[hpsdr] KXPA100 Predistortion

[Scott Traurig]

Which radio? Are you using an external coupler on the amp output? What kind
of coupler? What are you seeing for an S-ATT level on transmit?

73,

Scott/w-u-2-o


On Mon, Mar 12, 2018 at 11:06 AM, <dx at hb9emp.ch> wrote:

> ***** High Performance Software Defined Radio Discussion List *****
>
> Dear all,
>
> I recently got a Elecraft KXPA100 PA. The Predistortion tests were not
> very nice at all. Max -40dBc at IM3. As a comparison, with a small 16W
> amplifier (minikits.au, also 13.8V supply) I reach more than -60dBc. With a
> SPE 2k I easily reach -50dBc. This makes me think why the KXPA100 is
> performing so badly. Is somebody experienced with this PA?
>
> Any modification ideas? The TRX switching is done by PIN diodes, did this
> cause any problems in relation to predistortion to somebody? I can imagine
> that the decoupling between input and output is not very high (probably
> somewhere about 30 dB?) I could bypass the full TRX switching path since I
> use it in TX only.
>
> Any other ideas what can cause degradation of IM? I know about saturated
> ferrites. Since I also have this bad performance on low output power I
> don't think this is the reason.
> DC Supply is well buffered with large capacitors at the input. Even a DC
> ripple reduction by factor 5 did not have any impact.
>
> Generally spoken did somebody improve an IM in an amplifier? If so, what
> was the main degradation reason?
>
> Thanks for your comments.
>
> 73
> Mischa HB9EMP
>
>
>
>
>
>
>
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