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eHam Forums => Misc => Topic started by: KT0DD on August 21, 2012, 05:40:15 AM



Title: S-Meter accuracy...LED or needle types
Post by: KT0DD on August 21, 2012, 05:40:15 AM
Looking at my LED type Yaesu FT-950 s-meter, I was reminded of a sales pitch by a stereo audiophile salesman I dealt with years ago.

I was looking at a high end Nakamichi casette deck with LED bar type V/U meters when they first came out in the 80's. The salesman said the new LED meters were much faster and accurate than the mechanical meters because they worked electronically at "The speed of light" where mechanical meters were subject to slower response due to their mechanical movements.

While it was quite a sales pitch, It seemed to be logical.

Is this necessarily true? I know alot of hams still like the needle type S-meters, probably out of nostalgia reasons.

Just wondering about this useless little memory running around in my head...Hi Hi.

73. Todd - KT0DD


Title: RE: S-Meter accuracy...LED or needle types
Post by: AD4U on August 21, 2012, 05:47:40 AM
LED meters probably move faster and follow a signal faster than mechanical meters.  As far as S meter "accuracy" is concerned, very few S meters of any kind are "accurate", especially if you compare them to the old standard of 50uV = S9.  A typical S meter is no more than a relative signal strength meter which is not calibrated to any specific standard.

Dick   AD4U


Title: RE: S-Meter accuracy...LED or needle types
Post by: AA4PB on August 21, 2012, 05:57:47 AM
While an LED meter may have the ability to move faster, they are still limited by the time constants in the receiver AGC which supplies the voltage that the S-meter reads.

With VU meters, the designers build in time delays that slow the LED meter down so that you can read them. There are specs regarding these time constants. If the LED meter were permitted to follow the audio waveform in real time it would appear as a blur. I think you were given some sales guy's marketing hype  :D



Title: RE: S-Meter accuracy...LED or needle types
Post by: K0OD on August 21, 2012, 07:20:48 AM
Had a Radio Shack guy try to sell me those high end "gold" cables by telling me electricity moved faster in them.



Title: RE: S-Meter accuracy...LED or needle types
Post by: K8AXW on August 21, 2012, 07:58:40 AM
OD:  You mean it doesn't?


Title: RE: S-Meter accuracy...LED or needle types
Post by: AC4RD on August 21, 2012, 09:12:29 AM
Had a Radio Shack guy try to sell me those high end "gold" cables by telling me electricity moved faster in them.

 :->  :->  :->

Gosh, explain to me again, Mister Salesman, how if I spend enough money, the laws of physics no longer apply to my stereo.  :-)


"Radio Shack:  You've got questions, we've got blank stares, lies, and overpriced cellphone contracts."



Title: RE: S-Meter accuracy...LED or needle types
Post by: KA5N on August 21, 2012, 10:29:30 AM
Meters that measure with "globs" of light go against nature and the radio gods.
I like real electromecanical meters.  Suppose you gave a signal report that was a half a
dB low because the led resolution wasn't good enough to read exactly?   Why the affront
to the other ham would be unforgiveable!!
Real meters forever!

Allen KA5N


Title: RE: S-Meter accuracy...LED or needle types
Post by: AD4U on August 21, 2012, 10:43:10 AM
OM UR signal report on this end is 2 red LEDs over 5 green ones.  I just love technology.

Dick  AD4U


Title: RE: S-Meter accuracy...LED or needle types
Post by: G3RZP on August 21, 2012, 10:49:46 AM
The 'S' stands for 'suspicious'.


Title: RE: S-Meter accuracy...LED or needle types
Post by: WB2WIK on August 21, 2012, 11:03:13 AM
I don't really care and hardly ever look at any of my "S" meters on anything.

Being able to copy the station = good.

Not being able to copy the station = bad.

My S-meter really only needs a red light (bad) and a green light (good).

But anyway, there are modern LCD meters that look so much like vane type meters it's almost scary.  The technology is certainly available and has been for a long time, you just need a TFT panel or similar to make it work.  Take a look at the "meters" on an IC-7800.  You can almost feel the breeze from the meter "needles" going up and down...until you realize there aren't any.


