S Meter Reading after Service

  • 2
  • Problem
  • Updated 2 months ago
  • Not a Problem
My Open Response to Flex Service Survey

The service agent was great in communication via email on the updated on my repair and also showed concern on the care and treatment of my transceiver.  I would give that person a 10.  "However, my S meter problem is still NOT fixed."  I have spent the time reading all the back posts dealing with S meter readings, and I join the group in frustration that you seem to want to re-create the whole purpose for the readings, rather than fixing the issue.  So, in the future do to my Flex, with or without an antenna connected or pre-amp on or off, RF/AGCT turned off or full, the S meter readings remain 5-6 plus at ALL times.  I will report back to all my contacts that, SINCE I have a FLEX radio I am UNABLE to give you even a close, approximate, true reading of your signal level. 
Photo of Joseph Rodick

Joseph Rodick

  • 54 Posts
  • 14 Reply Likes

Posted 2 months ago

  • 2
Photo of Mike - VE3CKO

Mike - VE3CKO, Elmer

  • 552 Posts
  • 289 Reply Likes
Everyone is entitled to their opinion and when presented with facts, not fiction, you would think it would be better to take off the blinders and be acceptable to new information, new possibilities. If you own a Flexradio you are on a voyage to new frontiers and to go where man (ufacturer) has gone before.
Some people fear change, legacy is what they know and understand and that is all ok. Loyalties to your favourite radio (yes, that;s the Canadian spelling), is ok too. But me thinks it crosses the line of common sense when loyalties or stubbornness lead to spreading fake news. So glad we have so many tremendously knowledgeable folks here to set the record straight.
Photo of Joseph Rodick

Joseph Rodick

  • 54 Posts
  • 14 Reply Likes
Mike thank you for your input, I used to teach electronics for Sears and STAC and have been retired for 5 years.   I just, however, can by the life of me understand how a short RF input can show an S5-S6 other than it being an internal noise level.   I must have taught a lot of people wrong, I used to teach them to short out the input to zero it.  wow, if that's the case I feel really bad.
Photo of Pat N6PAT

Pat N6PAT

  • 855 Posts
  • 271 Reply Likes
Joseph,

have you tried moving your Flex to another location? Perhaps a friend's house a few miles away? That way you can eliminate the possibility of a noise source within your own home.
Photo of John KB4DU

John KB4DU

  • 125 Posts
  • 35 Reply Likes
Joseph;

I've been testing my 6400 based on your concern. Can you try an experiment to see how your radio compares to mine?

1. Click on the S-meter reading to change the scale to dBm.
2. Select RX A on the ANT slide out.
3. Set the RF Gain to the very left on the ANT slide out.
4. Set the Mode to CW.
5. Set the Bandwidth to 500.
6. Set all the DSP items to OFF.
7. Select a Frequency on 80M, 40M, and 20M and record the dBm reading for each one.
8. Post it on here so I can look at it.

Thanks
Photo of Rolf Auras

Rolf Auras

  • 12 Posts
  • 3 Reply Likes
John,

this should be done by several users. So we can compare the results and see certain irregularities, perhaps.

And we are NOT talking of atmospheric noise or man made noise (see graphs below) coming in via the antenna port (which should be terminated in this test), we are talking of noise only which causes the S-meter to go up to e.g. S6 and can be listened in the phones; and which source is unknown at present.

By the way, the Elecrafts did not show such a behavior. The reflector clips (s.a.) do not deal with this problem.
Photo of Joseph Rodick

Joseph Rodick

  • 54 Posts
  • 14 Reply Likes
John thank you for your input, however, I lost friendship with two individuals that came over to compare my flex to their Elecraft and Icom.   Both were upset that the flex far outperformed their radio.  Even though I tried to make them feel good about their radio, it was apparent that they were upset.  Sad, one was a 40-year friendship.
Photo of Pat N6PAT

Pat N6PAT

  • 855 Posts
  • 271 Reply Likes
Not much of a friendship if it can be ruined by a a simple ham radio.

