s-meter reading?


Brad (KE7HFP)
 

This is going to sound like a really silly question but how to you read the s-meter on a TMD700?  Generally, a S-meter will have 9 levels.  My Kenwood TH-F6 has 9 bars.   But on my TM-D700 it only has 7 bars?  Does it skip the first two and start at S3 or is there some other scaling?

 

Thanks.


Don Rolph
 

I was provided the following data for the D710G/A

Email from J. D. Barron jeter.d.barron@... via group.io to main, Nov. 18, 2021, 2:01 PM:

“1 bar means a weaker signal and all bars means a lot of signals.
I don't think that the correlation to a relative S meter reading is particularly meaningful, especially as it makes little difference if the signal is strong enough for full quieting. 
Full Scale 144 MHZ  –96dBm (3.54µV)
Full Scale 440 MHZ   –96dBm (3.54µV)
Min Scale 144 MHZ  –118dBm (0.28µV)
Min Scale 440 MHZ  –118dBm (0.28µV)
Other bands may vary 
As far as S meters and calibration I never thought much about it myself.”


The S meter scale is typically:


https://en.wikipedia.org/wiki/S_meter


  

image.png


so it looks like the D710G/A scale goes from about S1 to perhaps S5.


On Mon, Feb 7, 2022 at 8:20 PM Brad (KE7HFP) <BradBartz@...> wrote:

This is going to sound like a really silly question but how to you read the s-meter on a TMD700?  Generally, a S-meter will have 9 levels.  My Kenwood TH-F6 has 9 bars.   But on my TM-D700 it only has 7 bars?  Does it skip the first two and start at S3 or is there some other scaling?

 

Thanks.



--

73,
AB1PH
Don Rolph


Brian / KB5EO
 

Don Rolph's reply is right on.  I've "calibrated" many of my S-meters (including my TM-D700) in my lab using properly calibrated RF power sensors.  In my experience, it's most practical to think of even a "calibrated" S-meter as measuring in "grains of salt".  I find the linearity (logarity?  LOL) of digital S-meters to be no better than old mechanical movements.

Most S-meters are as precise as a hand grenade, but their value as a relative indicator between various signals on the same receiver is excellent -- calibrated or not.  Having a weird number of bars (like 5 or 7) is frustrating when you're trying to tell someone their signal level on your rig though.  Just gotta live with the ambiguity, I suppose.

-- Brian / KB5EO


On Mon, Feb 7, 2022 at 7:30 PM Don Rolph <don.rolph@...> wrote:
I was provided the following data for the D710G/A

Email from J. D. Barron jeter.d.barron@... via group.io to main, Nov. 18, 2021, 2:01 PM:

“1 bar means a weaker signal and all bars means a lot of signals.
I don't think that the correlation to a relative S meter reading is particularly meaningful, especially as it makes little difference if the signal is strong enough for full quieting. 
Full Scale 144 MHZ  –96dBm (3.54µV)
Full Scale 440 MHZ   –96dBm (3.54µV)
Min Scale 144 MHZ  –118dBm (0.28µV)
Min Scale 440 MHZ  –118dBm (0.28µV)
Other bands may vary 
As far as S meters and calibration I never thought much about it myself.”


The S meter scale is typically:


https://en.wikipedia.org/wiki/S_meter


  

image.png


so it looks like the D710G/A scale goes from about S1 to perhaps S5.


On Mon, Feb 7, 2022 at 8:20 PM Brad (KE7HFP) <BradBartz@...> wrote:

This is going to sound like a really silly question but how to you read the s-meter on a TMD700?  Generally, a S-meter will have 9 levels.  My Kenwood TH-F6 has 9 bars.   But on my TM-D700 it only has 7 bars?  Does it skip the first two and start at S3 or is there some other scaling?

 

Thanks.



--

73,
AB1PH
Don Rolph


Brian / KB5EO
 

Sorry, I should have included that the TM-D700 service manual calibration procedure specifies that S1 is represented by one segment at -118 dBm and all segments should show for S7 at -96 dBm.

The S-unit to signal strength chart I've always used differs from Don's a bit (https://www.giangrandi.ch/electronics/radio/smeter.shtml), so that would make the Kenwood specs correspond to a range from S5-ish to S8.5-ish if you go by the values I use.


On Tue, Feb 8, 2022 at 11:45 AM Brian Beuershausen <KB5EO.radio@...> wrote:
Don Rolph's reply is right on.  I've "calibrated" many of my S-meters (including my TM-D700) in my lab using properly calibrated RF power sensors.  In my experience, it's most practical to think of even a "calibrated" S-meter as measuring in "grains of salt".  I find the linearity (logarity?  LOL) of digital S-meters to be no better than old mechanical movements.

Most S-meters are as precise as a hand grenade, but their value as a relative indicator between various signals on the same receiver is excellent -- calibrated or not.  Having a weird number of bars (like 5 or 7) is frustrating when you're trying to tell someone their signal level on your rig though.  Just gotta live with the ambiguity, I suppose.

-- Brian / KB5EO

On Mon, Feb 7, 2022 at 7:30 PM Don Rolph <don.rolph@...> wrote:
I was provided the following data for the D710G/A

Email from J. D. Barron jeter.d.barron@... via group.io to main, Nov. 18, 2021, 2:01 PM:

“1 bar means a weaker signal and all bars means a lot of signals.
I don't think that the correlation to a relative S meter reading is particularly meaningful, especially as it makes little difference if the signal is strong enough for full quieting. 
Full Scale 144 MHZ  –96dBm (3.54µV)
Full Scale 440 MHZ   –96dBm (3.54µV)
Min Scale 144 MHZ  –118dBm (0.28µV)
Min Scale 440 MHZ  –118dBm (0.28µV)
Other bands may vary 
As far as S meters and calibration I never thought much about it myself.”


The S meter scale is typically:


https://en.wikipedia.org/wiki/S_meter


  

image.png


so it looks like the D710G/A scale goes from about S1 to perhaps S5.


On Mon, Feb 7, 2022 at 8:20 PM Brad (KE7HFP) <BradBartz@...> wrote:

This is going to sound like a really silly question but how to you read the s-meter on a TMD700?  Generally, a S-meter will have 9 levels.  My Kenwood TH-F6 has 9 bars.   But on my TM-D700 it only has 7 bars?  Does it skip the first two and start at S3 or is there some other scaling?

 

Thanks.



--

73,
AB1PH
Don Rolph


Brad (KE7HFP)
 

Thanks for the insights.  I never really thought about this before.  The only reason this came up is because I'm studying for my general, and one of the refresher topics was on reporting signal strength with an s-meter.  That got me wondering how I would report this with my radio?  I'm a visual person so I put together this graphical representation approximating of the Kenwood s-meter bars on the s-unit chart.  I guess I also have too much time on my hands if I'm doing this.  At any rate sounds like the best report is "1 bar means a weaker signal and all bars means a lot of signals."

Thanks!


 


 

I found this interesting, when I set up all my radios, I have always used 50mv signal to set the S-meter to S9, but that is for an SSB or CW radio! While an S-meter is not important on FM because we use Q1-Q5, Q1 very noisy - Q-5 full quieting, the S-meter functionality wasn't  of concern! I never gave any thought to my 3 TMD-700A(G) or 2 TM-271A's! 
When I have a couple of minutes I'm going to set all my meters, why? I have no idea, except you guys got my interest! 😀

de RON K1VSC