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KPA-500 "Output for Input" schedule?

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Gary Gregory

Re: KPA-500 "Output for Input" schedule?

Al,

Output was measured using the KPA FW which has proven to be very accurate so
far in FT units.

Gary

On 12 May 2011 10:10, Al Lorona <[hidden email]> wrote:

> I imported Gary's measured data to analyze it. It's a little bit difficult,
> because I'm just using a graphical method (a.k.a. 'eyeballing') to try and
> find
> the 1 dB compression point, but it is only compressed about 0.6 dB at
> Gary's
> highest power point. I estimate, if we extrapolate out a little bit, that
> the
> 1dB point is at about 45 W input power (at approx. 700 W output). One of
> the
> obvious sources of error, if you plot the data, is the linearity of Gary's
> power
> meter, but anyway that's what a first cut at it looks like.
>
> Al W6LX
>
>
>
>
> ________________________________
> From: Gary Gregory <[hidden email]>
> To: "Joe Subich, W4TV" <[hidden email]>
> Cc: [hidden email]
> Sent: Wed, May 11, 2011 3:46:57 PM
> Subject: Re: [Elecraft] KPA-500 "Output for Input" schedule?
>
> The RFsensing on the K3 is a real trick. The frst 'dit' may suffer a mild
> truncation on band change, but this only happens if you don't press a band
> button prior to transmitting.
>
> Low power band changing does occur with 1W on CW. Tested it just now with a
> band change from 10M to 15M
>
> Maybe this is of help?
>
> Gary
>
> On 12 May 2011 08:41, Gary Gregory <[hidden email]> wrote:
>
> > Joe,
> >
> > Just to clarify, the last measurements were on 28.447.44 (a clear
> frequency
> > here at the moment), SWR is 1.1:1, tri-band yagi.
> >
> >
> > On 12 May 2011 08:40, Gary Gregory <[hidden email]> wrote:
> >
> >> Joe,
> >>
> >> 325W @ 15W drive
> >> 410W @ 20W drive
> >> 490W @ 25W drive
> >> 510W @ 26W drive
> >> 530W @ 27W drive
> >> 560W @ 28W drive
> >> 580W @ 29W drive
> >> 600W @ 30W drive
> >> 630W @ 31W drive
> >> 650W @ 32W drive
> >> 675W @ 35W drive
> >> 690W @ 37W drive
> >> 700W @ 40W drive
> >>
> >> Is this still about right for your calculations.....
> >>
> >> Gary
> >>
> >>
> >> On 12 May 2011 08:18, Joe Subich, W4TV <[hidden email]> wrote:
> >>
> >>>
> >>> Adding gain calculation ...
> >>>
> >>>
> >>> > 2W = 30W 11.8 dB
> >>> > 2.5W = 40W 12.0 dB
> >>> > 3w = 50w 12.2 dB
> >>> > 3.5w = 60w 12.3 dB
> >>> > 4w = 70w 12.4 dB
> >>> > 4.5w = 75w 12.2 dB
> >>> > 5w = 80w 12.0 dB
> >>> > 5.5w = 90w 12.1 dB
> >>> > 6w = 100w 12.2 dB
> >>> > 6.5w = 110w 12.3 dB
> >>> > 7w = 120w 12.3 dB
> >>> > 7.5w = 130w 12.4 dB
> >>> > 8w = 150w 12.7 dB
> >>> > 8.5w = 160w 12.7 dB
> >>> > 9w = 170w 12.8 dB
> >>> > 9.5w = 180w 12.8 dB
> >>> > 10w = 190w 12.8 dB
> >>> > 11w = 200w 12.6 dB
> >>> > 12w = 225w 12.7 dB
> >>>
> >>> The numbers look about right including the decreased gain at low level
> >>> (as expected). Using 12.6/12.7 dB would indicate 33W drive for 600W
> >>> out. 40W drive for 600W output would indicate ~1 dB of compression.
> >>>
> >>> 73,
> >>>
> >>> ... Joe, W4TV
> >>>
> >>> On 5/11/2011 5:28 PM, Gary Gregory wrote:
> >>> > Stan,
> >>> >
> >>> > Allow some variation to antenna variations also.
> >>> >
> >>> > This on 15M, swr is 1.0:1
> >>> >
> >>> > 2W = 30W out
> >>> > 2.5W = 40W
> >>> > 3w = 50w
> >>> > 3.5w = 60w
> >>> > 4w = 70w
> >>> > 4.5w = 75w out
> >>> > 5w = 80w
> >>> > 5.5w = 90w
> >>> > 6w = 100w
> >>> > 6.5w = 110w
> >>> > 7w = 120w
> >>> > 7.5w = 130w
> >>> > 8w = 150w
> >>> > 8.5w = 160w
> >>> > 9w = 170w
> >>> > 9.5w = 180w
> >>> > 10w = 190w
> >>> > 11w = 200w
> >>> > 12w = 225w
> >>> >
> >>> > NOTE to ALL: This was not done with lab equipment or even a dummy
> load.
> >>> This
> >>> > was measured using a K3 and a tri-band yagi and a cw tone.
> >>> >
> >>> > Gary
> >>> >
> >>> > On 12 May 2011 07:13, Al Lorona<[hidden email]> wrote:
> >>> >
> >>> >> It's very easy to measure the 1-tone gain compression
> characteristics
> >>> of an
> >>> >> amplifier. The desired result is a graph of Pout vs. Pin, with Pin
> on
> >>> the
> >>> >> horizontal axis and Pout on the vertical.
> >>> >>
> >>> >> So what one needs to do is set Pin to the amp, and measure Pout into
> a
> >>> >> dummy
> >>> >> load. If you do this for several values of Pin, you'll be able to
> plot
> >>> all
> >>> >> of
> >>> >> those measured points on the graph. It will look like a pretty
> >>> straight
> >>> >> line
> >>> >> toward the lower Pin values, then it will flatten out (become more
> >>> >> horizontal)
> >>> >> as Pin (and Pout) get higher.
> >>> >>
> >>> >> The slope of the line is the gain of the amplifier.
> >>> >>
> >>> >> Very often the Pin values are 1 dB apart. One dB is about a 25%
> >>> increase in
> >>> >> power. Meaning that if you are measuring Pin in Watts, then you can
> >>> set Pin
> >>> >> to
> >>> >> roughly the following values:
> >>> >>
> >>> >> 1, 1.5, 2, 3, 4, 5, 7, 10, 13 Watts, etc.,
> >>> >>
> >>> >> and measure the Pout at each value. The values should be converted
> to
> >>> dBm
> >>> >> before
> >>> >> plotting. That's all there is to it.
> >>> >>
> >>> >> This is all done in CW mode. If you want to go further, you can go
> >>> into SSB
> >>> >> mode
> >>> >> and apply two tones to the amp (which a K3 has the ability to do)
> and
> >>> then
> >>> >> look
> >>> >> at the output of both the K3 and the KPA500 with a spectrum
> >>> analyzer... but
> >>> >> I'll
> >>> >> leave that explanation for another day... or it can be found on the
> >>> web.
> >>> >>
> >>> >> Al W6LX
> >>> >> ______________________________________________________________
> >>> >> 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
> >>>
> >>
> >>
> >>
> >> --
> >>
> >> VK4FD - Motorhome Mobile
> >> Elecraft Equipment
> >> K3 #679, KPA-500 #018
> >> Living the dream!!!
> >>
> >>
> >
> >
> > --
> >
> > VK4FD - Motorhome Mobile
> > Elecraft Equipment
> > K3 #679, KPA-500 #018
> > Living the dream!!!
> >
> >
>
>
> --
>
> VK4FD - Motorhome Mobile
> Elecraft Equipment
> K3 #679, KPA-500 #018
> Living the dream!!!
> ______________________________________________________________
> 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
>

