How does the output load become part of the S11 measurement?
I agree you need it to keep the amp happy, but when you make your?amplitude and phase measurements on the antenna tuner, the load should?not be part of that.? ? ? Kent G8EMY
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On Sunday, August 15, 2021, 01:48:51 PM CDT, David Eckhardt <davearea51a@...> wrote:
No....n o ....... N? O.....? ? ? I was dealing and referring to the INPUT
which is what you requested!
Yes, then read the combination looking back into the 50-ohm load and
matching network which you have adjusted on the INPUT for minimum SWR.
Please carefully read what I originally wrote.
On Sun, Aug 15, 2021 at 6:30 PM KENT BRITAIN <WA5VJB@...> wrote:
? "Then use the Nano to read the impedance
of the tuner/dummy load?"
This configuration would be on the output of an amp, not the input.
Measurement of S22 and very often S12 can be very helpful as you know in
amp development and trouble shooting.? ? Oh the fun of finding out your 20
dB gain amp has an S12 of only 19 dB!? ? (On the very edge of becoming an
oscillator)
? ? On Sunday, August 15, 2021, 01:17:42 PM CDT, David Eckhardt <
davearea51a@...> wrote:
? I was addressing the INPUT as the requester!? Why would I feed an RF
source to the output???????????
Dave - W?LEV
On Sun, Aug 15, 2021 at 5:54 PM Jim Lux <jim@...> wrote:
On 8/15/21 10:04 AM, Joe wrote:
What about connecting the amplifier to a dummy load thru an antenna
tuner. Tune for minimum SWR. Then use the Nano to read the impedance
of the tuner/dummy load?
Joe
That's more about measuring the amplifier's output impedance, I think
the OP is looking for amplifier input impedance.
Here's what's great about the NanoVNA - There's going to be people who
figure out how to make high power measurements with it, what sort of
"test set" is needed.? Maybe modified versions perhaps.
And someone is going to come up with clever inexpensive ways to do this
with "reasonable" accuracy.
But there's been a lot of discussion over the years about what the
actual output Z of a transmitter is. (often with long threads about
Thevenin matches, arguments about efficiency, the limitations of simple
models, etc.).? Hey, now we're close to being able to *measure* it, at
different output powers and into different loads.? This is way cool.
See, e.g., Maynard Wright's article in QEX a couple months ago.
--
*Dave - W?LEV*
*Just Let Darwin Work*
--
*Dave - W?LEV*
*Just Let Darwin Work*
