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KPA-500 "Output for Input" schedule?

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stan levandowski

KPA-500 "Output for Input" schedule?

The documentation on the Elecraft site says the KPA-500 requires 40
watts drive for full output.

Nowhere (at least not that I could find) is the minimum drive
requirement specified nor is there any schedule of "output for input"
such as 40 watts = 500 watts; xx watts = 250 watts, etc.

More to the point -- can a K3/10 or a K2/10 be connected to the KPA-500
and deliver something between 75 and 100 watts output?

??

Thanks,

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

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Don Wilhelm-4

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

Stan,

Of course it can be driven by lower power. The KPA500 is a linear
amplifier. If 40 watts in produces 500 out, then 20 in will give 250
out and 10 in will produce 125 watts. If the relationship is otherwise,
then it is not acting as a linear amplifier. The same thing should be
true for any linear amplifier - that is the definition of linear operation.

73,
Don W3FPR

On 5/11/2011 1:06 PM, stan levandowski wrote:

> The documentation on the Elecraft site says the KPA-500 requires 40
> watts drive for full output.
>
> Nowhere (at least not that I could find) is the minimum drive
> requirement specified nor is there any schedule of "output for input"
> such as 40 watts = 500 watts; xx watts = 250 watts, etc.
>
> More to the point -- can a K3/10 or a K2/10 be connected to the KPA-500
> and deliver something between 75 and 100 watts output?
>
>

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James Maynard-2

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

On 2011-05-11 10:16 AM, Don Wilhelm wrote:

Um, linear with respect to power, or linear with respect to voltage?
Assuming a resistive load, P = I*I*R, or E*E/R. I *think* a "linear
amplifier" means linear with respect to voltage (or current).

If I'm wrong, I expect that I will be promptly corrected!

Jim K7KK

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Joe Subich, W4TV-4

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

> Um, linear with respect to power, or linear with respect to voltage?

Linear with respect to power. Both the input and output are fixed Z
thus an increase in drive results in increases in both the current
and voltage variation which given a linear amplifier causes increases
in both current and voltage swings at the output.

73,

... Joe, W4TV

On 5/11/2011 1:27 PM, James Maynard wrote:

> On 2011-05-11 10:16 AM, Don Wilhelm wrote:
>> Stan,
>>
>> Of course it can be driven by lower power. The KPA500 is a linear
>> amplifier. If 40 watts in produces 500 out, then 20 in will give 250
>> out and 10 in will produce 125 watts. If the relationship is otherwise,
>> then it is not acting as a linear amplifier. The same thing should be
>> true for any linear amplifier - that is the definition of linear operation.
>>
>> 73,
>> Don W3FPR
> Um, linear with respect to power, or linear with respect to voltage?
> Assuming a resistive load, P = I*I*R, or E*E/R. I *think* a "linear
> amplifier" means linear with respect to voltage (or current).
>
> If I'm wrong, I expect that I will be promptly corrected!
>
> Jim K7KK
>
> ______________________________________________________________
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Julian, G4ILO

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

In reply to this post by Don Wilhelm-4

Don Wilhelm-4 wrote

Of course it can be driven by lower power. The KPA500 is a linear
amplifier. If 40 watts in produces 500 out, then 20 in will give 250
out and 10 in will produce 125 watts. If the relationship is otherwise,
then it is not acting as a linear amplifier. The same thing should be
true for any linear amplifier - that is the definition of linear operation.

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.

Julian, G4ILO. K2 #392 K3 #222 KX3 #110
* G4ILO's Shack - http://www.g4ilo.com
* KComm - http://www.g4ilo.com/kcomm.html
* KTune - http://www.g4ilo.com/ktune.html

stan levandowski

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

In reply to this post by stan levandowski

Thank you, Don. I have no experience with any kind of outboard
amplifier since I've been QRP for nearly my entire ham life, but I do
seem to recall that in 'the old days' of tube amps, there was always a
minimum drive requirement and sometimes distortion problems occured at
the lower drive levels. At least, this is what I've gathered from
reading about it. No first hand experience.