Excuse me but something appears to be pulling my leg
Photo of Burt Fisher

Burt Fisher

  • 1274 Posts
  • 486 Reply Likes
Why would anyone not be friends over a disagreement about which rig is better? I could see it if you insulted them personally but if someone said my rig was a piece of crap, so what. If they said I was an a-hole for selecting a Flex different story.
Photo of WW1SS - Steve

WW1SS - Steve

  • 822 Posts
  • 271 Reply Likes
Then they were not really friends
Photo of John KB4DU

John KB4DU

  • 125 Posts
  • 35 Reply Likes
OK So I'll go first.

Freq           0              +32   

14.140    -113dBm    138dBm

7.190    -112dBm    -132dBm    -125dBm on RXA (open)

3.900    -114dBm    -130dBm    -125dBm on RXA (Open)

Readings all taken with a 50 Ohm load on ANT1, preamp zero (no Att) and preamp +32.  I compared readings on RXA (Open), and they were the same on 20M, but different (more noise) on 40 and 80. Don't know why.

Pretty close to the charted expectations. I am in a high noise environment (next to an Army post), so not really ideal for precise testing.

Photo of Brian Denley  KB1VBF

Brian Denley KB1VBF

  • 99 Posts
  • 13 Reply Likes
Mode and bandwidth?
Photo of John KB4DU

John KB4DU

  • 125 Posts
  • 35 Reply Likes
cw and 500 Hz as on the previous post.
Photo of Brian Denley  KB1VBF

Brian Denley KB1VBF

  • 99 Posts
  • 13 Reply Likes
Damn didn’t see that until late.  I will take my reading tomorrow.

Brian KB1VBF
Photo of Lawrence Gray

Lawrence Gray

  • 182 Posts
  • 87 Reply Likes
For what it might be worth:

6500 running v3.1.7, 50 ohm dummy load on ANT1--all others open, DSP functions off, Preamp 0 :

Band   Mode  BW          Signal
20 M   USB    2.1 kHz    -114 dBm
20 M   CW      100 Hz    -129 dBm
40 M   LSB     2.1 kHz   -114 dBm
40 M   CW      100 Hz    -129 dBm
80 M   LSB     2.1 kHz    -114 dBm
80 M   CW      100 Hz    -129 dBm

The readings bounce around +- 1 dBm,

Larry, W1IZZ
Photo of Michael N3LI

Michael N3LI

  • 240 Posts
  • 81 Reply Likes
Looks like that is working pretty much correctly. There is a proper way to measure the noise floor on a Flex, and there it is. Go as narrow as you can. The only inaccuracies I've had are eyeballing where the peaks of the static are. Some SDR software has peak measuring. But I certainly wouldn't want it on a request list for SSDR
Photo of Lawrence Gray

Lawrence Gray

  • 182 Posts
  • 87 Reply Likes
Yes, I'm aware of the measurement technique.  I used 100 and 2.1 for illustration of the effect of bandwidth on the noise measurement.  Sherwood uses a CW bandwidth of 500 for his published noise floor measurements.  At a CW BW of 500, my 6500 reads -121 dBm (20M with conditions as as above), which is 3 dBm lower than Sherwood measures.  Seems reasonable, since we are checking the radio with itself and the "meter" is averaging the noise in some manner.

Too bad the source code for the Woodbox S meter+ is not available.  Probably could add a feature to display legacy "S" meter readings for anyone who wanted it.