Title: RE: S-Meter accuracy...LED or needle types
Post by: AA4PB on August 21, 2012, 12:33:05 PM
I think all S-Meters should have mirrored scales so that we can read it down to the nearest tenth of a dB  :D


Title: RE: S-Meter accuracy...LED or needle types
Post by: N9RO on August 21, 2012, 02:10:08 PM
I use the Smeter readings as a reference when analyzing signals.  I use a Smeter logger that writes the readings (from two different receivers and antennas) to a file and graphs them out over time, I can then go back and analyze the file with tools like R.  The correlation between the listener's qualitative impression of signal strength and the actual strength due to AGC holding the signal constant is poor so I find little use for it.

Interesting the things we do when we have time on our hands.

Tim  N9RO


Title: RE: S-Meter accuracy...LED or needle types
Post by: NO2A on August 21, 2012, 02:50:25 PM
I like the multicolor led on my FT-857D. The zero beat function is very accurate for cw use. Even with weaker signals.


Title: RE: S-Meter accuracy...LED or needle types
Post by: W4OP on August 21, 2012, 03:08:17 PM
The Elecraft K3 and its companion P3 can be accurately calibrated to read dBmV. I regularly depend on the P3 for spectrum analyzer measurements.
The only other  rig I know of (non SDR) that has a calibrated S meter is the ADT 200A out of Europe.
I am quite sure the HPSDR unit from TAPR also has the capability of absolute calibration.

Unfortunately, the rest of  the rigs are a guess and even worse, the preamp effects the S meter reading.

Dale W4OP


Title: RE: S-Meter accuracy...LED or needle types
Post by: K0OD on August 21, 2012, 03:54:07 PM
Quote
The only other  rig I know of (non SDR) that has a calibrated S meter is the ADT 200A

Flex S-meters are calibrated in dBm and several other selectable scales. Precise.

I don't understand why some still focus on the ADAT. Their group is moribund... has been for several years.


Title: RE: S-Meter accuracy...LED or needle types
Post by: K0OD on August 21, 2012, 03:58:34 PM
Like that ADAT?  Here... you can be the 76th member of that Yahoo Group

http://groups.yahoo.com/group/adat/


Title: RE: S-Meter accuracy...LED or needle types
Post by: K2OWK on August 21, 2012, 04:17:45 PM
S meters are good for a reference source. They are really not needed everyone just says 599 if they hear you. No reply if they don't. In the old days we would give the S meter reading S4, S6, S9, 20 over etc. Q5 meant quality 5 perfectly clear audio. Now 599 is the norm regardless of the signal strength or the quality.

5/9 voice 5/99 CW.

73s

K2OWK


Title: RE: S-Meter accuracy...LED or needle types
Post by: AA4PB on August 22, 2012, 05:28:20 AM
Since most modern rigs contain a microprocessor (even non-SDR), having a calibrated S-meter is not as difficult as it used to be. The calibration (per band, pre-amp on or off) can be done in firmware. The biggest issue is probably that somebody has to spend the time to do the calibration and it needs to be redone periodically to account for changes caused by ageing components.


Title: RE: S-Meter accuracy...LED or needle types
Post by: KC9TNH on August 22, 2012, 01:12:50 PM
Having read the well-published table when getting my civ amateur license (coming from 5x5 being the ultimate) I once gave someone I with whom I was having a perfectly good conversation a 45. Holy Emotional Events, Batman!

I have a couple of Yaesu's on the table so the 'S-' stands for stingy.
 :D


Title: RE: S-Meter accuracy...LED or needle types
Post by: W4OP on August 22, 2012, 05:55:48 PM
Like that ADAT?  Here... you can be the 76th member of that Yahoo Group

http://groups.yahoo.com/group/adat/

Good grief, all I said was that it had a calibrated S meter.
Dale W4OP


Title: RE: S-Meter accuracy...LED or needle types
Post by: STAYVERTICAL on August 23, 2012, 01:20:24 AM
Like that ADAT?  Here... you can be the 76th member of that Yahoo Group

http://groups.yahoo.com/group/adat/

Good grief, all I said was that it had a calibrated S meter.
Dale W4OP

You did it Dale, you broke the rule " He who shall not be named".
Now Voldemort is looking for you.

