[Elecraft] K3 SWR Readout Accuracy Question

[Edward R. Cole]

Stan,

It sounds like you assume the 48-inch jumper is OK.  That it first 
think I would swap out to determine if it is affecting your 
readings.  Bad cables sneak up and "bite me in the rear" way too 
often (because I assume they are good).  Or If you can connect the K2 
thru the same 48-inch cable used with the K3, that will be a better comparison.

If you have a dummy load, directly connect it to the K3 and read the 
SWR.  If you have two dummy loads connect them to the K3 with a 
coaxial tee.  This will present a 25-ohm load  (VSWR=2:1).

If the K3 SWR reads significantly different using the dummy loads 
then you have a problem in the K3.

That being said I never depend on internal SWR meters.  When I want 
to know exactly then its either the Bird43 power meter or directional 
couplers and calculate VSWR from forward and reflected readings.

73, Ed - KL7UW

------------------------------

Message: 2
Date: Thu, 31 Mar 2011 12:19:44 -0400 (EDT)
From: stan levandowski <sjl219 at optonline.net>
Subject: [Elecraft] K3 SWR Readout Accuracy Question
To: elecraft at mailman.qth.net
Message-ID:
         <4097185.180346.1301588384528.JavaMail.sjl219 at mstr20.srv.hcvlny.cv.net>

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On my newly assembled kit K3/10 without the internal ATU, I've noticed
that the SWR readouts are "higher" than those on my K2 which agrees with
my analog inline meter.  Into a 50 ohm dummy load all three readings are
1.0:1, but on an actual antenna the readings differ.

For example, where my K2 and  the analog meter read 1.4:1, the K3 says
1.9:1.  this variance increases as the SWR increases and decreases as
the actual SWR decreases, hence the agreement among all three measures
on 1:1 when operating into a dummy load.

All readings taken at 5 watts, same antenna, same  SG-237 autocoupler,
same cable routings, and the internal ATU in the K2 bypassed.  The only
variable is the actual 48"coax jumper going from the K3 to the patch
panel.

I just finished the K3 yesterday so I am just a K3 beginner. However I
could find nothing in the manual about SWR calibration.

Any pointers would be appreciated.  Other than this, everything appears
to be working great and the K3 DSP is fabulous.

Stan WB2LQF
K3 #5244



73, Ed - KL7UW, WD2XSH/45
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