Thus far it would seem we are getting exactly where we want to be. A HUGE thanks to everyone for all of this help. I love learning. Also this is a topic in the QRZ dot com Q&A forum. I am following both threads and saving all the replies as I would like to make an article of this mod after it all works and make photos of the procedures as well. Crediting all replies in the article will be done as well, if each person is OK with that.
I have a further query on this topic for everyone...
Looking at the Sensor Schematic I am seeing:
LOW REF CAL followed up by X-101 @ 2200 ohms
HIGH REF CAL followed up by X-102 @ 22K ohms
HIGH FWD CAL followed up by X-103 @ 100K ohms
LOW FWD CAL followed up by X-104 @ 4700 ohms
So far I have ascertained that this mod will
be done in the sensor unit?
Am I correct in thinking that I will need to modify both the
FWD and REF resistors for both meters to read accurately? If so:
I am thinking that if I install a DPDT switch
in the sensor unit to facilitate 2 each resistor
values for both the FWD and REF section of the
LOW end of the circuit; that this may be the
After the correct resistor values are found I am wondering
if recalibrating the variable resistors of
R-104 for LOW REF CAL and R-107 for LOW FWD CAL
on the QRP settings, if this is going to make the
standard 200W settings inaccurate...
If this would make the standard 200W settings no
longer calibrated; my thinking is that a permanent mod
to QRP would be more feasible. Then, in the event of
possibly selling the meter either sell it as modified
for QRP or switch it all back to factory.
Am I on the right track with the mod being performed
in the sensor circuit?
Here is the circuit schematics link
just scroll down to HM-2140A:http://www.tech-systems-labs.com/heath_schematic.htm
Again, Many many thanks, & 73,
Jim N8NSN (former kc8byf)