S-Meter Accuracy of FLex and Others - Rob Sherwood

HCampbell WB4IVF

Jim Gilliam

KY6LA_Howard

@Jim

Traditional S-Meters circuits were designed to INTEGRATE A 500HZ passband not peak In fact NONE of the Japanese radios do either

Bob - W7KWS -

For me, the accuracy of an S-meter's calibration is useful for testing but is over rated and over used for communications purposes. To me, S-meter accuracy is of little value on any manufacturer's radio. Any relative indication of signal and noise strength is all one needs for letting the other station know if you can copy them. The meter reading is more an indication of the path. The station is a factor but only a small part of the equation at best with propagation being, by far, the dominant factor. It seems to me that absolute S-meter readings are used most often these days to feed the ego of the person on the opposite end of a QSO and does little to help the distant station make adjustments such as turning on the AMP or rotating the beam, Etc. So often I hear "you're rig is doing a great job. 30 over here", when it's the propagation that was contributing the most to the meter reading and QRP would have been entirely adequate. You've probably heard the old adage that I worked that station with a wet noodle. In other words, propagation was great and the main reason for the success of the contact. In reverse, the same "he-man" kilowatt station is received with an S-9 meter reading but a local noise source is also S-9 so the communications is marginal or non-existent. What did the S-meter reading tell the distant station in either of these two cases? In my estimation, nothing of real value. For me, the real indication of signal value is the signal to noise ratio. In other words, the signal strength above the total noise strength in the receiver pass band. Any somewhat linear relative strength meter will give you these values, calibrated or not. This SNR, communicated to the the distant station, versus an S-meter reading, is a much better indication of your ability to copy the intelligence being transmitting. No egos involved!

Jim Gilliam

Is that 500 Hz. bandwidth of sampling for 0 to 500 Hz. or some where in between. It would seem if the latter were true, a person with a low voice response would register higher on the S-meter than one with a higher pitched voice.

KF4HR

Burt Fisher

I'll make it simple when the receiver has a dummy load for an antenna I want it to read zero on my 6400M like on my KX3 and formally on my 7300.  Currently it read S7 on 80 meters on the 6400M and slightly lower on other bands.

KY6LA_Howard

@Burt

What you are asking for is that the S-Meter Read a TOTALLY MEANINGLESS IRRLEVENT NUMBER...which while it gives you great comfort that there is no external signal on the terminals is not related to anything that the radio may actually be hearing.

Burt Fisher

How could the radio be hearing anything when I have a dummy load for an input?
My power meter reads zero if I turn the power down to zero, that is nothing going out, zero, so nothing coming in should be zero.

Bob - W7KWS -

Thermal noise in the front end of the radio?

James Kennedy-WU5E

Flex good job on my FLEX 6600 S-Meter , it may seem strange I kept a log from 6500 to now on FLEX 6600 on S-meter reading I would change the normal 59 reading in AC LOG to the actual reading from the FLEX Smart SDR screen. One Ham said I'm only S-9+10 I'm running 1500 watts I discounted him as a rookie with deep pocket. well don't shoot me for that statement. hi hi . ... 

Bill -VA3WTB

All radios have internal noise, the flex is simply reporting the signal in the Receiver bins,  sampling..coverting that noise to RF and sending that to the meter. So yes the radio hears internal noise.
Steve Hicks has writen so much on this explaining all this and yet so many still can't get their heads around the technology.

KC2QMA_John

Matt NQ6N

I think this is true. It could be a Flex feature or someone could write it using the API and make a "traditional s-meter" available as an application that could be run alongside SmartSDR. 

Bill -VA3WTB

Never thought people would be upset having an accurate meter...lol

Jay Nation

KY6LA_Howard

@Burt


The S-Mater is reading the actual receiving level at the radio's antenna,


This may be hard to get your head around on...

But I will try to explain.


If your radio on 20M is capable of a Minimum Discernible Signal of say -115dBm then it should be reading S2 (-127dBm plus 2x6dBm - 115dBm)... If you short the antenna, it still can't hear any better than S2.. so reading an Arbitrary S0 is absolutely meaningless because its not hearing S0 but it is hearing S2.

In fact, if the shorted across the antenna were perfect and it was really cold (like absolute zero)  then the true number should be -143dBm  or  MINUS S2.5

The Japanese Radios copied the Old AGC Voltage Circuits to give an arbitrary S Meter reading... so if you shorted the antenna, you got 0 AGC voltage and it displays as S0  - which of course is absolutely meaningless... except that it feels logical even if it is not...

KY6LA_Howard

I would label the Relative S Meter as the Bu** SH*$ meter

Bob - W7KWS -

I can hear it now! "You're S-9 plus 20 dB on my Flex. To understand what I'm telling you, go to www.flexradio.com and download the manual. Note that I've selected S-meter option 47. From this, use your scientific RPN calculater to determine what 20 over means with option 47. You'll still have a meaningless indication of what I'm hearing because I've not yet told you the band noise level at my station. GOOD LUCK".

73 & LOL!

AA0KM

Ross - K9COX

WQ2H - Jim Poulette

KC2QMA_John

Lets call it the "Feel Good Meter"

It might make you feel good but it's still meaningless.

WQ2H - Jim Poulette

Roger out.

Michael Coslo

Wait... do y'all people actually look at the S-Meter?  I tell everyone I like that they are 20 over 9.  Then they like me!

Ken - NM9P

Jay Nation

Stan VA7NF

WA5GP

I am with you Burt:
Not caring about the mombo jumbo overly complicated math and convoluted explanations on this that and the other hearing one thing or another inside the radio. If the antenna connector is shorted or disconnected/ connected to a dummy load I want to see "0"  because that is what it is actually seeing.  No signal No reading ~:~

KY6LA_Howard

NOT TRUE... Definitely NOT MUMBO JUMBO... Basic Math...

When you short the Antenna, you are seeing the Minimum Discernible Signal that the radio is capable of receiving at that Frequency.

S0 by International Standard Definition is -127dBm

If your radio reads Zero when you short the antenna... then any and all S-Meter Readings on that meter are totally wrong.

BUT if it makes you happy to see a totally wrong and totally irrelevant number suggest you buy any Japanese radio.

Burt Fisher

Every other receiver, transceiver I ever owned (S-76, Swan-240, Kenwood TS-940, Hallicrafters, HQ-145, HQ-170,  Icom 751, Icom 746, 756), from 1959 read zero or near zero with no antenna. That's what I want now  I am not interested in the purity argument. I am not interested in random electrons and holes crashing and making INTERNAL receiver noise. Although the pretty colors on the S-meter are nice let zero be zero.