73 - Rob


Title: RE: S-Meter accuracy...LED or needle types
Post by: G3RZP on August 23, 2012, 01:53:50 AM
Even if it is well calibrated, unless you know the applicable antenna factor, it doesn't really tell you very much.


Title: RE: S-Meter accuracy...LED or needle types
Post by: ZENKI on August 24, 2012, 01:55:05 AM
If it was properly calibrated you would have a realistic idea of what the noise level at your QTH is. Unlike the 10,000 dollar radio manufacturers who deliberately compress the bottom end of the S-meter scale so it looks like you have a
low noise QTH.  A calibrated S-meter would  also would  give you a true indication of galactic noise on the higher bands which on a dipole antenna in 2.4khz bandwidth  should be something from S3 to around  S1 on a calbrated S-meter.

Radios should have their pre-amp settings with labels like Quiet Rural, Suburban, City, and Industrial. This way you can set the gain of the receiver to the noise floor of the location using just the right amount of sensitivity.
The worst feature of modern radios is the excess gain on the lower bands that is really  not needed or cant be realistically exploited. Its pointless amplifying galactic noise and QRM.

Talking about antenna factor and other factors. If the receivers did have calibrated S-meters, Antenna factor offset, EMC 9khZ bandwidth plus Quasi peak detectors we could use our radios as legitimate EMC receivers for measuring
radiated  emissions and reporting these levels.  We have 10,000 dollar radios with useless S-meters that are as bad as 50 dollar CB radios, why are we paying such high prices for expensive junk? I can buy a Rigol spectrum Analyzer for 2000 US dollars that is accurate to within 0.3db with a color screen. Why  do useless radios like the Icom IC7700 and IC7800 cost so much and are nothing more than useless toys with a meter that us totally useless?

Calibrated S-meters are very handy if designed and implemented correctly to be a true reference 50 ohm source impedance level meters. This  should be easily accomplished in software defined radios.

It would be nice having S-meter in radios that can be switched to the commonly used scales such as Dbm, DbUv, S-units, Uv. Just about every commercial radio that I have used has an RSSI(received signal strength indicator) that is calibrated. Only hams buy 10,000 dollars pieces of equipment with 10,000 % inaccuracy. We should demand better.


The ADAT radio has the most accurate S-meter that I  have ever used. The K3 is reasonably good, however its resolution is limited to chunky S-units. All my SDR receivers, Perseus and Winradio have super accurate S-meters
The is absolutely no reason why a  Analog S-meter cannot  be made to closely match a LED bargraph for level indication. High speed wide bandwidth op amps are cheap these days. But I suppose it depends what you are actually measuring, deep fades of 20 db or following voice peaks, it depends on the application. With the appropriate sampling and detection algorithms, every possible  measurement should be able to be plotted and displayed.

Anyway dont expect  calibrated S-meters from ham companies any time soon, they committed to delivering the same radios with poor TX IMD, poor receivers and uncalibrated S-meters year after year. Its only because hams
appear to be consumer suckers.  We really deserve what we get because we dont complain about anything and just take the junk that they manufacture.

You have more chance of getting decent ham equipment from groups such as the HPSDR groups who understand these issues more than the manufacturers who are just in it for the money and not the science.

Its a real pity ADAT is not more proactive about marketing its radio. In my opinion this  one of the best pieces of  equipment a ham can buy for the money, its a true test receiver. Its transmitter is almost perfect with very low TX IMD.
They have such a good product, I dont know why they dont point a good marketing company like DXENGINEERING  in the USA to  market their products. I am sure it would be top seller in the USA. The S-meter is godly accurate.




Even if it is well calibrated, unless you know the applicable antenna factor, it doesn't really tell you very much.


Title: RE: S-Meter accuracy...LED or needle types
Post by: K1CJS on August 24, 2012, 04:14:50 AM
One thing not mentioned yet (except by the originator) is the time difference between the two types of s-meters.  The analog meter may lag a bit but it will show the actual reading better.  The electronic LED meter responds so quickly that you may miss a spike that the analog meter would show.

There can't really be a set standard because of the differences in the sensitivity of the different radios--even between two identical radios. 