Anyway, it is always fun to have an excuse to deep dive into an issue.  A great discussion, other than the elementary school name calling stuff.
(Edited)
Photo of Burt Fisher

Burt Fisher

  • 1274 Posts
  • 486 Reply Likes
Most here are way more talented than I, I am not like the guy with the sword. I am the one with a gun, no match for the talent here. But I represent Joe Ham, who wants an S-0 when there is no signal. The attitude shown by some here of superiority could make Flex a niche player.
https://www.youtube.com/watch?v=kQKrmDLvijo 
Photo of James Whiteway

James Whiteway

  • 1061 Posts
  • 303 Reply Likes
Burt, if you're that unhappy with the Flex, maybe the K4 will end up being what you want.
Being a teacher I would have thought you would be more open minded and receptive to new things.
While I understand how you feel about having an S Meter that reads zero with no signal present, at the same time, I also know that the technology behind SDR radios is radically different than the radios I have used in the past.( and still use some I cannot seem to let go of)
But, technology moves on and with it, things like signal measurement change with it. It doesn't make it less enjoyable for me. I like the challenge of learning new things. Keeps my 68 year old mind active.
James
WD5GWY

Oh, and I speak for myself. As I don't presume to know what other hams want or need.
(Edited)
Photo of Winston VK7WH

Winston VK7WH

  • 337 Posts
  • 89 Reply Likes
I totally agree with you, James.

I’ve also got an old mind,I will be 80yo next year, and one of the many reasons I purchased my 6700 was to help keep my mind active. I am also very happy with an S Meter that is correctly calibrated.

Good DX and 73 Winston.
Photo of Bill -VA3WTB

Bill -VA3WTB

  • 4055 Posts
  • 979 Reply Likes
What about the RF energy in the rceiver? were did that go? It's there!!
But of course with the antenna connected that inboard RF is not shown.

I know you had a back and forth discussion with Gerald, and he said they are not going to break the meter to make a few happy.
Photo of N2WQ

N2WQ

  • 33 Posts
  • 8 Reply Likes
This debate sounds very much like how some drivers blindly follow their GPS, never looking out the window, and not asking themselves the basic question “Does this make sense? Am I going where I want to go rather than where the GPS is taking me?”

Nobody here is arguing the technical basics of why the S-meter reads whatever number it does when the antenna input is shorted. The question some of us are debating is if it should. Just because the AD reads its own noise level it doesn’t mean that we the humans should take it at face value and not apply some common sense. The S-meter is meant to measure signal strength, not internal noise.

For the record, I know my math and DSP algos, having created several DSP platforms, including my favorite system Hera for extracting human voice from a very noisy environment. Think extracting single person’s voice from the crowd at a large cocktail party. In 1987! I am not intimidated by the bullies who casually throw techie jargon left and right, trying to impose their personal views as the Bible.
Photo of Michael N3LI

Michael N3LI

  • 240 Posts
  • 81 Reply Likes
So here's the basic question - Why is Flex completely wrong with their implementation of an S-Meter? 

I'll never be as smart a guy as you, but to my admittedly poor intellect and technical acumen, a signal strength meter is a rather poor, almost useless example of a measurement instrument. Are you as adamant about the implementations of S-Meters in Japanese equipment? The measurements show their accuracy is nil. Often calibrated only at S9. Wildly different levels for  differnet S-Units. This is not just me parroting something I've heard - this is actual measurements by me. Enough to convince me that the S-Meter on legacy radios is pretty worthless. 

About the only function they have is reporting zero on a dummy load, like some people demand. 

I look at S-Units as an extremely rough, innacurate and often wildly wrong talking points. About as useful  as a contest exchange of 5 of 9. 

So I use dbm, or if pressed, I use as narrow a bandwidth as I can and get an S-number that agrees with the dbm scale. I want to see the noise that is present. I want to know what level it is. 

How do we subtract the noise from the instrument, but have the local RF noise show up yet maintain accuracy?

