute to flame spread and that does not produce toxic fumes.

BTW -- the triplen harmonics also appear on equipment ground, and are
the reason why we mostly hear power line noise in the audio as "buzz"
(triplen harmonics of 50/60 Hz) rather than "hum" (pure 50/60 Hz).

There's a not-too-technical discussion of all of this written for hams
in http://k9yc.com/GroundingAndAudio.pdf
and a more detailed one written for sound and video professionals in
http://k9yc.com/SurgeXPowerGround.pdf

73, Jim K9YC
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Adrian-3

Re: Power Factor

Jim, Ok on that, I am a retired tradesman in the electrical industry, and
looking at why an antenna radiates best when reactance is zero leaving only
a resistance load (not taking radiation angle into account),
would seem to be because the voltage and current across the radiated load
are in phase providing maximum power dissipation, whereas any added
reactance with phase shift would diminish that ,
as well as change the impedance.

I understand there are other factors in efficient power transfer, but I am
confident above is part of the picture. As you know it's the reason
capacitors were used in fluorescent light fittings with inductive ballasts
for power factor correction . On my Delta loop it is great on 80m, but on
40m and up I switch in a 100pF capacitor to null the inductive reactance I
see on the antenna there, reducing swr from 5.1:1 to 1.7:1
at the feedpoint.

It should be better, not needing that, but not all antennas follow a
resonant trend through the bands. Due to compromises etc working around
buildings and structures to do the best with what you have.

Adrian ... vk4tux

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Jim Brown
Sent: Thursday, 5 March 2020 4:45 PM
To: [hidden email]
Subject: [Elecraft] Power Factor

On 3/4/2020 10:15 PM, Jim Brown wrote:
> Power factor is a quantity associated with mains power (and similar
> power distribution systems). In the old days (when I went through EE),
> it was, indeed, related to the phase angle.

I meant to add that power factor now includes the triplen harmonics
resulting from non-sinusoidal current with power systems that are mostly
electronic loads. Current flows mostly in short peaks at the positive and
negative peaks of the mains waveform to charge the filter capacitors in the
power supply; as a result, the voltage waveform is rounded off and the
current is rich in harmonics of the mains frequency, 50 or 60 Hz.

Nearly all power distribution uses 3-phase wiring, and "triplen"
harmonics (those whose number is divisible by 3) add in the neutral, no
matter how well balanced the load between phases. This turned into a major
problem roughly 50 years ago, when a very high fraction of current in these
systems was delivered to electronic loads, everything from fluorescent
lights to computers to anything with an AC to DC power supply. The most
dangerous side effect is that triplen currents in the neutral of 3-phase
systems can be almost twice the current in the phases, which can cause
destructive failures in older systems, where the neutral used conductors and
hardware rated for half the current in the phases! The movie "The Flaming
Inferno" is based on the true story of a massive fire in a high rise that
was started by that neutral current, spread through the building in vertical
"riser" spaces, and that was fueled by the insulation on the cables
themselves! Sometime in the last century, a major TV station almost went off
the air because excessive heating of their power distribution was close to
catching on fire! I attended an SBE (Society of Broadcast Engineers) meeting
led by the consultant who worked with the station engineers on the problem.

MAJOR changes were made to standards for mains wiring after this event,
including the rating of transformers and neutral hardware to handle the peak
currents and the harmonic content, conduit requirements for the wiring, and
requirements for insulation on the wiring that does not contribute to flame
spread and that does not produce toxic fumes.

BTW -- the triplen harmonics also appear on equipment ground, and are the
reason why we mostly hear power line noise in the audio as "buzz"
(triplen harmonics of 50/60 Hz) rather than "hum" (pure 50/60 Hz).

There's a not-too-technical discussion of all of this written for hams in
http://k9yc.com/GroundingAndAudio.pdf
and a more detailed one written for sound and video professionals in
http://k9yc.com/SurgeXPowerGround.pdf

73, Jim K9YC
______________________________________________________________
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David Gilbert

Re: High Current only on 20 Meters

In reply to this post by Jim Brown-10

Completely true. According to TLW, 1,000 feet of RG-58 with a dead
short on the far end will also have a 1:1 SWR at the near end. Even 500
feet will have an SWR less than 1.1:1 at the near end.

In fact, as little as 100 feet of RG-58 will turn a 2:1 SWR at the far
end into roughly 1.5:1 at the near end even at 14 MHz. All of the
difference is line loss, although I'm sure someone would point out that
it's "only" about 2.2 db worth and doesn't really change the SNR for
receive on this end of the path (not true on the other end of course).

73,
Dave AB7E

On 3/4/2020 11:15 PM, Jim Brown wrote:

>
>
> Remember I said that VSWR in a system is set by the load (the antenna)
> and is decreased by the loss in the line. If the line is long enough
> and mismatch is great enough, the VSWR eventually ends up a 1:1. I've
> used this example as an extreme case: a 1,000 ft spool of RG58 with a
> 10K ohm load would look like a perfect 50 ohm load to a transmitter at
> 28 MHz, the SWR would read 1:1 at the transmitter end of the line, and
> loss in the feedline would be huge.
>
> 73, Jim K9YC