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S-Meter Accuracy of FLex and Others - Rob Sherwood

13

Comments

  • KY6LA_Howard
    KY6LA_Howard La Jolla, CA. Paris and Sablet FranceMember ✭✭✭
    edited October 2018
    @Bill I always respect others OPINIONS But there is a big difference between OPINIONS and SCIENTIFIC FACTS. I do not respect deliberate promotion of ignorance of scientific acts.
  • KY6LA_Howard
    KY6LA_Howard La Jolla, CA. Paris and Sablet FranceMember ✭✭✭
    edited October 2018
    Read my posts above. No insult intended just stating facts
  • Michael Coslo
    Michael Coslo Member ✭✭
    edited October 2018
    Perhaps  third party can code up an inaccurate S meter app for SSDR? In fact, an adjustable meter, that will read any level the user insists is the right level. 

    It really isn't realistic to expect a company to purposely implement a signal strength meter that is known as wrong. 
  • Burt Fisher
    Burt Fisher Member ✭✭
    edited October 2018
    You did not say regular outlandish opinions are not appreciated, you did say, " your regular outlandish opinions", when you add your it becomes a personal insult. It is possible I feel the same about your opinions but I don't feel the need to be personally insulting. In your second paragraph you used the word "people" which is not personally insulting. However when you said, "you are spouting nonsense ", that was a personal insult. 

    My opinion is that the S-meter is not like a voltmeter, ammeter or an ohmmeter, it reads facts. An S-meter is a relative meter subject to almost infinite variables. Thus trying to assign a constant to an S-meter is like trying to heard cats. What I did not say is any other opinion is outlandish, ignorant, nonsense even if I were to believe so, as that would be unnecessarily insulting. 
    When you said, "@Burt. No insult intended. " I will not comment. I am trying to follow the Flex Community guidelines.
  • Gerald-K5SDR
    Gerald-K5SDR FlexRadio Employee ✭✭
    edited April 2019
    Please read my post https://community.flexradio.com/flexradio/topics/6600-noise-levels-10db-higher-on-my-new-6600-vs-my-older-6500 to understand how to use a properly calibrated dBm S meter to properly set radio gain.  I know for an absolute fact that Sherwood agrees with me on this.  He and I have discussed many times.  Let me just for the record state that we have no plans to change it to an inaccurate S meter. 

    Here is the correct calibration taken from the Wikipedia S Meter page:


    And here is typical atmospheric noise in 500 Hz depending on location:


  • Burt Fisher
    Burt Fisher Member ✭✭
    edited October 2018
    Paul you said, "ham radio is merely a hobby" , I looked at Part 97  FCC regulations Basis and purpose, no where is the word hobby mentioned. What did I miss? In fact the ARRL rarely uses the word.
    Michael, Professional field strength meters used by broadcast stations are calibrated  using a specific antenna and results can be compared. S-meters are not so how can any reading be, "wrong?"
  • Burt Fisher
    Burt Fisher Member ✭✭
    edited October 2018
    When read an S7 on 80 meters with a dummy load on the antenna are you saying there is 12.6 microvolts coming in on the PL-259 jack? You are selling to amateurs who are used to transceivers, and receivers that read near S-0 when nothing is connected to the antenna input. Most of them are not as talented as those posting here nor seeking a scientific instrument.
  • Michael Coslo
    Michael Coslo Member ✭✭
    edited October 2018
    I'm not certain what to say, Burt.

    The levels that correspond to "S" are measured at the antenna input on the receiver, and not related to the antenna.

    Your example is based on measuring  the strength of the transmitter, not the device you are measuring the transmitter with. Of course you want a specific antenna.

    I offered a solution that would allow you to have a S-Meter reading that you want. Others can have a meter that reflects exactly what they want, in fact they could possibly even choose between 3 db per S-Unit and the standard 6 db per S-unit. 


  • Gerald-K5SDR
    Gerald-K5SDR FlexRadio Employee ✭✭
    edited October 2018
    No, that is not what I am saying.  On a dummy load, you are seeing the receiver noise floor, which is directly affected by the preamp gain.  Please go read the other post about how to use this "scientific" instrument for an amateur operator to properly set the preamp gain.  https://community.flexradio.com/flexradio/topics/6600-noise-levels-10db-higher-on-my-new-6600-vs-my-older-6500 

    Oh, you really can't properly use that procedure on a non-calibrated S meter since you have no idea how it is calibrated and is thus meaningless.  

    Our S meter is calibrated exactly as the chart from Wikipedia.  https://en.wikipedia.org/wiki/S_meter

    Here are the default gain/sensitivity settings for the 6400 and 6600.  You can change the gain as needed to match per my referenced post.


  • Geoff AB6BT
    Geoff AB6BT Member ✭✭
    edited October 2018
    Correct. 

    "field strength means the magnitude of a vector-valued field (e.g., in volts per meter, V/m, for an electric field E)."

    So without knowing the length of the antenna used the field strength measurement would be  meaningless.

