Heath HW-100 Plate Modulation Mod

kd4e doc at KD4E.COM
Sun Aug 19 15:02:47 EDT 2007

I'd like to add an external plate modulator to my
Heath HW-100.

I have the rig, HP-23B/SB-610 PS/Speaker, and a dual-807

I'd like to be minimally invasive to the HW-100 to retain
the CW/SSB capability and switch-in the plate modulated
AM mode only as needed.

I am now told that the final dual-6146 rf section of the
HW-100 contains components that are not adequately robust
to handle the doubled-voltage stress of plate modulation.


1.  If I replace plate inductor-resistor pairs L902 & L902 with
heavier wire and upgrade the 47K resistors to 5W from 2W, also
the L901 425 uH choke am I getting close to beefing-up all that
is necessary?  The .005 caps are already rated for 1.5K but given
their age *may* they may also benefit from an upgrade.

2.  Is there a way to squeeze some extra drive out of the 6CL6
driver?  I am told that the voltage drops to 190 by design on
transmit - can the circuit be modified to provide the 250-300V
needed to get the needed 4-5W of drive for full plate-modulated
AM out of the dual 6146's?

3.  Am I underestimating the significance of the necessary mods
to the HW-100?

4.  If the HW-100 proves unsuitable is there an 80-10M tube
transceiver that would be more suitable?


Thanks! & 73, doc, KD4E
Personal: http://bibleseven.com/kd4e.html

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