--

VK4FD - Motorhome Mobile
Elecraft Equipment
K3 #679, KPA-500 #018
Living the dream!!!
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Guy, K2AV

Re: KPA-500 "Output for Input" schedule?

In reply to this post by Gary Gregory

Adding a power gain and rounding to nearest two digit integer,
considering accuracy of measuring device (rarely more than two
significant digits), it is safe to say that the amplifier keeps its
linearity to 650 watts. The variability at 325 and 410 is most likely
the measuring instrument's issues at lower powers.

The linearity at the top PEP level is the most important, as squaring
at that level will produce the most distortion energy. Really quite
good.

............................. Power Ratio

325W @ 15W drive 21.67 22
410W @ 20W drive 20.50 21
490W @ 25W drive 19.67 20
510W @ 26W drive 19.61 20
530W @ 27W drive 19.63 20
560W @ 28W drive 20.00 20
580W @ 29W drive 20.00 20
600W @ 30W drive 20.00 20
630W @ 31W drive 20.32 20
650W @ 32W drive 20.31 20
675W @ 35W drive 19.29 19
690W @ 37W drive 18.65 19
700W @ 40W drive 17.50 18

On Wed, May 11, 2011 at 6:40 PM, Gary Gregory <[hidden email]> wrote:

> Joe,
>
> 325W @ 15W drive
> 410W @ 20W drive
> 490W @ 25W drive
> 510W @ 26W drive
> 530W @ 27W drive
> 560W @ 28W drive
> 580W @ 29W drive
> 600W @ 30W drive
> 630W @ 31W drive
> 650W @ 32W drive
> 675W @ 35W drive
> 690W @ 37W drive
> 700W @ 40W drive
>
> Is this still about right for your calculations.....
>
> Gary
>
> On 12 May 2011 08:18, Joe Subich, W4TV <[hidden email]> wrote:
>
>>
>> Adding gain calculation ...
>>
>>
>> > 2W = 30W 11.8 dB
>> > 2.5W = 40W 12.0 dB
>> > 3w = 50w 12.2 dB
>> > 3.5w = 60w 12.3 dB
>> > 4w = 70w 12.4 dB
>> > 4.5w = 75w 12.2 dB
>> > 5w = 80w 12.0 dB
>> > 5.5w = 90w 12.1 dB
>> > 6w = 100w 12.2 dB
>> > 6.5w = 110w 12.3 dB
>> > 7w = 120w 12.3 dB
>> > 7.5w = 130w 12.4 dB
>> > 8w = 150w 12.7 dB
>> > 8.5w = 160w 12.7 dB
>> > 9w = 170w 12.8 dB
>> > 9.5w = 180w 12.8 dB
>> > 10w = 190w 12.8 dB
>> > 11w = 200w 12.6 dB
>> > 12w = 225w 12.7 dB
>>
>> The numbers look about right including the decreased gain at low level
>> (as expected). Using 12.6/12.7 dB would indicate 33W drive for 600W
>> out. 40W drive for 600W output would indicate ~1 dB of compression.
>>
>> 73,
>>
>> ... Joe, W4TV
>>
>> On 5/11/2011 5:28 PM, Gary Gregory wrote:
>> > Stan,
>> >
>> > Allow some variation to antenna variations also.
>> >
>> > This on 15M, swr is 1.0:1
>> >
>> > 2W = 30W out
>> > 2.5W = 40W
>> > 3w = 50w
>> > 3.5w = 60w
>> > 4w = 70w
>> > 4.5w = 75w out
>> > 5w = 80w
>> > 5.5w = 90w
>> > 6w = 100w
>> > 6.5w = 110w
>> > 7w = 120w
>> > 7.5w = 130w
>> > 8w = 150w
>> > 8.5w = 160w
>> > 9w = 170w
>> > 9.5w = 180w
>> > 10w = 190w
>> > 11w = 200w
>> > 12w = 225w
>> >
>> > NOTE to ALL: This was not done with lab equipment or even a dummy load.
>> This
>> > was measured using a K3 and a tri-band yagi and a cw tone.
>> >
>> > Gary
>> >
>> > On 12 May 2011 07:13, Al Lorona<[hidden email]> wrote:
>> >
>> >> It's very easy to measure the 1-tone gain compression characteristics of
>> an
>> >> amplifier. The desired result is a graph of Pout vs. Pin, with Pin on
>> the
>> >> horizontal axis and Pout on the vertical.
>> >>
>> >> So what one needs to do is set Pin to the amp, and measure Pout into a
>> >> dummy
>> >> load. If you do this for several values of Pin, you'll be able to plot
>> all
>> >> of
>> >> those measured points on the graph. It will look like a pretty straight
>> >> line
>> >> toward the lower Pin values, then it will flatten out (become more
>> >> horizontal)
>> >> as Pin (and Pout) get higher.
>> >>
>> >> The slope of the line is the gain of the amplifier.
>> >>
>> >> Very often the Pin values are 1 dB apart. One dB is about a 25% increase
>> in
>> >> power. Meaning that if you are measuring Pin in Watts, then you can set
>> Pin
>> >> to
>> >> roughly the following values:
>> >>
>> >> 1, 1.5, 2, 3, 4, 5, 7, 10, 13 Watts, etc.,
>> >>
>> >> and measure the Pout at each value. The values should be converted to
>> dBm
>> >> before
>> >> plotting. That's all there is to it.
>> >>
>> >> This is all done in CW mode. If you want to go further, you can go into
>> SSB
>> >> mode
>> >> and apply two tones to the amp (which a K3 has the ability to do) and
>> then
>> >> look
>> >> at the output of both the K3 and the KPA500 with a spectrum analyzer...
>> but
>> >> I'll
>> >> leave that explanation for another day... or it can be found on the web.
>> >>
>> >> Al W6LX
>> >> ______________________________________________________________
>> >> 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
>>
>
>
>
> --
>
> VK4FD - Motorhome Mobile
> Elecraft Equipment
> K3 #679, KPA-500 #018
> Living the dream!!!
> ______________________________________________________________
> 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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Don Wilhelm-4

Re: KPA-500 "Output for Input" schedule?

While those results are very good, I would like to point out that it
is from a sample of one KPA500. I would suggest that an allowance of
10% be considered over the entire population of KPA500s just due to
component tolerances giving rise to some unit to unit variation. Even
using the 10% variation criteria, the KPA500 is more linear than many
other available amplifiers. Elecraft has created another winner.

Those measurements Gary made have substantiated that the KPA500 can be
useful whether the driving transceiver is a K1, or K2/10, a K2/100 or a
K3/10 or a K3/100 or some other brand of transceiver from QRP levels to
100 watt class transceivers.

73,
Don W3FPR

On 5/11/2011 11:05 PM, Guy Olinger K2AV wrote:

stan levandowski

Re: KPA-500 "Output for Input" schedule?

In reply to this post by stan levandowski

I hope that Elecraft considers making this a published selling point in
print large enough to gain the attention of those of us who do indeed
own lower powered rigs. It presents us with another flexible option if
and when we decide to add more power. When the KPA-500 was announced, I
immediately dismissed it as a product that was not compatible with my
equipment, especially after all those references to "40 watts drive" in
the documentation. I offer this from the perspective of a 'hobby ham'
with nowhere near the technical acumen demonstrated by so many of those
on this great Reflector.

Now, work on the XYL can begin in earnest...

73, Stan WB2LQF
KX1 #2411 K1#2994 K2# 6980 K3#5244 K9 #1 (Cocoa the
Chihuahua)
Everything is QRP, even the dog.

On Wed, May 11, 2011 at 11:30 PM, Don Wilhelm wrote:

> Those measurements Gary made have substantiated that the KPA500 can be
> useful whether the driving transceiver is a K1, or K2/10, a K2/100 or
> a K3/10 or a K3/100 or some other brand of transceiver from QRP levels
> to 100 watt class transceivers.

