[SOC] OHR WM1-1

[Neal Enault]

Hi Tom,
   
  I have a WM-1 that I got in 1995, and It has a black border on the meter.
   
  Departing SOC mode.
   
  To calibrate, jumper JP1 must be in place.  It is severed after calibration.
   
  Calibration is straightforward.  Be sure you have a battery in the wattmeter.  :-)
   
  1. Positive lead of a DMM goes to the "test loop".  Negative to gnd (chassis).
  2. Turn R6 fully CCW, and set the wattmeter to the 10W posiiton.
  3. Adjust R6 for 2.56V on the DMM.
  4. Adjust R9 for a FS reading of 10W.
  5. Adjust R6 (yes, R6 again) for a reading of 0.8V.
  6. Set the wattmeter to the 1W position and adjust R12 for a FS reading of 1W.
  7. Adjust R6 (again) for a reading of 0.251V.
  8. Set the wattmeter to 100mW.  Adjust R15 for a FS reading of 100mW.
  9. Turn off the wattmeter, disconnect the DMM, and sever JP1.
   
  You are done.  Make sure that JP1 doesn't "disappear".  You may want to recalibrate in the future.
   
  Now returning to SOC mode.
   
  72, Neal WA6OCP  SOC #625

Tom McCulloch <thom2 at att.net> wrote:
  I have an OHR WM-1 Wattmeter. Apparently there was an older version and a 
newer version of the WM-1 (this is before the WM-2 came out). I'm pretty 
sure I have the newer version, I'm told the difference is that the older 
version's meter is 100% clear plastic and the newer version has a black 
border along the bottom of the meter.

So, I have the black bordered meter and I was wondering if anyone has the 
instructions for the WM-1 (or can point me to a web site that has them) and 
can tell me how to calibrate it. There are two pots inside, one is for the 
10 watt range and the other for the 1 watt range. R6 and R-something else. 
You are supposed to adjust them back and forth until some magical reading is 
arrived at, but that's all I know.

Any help would be appreciated.

Thanks
Tom
WB2QDG 

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