[Elecraft] K2/100 low output power on 10-15 meters

[Don Wilhelm]

  Mike,

Your base K2 power output on the higher bands is the root of the 
problem.  The KPA100 has a 10 dB gain, so 8 watts in gives you 80 watts out.

I would suggest you check the winding and position of T2 in the base 
K2.  It should be wound just like the diagram in the manual and mounted 
1/16 to 1/8 inch above the board.

73,
Don W3FPR

On 8/29/2010 1:44 AM, Mike and Alicia Fanning wrote:
> Hi all,
> I have just finished building and testing my KPA100 kit, and the power
> output seems low (87-89 Watts) on 10, 12, and 15 meters.  Is this
> typical?  I have triple checked that the parts are installed properly
> in the 10-15m low pass filter stage, and everything looks good there.
> After verifying the LPF was okay, I went back and measured output
> power from the K2 without the KPA100 installed.  Here are the
> numbers.  The first column is the band in question, second is the
> transmit power without the KPA100 installed (barefoot), third is with
> the KPA100 installed but powered through the original low power DC
> input (amp installed but bypassed), and the fourth is with the KPA100
> installed and powered through the KPA100 high power DC input (amp
> installed and active).
>
> 10m    8W       7.5W    87W
> 12m    9.75W  9W       87W
> 15m    11.5W  10.5W  89W
> 17m    12W     11W     106W
> 20m    12W     11W     100W
> 30m    13W     11W     106W
> 40m    14W     11.5W  107W
> 80m    13.5W  11W     105W
> 160m  12.5W  12W     111W
>
> When the KPA is hooked in but bypassed (column 3), why is the power
> output lowered?  Is it because of the second set of low pass filters
> (on the KPA100 board) coming in line?  I was surprised to see the
> transmit power level drop so much if this is the cause.
>
> Are my barefoot numbers fairly typical?  Looks like the KPA is giving
> me pretty consistent gain, so do I need to be looking upstream
> somewhere in the original K2?  If so, why the big jump on the KPA100
> output between 15 and 17 meters?
>
> Any thoughts or ideas appreciated.
>
> Thanks and 73,
> Mike Fanning, K4GU
> K2 #5882
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