I tube the tbd inputs on all the amps I work on at full drive power. When you
get 1 to 1 at full drive the amp makes the most power it will.
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On Tuesday, December 12, 2023, 4:39 PM, Alek Petkovic via Amps
<amps@contesting.com> wrote:
For what it's worth, I have had terrible problems getting the input
matching right on several amplifiers using the VNA, yet when using
normal drive levels, as reccommended in the user/service manuals, tuning
is a breeze. Therefore, I think that there is some truth in the
assertion that tuning at low levels does not work properly.
73, Alek VK6APK
On 12/12/2023 7:27 pm, Rob Atkinson wrote:
>> If you try
>> to use the internal auto tuner it will not tune properly as it tunes up at
>> low
>> power and the input impedance of the amp changes as the power increases.
> Power level should not affect the impedance of a load. If it does,
> then something is wrong. A part may be heating up and changing value,
> in which case the matching network should be fixed. You should be
> able to put a vswr analyzer on the amp input and see the R + X for
> some frequency, and those values should hold for whatever drive power
> you use on the same frequency.
>
> 73
>
> Rob
> K5UJ
>
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