Title: RE: S-Meter accuracy...LED or needle types
Post by: AA4PB on August 24, 2012, 08:00:41 AM
LED meters can have any response time you like if you design the circuit correctly.


Title: RE: S-Meter accuracy...LED or needle types
Post by: G3RZP on August 24, 2012, 08:12:32 AM
Strange thing about the ADAT radio is that there's no mention of what standards it meets. For Europe, it needs to meet EN301 489-1, EN301 489-15, EN301 783-1 and EN301 783-2.

Also it specifies spurious emissions beyond +/- 200 kHz, but the limits are +/-10kHz.


Title: RE: S-Meter accuracy...LED or needle types
Post by: K1CJS on August 25, 2012, 06:32:32 AM
LED meters can have any response time you like if you design the circuit correctly.

The LED meters still can't show a spike correctly because they respond so quickly.


Title: RE: S-Meter accuracy...LED or needle types
Post by: ZENKI on August 26, 2012, 02:54:41 AM
They can if they have proper peak detector and sample and hold circuits.


LED meters can have any response time you like if you design the circuit correctly.

The LED meters still can't show a spike correctly because they respond so quickly.


Title: RE: S-Meter accuracy...LED or needle types
Post by: K1CJS on August 26, 2012, 06:56:09 AM
Now your getting from the sublime to the ridiculous.  It is true that LED meters can be made to show a peak while still showing the second by second signal just as it is done on the more expensive audio gear, but then the costs of manufacture go up.  You really think that the manufacturers are going to put such a meter in every rig--for the less than one percent of the users who may want it--or actually use it?

It they're going to do that, it probably would be mose cost effective for them to use analog meters--and we've seen already where that's gone--simply by looking at how many rigs now have the LED meters.


Title: RE: S-Meter accuracy...LED or needle types
Post by: AA4PB on August 26, 2012, 07:54:10 AM
I would think that a couple of ICs for a peak detector and an LED meter would be less expensive to mfg than a decent quality analog meter.


Title: RE: S-Meter accuracy...LED or needle types
Post by: ZENKI on September 07, 2012, 04:06:16 AM
Thats correct, analog meter manufacturers are disappearing fast. The Chinese factories produce garbage and who really would want to depend on a Chinese manufactured mechanical meter?

Peak detector circuits or even a high speed A/D converter can sample the signal voltage anyway you want and present the data in umpteen formats for display. These is absolutely no reason why ham radio
receiver should have the crap S-meters like they have on them today. They should all be calibrated considering the price that we are paying for radios. Its just pathetic reasoning  and making excuses for the manufacturers by saying
that producing a calibrated S-meter  is somehow rocket science and expensive.

As for the arguments  that S-meters are not meant to be exact and only relative, this is just a nonsense argument by people who have no idea what  a calibrated S-meter could be used for and how useful it could be.
More hams are partial too inaccurate  S-meters because they think people are fooled by silly and ridiculous reports. They somehow use inaccurate reports to make others believe that their stations and  antennas are working better
than some other hams. This kind of behavior is really evident by stations whose licensed restricts them to a very low output power. Giving idiotic reports seems to make them believe that they covering up their breach of their  license power rules by inferring that their stupid signal reports is their great antenna.  Experienced hams can see through this act of technical deficit disorder.


I would think that a couple of ICs for a peak detector and an LED meter would be less expensive to mfg than a decent quality analog meter.



Title: RE: S-Meter accuracy...LED or needle types
Post by: K7KBN on September 07, 2012, 05:40:20 PM
My first receiver didn't have a meter at all - it was a GE console AM broadcast receiver (pre-television), with a "short wave" band thrown in.  I could tell if a station was loud or not.  My next receiver was an SX-99.  I never bothered looking at the S-meter.  It moved fine and probably indicated something, but I could still tell if a station was loud or not.

If you guys are so adept, why not invent an S-meter that plugs into ANY radio and gives an absolute "S" reading referenced to anything the operator might want.  I'll keep using my ears to tell me if the other station is loud or not.


Title: RE: S-Meter accuracy...LED or needle types
Post by: G3RZP on September 08, 2012, 01:21:53 AM
The S meter can be useful as a relative strength indicator - for example, when switching between antennas. On the very few occasions that I want to make noise measurements, I either use the spectrum analyser, or calibrate the receiver with a signal generator for what I need.

