Re: s-meter reading?


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

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