______________________________________________________________
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Geoffrey Mackenzie-Kennedy

Re: KPA-500 "Output for Input" schedule?

In reply to this post by n7ws

Hello Wes,

The practical question "how much non-linearity is acceptable" in commercial
HF systems has been debated by some Regulators and their advisers from
industry for years - certainly since the early 1960s in my experience.

In the context of linear amplifiers (or complete transmitters) designed for
commercial single channel voice SSB, their linearity (or lack of) is usually
expressed in terms of occupied bandwidth - from which the acceptable levels
of odd order intermodulation products can be determined, which in turn leads
to the commonly used specification limit for 3rd Order Intermodulation
products. Even back in the 1960s the Type Approval specification limit for
3rd Order products was typically 30db below test tone for HF transmitters
rated up to and including 1 kW PEP output. This spec had to be met over the
supply voltage range as specified by the manufacturer, together when driving
a RF load whose impedance was not only fixed at nominal (e.g. 50 +j0) but
also at other values which escape me.

For some reason this magic number of 30db appears to have remained as part
of our ham folklore, worse yet 30db below PEP not test tone, and IMHO needs
to be increased now that the bands are more crowded. Driving a so-so
"linear" with a transceiver whose IMD performance is poor is a recipe of
course for wideband crud, and there are many crud generators here in Europe.

Whereas a plot of output power vs input power will give some idea of
linearity, in particular when an amplifier enters compression, unfortunately
it will not expose any "misbehaviour" of the level of IMD products at lower
output levels even if the plot appears to be "linear" at these levels.

To give a SSB rig a clean bill of health you really do need to perform
two-tone tests at vaious power output levels, which I suspect Elecraft has
done.

73,

Geoff
GM4ESD

----- Original Message -----
From: "Wes Stewart" <[hidden email]>
To: <[hidden email]>; "G4ILOJulian" <[hidden email]>
Sent: Wednesday, May 11, 2011 8:02 PM
Subject: Re: [Elecraft] KPA-500 "Output for Input" schedule?

> Then by definition, they aren't linear.
>
> A graph of output power vs. input power should be a straight line. It it
> isn't then it's non-linear. The practical question is how much
> non-linearity is acceptable.
>
> --- On Wed, 5/11/11, Julian, G4ILO <[hidden email]> wrote:
>
>>
>> If it does that then it will be the first linear amplifier
>> I have ever seen
>> that actually keeps that relationship across the whole of
>> its range.
>>
>> Most solid state amplifiers exhibit noticeable compression
>> as you increase
>> the input power, so you get a lot more than half the rated
>> power out for
>> half the specified drive power.
>>
>> Take a look at the figures for this Mirage amp (selected at
>> random as being
>> the first spec sheet I could find that proved the point.)
>> It is only truly
>> linear up to half its rated output. 10W in gives the rated
>> 160W output, but
>> 5W gives you 150W 2.5W would give you somewhere around
>> 120W. The VHF amp I
>> have here has a similar characteristic. Although it is
>> designed to be driven
>> with 5W input I am actually driving it with the K3/K144XV
>> with less than
>> half that power and still get virtually full output.
>>
>> So I think the OP actually asked a very reasonable
>> question.
>>
> ______________________________________________________________
> 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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Guy, K2AV

Re: KPA-500 "Output for Input" schedule?

I would like to know if some kind of feedback (maybe complicated)
could bring about a quantum leap in linearity, like sampling the
output of the amp and feeding that back to the K3 to digitally
pre-alter the audio to cancel the distortion going out.

On Thu, May 12, 2011 at 9:12 AM, Geoffrey Mackenzie-Kennedy
<[hidden email]> wrote:

