[AMRadio] Amplifier to use with my DX-60

W7QHO at aol.com W7QHO at aol.com
Sat Mar 18 23:07:39 EST 2006

For a simple and very effective modulator for rigs in this power class that 
doesn't require increasingly hard to find modulation iron, let me recommend a 
Heising circuit originally described in the April  1955 issue of Radio and 
Television News and revisited in ER #91, Nov. 1996.  The scheme utilizes a clever 
bias shifting scheme to squeeze 30 - 40 watts of audio out of a single 807 
modulator tube.  No transformer required, only a 10 H filter choke.  Won't 
modulate 100% in the negative direction (in common with other Heising circuits) but 
comes so close you can't tell the difference.

The original author called it a "Reference Shift Modulator."  Can provide 
more information if anyone's interested.

Dennis D. W7QHO
Glendale, CA

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