[Elecraft] KAT100 null

[Bill Carpenter]

Well, as almost always happens this was self-inflicted.  I have extra 
toriods and wire left over from my previous Elecraft kits so I wound a new 
T1, put it in and guess what?
It works!  Very well I might add.

Thanks to all who offered help!
----- Original Message ----- 
From: "Bill Carpenter" <nz0t at cox.net>
To: "elecraft list" <elecraft at mailman.qth.net>
Sent: Saturday, December 08, 2007 4:17 PM
Subject: Fw: [Elecraft] KAT100 null


>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" <nz0t at cox.net>
> To: <w3fpr at arrl.net>
> 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" <w3fpr at embarqmail.com>
>> To: "Bill Carpenter" <nz0t at cox.net>
>> Cc: "elecraft list" <elecraft at mailman.qth.net>
>> 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
>>>>
>>>
>>
>
>
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