> Hello Wes,
>
> The practical question "how much non-linearity is acceptable" in commercial
> HF systems has been debated by some Regulators and their advisers from
> industry for years - certainly since the early 1960s in my experience.
>
> In the context of linear amplifiers (or complete transmitters) designed for
> commercial single channel voice SSB, their linearity (or lack of) is usually
> expressed in terms of occupied bandwidth - from which the acceptable levels
> of odd order intermodulation products can be determined, which in turn leads
> to the commonly used specification limit for 3rd Order Intermodulation
> products. Even back in the 1960s the Type Approval specification limit for
> 3rd Order products was typically 30db below test tone for HF transmitters
> rated up to and including 1 kW PEP output. This spec had to be met over the
> supply voltage range as specified by the manufacturer, together when driving
> a RF load whose impedance was not only fixed at nominal (e.g. 50 +j0) but
> also at other values which escape me.
>
> For some reason this magic number of 30db appears to have remained as part
> of our ham folklore, worse yet 30db below PEP not test tone, and IMHO needs
> to be increased now that the bands are more crowded. Driving a so-so
> "linear" with a transceiver whose IMD performance is poor is a recipe of
> course for wideband crud, and there are many crud generators here in Europe.
>
> Whereas a plot of output power vs input power will give some idea of
> linearity, in particular when an amplifier enters compression, unfortunately
> it will not expose any "misbehaviour" of the level of IMD products at lower
> output levels even if the plot appears to be "linear" at these levels.
>
> To give a SSB rig a clean bill of health you really do need to perform
> two-tone tests at vaious power output levels, which I suspect Elecraft has
> done.
>
> 73,
>
> Geoff
> GM4ESD
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> ----- Original Message -----
> From: "Wes Stewart" <[hidden email]>
> To: <[hidden email]>; "G4ILOJulian" <[hidden email]>
> Sent: Wednesday, May 11, 2011 8:02 PM
> Subject: Re: [Elecraft] KPA-500 "Output for Input" schedule?
>
>
>> Then by definition, they aren't linear.
>>
>> A graph of output power vs. input power should be a straight line. It it
>> isn't then it's non-linear. The practical question is how much
>> non-linearity is acceptable.
>>
>> --- On Wed, 5/11/11, Julian, G4ILO <[hidden email]> wrote:
>>
>>>
>>> If it does that then it will be the first linear amplifier
>>> I have ever seen
>>> that actually keeps that relationship across the whole of
>>> its range.
>>>
>>> Most solid state amplifiers exhibit noticeable compression
>>> as you increase
>>> the input power, so you get a lot more than half the rated
>>> power out for
>>> half the specified drive power.
>>>
>>> Take a look at the figures for this Mirage amp (selected at
>>> random as being
>>> the first spec sheet I could find that proved the point.)
>>> It is only truly
>>> linear up to half its rated output. 10W in gives the rated
>>> 160W output, but
>>> 5W gives you 150W 2.5W would give you somewhere around
>>> 120W. The VHF amp I
>>> have here has a similar characteristic. Although it is
>>> designed to be driven
>>> with 5W input I am actually driving it with the K3/K144XV
>>> with less than
>>> half that power and still get virtually full output.
>>>
>>> So I think the OP actually asked a very reasonable
>>> question.
>>>
>> ______________________________________________________________
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Geoffrey Mackenzie-Kennedy

Re: KPA-500 "Output for Input" schedule?

Hello Guy,

The short answer to the first part of your question is yes, and the generic
term for such a scheme is Predistortion. A term that has been used to
identify a Predistortion scheme which employ digital techniques is a
"Digital Predistortion Linearizer" (DPL), and its use can bring about a
significant reduction in the level of IMD being transmitted compared to a
classic class AB design. Unfortunately the relevant data that I have is
packed ready to leave for Luxembourg.

I don't know how easy or difficult DPL would be to implement in the K3, or
in any other "already designed" rig which employs DSP, but I suspect that
somebody else reading this could tell you.

73,
Geoff
GM4ESD

On Thursday, May 12, 2011 at 4:15 PM, Guy Olinger K2AV wrote:

> I would like to know if some kind of feedback (maybe complicated)
> could bring about a quantum leap in linearity, like sampling the
> output of the amp and feeding that back to the K3 to digitally
> pre-alter the audio to cancel the distortion going out.

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Guy, K2AV

Re: KPA-500 "Output for Input" schedule?

That would be a KEEN addition to a K3/KPA500 combo. Put it way out
there and give the industry yet another bone-breaking kick in the *ss.

On Thu, May 12, 2011 at 12:44 PM, Geoffrey Mackenzie-Kennedy
<[hidden email]> wrote:

> Hello Guy,
>
> The short answer to the first part of your question is yes, and the generic
> term for such a scheme is Predistortion. A term that has been used to
> identify a Predistortion scheme which employ digital techniques is a
> "Digital Predistortion Linearizer" (DPL), and its use can bring about a
> significant reduction in the level of IMD being transmitted compared to a
> classic class AB design. Unfortunately the relevant data that I have is
> packed ready to leave for Luxembourg.
>
> I don't know how easy or difficult DPL would be to implement in the K3, or
> in any other "already designed" rig which employs DSP, but I suspect that
> somebody else reading this could tell you.
>
> 73,
> Geoff
> GM4ESD
>
>
>
> On Thursday, May 12, 2011 at 4:15 PM, Guy Olinger K2AV wrote:
>
>> I would like to know if some kind of feedback (maybe complicated)
>> could bring about a quantum leap in linearity, like sampling the
>> output of the amp and feeding that back to the K3 to digitally
>> pre-alter the audio to cancel the distortion going out.
>
>
>
>
>
>
>
>
>

Jack Smith-6

Re: KPA-500 "Output for Input" schedule?

In reply to this post by Geoffrey Mackenzie-Kennedy

Geoff & list readers ...

There's an article in the current Electronics Design News, as a matter
of fact, on pre-distortion.

http://www.edn.com/article/518070-RF_predistortion_straightens_out_your_signals.php

Although aimed at cellular radio digital modulation, the concepts apply
to analog SSB as well.

Jack

On 5/12/2011 12:44 PM, Geoffrey Mackenzie-Kennedy wrote:

Ross Primrose N4RP

Re: KPA-500 "Output for Input" schedule?

In reply to this post by Guy, K2AV

I dunno, seems more like a solution in search of a problem to me....

