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S-Meter Accuracy of FLex and Others - Rob Sherwood

24

Comments

  • WA5GP
    WA5GP Member ✭✭
    edited October 2018
    Actually Howard I do have an IC 7600 and an IC 7610 and two other Icoms that I use regularly.  The 7610 has a better receiver than the 6400 in my opinion.  I use the 6400 daily on 75 Mtrs. I like the display and waterfall.  For digital and DX chasing the Icom wins hands down.  Easier to use in all modes and much more user friendly to setup and use digital.  I really love the fact that the USB ports on an Icom are actually usable,,, what a novel idea. Nuff of that!!! Like Burt said let 0 be 0... If a device Ie: Flex Radio doesn't read or represent a 0 reading with no signal present why waste the programming lines designing and displaying an S Meter that starts at 0  If bottom line reading with the lack of input is displayed at 5, why not just delete the first half of the Meter and let 5 be 0.  Oh wait that doesn't make sense either not even here in Texas.  I admit that I am new to the Flex concept and it is a learning curve.  No signal still should start at the bottom of a scale not some where in the middle.
  • Bill -VA3WTB
    Bill -VA3WTB Member ✭✭✭
    edited October 2018
    That is just it,,there is no such thing as no signal. I bet you guys never bothered going back to read Steve Hicks papers explaining this. This is simply SDR education.
    I know what your thinking, that Steve does not know what he's talking about..lol,,,,too funny.
  • Burt Fisher
    Burt Fisher Member ✭✭
    edited October 2018
    Steve Hicks is the measure of talented. In weather the public does not get a reading of absolute humidity, but rather relative humidity. As such it is almost 100% that those using a receiver with an S-meter want relative signal strength rather than absolute. In weather as one with deep knowledge of the science I prefer absolute humidity but as a ham I want zero to be zero. Maybe give us the option? 
  • KC2QMA_John
    KC2QMA_John Member ✭✭
    edited October 2018

    Since we are commenting on S-Meter here is my only complaint and it’s a tiny one.

    It would be nice if you could select in the software to go from the current gradient color scheme of the S-Meter to switch to Solid green up to S-9 and from S-9 to +40 solid Red. Would also like a longer peak hold.

    Not really that important but I just think it would be slightly easier to read.

  • Thomas NE7X
    Thomas NE7X Member ✭✭
    edited October 2018
    There is really two different schools of thought here:

    1) Technical engineer who wants a precision lab instrument S-Meter
    2) General Ham who just want to know what the S-Meter reading of a signal is above the internal nose of the radio with no antenna connected

    Both are correct and have valid points..

    This is why a good compromise for both would be if Flex would add a menu switch to allow both users to have the S-meter of their choice.


  • KY6LA_Howard
    KY6LA_Howard La Jolla, CA. Paris and Sablet FranceMember ✭✭✭
    edited November 2019

    Wrong

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

    A S0 Reading Implies -127dBm NOT ZERO.

    At -273degrees C Zero would be -143dBm or MINUS S2.5 NOT ZERO

    I see no value whatsoever in a relative to no reference whatsoever strength meter.

    its absolutely meaningless except to give false comfort to those who do not understand that what they are seeing is absolutely useless...

