[Elecraft] K1 #1720 lives

Sat Nov 29 10:51:00 2003

Hi

I use a different method that I developed to adjust the SWR meters in =
the tuners (KAT2, KAT1 KAT100 and KX1 tuner). I first adjust the trimmer =
cap to the lowest voltage on the test point but I don't get overly =
critical about because it will be adjusted later for the optimum =
setting. Then I set the forward pot for the correct power out =
indication. This is all done with a 50 ohm load. Then I change to a 100 =
ohm resistor and adjust the reverse pot for approximately  2:1 SWR =
reading. Then connect a 25 ohm load and check to see if the SWR is still =
2:1. If not then very gently adjust the trimmer cap to make the SWR =
reading the same with a 25 ohm and 100 ohm resistor. Go back and forth =
with the 100 and 25 ohm until the reading is the same but not =
necessarily 2:1 . Once the reading is the same then adjust the reverse =
pot to make the SWR read 2:1. Finally reconnect the 50 ohm load and make =
sure the forward power is correct if not touch up the forward power pot. =
The idea is to get everything so the power out is correct at 1:1 with 50 =
ohms and close to 2:1 with the 25 ohm and the 100 ohm load. You may not =
be able to get it exact, you may get 2.1:1 with one resistor and 1.9:1 =
with the other but that is good enough. The trim cap will very touchy so =
make very small adjustments and recheck the SWR with both resistors. The =
reverse pot will end up set somewhat more clockwise than the forward =
pot.

I made the loads by installing two 51 ohm 3 watt MOS resistors in =
parallel for the 25 ohm into a PL-259 connector and two of the same =
resistors in series for the 100 ohm load. For the 50 ohm I installed a =
51 ohm 5 watt MOS resistor (hand selected for as close to 50 ohms as I =
could find) into a PL-259 connector. You could also use two 100 ohm 3 =
watt MOS resistors in parallel in a PL-259. Another option would be to =
use the new dummy load from Elecraft. If you wanted to use all of the =
same value resistor then buy a bunch of 100 ohm 3 watt MOS resistors =
(you can get them from Mouser P/N 283-100). Use four in parallel for the =
25 ohm, two in parallel for the 50 ohm and one for the 100 ohm.

It is important that the load connect directly to the antenna connector =
without any coax so get the dual BNC male to male connector for the =
Elecraft load and get some PL-259 to BNC connectors for the 100 and 25 =
ohm loads. I make the adjustments at about 5 to 10 watts on the K2 and =
about 2 watts on the K1 and KX1.

The method seems to work and I have not seen any problems with it.

Don Brown
KD5NDB

  ----- Original Message -----=20
  From: James R Giammanco=20
  To: [email protected] ; [email protected] ; [email protected] ; =
[email protected]=20
  Sent: Friday, November 28, 2003 7:12 PM
  Subject: [Elecraft] K1 #1720 lives

  Just finished K1 #1720, which Wayne, K5EOA, and I built for Wes, =
W5DPM.
  Four band K1, plus ATU and noise blanker. Everything was nominal and =
all
  items function as designed. First QSO was W5DPM with Chris, KD5UDB, =
also
  a K1.

  One question lingers. Has any further method of calibrating the =
reflected
  power on the KAT1 been suggested beyond the "set visually to the same =
%
  rotation as the forward power potentiometer" method?=20

  72
  Jim N5IB
  K2 #1233 =20

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