[Elecraft] KPA-500 "Output for Input" schedule?
Guy Olinger K2AV
olinger at bellsouth.net
Wed May 11 23:05:39 EDT 2011
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 <garyvk4fd at gmail.com> 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 <lists at subich.com> 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<alorona at sbcglobal.net> 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
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>> >
>> >
>> >
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>
>
>
> --
>
> VK4FD - Motorhome Mobile
> Elecraft Equipment
> K3 #679, KPA-500 #018
> Living the dream!!!
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