  • Burt Fisher
    Burt Fisher Member ✭✭
    edited October 2018
    When I talk into the mike the meter moves up from zero to a  relative number, not a calibrated meter. Even though there is noise in the house like birds tweeting, fan on a rig, the meter remains at zero when I am not talking. I will make it simple when there is nothing coming in the antenna connector I want the S-meter to do the same as the audio meter monitoring the mike, zero. 
  • Ria
    Ria Member ✭✭
    edited October 2018
    Colonoscopies?
  • James Whiteway
    edited October 2018
    Bert, No disrespect intended, but you should read the article that Howard posted a link to above. There is a clear explanation of the differences between a traditional analog radio's S meter and how it arrives at the readings it gives as opposed to an SDR radio's S meter and how it arrives at the readings it shows. Flex could have the S meter read zero when signal strength drops below a certain level. But, it would not reflect the true state of the receiver as it really is. Antenna connected or not. My 6600M with the coax connected to my dummy load reads S2 to S4 fairly consistently, unless my neighbors A/C unit which is on it's last legs, kicks on. Then even connected to the dummy load, it reads S5 or more. I really don't use the S meter for signal reports. Even with my tube radios I judge signal strength by listening to it. Besides, as someone else mentioned, on analog rigs turning down the AGC messed up readings anyway. SDR radios are a very different breed. In time, as more manufacturers support SDR radios, they'll all be using methods like Flex and Anan, to arrive at signal strength. We are just getting a head start on the rest of them. James WD5GWY
  • Bob - W7KWS -
    Bob - W7KWS - Member ✭✭
    edited June 2020
    The S-meter formula that Howard refers to has been an accepted standard for S-meters for as long as I can remember. Probably from when I was first licensed in 1957. How has this agreed-upon standard become so convoluted? When I make a contact, I 'd like to know my TRUE signal report, not some arbitrary strength report made up by feel good radio manufacturers. The only way to get the accurate information is by everyone following the same standard, even if it isn't your favorite. Kenwood, Icom, Yaesu and many of the other manufacturers are all different when receiving the same signal. How am I to know my true strength if my report is from any of those manufacturer's radios? The only way is by using a standard. It's such a shame that so many don't. What a mess it would be if we used arbitrary dits and dahs to communicate instead of Mr. Morse's standard. If the standard is to be changed, fine but it has to be done via agreement of a majority of those effected, not by a few manufacturers that have decided they have a way to fool folks into buying more of their equipment. If this forum is representative, the majority here are with Flex and the existing standard and not with the others. It's clear that a meter showing S0 with no signal is ignoring the total noise strength in the receiver pass band which is important information if you are really a true radio person. Ignoring this is poor practice at best? In the mean time, if we happen to meet up on the air, please report my signal strength by using the current standard, whatever that is at the time. This way I can avoid being confused over what you're trying to say. Currently, Flex is one of several radios that make that easy for you. All you have to do is look at their S-meter and report what it says. I assume most of you reading this are here because you own a Flex. Reports from other radios that aren't standardized will likely be very confusing as they usually don't agree with each other let alone reality. While you're at it, the Flex is also giving you a fairly accurate noise strength reading on the S-meter. If you pass this along as well, I'll know my signal to noise ratio and will have a pretty good idea of any need to use phonetics, repeats or anything else that might help to get my message across to you. As Elvis would have said, Tha=×#$@&%$= (Oh yea, I forgot, STANDARDS) Thank you, thank you very much! 73!
  • Bill -VA3WTB
    Bill -VA3WTB Member ✭✭✭
    edited October 2018
    Bob, more to your comment.
    Setting the standard aside, we can look into the way the signal is reported.
    On an non SDR radio the signal voltage is sent from the AGC path. In this there are problems. Depending on AGC settings and the circuit design the meter can be a long ways off. And when you consider filters, preamps, all effecting what it reads.

    A Flex radio is very simple. It takes the signal off the antenna connector and converts the signal to voltage, 50uv = S9 @50 ohms. Note, there is nothing in the radio influencing the signal report.

    As I mention above, the receiver is sampling the bins in the receiver, the problem is there is always energy in the bins, always. some people wrongly think that with out an antenna connected there should be no energy in the receiver bins.

    Have you noticed that by widening the band pass filter more bins are called on and the S meter reports this? The signal goes up. However as Steve explains the energy in the bins comes from many places within the radio itself. Even the connector itself sticking out the back acts as an antenna and can pick up noise outside the radio. In a direct sampling receiver even a dummy load can be an antenna. the smallest amount of energy outside the radio can be heard in the receiver. This energy would never be heard with other types of receivers, so, the Meter would never report it.

    That is why many radios report 0 without an antenna, they simply can not hear the energy and they don't have receiver bins at all.

    This is all part of direct sampling technology love it or hate it.
    Flex spends a lot of time and energy to make the Flex Radio as lab accurate as possible. I can't see them making changes so the S meter that would report random non effective readings simply because older or non SDR radios do.

    It is hard to believe so much has been writen on this, because really? who cares. Every station is reported to be S9+ anyway.

    The only value in this discussion for me, is the fascienation in the understanding how our cutting ege Flexes work.
  • Burt Fisher
    Burt Fisher Member ✭✭
    edited October 2018
    I know you are respectful, not an issue on the other hand you don't get me, if I short the inputs to any other type meter it reads zero. A digital VOM does not have a reading above zero even though active circuits inside it may have electrons flying around inside. Zero ought to be zero.
    Flex is appealing or should be appealing to most amateurs not just the purists. Most hams don't care about Sherwood, whether distortion is .01% or .1%. S-meter calibration means little as there is such a variety of antennas, it is a relative meter. If I switch from vertical to beam it acts as a comparison of relative strength  not absolute.
    Flex may win the purists but the Icoms will win the market.
  • Bob - W7KWS -
    Bob - W7KWS - Member ✭✭
    edited October 2018
    But Burt! That isn't the standard that was agreed to in 1931 and refined fifty years later in 1981.
  • KY6LA_Howard
    KY6LA_Howard La Jolla, CA. Paris and Sablet FranceMember ✭✭✭
    edited October 2018

    @Burt


    You are a school teacher so you must know about participation medals which are awarded for just showing up.