    S unit measurements are not field strength measurements.
  • Bob - W7KWS -
    Bob - W7KWS - Member ✭✭
    edited October 2018
    Hello once again Burt! Again, your comparison of a broadcast quality field strength meter and a S-meter appears to be comparing apples to oranges. The two are used for somewhat different purposes. Your thoughts imply to me that you embrace the FCC rules (standards) describing the Amateur Radio Service and standards set for broadcast quality field strength meters. https://en.m.wikipedia.org/wiki/Field_strength_meter If my understanding is correct, I suppose this comes from your career as a broadcast chief engineer. What is a mystery to me is why you accept some standards and not anothers. To me, your many posts only express "what YOU want" but have completely missed the mark in showing anyone of us why we should want it or why it's a good idea.
  • Burt Fisher
    Burt Fisher Member ✭✭
    edited October 2018
    I will have to try that on my 6400M.
    Note there is a  discussion on the Flex S-meter on a QRZ forum where the opinions are not the same as here. As a 6400M owner I would rather the 6000 series be in demand to enhance  my value. I bought it because it has the right amount of knobs and I don't need a  computer. I rarely use it with a computer. Also customer service. The S-meter is consistent with another receiver above S-7. I wonder what percentage of hams care about S-meter purity and Rob Sherwood. 
  • Michael Coslo
    Michael Coslo Member ✭✭
    edited October 2018
    Of course the opinions are different on the QRZ forum. How many of those folks even own a Flex? The internet is full of Ford versus Chevy trolls, and if a person doesn't like Flex Radios, that accurate S-Meter on their rigs is a real deal breaker, and for a radio they'll ever own because they chose to like a different one. Make no mistake, if every S-Meter out there was accurate, but Flex had an inaccurate one, they'd still be deriding it

    I want an accurate, reality based signal strength meter. The concept of arguing for an inaccurate one is pretty amusing. But entertaining, and no doubt.
  • Bill -VA3WTB
    Bill -VA3WTB Member ✭✭✭
    edited October 2018
    I hear a remark a lot here with the word purity. It is NOT about purity. Flex just simply pride them selves for making presission radios, not for purity but rather a business decission. But while using the techology that Flex uses in their radio, presission is a byproduct of such a platform. It would take a fare amount of effort and programing to build old technology type performance into the Flex radio.

    As Gerald stated they are not inclined to dumb down the S meter to reflect older technology.

    It seems that this discussion has run it's cource, and it is not up to me to decide that, but for me I have little more I can add. It has been interesting.
  • Burt Fisher
    Burt Fisher Member ✭✭
    edited October 2018
    Michael yes many on QRZ forums are not Flex customers but does that invalidate their opinion? Isn't that where new customers are coming from? I have a KX3 whose S-meter reads zero on 80 meters, a good American company with great customer service like Flex. Are they doing it wrong? I have an anemometer it's measurements are interesting to me but my house is surrounded by trees thus not meeting a standard, just like hams that live in various environments invalidating the most carefully calibrated S-meter. My anemometer does not read 10MPH   in a calm to account for its protected situation. 
  • KY6LA_Howard
    KY6LA_Howard La Jolla, CA. Paris and Sablet FranceMember ✭✭✭
    edited October 2018
    @Burt I have a Barometer at my house that reads 760Mm Hg. It’s just as ridiculous that it should read zero as the failure of the KX3 to follow accepted standards. Time we closed this ridiculous topic
  • Bob - W7KWS -
    Bob - W7KWS - Member ✭✭
    edited October 2018
    If your description of the KX3 is accurate, it means the KX3 doesn't conform to good engineering practice. Either that or it's a defective radio in light of the K3 which is reported by Rob Sherwood, via Howard's post above, to follow the established S-meter standard.

    How could it be good practice for Elecraft to embrace two different calibrations in the same product line? If they have, it doesn't say much for using either as an example for establishing a convincing argument.
  • HCampbell  WB4IVF
    HCampbell WB4IVF Member ✭✭
    edited June 2019
    No horse is too dead to beat.  (-:



    Howard
  • KY6LA_Howard
    KY6LA_Howard La Jolla, CA. Paris and Sablet FranceMember ✭✭✭
    edited March 2020
    image
  • WQ2H - Jim Poulette
    edited October 2018
    image
  • Burt Fisher
    Burt Fisher Member ✭✭
    edited October 2018
    Here is my S-meter comparison between the Flex 6400M and the Elecraft KX3 with no opinion expressed.
    https://youtu.be/B6B89jvjto8 
  • WQ2H - Jim Poulette
    edited October 2018
    Interesting - On a 50-ohm dummy load with a 1m LMR-195 (soldered connectors) - I get about S3 on most bands. That's with everything in the shack on (lights, laptops, monitors, amp, etc.).
    73
    Jim, WQ2H

    image
  • Burt Fisher
    Burt Fisher Member ✭✭
    edited October 2018
    Although I would  not sell my 6400M based on an S-meter issue (I think it is also very beautiful to look at) this guy might: (consider the market, I want Flex to beat the others), but scroll down to a comment by  Michael Walker from Flex.

