Re: Fancy S-meter #eladduo #eladsw2 #smeter

Neil Smith G4DBN

If the noise blanker is enabled in SW2, or if the bandwidths in SW2 and on the DUO are not exactly the same, you will see differences.  Also the time constant on the DUO is long, but short on SW2, so getting a steady reading on noise is hard.  Much easier on a solid tone of course.  The calibration is within a dB or so of my HP signal generator all the way through the range on single tones.  Superhet S meters measure AGC voltage rather than the actual signal power, and things get very tricky with roofing filter IFs being in the AGC loop.

Can't say I ever use S meter readings though, they are pretty meaningless.  Signal to noise ratio or relative signal levels are much more useful.  The advanced marker measurement is very useful for that.

If Rob Sherwood says it is "close to perfect", that is pretty much case closed.

Check the bandwidths and frequecies are identical and that notches and noise reduction and noise blankers are off.  Check if the readings are different on a very strong pure tone and on band noise and a STANAG signal that is fairly constant level and see if there is anywhere the readings do match up.

Neil G4DBN

On 18/03/2020 23:15, Chris Moore wrote:
Here's what Rob Sherwood said:

S meter linearity and dBm meter linearity is as close to perfect as one could ask for.  Each S unit from S1 to S9 is 6 dB.  The dBm scale is within 1 dB from -120 dBm to -30 dBm, and is often perfect.  There is an occasional error of up to 2 dB when decreasing the signal in 5 dB steps vs. increasing the level in 5 dB steps. The S meter / dBm readings are not significantly affected by the 12 dB attenuator.  These readings are corrected in software to give the true signal level, which should be commended

I always assumed he was talking about the meter in SW2, but not sure.

On Wed, Mar 18, 2020 at 5:51 PM Neil Coley <coleyneil1@...> wrote:
In my experience, I’d say the duo is the most accurate. I’d do away with the S meter on sw2. Its obviously just decoration. 
I think real S meters are for superhets or Japanese hybrid sdrs - 7300/7610

The Elad S meters will get there eventually but for now......shite

On 18 Mar 2020, at 22:00, Ivo Frigo <ivo.frigo@...> wrote:

Good evening, everyone,
I noticed that the S-meters on the Duo and the SW2 indicate absolutely different values. For example, the same signal on the DUO is at S9, the software SW-2 indicates 9+20 (even just beyond) and Studio1 about 8.
What's going on? Who is right? Have I done something wrong? 
Thank you.
IN3EFR - Ivo

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