Re: {Collins} Question on setting up bias on KWM-2

It is definitely best to set the bias up with the set connected to the PS and using the current read on the meter.

That being said, the current being read is really the voltage across the sensing resistor and, as with all old resistors, is subject to suspicion. I would check the value of the resistor and also, maybe, put a calibrated mA meter in series with the HV plate supply to check on the "real" idling current. I don't have my KWM-2 manual available, but in some cases, what the "plate" meter reads is actually cathode current so you have to factor in the screen current into the calibration problem. As with all high voltage servicing - be careful.

Hope this helps,


----- Original Message ----- From: <OTAKEBI@xxxxxxx>
To: <collins@xxxxxxxxxxxxx>
Sent: Wednesday, January 07, 2009 9:31 AM
Subject: {Collins} Question on setting up bias on KWM-2

When setting up the bias on the KWM-2 is it best to set it up on the power
supply with the radio disconnected from the supply using a DVM or should it be
done while supply is connected to the KWM-2 using the procedure in the
With supply and DVM I show a -86 of bias.
with the supply connected to the rig I show 40ma after a 10 minute warm up.
If I speak for an extended QSO I notice the bias goes up to 55 on the rigs
If I set it for 50ma it goes up to 65ma after long winded QSO on 80 meters.
RF output is stable at 100 watts on 80 meters and plate is good  too.
Is this normal?
Supply bias seems to hold steady when off the rig.
Can I trust the KWM-2 meters or is this part of the meter as flaky as the 0
Could someone shed some light on this I have searched past post and found
Thanks in advance

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