Tell me why exactly Flex and the rest of us are wrong. Tell me why a legacy radio that adjusts the higher noise floor to zero is correct/

I hope you don't consider disagreement as bullying. If so, let me know, and I'll stop.
Photo of KY6LA - Howard

KY6LA - Howard, Elmer

  • 3790 Posts
  • 1640 Reply Likes
@N2WO

Why is it so difficult for you to understand the COMMON SENSE of the Frozen Thermometer Paradox

Mercury Freezes at -38F.
If you put a mercury thermometer in -50F then it will still read -38F

The Same is true for an S-Meter... 
If the radio (as you can see from the charts below) can only hear -115dBm or S2 then common sense should tell you that it should not display -127dBm or S0


Further COMMON SENSE... S0 does NOT MEAN the total absence of signal but it means that the signal level is -127dBm... as agreed by the ITU international Definition.

So if shorting the antenna would give you S0...it means that you have -127dBm signal

But clearly you do not...

A truly accurate S Meter is definitely not a market killer for Flex Radio as their sales prove... so the market has decided

Like I predicted many years ago that every manufacturer - even the Japanese would ultimately make a SDR

I will also predict that now that they have the tools, then every manufacture will also start producing accurate S Meter instead of Fake News S Meters
Photo of Brian Denley  KB1VBF

Brian Denley KB1VBF

  • 99 Posts
  • 13 Reply Likes
But the real issue is this:  ALL new SDR xcvrs available now are basically spectrum analyzers.  That’s not going to change.  They comply with the published standard for S meters.  The older xcvrs do not!  So this in not a Flex issue: Elecraft, ANAN, Flex, Perseus, etc. all comply with that  current standard.  So what are they to do?  Not comply with the standard?  There is no going back.  What would we go back to?  I guarantee you that the new Elecraft K4 will match Flex on S meter readings.

Brian KB1VBF
Photo of N2WQ

N2WQ

  • 33 Posts
  • 8 Reply Likes
I think there are two parallel themes here that are getting mixed and contribute to some of the confusion.

The first one is that regardless of the temperature, S5 for a shorted input is just wrong. -97 dbm is a lot of signal that can’t be attributed to the frozen thermometer.

This leads to the second debate, which is what the S-meter should be reading. Or more precisely, what should S0 be. This is where the debate becomes philosophical.

Rob Sherwood lists the 6700 having a noise floor of -118 dbm with preamp off. One of the arguments here is because the radio can’t hear anything weaker than -118 dbm the S meter should not be showing anything less than the S value matching -118 dbm.

However, as the preamp is dialed up 10, 20, or 30 dB, the 6700’s noise floor drops and the radio can in fact “hear” -127 dbm or S0. Therefore, the S meter should be able to read S0.

Personally I don’t use the S meter and don’t care about its reading. What bugs me is when those who express a reasonable contrarian views get crucified for not following the party line. A good, civilized debate is healthy, but not when it turns into name calling.

Technology is amazing and I am thrilled how it creates innovation and competition in the ham market.
(Edited)
Photo of KY6LA - Howard

KY6LA - Howard, Elmer

  • 3791 Posts
  • 1640 Reply Likes
I guess it’s Time to Repost this very informative graph which clearly demonstrates what you can and cannot hear.  It’s really sad that the Trolls keep on crawling out of their caves to pollute this reflector with fake news.   
Photo of AC9S

AC9S

  • 121 Posts
  • 28 Reply Likes
This graph is even better with the various S meter levels indicated on the vertical axis.  I keep a paper copy in my desk for the occasional question about my quiet band S meter readings.

Keith - AC9S
Photo of KY6LA - Howard

KY6LA - Howard, Elmer

  • 3791 Posts
  • 1640 Reply Likes
Photo of Brian Denley  KB1VBF

Brian Denley KB1VBF

  • 100 Posts
  • 13 Reply Likes
After all this, if Joseph still has that Perseus, this issue will be resolved.  Rob Sherwood rated that radios s-meter as one of the most accurate.
Photo of Joseph Rodick

Joseph Rodick

  • 54 Posts
  • 14 Reply Likes
I had to sell the Perseus to raise money to buy the Flex 6400M.  I have found Flex to be the most honest, caring company I have had the pleasure to deal with from my first purchase of their 3000.   I am starting to feel bad in two different ways.   I used to teach electronics, and in the past, I taught my students to short out the input to zero out the meter or scope and because I my ignorance I may have taught them wrong and have caused this issue to prevail in this community.  Thank you for your input and God Bless.
Photo of KY6LA - Howard

