[Elecraft] Current Draw on 20M

[Randy Farmer]

I'm beginning to believe we're up against a harmless component tolerance 
stack-up that's peculiar to the K3S lineup design for 20 meters. For 
what it's worth, I've done many hours of pretty hard CW contest 
operation with my K3S and it hasn't shown the slightest problem 
operationally. What originally caused me to notice the 20 meter current 
draw phenomenon was that my radio seemed to be shutting down once the 
supply current hit about 23A, despite being supplied from an Astron 
RS-35 that measured around 12.8V at the radio with key down on 20. I had 
attributed the shutdown to the radio, but after it went for the factory 
checkout and still produced the same behavior, I swapped the power 
supply for its supposedly identical twin that was used for the K3 on the 
second station. No more shutdown, so I'm chalking it up to a premature 
overcurrent shutdown in the original power supply. Despite the fact that 
the radio draws significantly more current on 20 than on other bands, 
it's given no indication of any problem since.

73...
Randy, W8FN

On 6/20/2020 1:30 PM, Russ Tobolic wrote:
> After reading your numbers here I was curious since my K3 is the same 
> vintage as yours, serial 732, Apr'08.  I did a quick check on 20M and 
> I am reading 15.5A, @13.5V (on my Astron 20M meters) at 100W into a 50 
> ohm dummy load.  I checked other bands and read the following: 
> 160M-15.5A, 75M-14A, 40M-14A, 15M-13.6A, 10M-13A.  All readings were 
> in the tune position using a LP-100.  I don't think the higher reading 
> on 20 (or 160) is really significant.
>
> Russ, N3CO
>
>     On Fri, Jun 19, 2020 at 1:55 PM, Mike Maloney
>     <ac5p at sbcglobal.net> wrote:
>     FWIW, my old K3 (Nov'08) only pulls 17.8Adc at 12.5V for 100W into
>     50ohm dummy load at 14MHz.
>     Seems to follow your PA temp is gonna run hotter also.  WHY such
>     poor efficiency Elecraft, (Wayne) ?
>     73,Mike, AC5P
>