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 <li...@subich.com
> <mailto:li...@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<alor...@sbcglobal.net
> <mailto:alor...@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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> >
> >
> >
> ______________________________________________________________
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>
> --
>
> VK4FD - Motorhome Mobile
> Elecraft Equipment
> K3 #679, KPA-500 #018
> Living the dream!!!
>
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