Hi Steve: 

When employing the VCO, where does it sit? 
Is it mounted internally and how do you turn it off and on for tuning purposes? 
I'm very interested in this because I think this can be adapted into Tom, W8JI's TOF, a device for monitoring grid current with the aid of a lamp that lights when the max grid current is reached. 
Tom is a little bit of an expert on the Ameritron 811/80B and 82 amps. 
I wrote him this morning to see if this device could be adapted to use a VCO instead. 

73: 
Mike VO1AX