[Drake] R4C Sensitivity Part 2

[Gary Poland]

Scott,
  I also ordered one of the Elecraft XG2 tri-band receiver test oscillators 
and also their 2 tone test oscillator after reading your email, thanks for 
the information. I am including readings I have collected over the years 
with a few R-4C's that I had in for repair as well as my own. Most of these 
readings were taken using a URM-25F or Singer CSM-1 signal generator. The S 
meters of some R-4C's under test would not always align per Drakes 
instructions, some were simply set with the AGC threshold at -1.35 volts, 
zero at no signal,  and full scale sensitivity set with the RF gain fully 
CCW. As you will see S 8.5 to 9 is too much AGC too soon. I suggest you 
check the AGC Bias adjustment for approximately -1.35 volts / -1.00 on V1.

                                                      1uv    3uv    10uv 
30uv    100uv    30kuv
R-4C SN 19671 @ 7.0 mhz               S3     S5      S8      S9+5    S9+20 
S9+60
R-4C SN 27345                                S3     S5     S7.5     S9+5 
S9+18   S9+60
R-4C SN 18074                                S3      ---       ---  
          ---      S9+60


R-4C SN xxxx  @ 14.0 mhz              S4     S5      S8       S9+5    S9+15 
S9+45
R-4C SN xxxx                                  S2     S5      S8       S9+5 
S9+15   S9+45
R-4C SN xxxx                                  S4     S5      S7         S9 
S9+10   S9+40


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