While we're on this subject, and I know it has been asked before, but can I
piggyback a 1500W PA onto my KX3 and my KPA100, if so what settings? Thanks.
On Sunday, February 15, 2026 at 04:21:36 PM EST, dyno lab via Elecraft
<[email protected]> wrote:
It was my study.
I have not shared it with Elecraft because it seems I am persona non grata with
them.
Possibly because I manufacture upgrade low voltage/low IMD PA modules for the
K3, K3s, and K4.
73, Hal W7YNC
> On 02/15/2026 12:05 PM PST Jon Zaimes, AA1K <[email protected]> wrote:
>
>
> Was this your study Hal? Has it been shared with Elecraft?
>
> Kind of defeats the purpose of buying a 1500 watt amp if it needs to be run
> at lower levels to survive. There are less expensive amps for that.
>
> 73/Jon
>
> Jon P. Zaimes, AA1K
> Tower climber for hire
> http://www.aa1k.us/
> Cell: 302-632-2353 tel:302-632-2353
>
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>
> Hug your favorite tower every day, and always stay connected to it.
>
>
>
> On Sunday, February 15, 2026, 2:52 PM, dyno lab via Elecraft
> <[email protected]> wrote:
>
> > An independent engineering study has identified internal electrical stress
> > conditions within the Elecraft KPA1500 HF power amplifier that occur during
> > normal operation at 1500 W output. The analysis, based on oscilloscope
> > measurements, spectrum analysis, LTspice modeling, and PCB layout review,
> > shows that the PA Output Board experiences elevated drain voltage peaks and
> > significant RF ripple on the 50 V supply rail.
> > Testing into a 50 Ω dummy load indicated drain voltage peaks exceeding 150
> > V and RF ripple greater than 40 V peak to peak on the supply rail. These
> > effects are attributed to an inadequate FET drain choke, insufficient
> > center tap bypassing, and inductive PCB traces on the PA Output Board
> > layout.
> > The high drain voltage peaks far exceed the BLF188 maximum drain voltage
> > rating of 135 volts which can cause "Hot Carrier Injection" and FET failure
> > under normal operating conditions. And the very high RF ripple on the
> > supply rail causes extreme drain voltage distortion resulting in high
> > harmonic output and intermodulation distortion.
> > The internal stress mechanisms may therefore affect long term device
> > reliability when operated continuously at full power. The study recommends
> > everyday operation in the 800–1000 W range, with full 1500 W output
> > reserved for short SSB bursts. High duty cycle digital modes such as FT8
> > and RTTY are best operated at 600–800 W.
> > Test data available upon request.
> > Hal
> > W7YNC
> >
> > > On 02/15/2026 9:32 AM PST dlrwild1--- via Elecraft
> > > <[email protected] mailto:[email protected]> wrote:
> > >
> > >
> > > Does anyone have knowledge of what is causing 15+ repair returns of the
> > > $7K KPA1500 amp?
> > > Bob WildermanK3SRO
> > >
> > >
> > > Sent from the all new AOL app for iOS
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