[Elecraft] Re: KPA100 over current on 160m

[Bob Henderson]

Bob Henderson wrote:

> I like to keep my K2 S/N 997 up to date.  I fitted a KPA100 two years 
> ago and routinely apply other enhancements as they arise.  Whilst at 
> Dayton this year I bought the components to increase the tolerance of 
> the KPA100 to hi SWR.  I have just completed fitting the modkit and 
> have replaced the firmware with 1.09.  Having done so, I decided to 
> check the power output of the K2/KPA100 against DC current input 
> accross all bands.  As I expected, there is a variation of DC current 
> input and RF output.  However, from 80m thru 10m old 997 produces 
> 90-110W at nominally 20 Amps.  The big shock is that on 160m it 
> produces 110W but draws a huge 30 Amps from the DC supply.  Concerned 
> that I might have a problem with the LPF for 160m, I terminated the 
> KPA100 LPFs in 50ohms and used my MFJ antenna analyser to check the 
> SWR of the filter.  On 160m it is around 1.2:1.  The filters for other 
> bands are all 1.3:1 or less.  It doesn't seem like the problem is the 
> LPF.  I wonder if any other KPA100 owners might have seen this problem 
> or have a clue to its cause?   I should point out that I didn't 
> measure current input to the rig on 160m prior to applying this mod so 
> it may quite possibly have already been at that level already.
>
> 73  Bob, 5B4AGN
>