Yaesu FT-100 Undocumented page 40

• Next, to get into the alignment mode, turn the radio off, now press the [A], [B],
and [C] keys, and hold them in while you turn the radio on. Now press and hold
the [FUNC] key, as you normally would to get into the Menu. You'll find that the
Menu is now different.
• Rotate the selector knob until you find "F-07 [S FULL SCALE]" on the display.
Make a note of the current setting of this item, so you can go back to it if you
want to. Now adjust this item just like any other Menu item, by rotating the main
dial, until you get a full scale reading on the S-meter.
• There also is an adjustment of the 144 MHz RF Gain (F-01) and the 144 MHz IF
Gain (F-05). Perhaps a little adjustment to the RF Gain would help with the weak
repeaters. Whatever you do, make a note of the original settings of these items.
Adding too much front end gain can degrade the intermodulation performance of
the receiver section. Also, if you change the RF or IF Gain, the S-meter indication
will change, too.
• Press the [FUNC] key to exit the alignment mode.
If you have the equipment for it, you can more accurately adjust the s-meter by injecting
a 14.200 MHz signal in USB mode into the antenna at +95dbmicroVolt and adjust F07 to
read S9+60dB. You could also adjust it for an S9 reading on 40 Meters using 50
microvolts rms for S9, then "re-calibrate" the S meter mentally by remembering that
above S5 the "S reading" is one S unit higher than actual, and also that S9+20dB is
actually S9+15dB, S9+40 is S9+25 and S9+60 is S9+35.
There is only a single adjustment for the S meter which amounts to a DC offset. (It's NOT
a scalar!) All you can do is shove the entire curve one way or the other. Most simple RSL
indication circuits at least use a DC offset along with a DC gain setting. The latter allows
you to set the steepness of the indicated RSL (receive signal level) function. The whole
business is about proper interpretation of either a detector output or the AGC voltage. The
FT-100D uses the AGC voltage to generate the indicated RSL. But they only included
one control (DC offset) to you're really limited in terms of setting the accuracy of it.
Probably the best thing to do is to calibrate it on your favorite band for the standard
50 microvolts RMS (single sinusoid) for S9 and perhaps characterize your "indicated
RSL versus actual RSL" so at least you know how to translate what the meter is
indicating.
FT100D CW signal. Assume first segment is S2 based on relationship to segment which
corresponds to S9.
7.2 MHz setting 205
Segments Display Equivalent
readout standard
level (dBm)
1 S2 -115
2 S3 -109
3 S4 -103
4 S5 -97
5 S6 -91
With S9 set for -73 dBm
Actual level Actual level
in dbm in "S" units
-102 S4
-101 S4
-99 S5
-98 S5
-96 S5
Display
error
2 S units low
1 S unit low
1 S unit low
0
1 S unit high
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