    Everyone knows that participation medals are meaningless except that they make the kid feel good in spite of his failure to succeed.  I would postulate that in the long run participation medals do more harm than good because they not only reward his current failure but also tell the kid continuing to fail is OK because he will get a medal. 

    Shorted antenna to get a participation medal of Zero is just as meaningless as any other participation medal.. it makes you feel good that you shorted the antenna terminal but in the long run it rewards the manufacturers for failing to include an accurate meter that reads something that means something or conforms to standards.

    Using your voltmeter example.. What if every Voltmeter manufacturer used a different  standard definition for a Volt.. So Icom would read 10volts and Yaesu would read 35 volte but Flex would read 12 V which conformed to the standard

    Since you are by nature stubborn and will never concede a point.. I will no longer bother you with trying to explain how S meters actually do work according to the original STANDARD set in 1931 and memorialized in 1981. 
  • Ross - K9COX
    Ross - K9COX Member ✭✭
    edited October 2018
    Contesters don't need no stinking S meter, everyone is 59...
  • Burt Fisher
    Burt Fisher Member ✭✭
    edited October 2018
    I concede many points, just not this one. What an S-meter reads on a signal whether it be +10db over 9 or 40 matters little, I am not into participation awards or feel good S-meter readings, I just want it to start at zero when there is no antenna attached. I don't care about thermal activity inside a receiver. In racing when all races start at the start line why should one race start at the 9 meter line? Why do you think    every other manufacturer of receivers starts at zero? 
  • Burt Fisher
    Burt Fisher Member ✭✭
    edited October 2018
    Bob, W7KWS, does everyone you talk to use the same exact antenna mounted at the same height in an open field with the exact same ground conductivity? If not the purist S-meter means nothing.
    Lacking that  you are not getting a TRUE signal report, you are getting an arbitrary strength report. 
  • Barry Simpson
    Barry Simpson Member
    edited November 2018
    I must admit that I, like Burt , would very much like the S Meter to read zero when there is zero signal, ie a dummy load. That is what the K3 does. When I first got my 6600M I found the S Meter readings to be very disconcerting, especially when I discovered that the higher that I turned up the pre-amp, the lower the S Meter reading becomes. Based on the explanations on this forum, I understand that the minimum S Meter reading is not measuring the minimum signal level but the receiver MDS level. Therefore the experience of the S Meter going down whilst the pre-amp settings go up is logical. However I would much prefer the Elecraft implementation which does measure signal levels such that , for example, on 80m into a dummy load, it reads zero. With an antenna connected it reads S4 being the ambient noise level and signals above S4 register their true S reading. None of the K3 S Meter readings is affected by turning on the attenuator or the pre-amps. Therefore what Elecraft have done surely can be emulated by Flex as it is a software issue. That’s my take on the S Meter debate. Barry Simpson VK2BJ
  • Ken - NM9P
    Ken - NM9P Member ✭✭
    edited October 2018
    Burt, that makes no difference. Because my S-Meter reads the signal strength at MY antenna system. What others use, and the signal levels at THEIR antennas are irrelevant. In the same way, I could say that the other operator’s signal report is meaningless because I COULD be using a five over five and/or a 1500 Watt amp instead of 100 Watts and a low log periodic. In either case, if everyone uses an accurate, calibrated signal strength meter, we can exchange information that reflects conditions at both ends of the exchange....except for contests and DXing, in which case it is all irrelevant. But the S meter is still helpful to aid antenna bearing adjustments. In any case, this whole discussion, while interesting, is academic, because I think it very unlikely that FRS is going to change their commitment to lab quality measurements in their rigs.
  • Bob - W7KWS -
    Bob - W7KWS - Member ✭✭
    edited October 2018
    Hi Burt, There hasn't been a standard established for antennas, but there is a standard for S-meters. By following this standard you can do me the favor of accurately telling me what your ability is to understand my message. It isn't meant to be for you.
  • Bob - W7KWS -
    Bob - W7KWS - Member ✭✭
    edited April 2019
    Hi Barry, I just wish all manufacturers would follow a standard so we know what it means on the far end of a contact. If the current standard needs an update, so be it, but as it is is now, there is no way for me to know what 569 means if you give that report since few radios are calibrated the same. It seems to me that we should either use the standard that exists or reach a consensus on a new one.
  • Bill -VA3WTB
    Bill -VA3WTB Member ✭✭✭
    edited October 2018
    They need to emulate Flex..Lol
    The K3 is not a direct sampling receiver.
  • Bob - W7KWS -
    Bob - W7KWS - Member ✭✭
    edited October 2018
    Hi Bill, you don't need a direct sampling receiver to follow the standard. Most IF type receivers have taken the easy way out and measure the AGC voltage instead of the actual passband power which is more involved. In the AGC approach, if the power in the pass band is below the AGC knee you get no voltage thus the zero reading, even if there is a signal present. Unfortunately, this is a totally misleading result.
  • Bill -VA3WTB
    Bill -VA3WTB Member ✭✭✭
    edited October 2018
    Because the K3 does not have direct sampling the receivers are very different in how they work is my point. When you take voltage from an AGC circuit it is not accurate, It is not the same as taking it from the antenna port by passing anything that could effect the reading witch is how direct sampling works. A direct sampling radio enjoys many advantages, this is one of them.
  • KY6LA_Howard
    KY6LA_Howard La Jolla, CA. Paris and Sablet FranceMember ✭✭✭
    edited October 2018