73, Ross N4RP

On 5/12/2011 12:58 PM, Guy Olinger K2AV wrote:

> That would be a KEEN addition to a K3/KPA500 combo. Put it way out
> there and give the industry yet another bone-breaking kick in the *ss.
>
> On Thu, May 12, 2011 at 12:44 PM, Geoffrey Mackenzie-Kennedy
> <[hidden email]> wrote:
>> Hello Guy,
>>
>> The short answer to the first part of your question is yes, and the generic
>> term for such a scheme is Predistortion. A term that has been used to
>> identify a Predistortion scheme which employ digital techniques is a
>> "Digital Predistortion Linearizer" (DPL), and its use can bring about a
>> significant reduction in the level of IMD being transmitted compared to a
>> classic class AB design. Unfortunately the relevant data that I have is
>> packed ready to leave for Luxembourg.
>>
>> I don't know how easy or difficult DPL would be to implement in the K3, or
>> in any other "already designed" rig which employs DSP, but I suspect that
>> somebody else reading this could tell you.
>>
>> 73,
>> Geoff
>> GM4ESD
>>
>>
>>
>> On Thursday, May 12, 2011 at 4:15 PM, Guy Olinger K2AV wrote:
>>
>>> I would like to know if some kind of feedback (maybe complicated)
>>> could bring about a quantum leap in linearity, like sampling the
>>> output of the amp and feeding that back to the K3 to digitally
>>> pre-alter the audio to cancel the distortion going out.
>>
>>
>>
>>
>>
>>
>>
>>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> Post: mailto:[hidden email]
>
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--
FCC Section 97.313(a) “At all times, an amateur station must use the minimum transmitter power necessary to carry out the desired communications.”

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Alan Bloom

Re: KPA-500 "Output for Input" schedule?

In reply to this post by Guy, K2AV

It may not be valid to estimate distortion based on measuring the gain
versus power level with a CW signal. The reason is that the supply
voltage sags somewhat at maximum power, which may affect the gain. But
that doesn't affect the distortion because the supply voltage is
(nearly) constant during a two-tone distortion test at any given power
level.

Al N1AL

On Wed, 2011-05-11 at 23:05 -0400, Guy Olinger K2AV wrote:

> Adding a power gain and rounding to nearest two digit integer,
> considering accuracy of measuring device (rarely more than two
> significant digits), it is safe to say that the amplifier keeps its
> linearity to 650 watts. The variability at 325 and 410 is most likely
> the measuring instrument's issues at lower powers.
>
> The linearity at the top PEP level is the most important, as squaring
> at that level will produce the most distortion energy. Really quite
> good.
>
> ............................. Power Ratio
>
> 325W @ 15W drive 21.67 22
> 410W @ 20W drive 20.50 21
> 490W @ 25W drive 19.67 20
> 510W @ 26W drive 19.61 20
> 530W @ 27W drive 19.63 20
> 560W @ 28W drive 20.00 20
> 580W @ 29W drive 20.00 20
> 600W @ 30W drive 20.00 20
> 630W @ 31W drive 20.32 20
> 650W @ 32W drive 20.31 20
> 675W @ 35W drive 19.29 19
> 690W @ 37W drive 18.65 19
> 700W @ 40W drive 17.50 18
>
>
> On Wed, May 11, 2011 at 6:40 PM, Gary Gregory <[hidden email]> wrote:
> > Joe,
> >
> > 325W @ 15W drive
> > 410W @ 20W drive
> > 490W @ 25W drive
> > 510W @ 26W drive
> > 530W @ 27W drive
> > 560W @ 28W drive
> > 580W @ 29W drive
> > 600W @ 30W drive
> > 630W @ 31W drive
> > 650W @ 32W drive
> > 675W @ 35W drive
> > 690W @ 37W drive
> > 700W @ 40W drive
> >
> > Is this still about right for your calculations.....
> >
> > Gary
> >
> > On 12 May 2011 08:18, Joe Subich, W4TV <[hidden email]> wrote:
> >
> >>
> >> Adding gain calculation ...
> >>
> >>
> >> > 2W = 30W 11.8 dB
> >> > 2.5W = 40W 12.0 dB
> >> > 3w = 50w 12.2 dB
> >> > 3.5w = 60w 12.3 dB
> >> > 4w = 70w 12.4 dB
> >> > 4.5w = 75w 12.2 dB
> >> > 5w = 80w 12.0 dB
> >> > 5.5w = 90w 12.1 dB
> >> > 6w = 100w 12.2 dB
> >> > 6.5w = 110w 12.3 dB
> >> > 7w = 120w 12.3 dB
> >> > 7.5w = 130w 12.4 dB
> >> > 8w = 150w 12.7 dB
> >> > 8.5w = 160w 12.7 dB
> >> > 9w = 170w 12.8 dB
> >> > 9.5w = 180w 12.8 dB
> >> > 10w = 190w 12.8 dB
> >> > 11w = 200w 12.6 dB
> >> > 12w = 225w 12.7 dB
> >>
> >> The numbers look about right including the decreased gain at low level
> >> (as expected). Using 12.6/12.7 dB would indicate 33W drive for 600W
> >> out. 40W drive for 600W output would indicate ~1 dB of compression.
> >>
> >> 73,
> >>
> >> ... Joe, W4TV
> >>
> >> On 5/11/2011 5:28 PM, Gary Gregory wrote:
> >> > Stan,
> >> >
> >> > Allow some variation to antenna variations also.
> >> >
> >> > This on 15M, swr is 1.0:1
> >> >
> >> > 2W = 30W out
> >> > 2.5W = 40W
> >> > 3w = 50w
> >> > 3.5w = 60w
> >> > 4w = 70w
> >> > 4.5w = 75w out
> >> > 5w = 80w
> >> > 5.5w = 90w
> >> > 6w = 100w
> >> > 6.5w = 110w
> >> > 7w = 120w
> >> > 7.5w = 130w
> >> > 8w = 150w
> >> > 8.5w = 160w
> >> > 9w = 170w
> >> > 9.5w = 180w
> >> > 10w = 190w
> >> > 11w = 200w
> >> > 12w = 225w
> >> >
> >> > NOTE to ALL: This was not done with lab equipment or even a dummy load.
> >> This
> >> > was measured using a K3 and a tri-band yagi and a cw tone.
> >> >
> >> > Gary
> >> >
> >> > On 12 May 2011 07:13, Al Lorona<[hidden email]> wrote:
> >> >
> >> >> It's very easy to measure the 1-tone gain compression characteristics of
> >> an
> >> >> amplifier. The desired result is a graph of Pout vs. Pin, with Pin on
> >> the
> >> >> horizontal axis and Pout on the vertical.
> >> >>
> >> >> So what one needs to do is set Pin to the amp, and measure Pout into a
> >> >> dummy
> >> >> load. If you do this for several values of Pin, you'll be able to plot
> >> all
> >> >> of
> >> >> those measured points on the graph. It will look like a pretty straight
> >> >> line
> >> >> toward the lower Pin values, then it will flatten out (become more
> >> >> horizontal)
> >> >> as Pin (and Pout) get higher.
> >> >>
> >> >> The slope of the line is the gain of the amplifier.
> >> >>
> >> >> Very often the Pin values are 1 dB apart. One dB is about a 25% increase
> >> in
> >> >> power. Meaning that if you are measuring Pin in Watts, then you can set
> >> Pin
> >> >> to
> >> >> roughly the following values:
> >> >>
> >> >> 1, 1.5, 2, 3, 4, 5, 7, 10, 13 Watts, etc.,
> >> >>
> >> >> and measure the Pout at each value. The values should be converted to
> >> dBm
> >> >> before
> >> >> plotting. That's all there is to it.
> >> >>
> >> >> This is all done in CW mode. If you want to go further, you can go into
> >> SSB
> >> >> mode
> >> >> and apply two tones to the amp (which a K3 has the ability to do) and
> >> then
> >> >> look
> >> >> at the output of both the K3 and the KPA500 with a spectrum analyzer...
> >> but
> >> >> I'll
> >> >> leave that explanation for another day... or it can be found on the web.
> >> >>
> >> >> Al W6LX
> >> >> ______________________________________________________________
> >> >> 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
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> >>
> >
> >
> >
> > --
> >
> > VK4FD - Motorhome Mobile
> > Elecraft Equipment
> > K3 #679, KPA-500 #018
> > Living the dream!!!
> > ______________________________________________________________
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David Gilbert