I am asking this question because I've been thinking about which of my
rigs -the K2 or the K3 - I want to equip with the 100 W PA option. The
KPA-500 might give me another option, albeit much more expensive but
perhaps a wiser economic choice in the longer term (and keep me on the
path toward a "K-line" station).

I would much prefer to leave both the K2 and K3 as 'virgin' QRP rigs as
that is my true love. If the KPA-500 can give me about 75 to 100 watts
output as a state-of-the-art outboard amplifier that both K2 and K3
could share, then it would be a very interesting prospect for me to
consider.

Especially since there will be no need to modify either K2 or K3.

And ---not to push it --- could my K1 conceivably drive a KPA-500 with
its 5 or 6 watts also??

What a great concept -- one all-purpose state-of-the-art amp sitting in
the shack ready to shake hands with any and all of my Elecraft
transceivers when called upon to do so.

I am on technically solid ground here?

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

May 11, 2011 at 1:16 PM, Don Wilhelm wrote:

> Stan,
>
> Of course it can be driven by lower power. The KPA500 is a linear
> amplifier. If 40 watts in produces 500 out, then 20 in will give 250
> out and 10 in will produce 125 watts. If the relationship is
> otherwise, then it is not acting as a linear amplifier. The same
> thing should be true for any linear amplifier - that is the definition
> of linear operation.
>
> 73,
> Don W3FPR
>
> On 5/11/2011 1:06 PM, stan levandowski wrote:
>> The documentation on the Elecraft site says the KPA-500 requires 40
>> watts drive for full output.
>>
>> Nowhere (at least not that I could find) is the minimum drive
>> requirement specified nor is there any schedule of "output for input"
>> such as 40 watts = 500 watts; xx watts = 250 watts, etc.
>>
>> More to the point -- can a K3/10 or a K2/10 be connected to the
>> KPA-500
>> and deliver something between 75 and 100 watts output?
>>
>>

Guy, K2AV

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

In reply to this post by Julian, G4ILO

That's a "linear" amp in name only". Amplifying SSB should only be
done on that amp with PEP set below the point at which compression
sets in. This of course does not matter on CW or FM, one of the
common uses of such an amp. I'd be surprised if that amp would do
better than 100 watts PEP cleanly.

Maybe a reasonable question, but your example is far below state of
the art for PEP at 160W. Whether the specs are honest or not is
another issue.

73, Guy.

On Wed, May 11, 2011 at 2:28 PM, Julian, G4ILO <[hidden email]> wrote:

>
> Don Wilhelm-4 wrote:
>>
>> Of course it can be driven by lower power. The KPA500 is a linear
>> amplifier. If 40 watts in produces 500 out, then 20 in will give 250
>> out and 10 in will produce 125 watts. If the relationship is otherwise,
>> then it is not acting as a linear amplifier. The same thing should be
>> true for any linear amplifier - that is the definition of linear
>> operation.
>>
>
> 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.
>
> -----
> Julian, G4ILO. K2 #392 K3 #222.
> * G4ILO's Shack - http://www.g4ilo.com
> * KComm - http://www.g4ilo.com/kcomm.html
> * KTune - http://www.g4ilo.com/ktune.html
>
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/KPA-500-Output-for-Input-schedule-tp6352735p6353030.html
> Sent from the Elecraft mailing list archive at Nabble.com.
> ______________________________________________________________
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n7ws

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

In reply to this post by Julian, G4ILO

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.
>

Peter Wollan-2

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

Perhaps that Mirage amp is intended for FM? Not all amps need to be linear.

Peter W0LLN

On Wed, May 11, 2011 at 2:02 PM, Wes Stewart <[hidden email]> wrote:

> 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
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Julian, G4ILO

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

You can read the detailed description at the link I gave. In fact, it claims to have "active bias for improved SSB linearity." So it is definitely intended for SSB use.

I agree that a graph of output power vs. input power should be a straight line. But I don't believe there is a "linear amplifier" out there in the real world, particularly a solid state one, where that is actually remotely true. The practical answer may be less how much non-linearity is acceptable so much as how much linearity the state of the art is capable of within the acceptable price range.

