Posted by
Earl W Cunningham on
Apr 18, 2005; 11:12pm
URL: http://elecraft.85.s1.nabble.com/XG1-Report-tp377307.html
I picked up an XG1 oscillator kit at the Elecraft booth at the DX
convention in Visalia. Assembled it this morning and used it's 50 uV
setting to check the S-meters in my four HF radios with the following
results:
Elecraft K2/100 = S9 (digital S-meter) (S-meter was calibrated by
adjusting the value of R1 for best AGC action and using the S-meter
calibration procedure described in the manual, i.e., full scale = RF gain
fully CCW and S0 = RF gain fully CW with antenna disconnected --
apparently done this way, there is no need to calibrate S9 on the meter
using the method described by others on this e-mail reflector).
Yaesu FT-1000MP = S9 (main and sub rx's, digital S-meters)
Icom IC-756Pro3 = S9+3 dB (analog S-meter), S9 (digital S-meter)
Kenwood TS-830S = S9+3 dB (analog S-meter) (1 uV setting = S4)
Years ago I calibrated the S-meter in the TS-830S using a metrology lab
calibrated HP-610C signal generator. I surmise that the Icom's S-meter
was factory calibrated at S9 using 50 uV. I therefore believe the -73
dBm output of the my XG1 is actually -70 dBm (70.7 uV).
If the 50 uV setting on the XG1 is actually -70 dBm, then the 1 uV
setting should be down another 34 dB, or -104 dBm (1.414 uV).
Interestingly, only the Kenwood has an accurate S-meter for signal levels
below S9. It's S-meter reading with the XG1 set for 1 uV was S4 (all
other radios were S0). Based on the 6 dB "standard" that each S-unit = 6
dB (and -73 dBm = S9) means that S4 is a signal level of -103 dBm, which
agrees quite closely with the presumed -104 dBm output of the XG1 at the
1 uV setting.
When I get ambitious, I'll perform the procedure for determining the
noise floor of each receiver as described in the XG1 manual.
All in all, the XG-1 is a neat piece of test equipment to add to the
shack and, as the saying goes, "Good enough for government work."
73, de Earl, K6SE
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