Re: KPA-500 "Output for Input" schedule?

In reply to this post by Guy, K2AV

How so? Most hams aren't looking for linearity. The great majority
merely want to be heard and understood ... and many don't seem to care
much about the latter. If they were they wouldn't have the mic gain
and compression cranked up beyond all rational measure. Predistortion
might have a certain coolness factor to it, but I doubt it would
generate even a ripple in the marketplace.

Just for grins, where do you usually have your Mic Gain and Compression
levels set? What power supply voltage do you run your K3 with, and what
is your power output setting?

Dave AB7E

On 5/12/2011 9:58 AM, Guy Olinger K2AV wrote:
> That would be a KEEN addition to a K3/KPA500 combo. Put it way out
> there and give the industry yet another bone-breaking kick in the *ss.

> On Thu, May 12, 2011 at 12:44 PM, Geoffrey Mackenzie-Kennedy
> <[hidden email]> wrote:
>> Hello Guy,
>>
>> The short answer to the first part of your question is yes, and the generic
>> term for such a scheme is Predistortion. A term that has been used to
>> identify a Predistortion scheme which employ digital techniques is a
>> "Digital Predistortion Linearizer" (DPL), and its use can bring about a
>> significant reduction in the level of IMD being transmitted compared to a
>> classic class AB design. Unfortunately the relevant data that I have is
>> packed ready to leave for Luxembourg.
>>
>> I don't know how easy or difficult DPL would be to implement in the K3, or
>> in any other "already designed" rig which employs DSP, but I suspect that
>> somebody else reading this could tell you.
>>
>> 73,
>> Geoff
>> GM4ESD
>>
>>
>>
>> On Thursday, May 12, 2011 at 4:15 PM, Guy Olinger K2AV wrote:
>>
>>> I would like to know if some kind of feedback (maybe complicated)
>>> could bring about a quantum leap in linearity, like sampling the
>>> output of the amp and feeding that back to the K3 to digitally
>>> pre-alter the audio to cancel the distortion going out.
>>

Vic K2VCO

Re: KPA-500 "Output for Input" schedule?

I'm a CW man, so I should keep my mouth shut, but wasn't the "Class A Mode" provided by
some Yaesu (and other?) transceivers considered a selling point?

Of course their are some 'turn the gain to 11' guys, but there are also those who care
about how they sound.

Now back to our regular bug sending practice.

