Posted by
Don Wilhelm-4 on
Feb 28, 2014; 1:49am
URL: http://elecraft.85.s1.nabble.com/KAT100-Power-Calibration-Problem-tp7584832p7584833.html
Jeremy,
You did not mention it, so I have to ask - when connected as you
describe, did you first obtain a good null at U5 pin 3 (by adjusting
C31)? That is a necessary first step. If you did not get a voltage
measurement in the single digit millivolt range (less than 10
millivolts), then 'all bets are off' and you need to first resolve that
problem.
Be certain to follow the manual instructions - no power to the KAT100
and no control cable attached.
Once you have achieved that (nulling) balance point, you can proceed to
the next step. While observing the actual power output, set the K2
power for 10 watts as observed on your external wattmeter.
Once you have established that power level, then adjust R4 to produce
1.8 volts on U5 pin 5.
After obtaining that adjustment, reverse the RF IN and ANT1 connections
and adjust R3 (with the external wattmeter reading 10 watts) for 1.8
volts on U5 pin 3.
Then do 'the math' as indicated in the manual to further adjust R4.
After that 'job done'.
If you fail to find a balance point on C31, that problem must be
resolved before continuing with anything else (unless you want to do it
over and over again). Should you not obtain a good null, investigate
the winding of T1. It must be wound *exactly* as indicated by the
illustration in the manual including the direction of the turns. If the
direction of the turns is reversed, the alignment voltages will be
reversed - hence your low voltage at U5 pin 5.
73,
Don W3FPR
On 2/27/2014 8:11 PM, JeremyJones wrote:
> I have just finished my KAT100, and am having an issue during the Power
> Calibration of R3 and R4. I am using a K2 with KAT2. I have a cable
> running from the Ant 1 jack of the KAT2 to the Ant 1 jack of the KAT100.
> The KAT100 RF In jack is connected to the Transmitter jack of the power
> sensor of my W2. The Load jack of the W2 sensor is connected to a 250W, 50
> ohm dummy load. The K2 is set for 10W. The W2 is inline only to check the
> actual power out, due to the strange readings I was getting.
>
> When I hit TUNE, I can only get a voltage range of 0.0 to 0.07 VDC at U5 pin
> 5 while adjusting R4. The table in the manual indicates that I need to set
> R4 so that I get 1.8V at U5 pin 5.
>
> I have double checked the orientation of the diodes, everything checkout in
> the previous tests. T4 has the correct windings, and continuity between
> pads 1 and 4 is good.
>
> What else should I be looking at.
>
>
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