[Amps] Acceptable SWR for Tube Amps

[Lukasz]

On Tue, 18 Feb 2025, 18:45 Jeff Blaine, <KeepWalking188 at ac0c.com> wrote:

> All the critical voltages and currents should be independently limited
> somehow by the amps protective circuitry.  And while operating the tube
> with a higher Ig (generally speaking) is not optimal, unlike a SS amp,
> it's not terminal.
>
> What is another consideration in the context you mention (tuned to QRG=X
> and then QSY to QRG=Y) is the impact on harmonic filtering.  I remember
> getting a notification that I was creating QRM on 80m when operating on
> a 160m contest once for that very reason.  The antenna was very narrow
> banded on 160m and the amp (a triode GG-type Alpha) was pretty sensitive
> on 160m band tuning as well.  I would tune it for 1825 and then work +/-
> 25 Khz and not worry about touching up the amp.  Cannot remember what
> the SWR was at that point but probably ranged up to 3:1 on the extremes.
> Unknown to me at the time, as I got further from the tuned point, the
> 2nd harmonic levels got to be significant and that brought the OO
> notice.  oooopppsss!
>

I have not thought about that. Although I use a trx that applies adaptive
predistortion so most likely something else would fail (likely my antenna
switch) before the signal deteriorated it is a very useful thing to bring
up.

>
73, Lukasz , SP4IT and SQ4KW


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