Good points, some of which I considered making in my last post. Regarding the
SWR measurement capabilities of the K3 (or many other devices) I wrote about
this too in another thread:
http://elecraft.365791.n2.nabble.com/K3-SWR-Numerical-Indication-td7643839.html
Wes N7WS
On 7/5/2019 10:37 AM, David Gilbert wrote:
It's not just a power issue. A filter only achieves its design goals if the
impedance feeding it and the load impedance it sees are as expected. Most
filters are going to want to be fed by 50 ohms and see a load of 50 ohms.
Most rigs (not sure about the K3) don't actually present a pure 50 ohm output
impedance, so using the internal tuner in the K3 supposedly would assure that
the filter sees the correct feed impedance, and for an operation like Field
Day having a properly performing filter might be more important than a bit of
power loss in the K3 tuner inductor.
On the other hand, I'm not sure that the SWR meter in the K3 is a perfect
indicator of a match to a 50 ohm load. I recently did some SWR measurements
on a new antenna setup for five different bands (three different antennas)
using four different indicators ... the SWR meter in the K3, an AEA HF-CIA, an
Elecraft W2, and a new FA-VA5. All four instruments were located in the same
spot on the transmission line for each band (I swapped them in and out), and I
plotted the SWR curves for frequencies across each band band. The readings
with the most deviation from the others came from the K3, and for certain
cable lengths (I did readings with and without an additional 7 foot length of
feedline inserted) it was significant.
73,
Dave AB7E
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