KY6LA - Howard, Elmer

  • 3791 Posts
  • 1640 Reply Likes
@Joseph.  What do you not understand about

1.  The FrozenThermometer Paradox

2.   S0=-127dBm

yes you were teaching the incorrect information about S meters to your students

but heck lots of stuff I taught students has later been revised new knowledge. .  
Photo of Michael Walker

Michael Walker, Employee

  • 1102 Posts
  • 328 Reply Likes
Another way to put it.  The 'other' radios can't read low enough into the noise floor.  They are not calibrated.
Photo of Alan

Alan

  • 87 Posts
  • 12 Reply Likes
Joseph, you wrote, "I used to teach electronics, and in the past, I taught my students to short out the input to zero out the meter or scope"

Yes, but the device being "shorted" had/has internal resistance/impedance (R/Z).  When you shorted the terminals, you created an internal series current flow path through the device, through the internal R/Z, through the shorted terminals, back to the device.  There was a un-measurable voltage drop across the series internal R/Z.

Much of the S-meter discussion is above my knowledge level, but perhaps the internal resistance/impendence is an analogy to what the others are saying about how Flex measures S level.   In your shorted terminal example above, you cannot measure the voltage drop across the internal (Rs) of the device, but you know it is there.  You could measure the voltage drop across the shorted terminals (VL =0V).  Measuring 0V at the terminals does not measure the voltage source (Vs) because it leaves out the voltage drop of the internal R/Z  (Rs).



Alan
Photo of Alan

Alan

  • 87 Posts
  • 12 Reply Likes
BTW, This is the circuit used to derive the maximum power transfer between two circuits.  Calculus is used to take the second derivative of the current as a function of RL when maximizing Power (P=I*2R).

Same as the idea of matching the antenna Z to the Rig Z for maximum power transfer.

Alan
Photo of Joseph Rodick

Joseph Rodick

  • 54 Posts
  • 14 Reply Likes
Alan, Thank you for your input, great post, God Bless.
Photo of Burt Fisher

Burt Fisher

  • 1279 Posts
  • 486 Reply Likes
Photo of James Whiteway

James Whiteway

  • 1062 Posts
  • 303 Reply Likes
Bert, each example he gives with the Flex differs because different slice bandwidths he has set on each band as well as modes. He starts with SAM at its widest setting. So, it's not a balanced comparison.
James
WD5GWY
Photo of Joseph Rodick

Joseph Rodick

  • 54 Posts
  • 14 Reply Likes
Burt;  Last year I lost a friend of over 40 years do to him having an Elecraft K3.   With his insistence, we compared rigs, side by side.  It quickly came apparent that the flex was the rig of choice and he just could not deal with it.   My other friend had an Icom 7610.  So after viewing your Youtube link, YES, I would choose Flex over Elecraft in a heartbeat.  I could go into reason after reason why the Flex side by side was the rig of choice, but this forum is not for that and I would never want to dismay a fellow ham on their rig.  The S meter reading is something I am truly trying to understand.  Thank you for your input and God Bless.
Photo of Michael N3LI

Michael N3LI

  • 240 Posts
  • 81 Reply Likes
Hi Joe. It's just an improvement that takes a bit of getting used to. When I first fired up my 6300, I was also struck by what seemed like a whacky S-Meter.

But after a few questions and some digging into how this radio works, I figured it was a much more sound way to do this signal level thing.

You're going to love this radio. Right now I'm listening to some CW where I'm hearing an Op that is down in the noise around -120 dbm. All the more impressive considering I'm about 3/4 of the way toward profound deafness. 

Don't let the axe grinders wear ya down Joe. Every time someone posts a perfectly norma question about the S-meter and SWR, they come out  to  confuse the issue.


