Phill, I had one here and it was very sensative.  The problem was to mark
where 50 ohms was on the bridge, and to be able to take it out of line
before transmitting.  I have 4 hf stations here so wasn't an easy thing to
do.  It's nothing compared to the voltage controled oscellator.  That
circuit put across a watt meter, is more accureate than a print meter.
I've compared it.