    Rob Sherwood on “S-Meter Accuracy”   6-OCT-2016

    While no Japanese rig has a properly tracking S meter, the following do:


     Flex 6000 series
     Apache ANAN

     Most K3 and K3S, though occasionally an individual radio cannot be calibrated properly.  This includes the option to have the reading correct regardless of preamp or attenuator setting .

     Orion II once Ten Tec updated software to allow S meter calibration

           Orion II does not correct for preamp or attenuator selection.
    -
    . Eagle is good, except the S meter is microscopic and I think it quits at S9+30 dB.  The Eagle reads correctly regardless of preamp or attenuator selection.


     Hilberling S meter is quite good.


     ADAT ADT 200A is very good but ergonomics in general are absurd.


     Elad DUO S meter is outstanding


     Perseus S meter is outstanding.


    With virtually all current products today having a virtual S meter, there is no
    technical reason the S meter cannot be programmed to read properly from
    S1 to S9+60 over.


    When an S unit is only 2 to 3 dB, it makes QSB look much worse.* 
    Rob, NC0B
    -------------
    *Note (by DJ0IP): Most recent Japanese transceivers are using just 3 dB per
    S-Unit.  This makes the received signal look stronger… but at the same time,
    the QRM, QRN, and QSB also look worse!

  • KY6LA_Howard
    KY6LA_Howard La Jolla, CA. Paris and Sablet FranceMember ✭✭✭
    edited October 2018

    For test purposes, I shorted the antenna on my Elad FM-DUO.

    The S-Meter Reads CORRECTLY... S2 (NOT S0) on 20Meters

    It's truly unfortunate that the Japanese continue to stick to the totally inaccurate AGC Voltage Circuit to FOOL PEOPLE into thinking that they have a real S-Meter.   As a result, Joe Ham has been SCAMMED into believing that by shorting his antenna he should see S0 when in fact nothing could be further from the truth.


    As Rob Sherwood says, none of the Japanese Radios are accurate and they have done a serious disservice to the ham community by promoting ignorance of technology.


    I guess I am personally upset when I see people actually wishing to revert to a ridiculously and totally incorrect and inaccurate mode of measurement when they already have a totally accurate lab grade instrument.

    When I see this sort of desire, I am reminded of the movie "Idiocracy"

    Coming from a school teacher like Burt, it makes you wonder if our children will be doomed to ignorance.
  • Burt Fisher
    Burt Fisher Member ✭✭
    edited October 2018
    If everyone uses an accurate, calibrated antenna in identical physical locations, we can exchange information that reflects conditions at both ends of the exchange.  Bob if your message isn't meant for me no need to respond.
  • Bill -VA3WTB
    Bill -VA3WTB Member ✭✭✭
    edited October 2018
    That is true Burt,,we need to always respect others opinions....
  • KY6LA_Howard
    KY6LA_Howard La Jolla, CA. Paris and Sablet FranceMember ✭✭✭
    edited October 2018
    @Burt. No insult intended. ‘My quoting that brilliant movie “Idiocracy ‘ which I believe everyone should see because it will make them think of a dystopian future where people prefer measurements that feel good rather than ones based on a scientific fact. Yes I worry about our children when educators like yourself would prefer to teach them things that feel good rather than basic science. As a scientist and engineer it obviously upsets me that people would deliberately choose a meaningless irrelevant measure over scientific fact especially when most will even admit that they know their measure is useless but it feels good. I must admit that you usually do not get under my skin with your regular outlandish opinions, but promoting ignorance over fact especially after it has been explained to you in great detail where you are factually wrong is just plain hard to take. Finally you are spouting nonsense about comparing apples to potatoes with the attempt to measure two sites with so called calibrated antennas Even you know that there are far too many variables in a propagation path like difference in near field obstructions and local terrain which caus real world asymetry for such to be possible.

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