[Elecraft] Re: Power Out of KPA100

[Steven Pituch]

Hi Don, and All,

All done.  Ken, K3IU, sent me his plots of various fixes and it convinced me
to change out the resistors.  The results seem to me to be dramatic.  Here
are the results before and after changing the resistors.

|--c80+c81=5600 pf only-------|	+new r19+r20
________________________	____________
SSB
80M	3773	100W	"80"	100W	"80"
40M	7251	100W	"99"	100W	"75"
30M	10114	90W	"110"	105W	"85"
20M	14290	70W	"110"	100W	"100"
17M	18136	100W	"90"	100W	"70"
15M	21350	110W	"100"	105W	"80"
12M	24950	100W	"110"	105W	"70"
10M	28400	100W	"110"	105W	"70"

CW
80M	3600	105W	"60"	100W	"60"
40M	7050	110W	"70"	100W	"60"
30M	10115	98W	"110"	100W	"60"
20M	14050	100W	"70"	100W	"60"
17M	18080	100W	"70"	100W	"60"
15M	21100	100W	"60"	100W	"60"
12M	24900	100W	"60"	100W	"60"
10M	28050	110W	"70"	100W	"60"

The fix definitely smoothed out the power on cw and ssb.  Still a dip at 20
and 30 meters, but Ken's plots show this and I get 100 W plus on all bands.

I got some hot rig here, a keeper.   I just got VC9W IOTA NA-014 on 14015,
first try with 100 Watts.  With all the techniques we have learned using 5
Watts or less, 100 Watts is like shooting fish in a barrel.  I can see how
the amp is nice for cracking really big pileups, and for traffic net work.

Someone, asked a while ago what K2 builders would have done different if
they could do it over again.  For me, I wouldn't change a thing!  The
mistakes I made were all inexpensively repairable, and I learned something
about the radio, and it gave me the confidence to know that whatever
happens, I can fix it.

I will redo the wattmeter calibrations soon for the KAT100/KPA100.  All
three of my external wattmeters were pretty close, so close enough for
government work.  I may even parallel a resistor in my MFJ-949E dummy load
to bring down the resistance a little bit.  I need to calibate my wattmeters
too with an rf probe.

Thanks to all,
Steve, W2MY
K2 #402

-----Original Message-----
From: W3FPR - Don Wilhelm [mailto:w3fpr at earthlink.net] 
Sent: Sunday, July 31, 2005 5:29 PM
To: Steven Pituch; elecraft at mailman.qth.net
Subject: RE: [Elecraft] Power Out of KPA100

Steve,

Put in the new resistors Scott sent to you (yes, the 5600 pf capacitors can
stay) and then calibrate the wattmeters in the KPA100 and the KAT100 and you
should be all set.  If you can buy, beg, borrow or otherwise acquire a good
50 ohm non-reactive dummy load you will find the wattmeter calibration much
more accurate.  I recommend using an RF Probe to measure the RF Voltage at
the dummy load rather than relying on any wattmeter - even the best are
spec'ed for only 5% of full scale when properly calibrated, so on a 100 watt
scale, even the best can be off by as much as 5 watts - the run of the mill
wattmeters can only be trusted to 20% of full scale (20 watts possible error
on a 100 watt scale) until proven otherwise.

73,
Don W3FPR


-- 
No virus found in this outgoing message.
Checked by AVG Anti-Virus.
Version: 7.0.338 / Virus Database: 267.9.7/60 - Release Date: 7/28/2005