XG1 Report

[Earl W Cunningham]

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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[KK7P]

> Elecraft K2/100 = S9 (digital S-meter)
>
> 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).

Or, you could surmise that the K2, FT100 MP main, FT100MP sub, and Icom
digital are accurate, the Icom analog is 3 dB high and that the Kenwood
has drifted 3 dB since the cal was done so long ago...

Or, that the XG-1 is 1.5 dB high and all the radios are +/- 1.5 dB of
that :-)

Enjoy!

Lyle KK7P

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[Ron D'Eau Claire-2]

Earl wrote:
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)
---------------------------

Someone I was chatting with recently said he had tested the S-meters of
several receivers and found that 1 S-unit can equal anything from 3 dB to
more than 6 dB. I had always assumed the target was 6 dB/S-unit. Apparently
not so.

Ron AC7AC


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[Earl W Cunningham]

Ron, AC7AC wrote:

"Someone I was chatting with recently said he had tested the S-meters of
several receivers and found that 1 S-unit can equal anything from 3 dB to
more than 6 dB. I had always assumed the target was 6 dB/S-unit.
Apparently not so."
==========

Years ago, there were two "standards" for S-meters.

1) The Collins standard was 100 uV = S9 and each S-unit was 8 dB.

2) The Hallicrafters standard was 50 uV = S9 and each S-unit was 6 dB.

Manufacturers naturally adopted the Hallicrafters standard because the
Collins standard resulted in a stingier S-meter (higher S-meter readings
= better receiver, right? - No!!!!)

It is rare, with the new transceivers currently on the market to find one
that strictly adheres to the "standard".  Virtually every tranceiver
today uses the 50 uV = S9 criterion, but the change per S-unit is much
less than 6 dB.  This results in a substantial signal such as 1 uV (which
should read S3.5 on an accurate S-meter).not even budging the S-meter on
most receivers today.

In dB above S9, the S-meters most transceivers today seem to be fairly
accurate.

If all manufacturers complied with the "standard" to the letter, S-meter
readings would be more meaningful.  As it is now, they are useful only
for reference readings such as when someone does an A/B check on his
antennas with you.

BTW, the values I posted originally were with the receiver preamp turned
off in all cases.

73, de Earl, K6SE
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[g4ilo-2]

Isn't that simply because most transceivers derive the S-meter reading from
the AGC level, and you don't want the AGC acting on weak, but still
readable signals?

Reports based on the actual S-meter reading are completely meaningless, due
to the lack of standardisation and the fact that whether the preamp or
attenuator are used affects the reading.

73,
--
Julian, G4ILO. (RSGB, ARRL, K2 #392)
G4ILO's Shack: http://www.tech-pro.net/g4ilo

Earl W Cunningham <[hidden email]> wrote:

[snip]

It is rare, with the new transceivers currently on the market to find one
that strictly adheres to the "standard".  Virtually every tranceiver
today uses the 50 uV = S9 criterion, but the change per S-unit is much
less than 6 dB.  This results in a substantial signal such as 1 uV (which
should read S3.5 on an accurate S-meter).not even budging the S-meter on
most receivers today.



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