RF Gain Control up, "S" meter goes down, WHY??

[KJ6HYC]

I'm a new ham, not understanding on my Yaesu 897D, and I have been told on other receivers this is also true. Why when you increase the RF gain, the "S" meter indication decreases. Why does this happen and how do you get/give accurate "S" readings?

73
Wayne - KJ6HYC

 

[Beetle]

I'm a new ham, not understanding on my Yaesu 897D, and I have been told on other receivers this is also true. Why when you increase the RF gain, the "S" meter indication decreases. Why does this happen and how do you get/give accurate "S" readings?
73
Wayne - KJ6HYC

Perfectly normal. The S-meter works off the AGC voltage, and as you decrease the RF gain, the system requires a stronger signal to "break through". The most "normal" operation of the S-meter would be with AGC turned on, and RF Gain all the way up.

As far as "accurate" S-reports, consider this: the RS/RST system has been in use for close to a hundred years. S-meters have only been around maybe 60 of those years. HowEVER did we give strength reports in the early years? By using our ears, that's how.

No two S-meters will give identical performance; they're all just relative readings. Use the guidance for RS/RST reports shown in the ARRL Handbook, or in their logbook, or find it on the Internet. If a station is weak but I don't have a lot of trouble copying him, I might give him an S3 or 4. A normal signal, S7. Really loud, S9. The system doesn't go higher than S9 because it harks back to pre-S-meter days.

 

[KE3W]

FYI...

Signal Strength

S1 Faint, signals barely readable
S2 Very weak signals
S3 Weak signals
S4 Fair signals
S5 Fairly good signals
S6 Good signals
S7 Moderately strong signals
S8 Strong signals
S9 Extremely strong signals

 

[WR0220]

Beetle hit the nail on the head. From page 21 of the operation manual:

If your transceiver is configured for “RF Gain” use, rotating
this control fully clockwise in the SSB/CW/Digital modes
will provide best sensitivity. To reduce the receiver’s RF
Gain somewhat, rotate this control counter-clockwise
slightly. You will observe an increasing number of bars on
the S-meter as you rotate the RF Gain control counter-clockwise;
this indicates increasing AGC voltage, which is causing
the front-end gain to be reduced. In the FM and Packet
modes, this control will automatically be set to “Squelch,”
even though the setting of Menu Mode No-080 [SQL/RF
GAIN] is “RF Gain.”
If this control is configured for “SQL” operation, the FT-
897’s RF Gain will be set for maximum sensitivity in all
modes, and the SQL/RF Gain control will function solely
as a Squelch control. In this case, rotate the SQL/RF Gain
control to the point where the background noise is just silenced;
this will provide the best sensitivity to weak signals,
while keeping the receiver quiet when no signal is received.
The LED just above the Main Dial will glow Green when
the squelch is opened by an incoming signal or noise.


The bold text talks about an increased number of bars on the S meter as you decrease RF gain, but if you increase the rf gain (reduce AGC voltage) the bars on the S meter will decrease.

 

[unit248]

The way I think of it, as you turn the RF gain control and the needle moves forward, the radio is telling you: "signals must now be at least this strong for you to hear them."

-Bill

 

[Beetle]

The way I think of it, as you turn the RF gain control and the needle moves forward, the radio is telling you: "signals must now be at least this strong for you to hear them."

-Bill

Not necessarily to HEAR them, but to make the meter move any higher. With RF Gain all the way up, you might hear a station that's registering about an S3. If you turn the RF gain down until the meter is showing an S4, you should still be hearing that station, but he will not be as strong, and he shouldn't be moving the meter at all.