I just checked my analyzer with a good known 50 Ohm load and it read 60 ohms
so I'm sure my dummy load is fine - the analyzer reads 10 ohms high I guess.
I have checked all connections/solder joints and yes the input wire goes
through T1 lol. I do get a null but at around 2 volts, not near zero as it
should be. When I attempt power calibration at 20 watts I can't get near
the 2.7 volts specified -I can only get to around 2 volts with full
clockwise on R4. Since that is the same as the null could U5 be bad? Just
occurred to me.
Ackkkkkk!
----- Original Message -----
From: "Bill Carpenter" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Saturday, December 08, 2007 1:54 PM
Subject: Re: [Elecraft] KAT100 null
Hi Don,
I'm using my old Heath dry dummy load/wattmeter which shows 60 ohms pure
resistive on my MFJ analyzer (who knows how accurate that is) and I'm
using a good, very short jumper. All connections look fine and yes, the
input jack wire goes through T1 lol. I do get a null but it's at around
1.9 to 2 volts on my DMM.
This is driving me crazy - it has to be something simple I'm missing!
----- Original Message -----
From: "Don Wilhelm" <[EMAIL PROTECTED]>
To: "Bill Carpenter" <[EMAIL PROTECTED]>
Cc: "elecraft list" <[email protected]>
Sent: Saturday, December 08, 2007 1:04 PM
Subject: Re: [Elecraft] KAT100 null
Bill,
That indicates something is wrong. Are you using a good dummy load with
a very short connecting cable? If you have any doubts about the dummy
load, check it (and the cable too) with an antenna analyzer - anything
other than a 50 ohm resistive load can cause problems with obtaining a
good null.
The other thing that can cause difficulty with the null is any reactance
in the tuner - there is a small amount of residual, but not enough to
change the null drastically. Look the tuner over carefully for
unsoldered connections in the relays and inductor and capacitor parts of
the tuner.
As for 'dumb' things, make certain the wire to the input jack goes
through the center of the toroid.
73,
Don W3FPR
Bill Carpenter wrote:
Everything has gone fine with my new KAT100 until I got to the SWR
bridge null adjustment. The best null I can get is about 1.9 to 2.0
volts. I checked T1 and even took it out and rewound it with new wire.
The 4 leads of T1 are in the correct holes and continuity checks fine.
Everything else in the bridge circuit looks fine to me and the coax
jumpers I'm using are fine. I have the KPA100 so I'm attempting the
adjustment at 20 watts. U5 is installed correctly.
Very frustrating! Any help is GREATLY appreciated!!
73,
Bill NZ0T
_______________________________________________
Elecraft mailing list
Post to: [email protected]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com
