[Elecraft] K3 (not S) Antenna tuner strangeness

[Don Wilhelm]

Brian,

There should have been an increase in SWR between L1 and L2 on 28MHz, 
but the results on 50MHz indicate that it may be OK.

I think the increase in SWR between C1 and C2 is normal, but why does 
the SWR drop when C3 is selected?  That to me indicates a problem with 
C3 - and possibly C4 for the same reason.

The problem can either be the capacitor or its associated relay. The 
relays clicking indicate that the coil is OK, but that says little about 
the contacts.

Take another look at the C1 through C5 sequence on 28MHz.  The SWR 
should increase with each successive capacitor selected - simply because 
the capacitor values are larger.
 From my experience with the KAT2 and KAT100, the SWR increase between 
C1 and C2 is normal, but the real question is "Why does it drop 
significantly with C3 and C4?"
The C5 SWR of 5.5 is more along the lines of what I would expect.

So I would suspect C3 and C4 -- or more likely their relays above all else.

Yes, those could be the reason you cannot achieve a good match to low 
impedance loads on 80 and 160 - it just may be that those values are 
needed and are not available.

73,
Don W3FPR


On 7/25/2016 5:23 PM, brian wrote:
> Thanks Don,
> Very instructive.
> All relays click.
> Tabulated below are the L/C test results.
> The only anomaly appears to be with C2.  It seems to act as a 100 pf 
> rather than the 22 pf it is supposed to be.
>
> SWR's 50 ohm dummy load attached to antenna port of K3
> -------------------------------------
> L test
> Bypass 1.0 50.1 MHz
> L1 1.1
> L2 1.8
> Bypass 1.0 28.1 MHz
> L1 1.0
> L2 1.0
> L3 1.5
> L4 3.3
> L5 14
> Bypass 1.0 14.10 MHz
> L5 3.9
> L6 9.8
> Bypass 1.0 7.05 MHz
> L6 4.2
> L7 8.9
> Bypass 1.81 MHz
> L7 2.3
> L8 4.6
> -------------------------------------------------
> 28.1 MHz Bypass = 1.0    21.0 MHz Bypass =1.0
> C1 1.4                    C1  1.3
> C2 2.5                    C2  2.1
> C3 1.5                    C3  1.4
> C4 1.7                    C4  1.5
> C5 5.5
> 14.1 MHz Bypass =1.0
> C5 2.6
> C6 5.2
> 7.05 MHz Bypass =1.0
> C6=1.7
> C7=3.9
> C8=10.9
> ----------------------------------------------------------
> Not sure if the C2 anomaly is relevant to 160/80 M
>
> 73 de Brian/K3KO
>
> On 7/25/2016 18:11 PM, Don Wilhelm wrote:
>> Brian,
>>
>> You might try going into the KAT3 menu and go through the L1-L8 and
>> C1-C8 settings to hear the relays click with each selection.
>>
>> If all the relays are working, you should be able to do a check on the
>> health of the inductors and capacitors using a method similar to that
>> shown for the KAT100 in the right column of page 35 - manually select
>> the inductors starting with L1 and see what the SWR is on a high band.
>> With each other inductor, the SWR should increase.  Change to a lower
>> band if the SWR gets too high to indicate (highest is 9.9).  Do the same
>> for the capacitors.
>>
>> I have not tried this technique with the KAT3 (but it should work) - I
>> have used it with the KAT100 and the KAT2.
>>
>> 73,
>> Don W3FPR
>>