Scott,
Full output is not real question for the bias - the questions are the
idle current draw (and heat dissipation) and the linearity of the output
stage.
One could measure the voltage across R7 instead of measuring the current.
Since the voltage across it divided by its resistance will indicate the
current.
The resistance of R7 is 0.005 ohms, and dividing by that value is the
same as multiplying by 200 - the units will be in amperes.
If you prefer to work with milliamperes, multiply the voltage across R7
by 0.2.
The current you will be measuring is in the range of 500 ma to 1000 ma,
so your voltmeter should be on a scale that will measure low millivolts
- 500 ma will create 2.5 mV across R7 and 1000 ma will produce 5 mv. Be
certain your DMM leads are not picking up a significant amount of noise.
The normal position for the bias adjustment pot is about 1/3 rotation.
73,
Don W3FPR
Scott McDowell wrote:
kpa100 swr bridge
Don
Thanks for the help on the swr bridge. You were right it was T4. I
re-wound it and the problem was cured. Now I am trying to adjust the
bias on the finals. I don't have a dmm that will handle the current so
guess I will have to buy one. I am getting full output on it.
Thanks for your help.
73
Scott N5SM
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