[Elecraft] KPA100 Bias and R26

[Mike Harris]

Hi,

Finally got the beast buttoned up.  Comments to add to those made by others:

Power Calibration (R26  and R27) - Page 45

I adjusted this as instructed at the 5W level.  I think this should only be
taken as a good starting point for further adjustment.  After completing the
construction full power tests indicated about 85W output max.

Re adjusted at 50W and now the output tracks OK all the way to 100W.

Output was measured into an OHR 100W load with a Bird 43 fitted with a 100W,
2-30MHz slug.
An immediate follow up measurement was made using a OHR WM-2 connected to
the coupler port (-20dB) I added to the 100W load.  I was pleased to see
that 100W indicated on the Bird 43 translated to 1W on the WM-2 (100W
at -20dB).  I can now have confidence that the coupling transformer on the
small FT37-43 core isn't saturating at 100W/1W.

Bias current adjustment - Page 47

Readings on my KPA100
Point #5 - 290mA
Point #6 - 475mA + 400mA for Q1+Q2 = 875mA
Quick adjust to 875mA +/-
Current slowly climbed to 975mA +/-

I would strongly recommend that when mating the KPA100 to the K2, remove the
right hand side panel so that the cables can be tucked in neatly, especially
the ribbon cable.

For what it's worth.

Regards,

Mike VP8NO (IOTA SA-002)
GQRP 10148
K2/100 #1400