Re: [K3] SWR - Numerical Indication

Posted by Elecraft mailing list on Jul 27, 2018; 9:44pm
URL: http://elecraft.85.s1.nabble.com/K3-SWR-Numerical-Indication-tp7643839p7643875.html

Dick, 
While Bob is correct, the bottom line is not SWR but the R and j numbers.  There are numerous values that will give you a 1.1:1, but only 50+j0 will be the true match of 1.0:1.  So,unless you do not have the equipment to measure the polar values, be thankful you have 1.1:1.  
Mel, K6KBE

      From: Bob McGraw K4TAX <[hidden email]>
 To: [hidden email]
 Sent: Friday, July 27, 2018 1:10 PM
 Subject: Re: [Elecraft] [K3] SWR - Numerical Indication
   
Yes, the K3S SWR display can show a 1.0:1 value.  But in my case,  it
does not exactly agree with another instrument in the feed line system.
     As to why you are showing two different values, as minute as they
are I might add, you are measuring 2 different places in the feed line.
   In my thinking, it is physically impossible to put two  SWR bridges
in the same place electrically.

In theory the SWR on a given line should be the same at all places, but
maybe not since there is loss of some minute value in the line.     
Since you are measuring on antennas, common mode current, may be the
contributing cause.  Difference in measurement calibration, may be a
factor as well.

VSWR bridges are calibrated with some specific value of load. Ideally,
it is 50 ohm non-reactive, but it could be 49 ohms or 51 ohms or some
other value.   Just because a load says "50 ohms" on the label is no
real indication that is actually fact.    To that end, I have 3 dummy
loads which are "50 ohm" loads according to the label but none are not
true 50 ohm loads.    I do have a Celwave load that says 50.5 ohms on
the label and measures 50.5 ohms per my General Radio bridge.    The
others are +/- something, but good enough to evaluate a ham transmitter
or amplifier.

Frankly, a difference between 1.1:1 and 1.0:1 won't make any realistic
difference in any form or fashion other than to appease the operator.

73

Bob, K4TAX



On 7/27/2018 9:58 AM, Dick Dickinson wrote:

> I've noticed that I'm not showing a reading of less than 1.1:1 SWR on my
> antennas per K3 SWR Numerical Readout.  K3EZ will record 1.0:1 SWR in band
> sweeps.
>
> Can the K3(S) Numerical Display show 1.0:1 SWR?  If so, is there a likely
> reason why K3EZ will show 1.0:1 while my K3 will only go as far down as
> 1.1:1?
>
>
> Dick -  KA5KKT
>
>
>
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