I would tune up any antenna matching network (if you have one) at low power,
that should be close.? Then increase power and tune again.
Alternantely, use something like an Antuino or nanoVNA to do the initial tune up.
If you have an antenna you know to be somewhat tuned, a matching network is not needed.
But you don't want to start at 40 watts, only to find that a windstorm took it down
and you have a 10:1 SWR.
For those who actually read my comments, it should be clear now.
I started out this morning by reading the most recent post and am working my way back.
Jerry, KE7ER
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On Wed, Aug 3, 2022 at 04:50 AM, Bob Benedict, KD8CGH wrote:
"Many recommend tuning at a lower power. This risky as well. That is because at lower power, the output impedance of the PA will be different. Once you are tuned at QRP level, increasing the power will result in a mismatch again! "
Interesting. Every auto tuner manufacturer's instructions I have ever seen recommend that you tune at low power. I have a remote auto tuner at the base of a wire vertical that I tune on every band change. I have always tuned with low power using several different rigs over the decades and never noticed a change in SWR. I'll pay closer attention, but if I'm getting a change it has been to small to notice.
Haven't received my sBitx yet, but it looks like there's room for a small board with SWR sensing and an absorptive bridge that you could manually switch in and out. If you wanted to get fancy you could route the measure to the Pi and integrate into the display.
