[Drake] TR4CW S Meter

[Gary Poland]

Tim
    R-13 is a calibration resistor for the plate meter. It has no effect on 
the S meter operation. The only calibration for the TR-4C S meter is S METER 
ZERO and the S meter sensitivity pot R187 on the audio board. The tubes 
associated with AGC and the S meter are V11, V13, and V17. V15 is connected 
in transmit to indicate transmit AGC. The S meter sensitivity is set for a 
full scale indication with the RF Gain fully CCW. The with a 30uv signal the 
S meter should move to anywhere from S7 to S8.  Typical is around S8. 100 uv 
will result in a S meter reading of S9 to S9+5. The AGC should begin to rise 
at 1 to 1.8 uv and the S meter will read S1 to S2. This info came from 
several TR-4's / C's. Since a lot of radios reference S9 as 30 uv the TR-4 S 
meter is typically scotch.
   Typically the S meter on the TR-4 will read well past 60 over 9 with the 
RF Gain fully CCW. The TR-4 lacks the sensitivity pot R187 to set full scale 
at 60. Over the production of the TR-4 the resistors in the S meter circuit 
changed values several times. In order the calibrate the TR-4 S meter it may 
be necessary to swap out resistors R143 and/or R71. Typical values for R143 
are 100, 180, and 270 ohm. R71 typically is 560 or 820 ohms.

Hope this helps...73, Gary W8PU
http://home.cinci.rr.com/w8pu