[Elecraft] KPA1500 Linearity

[Paul Baldock]

I received my KPA-1500 yesterday (#244) and did some linearity tests today

14.2MHz, Dummy Load, ATU Bypassed. Using KPA-1500 
internal Power Meter. Continuous carrier.

10W drive, Gain = 15.6dB 180W
15W drive, Gain = 15.8dB
20W drive, Gain = 15.9dB
25W drive, Gain = 16.0dB 1.0KW
30W drive, Gain = 15.9dB
35W drive, Gain = 15.7dB
40W drive, Gain = 15.6dB
43W drive, Gain = 15.4dB 1.5KW
45W drive, Gain = 15.4dB 1.57KW

Based on this it look like about .6dB compression 
at 1.5KW. I think that's pretty good for an SS Amp.

I also measured the gain on all the bands at 
1.5KW out. Drive varied from 31W on 80M to 47W on 
15M. or 16.8dB to 15.0dB. That amount of variation is rather disappointing.

I also noted that the internal power meter is 
pretty inaccurate at low levels. For Example at 
50W on 20M it reads 43W. Its pretty close above 
300W and right on at 1.5KW where its calibrated.

I would be interested to see any data that others have collected.

- Paul  KW7Y


At 02:26 PM 6/14/2018, K9MA wrote:
>The gain compression I measured, between 1000 
>and 1500 W on 40 meters, was 1.4 dB. I used the 
>K3 and KPA1500 power meters.  Factory calibration of the KPA1500.
>
>Scott K9MA
>
>----------
>
>Scott Ellington
>
>  --- via iPad
>
> > On Jun 14, 2018, at 2:51 PM, Paul Baldock <paul at paulbaldock.com> wrote:
> >
> > What you report of compression near the 
> maximum power is certainly true of the 
> amplifiers like the SPE-1.5K that use a single 
> device, but I would have thought this would not 
> be true of the KPA1500 that uses 2 devices. 
> This is the reason I returned my SPE and 
> ordered the KPA. Hopefully the compression is less than 1dB.
> >
> > Has anybody else measured it?
> >
> > - Paul  - KW7Y
> >
> >
> >
> > At 02:21 PM 6/9/2018, you wrote:
> >> I recently ran a two-tone test and measured 
> CW power gain. (SN1078)Â  It doesn't look 
> good.  The two-tone waveform shows distinct 
> "flat-topping", and the power gain drops 25 
> percent from 1000 to 1500 Watts.  My old 
> 3-500Z amplifier is much better.  Has anyone 
> measured IMD or linearity, or seen any test 
> results? While I'm primarily a CW operator, I'd 
> be very reluctant to use the amplifier on SSB. 
> 73, Scott K9MA -- Scott  K9MA 
> k9ma at sdellington.us 
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