Re the radio comparisons - our club has a 7610 and a K3S. Neither of them compare favorably to my 6600.

The only place where they are better is the Flex radios have issues with Windows 10. But then what doesn't? A forced Windows update and reboot just took my APRS station and iGate down. I'd take it off the internet, but that kinda defeats the purpose of an iGate.
Photo of Joseph Rodick

Joseph Rodick

  • 54 Posts
  • 14 Reply Likes
Thank you for your post,   Like I previously posted, I lost two long term friends just because of my 6400M.  In both cases, I did not want to do a side by side only because I feared what would and did happen.  I am slowly learning from past posts and do have a better understanding now on how Flex measures S/DB.  I thank the community for their input.  It has been a learning experience.  Maybe just maybe, you can teach an old dog. lol. God Bless
Photo of Michael Walker

Michael Walker, Employee

  • 1102 Posts
  • 328 Reply Likes
Joseph

Wow, we are sorry to hear that about your friends, especially in a hobby such as this.  I guess it is the same as arguing over Trucks or Cars or... anything.    Good friends are a hard find.  

The S Meter discussion is a very good one and some people provided some very positive perspectives and even I learned a few new tricks.

73
Photo of Joseph Rodick

Joseph Rodick

  • 54 Posts
  • 14 Reply Likes
I was sickened over the loss.   I knew the passion both had for their radio's and really did not want to make a side by side comparison do to past antenna and radio decisions.    I only brought it up do to one of the posts mentioning and promoting Elecraft.   I have always felt that my opinion and thoughts are subject to change without notice.  I have learned a lot from this post and feel it has been a benefit to most dealing with the S meter readings.  I thank you for removing some of the negative posts.   I question Michael,  when you personally give a signal report, do you give the straight S meter reading or do you subtract the noise?  
Photo of Michael N3LI

Michael N3LI

  • 240 Posts
  • 81 Reply Likes
Too many Michaels in this thread! Anyhow, when I give out a signal report, I simply eyeball the S meter and give whatever shows up on the right side. I also hand out the dbm, and give a sound quality report. Which I find that having a Flex, I get a lot of requests for quality reports.

Except when contesting, and then everyone gets a 5 of 9 or 5nn.

Then I ask them to repeat everything...... 8^)
Photo of Burt Fisher

Burt Fisher

  • 1279 Posts
  • 486 Reply Likes
I don't get why anyone would not be friends over an opinion related to ham radio, in fact even an opinion related to politics. I have a friend whose politics are way to the other side of mine. We debate the issues, not the person. Many times I see the accusation of troll, simply for expressing a different opinion on many different subjects. 
I find Flex users to be the most intellectual of hams but somewhat stuck in their beliefs.,
Photo of Lawrence Gray

Lawrence Gray

  • 182 Posts
  • 87 Reply Likes
Funny thing--when I used a calibrated signal generator with output -76 dB, my 6500 read S8.5,  With the output at -109 dB, it read S3--seems to work fine?

Larry, W1IZZ
(Edited)
Photo of Michael Walker

Michael Walker, Employee

  • 1102 Posts
  • 328 Reply Likes
So.. in the world of all of us trying to be nice, I have removed a few posts that didn't really contribute and I was worried about how it would go.  

If you have a concern, you can reach out to me personally.  

73
Photo of Lawrence Gray

Lawrence Gray

  • 182 Posts
  • 87 Reply Likes
Fine Job--needs to be done more often.  Negative comments such as calling people trolls or other pejoratives, have no place here and serve no purpose.

Each person is just trying to learn and some folks are more technical than others.  This was an interesting, if a little repetitive, discussion, providing good information to folks who may not understand the overall concepts discussed.
Photo of Mike - VE3CKO

Mike - VE3CKO, Elmer

  • 550 Posts
  • 288 Reply Likes
Trolls need to be called out for what they are. They add no value, they repeat and repeat and jump at opportunities to create division. A more politically correct phrase would be "Negative Nancies" but please continue to call them what they are. If it hurts their feelings, they can leave and troll some place else.
Photo of Pat N6PAT

Pat N6PAT

  • 855 Posts
  • 271 Reply Likes
It's very sad that so many threads end up this way. I've emailed both Gerald and Dan in the past about the rude behavior and name calling that happens in this forum.

