On Tue, 12 May 2020 at 13:41, Bob McGraw K4TAX <rmcg...@blomand.net> wrote:
Specifically: 100 watts indicated into dummy load via external power
> meter.
>
> for 40M the current was 15.3 amps {KAT3a bypassed} and 15.75 amps with
> KAT3a active/AUTO and resolved a match
>
> for 20M the current was 18.5 amps {KAT3a bypassed} and 17.26 amps with
> KAT3a active/AUTO and resolved a match.
>
Running the identical test, on 40m, I get 14.4A bypassed, 13A matched.
On 20m, I get 14.0A bypassed, 17.5A matched, a bit bigger delta than what
you saw, but perhaps not totally unreasonable.
The reported C/L values the ATU picked for 40 and 20 for this test with the
dummy load are 0 nF / 0.5uH and 0.06nF / 0.25uH respectively.
With my antenna, repeating the same test, I get 14A on 40m and 19A on 20m
(both with the KAT3A matched), so around an amp more than with the matched
dummy load.
> As concluded from my tests, the radio will draw different amounts of
> current on different bands for the same given and measured power
> output. Seems normal to me.
>
Thank you so much for taking the time to run these tests. I appreciate
it. I think the fact that we have a TX gain calibration per band also
implies that we'd see some differences in current draw for the different
bands too.
What I was really trying to determine is whether the results I'm seeing are
*typical*, and it sounds like the answer is "yes."
I guess what caught my eye in all of this is how much the configuration of
the matching network can affect the current draw of the amplifier. Not
having a great deal of engineering experience with RF amplifier engineering
myself, I kind of expected that presenting the amplifier with a nice 50 ohm
load would have implied similar characteristics regardless of what sat on
the other side of the network, vs causing the amplifier to draw another amp
or two. My expectation was that we'd see *loss* through the presence of
the matching network, but not so much an additional demand of current.
Kind of interesting, but not, it seems, abnormal or unexpected. Thanks
again for confirming!
Nick
--
*N6OL*
Saying something doesn't make it true. Belief in something doesn't make it
real. And if you have to lie to support a position, that position is not
worth supporting.
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com