    Mauro Rizzardo Hi Burt, this is also bugging the **** out of me, the noise floors on my Flex-6600 are always an S5+ with no antenna connected! I am seriously thinking about returning it due to this as my other much older superhet radios seems to be quieter than the Flex and comparable in S-Meter strength with incoming signals.

    Michael Walker
    The panadapter simply measures the signal in a given bandwidth and draws what it hears. If you look at any given pixel, it represents a certain amount of bandwidth. We call this the "bin size" of the FFT that is used to produce the display. If you cut the bin size into two pieces, the amount of noise in each piece goes down by half (3dB). In PowerSDR, the bin size is generally fixed for any given setup and does not change when you zoom. This is why the resolution gets worse as you zoom in on PowerSDR -- you begin to show one bin with multiple pixels. But for SmartSDR, we knew we wanted to have a larger range of zoom and this method was no longer acceptable. So we vary the bin size across a 1000:1 range. So the noise in each bin also varies. 1000:1 is a change of 30dB so from min zoom to max zoom, the noise in a bin will lower by 30dB and you see this change in the panadapter as you zoom in and out. When people talk about noise floor in ham radio they are generally talking about the noise level with a 500Hz bandwidth. When the panadapter is zoomed in to the max level, the bin size today is about 5.8Hz. This is a 19dB difference in noise from where a ham would say the noise floor is to what you can see on the panadapter. This means that the panadapter can see 19dB below what most hams would call the noise floor. Your ear and brain are also able to hear below the noise floor in 500Hz because of how they work. But there are limits to how well you can hear. If you've ever worked JT65 or another long-term integrating mode, you have noticed that your computer can copy signals that you cannot hear. So if you ask another ham "where is your noise floor on 80 meters" and he says "S5," what has he told you? Well with most hams, you don't know because you don't know the answer to these questions: 1. What bandwidth are you using to measure the signal? 2. Is your S-meter calibrated? An S5 signal corresponds to -97dBm. And if he's getting this on sideband set to, say 2.8kHz bandwidth then the actual noise floor in 500Hz would be -97 - 10*log(2800/500) = -104dBm. There's nothing magical about 500Hz, it just happens to be the convention for measuring noise in the ham radio world. In SmartSDR, if you set the passband filter to 500Hz, the S-meter in the slice will show you the 500Hz noise floor. If you start at maximum zoom and begin zooming out, you can see a point where the noise reading of the panadapter equals this number. What do you think this point is? ... if you've been following along, you will realize that this is the point where the FFT bin size is 500Hz. To get a rough idea if this is right, you could measure the width of your panadapter window and divide the amount of frequency displayed by this number. It should be in the 250-1000Hz range. The answer will not be exact because we do not continuously vary the FFT bin size -- we adjust it in steps and don't tell you where the steps are or what size they are. We do what's right for what you are viewing.

  • AC9S
    AC9S Member ✭✭
    edited October 2018

    This may not be the proper place to bring a related issue up, but I believe there is an error in the S Meter code with very high signal levels.  On the latest release the S Meter goes to zero with levels above +60. Actually the entire bar becomes black.  In the past it would read slightly above +60 and indicator bar would be fully filled.  Perhaps the highest level could become a different color or a "+" added to the right side of the meter.  A disappearing S Meter seems to send the wrong message.


    Keith - AC9S
  • Sergey R5AU
    Sergey R5AU Sergey Member ✭✭
    edited October 2018
    Never ending story abt S-meter )))I am appreciate start discussion from the target point - do we need indicator or we wanna to have kind of measurement device what calibrated based on known metrics and rules?

    from my point of view S-meter of  my 6700 radio calibrated well and i am appreciated use them for measurement tests:

    Dummy load on port ANT2, S-meter = 0 , looks good , isn't it ?



  • mlstutler
    mlstutler Member ✭✭
    edited October 2018
    I just tested my 6400 using my Elecraft XG3 Signal Generator.   Results were shocking.   The Flex shows S9 when the generator is set to -73(S9) on all bands. 
  • Sergey R5AU
    Sergey R5AU Sergey Member ✭✭
    edited October 2018
    Mike, looks like you have trusted selective measurement / calibrated receiver , congrats !
  • KF3F
    KF3F Member
    edited October 2018
    So, my backup radio is a Kenwood TS-850. Tuned to the same 20m frequency with the same filter bandwidth as the Flex 6600, the Flex shows S2 and the Kenwoood S0 with the antenna disconnected. Once the antenna is connected, the signal levels are the same. Same on the 40 band with compared signal strengths. In this case on 20m, I'm listening to VP6D and the signal is S3 on both radios. I don't listen to either of my radios with the antenna disconnected so it's a non-issue for me.
  • Burt Fisher
    Burt Fisher Member ✭✭
    edited October 2018
    The issue for me is with the antenna connected and tuned off any signal on 80 meters I get an S7 and on my KX3 same setup I get an S2 thus I cannot measure on the Flex any signal below S6. 

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