A big help would be the addition of an ignore button. I'm surprised there isn't one.
Photo of Dawg Fan

Dawg Fan

  • 32 Posts
  • 5 Reply Likes
OMG,  just pick an S number and use it, the importance of the signal report is not near as important as making the contact.....It doesn't matter if your work history is an an astro physicist instead of some electronic technician, you are placing way way too importance on a signal report...BUTT IN THE SEAT TIME AS A HAM MEANS MORE THAN SOME WORK HISTORY....I don't believe there is anything wrong with the radio....Just give them an S7 or S9, pick one and move on...
Photo of Rolf Auras

Rolf Auras

  • 12 Posts
  • 3 Reply Likes
After reading this interesting discussion I would like to check my understanding without diving in a pool of bins:

When listening to the phones I hear three types of noise:
1. the signal
2. atmospheric noise
3. receiver internal noise

A Flexradio shows all three on its S-meter, e.g. an Elecraft only 1 and 2.

Is this view acceptable?

Rolf, DJ1WT
Photo of Michael N3LI

Michael N3LI

  • 234 Posts
  • 80 Reply Likes
Hi Rolf,   "diving into a pool of bins"  Now that is the best statement in this whole thread!

How about if we look at it as the Flex radio determining Signal strength at the noise floor by virtue of bandwidth. If you are using a wider bandwidth, like SSB, it is seeing more peaks in the noise, which tends to make the reading higher. When reduced to a much narrower bandwidth like say CW 50 Hz, there are a lot less peaks to measure.

Then when a signal comes in that occupies the bandwidth, be it CW or an SSB width you are listening to,  you get a good reading of signal strength.

I managed to get through that without invoking the "B" word! 8^)
Photo of Bob Gerzoff

Bob Gerzoff

  • 3 Posts
  • 0 Reply Likes
I'm a statistician so I have to ask:  If the peaks (and valleys)  are a random phenomena due to noise then from my perspective, the expected (average) noise level in any bandwidth would be same.   A wider bandwidth would see more signals, and hence have a higher reading.  So I'm thinking the higher readings are  due to some type of sum of the signals within in the passband.  Am I thinking right?
73, Bob
WK2Y
(Edited)
Photo of Geoff - AB6BT

Geoff - AB6BT

  • 150 Posts
  • 34 Reply Likes
Here's some info regarding noise and some of the different types. If the noise is white then there is equal power in any specific bandwidth, say 1 kHz whereas pink noise has equal power per octave.

https://en.wikipedia.org/wiki/Colors_of_noise
(Edited)
Photo of k3Tim

k3Tim

  • 929 Posts
  • 197 Reply Likes
Bob,

You are correct.  For example, a 500 Hz BW measurement taken at the low end of the 40 meter band should show a similar reading reading at the high end (assuming atmospheric noise only in the passband).  As the BW increases the amount of noise within the passband also increases. The energy within the passband is used to find the PSD. That is, the FFT bin are used in the summation to find power spectral density. This power can be converted to a dBm reading or voltage (based on 50 ohms).  An interesting link:

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

That's my take on the S-Meter inner-workings. 

_..--
k3Tim/7
Photo of Bob Gerzoff

Bob Gerzoff

  • 3 Posts
  • 0 Reply Likes
Oh no.  Now I have to remember my calculus. ;-)  Thanks for the info and thanks to Geoff too.
73
Photo of Brian Denley  KB1VBF

Brian Denley KB1VBF

  • 100 Posts
  • 13 Reply Likes
Elecraft and Flex S meter reading are the same.
Photo of Brian Denley  KB1VBF

Brian Denley KB1VBF

  • 100 Posts
  • 13 Reply Likes
So is ANAN
Photo of Brian Denley  KB1VBF

Brian Denley KB1VBF

  • 100 Posts
  • 13 Reply Likes
 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.