Of course, it's not quasi peak - which is a very artificial thing derived from attempts to quantify noise into European AM receivers in about 1934 - and in any case, there is now a start to move away from QP in both ETSI and ITU.

There are, to my mind, too many attempts these days to make something for which there is a German term that translates roughly as ' egg laying milk producing pig that swims'. Scroggie's Radio Laboratory Handbook of the 1940s points out the dangers of that approach...


Title: RE: S-Meter accuracy...LED or needle types
Post by: K1CJS on September 08, 2012, 08:21:09 AM
....These is absolutely no reason why ham radio receiver should have the crap S-meters like they have on them today. They should all be calibrated considering the price that we are paying for radios. Its just pathetic reasoning  and making excuses for the manufacturers by saying that producing a calibrated S-meter is somehow rocket science and expensive....

There are reasons, some of which are problematical and some aren't.

First, calibrated to what?   The differences in the various rigs and the wide selection of antennas make 'calibrated' meters useless.  Say, for example, that you've got a 'gain' type antenna.  How do you calibrate the meter so you can get an accurate reading on the station you're receiving?  What if that station is using such an antenna?  There is no possible way of having a meaningful standard!

Second, hams are notoriously a cheap bunch.  A small percentage may want such a meter, but how do you justify the cost of such a thing to the rest?

Third, look at the D-Star standard.  Icom embraced it, but the other two of the big three didn't.  How are you going to get ALL manufacturers to conform to one standard for S meters if they won't do that for more important developments?

We would be better off stopping trying to make something out of this.  An S-meter shows relative signal strength, not exact signal strength.  Why not let it go at that--and stop worrying about trying to re-invent the wheel!


Title: RE: S-Meter accuracy...LED or needle types
Post by: N3OX on September 08, 2012, 02:36:56 PM
First, calibrated to what?   

Hard to beat dBm. 


Title: RE: S-Meter accuracy...LED or needle types
Post by: G3RZP on September 08, 2012, 03:11:47 PM
And at the end of the day, what does it tell you? So it's so many dBm. So what?


Title: RE: S-Meter accuracy...LED or needle types
Post by: YO9IRF on September 08, 2012, 11:08:17 PM

...

First, calibrated to what?   The differences in the various rigs and the wide selection of antennas make 'calibrated' meters useless.  Say, for example, that you've got a 'gain' type antenna.  How do you calibrate the meter so you can get an accurate reading on the station you're receiving?  What if that station is using such an antenna?  There is no possible way of having a meaningful standard!
...


The S-Meter is a tool that indicates the signal level at the reciever input, and that is all; you calibrate it with a signal generator. The S-Meter does NOT show real field strength at your QTH of the recieved signal, but the signal present at the reciever input, wich is a function of both antenna performance but also polarisation, impedance matching etc.


Title: RE: S-Meter accuracy...LED or needle types
Post by: TANAKASAN on September 09, 2012, 01:08:52 AM
All agreed and we should know the standard already, -73 dBm or 50 uV = S9 Also, when we engage an attenuator or pre-amp inside the rig the reading should NOT change.

Tanakasan


Title: RE: S-Meter accuracy...LED or needle types
Post by: KK4IKO on October 18, 2012, 03:59:39 AM
S-meter accuracy and speed?  It's all relative, and does it really matter one way or the other?  All I need to know is that the signal strength is sufficient to hear the other guy easily.  If he's over-modulating, you will politely let him know so he can change something.  The same applies if you can barely hear him, or you need to adjust something.  If an S-meter wasn't there, I wouldn't miss it.

I have one of those Nakamichi cassette decks.  Very fine equipment.  The VU meter is important for recording to get maximum strength and clarity without distortion, but that's all.  Using headphones for monitoring will tell you if there's significant distortion.

Bruce, KK4IKO


Title: RE: S-Meter accuracy...LED or needle types
Post by: WB2WIK on October 18, 2012, 09:24:03 AM
I would think that a couple of ICs for a peak detector and an LED meter would be less expensive to mfg than a decent quality analog meter.


Sure it is.  It's also less likely to fail or be damaged.  Cheap analog meters fail all the time.  Very good ones may not, but they're also expensive.