[Elecraft] How accurate is the K3 SWR meter

[Edward R. Cole]

Just a Post Script (or Note) to the discussion:

I was seeing high SWR using my K3 to drive my new 300w HF amplifier, 
with amp bypassed and QRO tuner (that follows the amp) switched 
directly to dummy load.  This was on 20m.  I have the K3 ANT1 (no 
internal tuner) connected to a MFJ tuner and then thru the 150w 
Mirage 6m amp and then to the HF amp. DPDT TR relay.  The 6m amp 
bypasses when powered off.

Well the solution was removing the 6m amp from the path.  Some ham 
equipment is not well designed for other frequencies it appears!  MY 
SWR went from 1.8 to 1.1 with this simple change.  Actual input SWR 
when driving the HF amp is about 1.4 but the bypass thru the TR relay 
shows no impedance issues as the 50-ohm dummy is seen by the K3 with no "bump".

Since I have a MFJ945E tuner follow the K3, I have two SWR 
indications to observe and I do often see a difference in indication 
if the SWR is high.  Once the MFJ tunes out any SWR they agree.  I 
have to use a tuner on my triband yagi (very old), but my 80/40m 
inverted-V is resonant so tuners are not needed.  HF amp input 
matches better at lower freq. bands, though the K3 has no trouble at 
any band with driving the amp.  The Drake MN2000 was added when I 
installed the new HF amp since it can run up to 2kW.  It makes sure 
the amp sees a good load and also gives me a monitor for the amp output.

Summarizing:  Check every part of your system from K3 to antenna; you 
may find some surprises!  Always check coax line by line!


73, Ed - KL7UW, WD2XSH/45
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