[Elecraft] KPA1500 Linearity

[Wayne Burdick]

Scott,

I’m not sure how you’re doing the test, but this is definitely not characteristic. 

We test every amp for IMD, and we see an average of about -35 dBc (3rd order, ARRL method) across all bands. This is state of the art for an LDMOS deign running class AB. Other SS amps using similar designs have have similar performance.  

Any amp’s gain levels off as it approaches peak power (ie, is slightly in compression). But it should not be flat-topping unless it’s over driven or is starved for supply current/voltage. 

Finally, both the transceiver and amp will vary from band to band somewhat in IMD. You might for example see -40 dBc on one, but in the low 30’s on the other, on a given band. Again, this is typical of all such SS rigs/amps except those running class A or using closed-loop feedback (predistortion). 

Please call Monday to discuss your test method with one of our technical staff. 

73,
Wayne
N6KR


----
http://www.elecraft.com

> On Jun 9, 2018, at 2:21 PM, K9MA <k9ma at sdellington.us> wrote:
> 
> I recently ran a two-tone test and measured CW power gain. (SN1078)  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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