[AMRadio] AF67 question

CL in NC mjcal77 at yahoo.com
Sun Jan 21 17:54:15 EST 2018

I've got an AF67/PMR7/M1070 up and running.  In lieu of the 22.5 volt battery, I put the unused winding meant for the vibrator supply to work and its making bias for the modulators and have it set to 22.5 volts.  The problem is, I can not find a spec for the modulator idle current, only that it should swing to 60-70% of PA current, which is does.  Is there an mod idle current spec?  

The other issue is grid drive.  I have plenty, actually too much for a single 6146.  It seems if I detune the grid a bit to lower the grid drive, I can approach 120ma plate current under load with great power out and modulation.  I know there is no clamper in this unit, and no grid drive means max plate current and that may be playing into the equation as I lower it.  Do you Elmac'rs just peak it out, or maybe roll grid drive back to 2.5-3ma range?

Charlie, W4MEC in NC

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This page last updated 22 Feb 2018.