So I think Stan WB2LQF deserved a better answer to his request for an "output for input" schedule than the statement that it was a linear relationship. If Elecraft is indeed claiming the relationship between input and output of the KPA500 is perfectly linear then let them say it. Otherwise I don't believe it.

Peter Wollan-2 wrote

Perhaps that Mirage amp is intended for FM? Not all amps need to be linear.

Peter W0LLN

On Wed, May 11, 2011 at 2:02 PM, Wes Stewart <[hidden email]> wrote:
> 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
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Julian, G4ILO. K2 #392 K3 #222 KX3 #110
* G4ILO's Shack - http://www.g4ilo.com
* KComm - http://www.g4ilo.com/kcomm.html
* KTune - http://www.g4ilo.com/ktune.html

Don Wilhelm-4

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

Julian,

From the words of Bob Freiss (the designer) on 9/8/2010 --
--------------------------------------------------------------------------------------------
The KPA500 requires 30 to 40 watts for full output. With 10 watts of drive
the output will be around 200 watts or a little less.

Bob, N6CM
--------------------------------------------------------------------------------------------

If one takes the lower figure of 30 watts for 500 watts out, that could
indicate a small amount of compression (non-linearity), and I have not
asked how much less than 200 watts with 10 watts drive, but it seems
that the KPA500 has a power gain factor near 16.7. Perhaps someone with
good wattmeters will measure it over a range of drive levels.

73,
Don W3FPR

On 5/11/2011 3:55 PM, Julian, G4ILO wrote:
> <snip>
>
> So I think Stan WB2LQF deserved a better answer to his request for an
> "output for input" schedule than the statement that it was a linear
> relationship. If Elecraft is indeed claiming the relationship between input
> and output of the KPA500 is perfectly linear then let them say it. Otherwise
> I don't believe it.
>
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alorona

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

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
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Gary Gregory

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

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]
>
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> Please help support this email list: http://www.qsl.net/donate.html
>

Joe Subich, W4TV-4

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

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
>>
>
>
>

alorona

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

Joe, I believe your hypothesis (extrapolation to high power) will be verified
once someone makes higher power measurements.

Regards,

Al W6LX

________________________________
From: "Joe Subich, W4TV" <[hidden email]>
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
______________________________________________________________
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

Gary Gregory

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

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

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
>

Gary Gregory

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

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!!!
>
>

Gary Gregory

Re: 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!!!
>
>

Joe Subich, W4TV-4

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

In reply to this post by Gary Gregory

Adding the calculations below ... it's obvious that a lot of
care went into the design - the gain is flat +/- 0.2 dB from
8 to 35W in (150 to 650W out). The 1 dB compression point
looks to be somewhere above 700W.

I don't think I would make a habit of running the KPA-500 at
less than 150 W or more than 650 W given that IMD tends to
increase significantly at the 1 dB compression limits.

73,

... Joe, W4TV

On 5/11/2011 6:40 PM, Gary Gregory wrote:

> Joe,
>
> 325W @ 15W drive 13.4 dB
> 410W @ 20W drive 13.1 dB
> 490W @ 25W drive 12.9 dB
> 510W @ 26W drive 12.9 dB
> 530W @ 27W drive 12.9 dB
> 560W @ 28W drive 13.0 dB
> 580W @ 29W drive 13.0 dB
> 600W @ 30W drive 13.0 dB
> 630W @ 31W drive 13.1 dB
> 650W @ 32W drive 13.1 dB
> 675W @ 35W drive 12.9 dB
> 690W @ 37W drive 12.7 dB
> 700W @ 40W drive 12.4 dB
>
> Is this still about right for your calculations.....
>
> Gary
>
> On 12 May 2011 08:18, Joe Subich, W4TV <[hidden email]
> <mailto:[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]
> <mailto:[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]
> <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] <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!!!
>

alorona

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

In reply to this post by Gary Gregory

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:

--

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
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