Photo of Michael N3LI

Michael N3LI

  • 240 Posts
  • 81 Reply Likes
Seems like some pretty good company our Flex's find themselves in. 8^)
Photo of Rolf Auras

Rolf Auras

  • 12 Posts
  • 3 Reply Likes
Brian,

as Joseph and other reported their Flex show S 5/6 and no antenna connected. The Elecrafts show S 0 under the comparable conditions...
Photo of Brian Denley  KB1VBF

Brian Denley KB1VBF

  • 92 Posts
  • 11 Reply Likes
Rolf:
Not true.  Look at the xcvr s-meter evaluations by Rob Sherwood.  NOW that doesn’t mean that Joseph’s radio is OK.  It would have been great if Flex had given him their measurement when they returned his xcvr.  Other than that, comparison with another calibrated SDR xcvr or trying a new location are the only ways I can think of to isolate the problem.  Where did Joseph say he lived?

Brian. KB1VBF
Photo of Rolf Auras

Rolf Auras

  • 12 Posts
  • 3 Reply Likes
Brian,

I think you will agree, that a S 5 (no antenna) needs an explanation. If Flex confirms that this is correct and my explanation is wrong (internal noise) we have to ask ourselves how to deal with it. 

The relationship of bandwidth and noise is understood however a S 5 with no antenna is an useless information.

Rolf, DJ1WT
Photo of Michael Walker

Michael Walker, Employee

  • 1097 Posts
  • 325 Reply Likes
If you look at the original notes from both Steve Hicks and Gerald, it has been explained.  
Photo of Michael N3LI

Michael N3LI

  • 237 Posts
  • 81 Reply Likes
Listening to radios with no antenna within itself is pretty useless information.

Now the idea that a S-meter should read S-0 when on a dummy load or shorted isn't correct unless you place some fudge factor that adjusts the ambient dbm to the value of 0. When things are quiet at my place and on a dummy load, I'm at around -123 dbm or so. WIthout the load and on an antenna, I'm around -120 dbm

I can get a reading where the S-number matches the dbm and S-number agree when the radio is on a dummy load. Which is around .5 to 1. This determines that my Flex is calibrated and operating accurately.

But I have trouble wrapping my head around the concept that we not only need to have purposefully inaccurate S-Meters, but use an incorrect way to measure S-Value on the Flex in order to say that the meters are inaccurate.
Photo of Lasse Moell

Lasse Moell

  • 149 Posts
  • 28 Reply Likes
With no antenna attached, turn on MAX pre-amp gain and you WILL see the S-meter drop! The explanation why has been given over and over again.
To get really low reading, decrease the IF BW to 50 Hz. I guess it might be hard to grasp the relation between receiver noise factor, IF filter BW and S-meter reading.
Photo of Rolf Auras

Rolf Auras

  • 12 Posts
  • 3 Reply Likes
Taking Josephs posts I'm convinced he tested all these settings and he did NOT see the S-meter drop.
Or does his Flex behave differently?

Joseph please give us a comment on this.

Thanks,
Rolf, DJ1WT
Photo of Michael N3LI

Michael N3LI

  • 234 Posts
  • 80 Reply Likes
Looking at the posts, he was complaining about the readings on SSB, which indicates the radio was functioning well.

When he was using a narrow bandwidth, the S-level dropped appropriately.

Read Brian's posts on Sherwood's comments on meter accuracy. Flex is in the elite class of radios, and no Japanese radios track properly.

I've yet to see a good reason for dropping the performance. Probably the best is Burt's comment that "Joe Ham" wants it that way. Still not a good reason. These things are Ferraris, it makes no sense to try to turn them into Toyota Corollas.