On 5/12/2011 11:15 AM, David Gilbert wrote:

>
> How so? Most hams aren't looking for linearity. The great majority
> merely want to be heard and understood ... and many don't seem to care
> much about the latter. If they were they wouldn't have the mic gain
> and compression cranked up beyond all rational measure. Predistortion
> might have a certain coolness factor to it, but I doubt it would
> generate even a ripple in the marketplace.
>
> Just for grins, where do you usually have your Mic Gain and Compression
> levels set? What power supply voltage do you run your K3 with, and what
> is your power output setting?
>
> Dave AB7E
>
>
>
> On 5/12/2011 9:58 AM, Guy Olinger K2AV wrote:
>> That would be a KEEN addition to a K3/KPA500 combo. Put it way out
>> there and give the industry yet another bone-breaking kick in the *ss.
>
>> On Thu, May 12, 2011 at 12:44 PM, Geoffrey Mackenzie-Kennedy
>> <[hidden email]> wrote:
>>> Hello Guy,
>>>
>>> The short answer to the first part of your question is yes, and the generic
>>> term for such a scheme is Predistortion. A term that has been used to
>>> identify a Predistortion scheme which employ digital techniques is a
>>> "Digital Predistortion Linearizer" (DPL), and its use can bring about a
>>> significant reduction in the level of IMD being transmitted compared to a
>>> classic class AB design. Unfortunately the relevant data that I have is
>>> packed ready to leave for Luxembourg.
>>>
>>> I don't know how easy or difficult DPL would be to implement in the K3, or
>>> in any other "already designed" rig which employs DSP, but I suspect that
>>> somebody else reading this could tell you.
>>>
>>> 73,
>>> Geoff
>>> GM4ESD
>>>
>>>
>>>
>>> On Thursday, May 12, 2011 at 4:15 PM, Guy Olinger K2AV wrote:
>>>
>>>> I would like to know if some kind of feedback (maybe complicated)
>>>> could bring about a quantum leap in linearity, like sampling the
>>>> output of the amp and feeding that back to the K3 to digitally
>>>> pre-alter the audio to cancel the distortion going out.
>>>
> ______________________________________________________________
> 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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--
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/
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Eric Swartz - WA6HHQ

Re: KPA-500 "Output for Input" schedule? [end of thread]

Administrator

Let's let this thread rest for now.

73, Eric
list moderator

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k6dgw

Re: KPA-500 "Output for Input" schedule?

In reply to this post by Guy, K2AV

On 5/12/2011 8:15 AM, Guy Olinger K2AV wrote:
> I would like to know if some kind of feedback (maybe complicated)
> could bring about a quantum leap in linearity, like sampling the
> output of the amp and feeding that back to the K3 to digitally
> pre-alter the audio to cancel the distortion going out.

I think they sort of do that with huge astronomical telescopes to reduce
optical distortion ... how hard could it be with a K3 :-)

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2011 Cal QSO Party 1-2 Oct 2011
- www.cqp.org

PS: It's a rhetorical question, let's not start a big thread on it
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P.B. Christensen

Re: KPA-500 "Output for Input" schedule?

> I would like to know if some kind of feedback (maybe complicated)
> could bring about a quantum leap in linearity, like sampling the
> output of the amp and feeding that back to the K3 to digitally
> pre-alter the audio to cancel the distortion going out.

That's exactly the function of adaptive pre-distortion.and is used in the
ADAT ADT-200A. Scarce as that rig is, it works well.

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.123.2357&rep=rep1&type=pdf

See the section entitled "The Predistortion Concept." The adaptive part of
predistortion comes from the use of a dynamic algorithm like LMS -- the
same, or nearly the same algorithm used in the K3's denoiser DSP function.

Paul, W9AC

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Cortland Richmond-2

Re: KPA-500 "Output for Input" schedule?

In reply to this post by stan levandowski

The INTERESTING thing about the article is that it is ANALOG predistortion.
Even a few dB would be an improvement, if 10 to 20 dB proves beyond reach
for such a broad (16:1) spectrum as HF.

Cortland

KA5S

____________________________________________________________________________
________________
Date: Thu, 12 May 2011 13:43:51 -0400
From: Jack Smith <[hidden email]>
Subject: Re: [Elecraft] KPA-500 "Output for Input" schedule?
To: [hidden email]
Message-ID: <[hidden email]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Geoff & list readers ...

There's an article in the current Electronics Design News, as a matter
of fact, on pre-distortion.

http://www.edn.com/article/518070-RF_predistortion_straightens_out_your_sign
als.php

Although aimed at cellular radio digital modulation, the concepts apply
to analog SSB as well.

Jack

On 5/12/2011 12:44 PM, Geoffrey Mackenzie-Kennedy wrote:
> Hello Guy,
>
> The short answer to the first part of your question is yes, and the
generic

> term for such a scheme is Predistortion. A term that has been used to
> identify a Predistortion scheme which employ digital techniques is a
> "Digital Predistortion Linearizer" (DPL), and its use can bring about a
> significant reduction in the level of IMD being transmitted compared to a
> classic class AB design. Unfortunately the relevant data that I have is
> packed ready to leave for Luxembourg.
>
> I don't know how easy or difficult DPL would be to implement in the K3, or
> in any other "already designed" rig which employs DSP, but I suspect that
> somebody else reading this could tell you.
>
> 73,
> Geoff
> GM4ESD
>
>