Give us a Choice with the S Meter

James Whiteway

I like it. Too bad the developer is not supporting it anymore. Well done graphics. James

Robert Lonn

1. My Analog Flex S-Meter is working perfectly.. Calibration is exact, and I love to see the meter move back and forth when receiving SSB signals.. It is very easy to install!! You need two parts.
2. One part is a Label Maker to print out the work FLEX
3. The second part is the radio to place the FLEX sticker on it
4. The result is a FLEX radio with a precision S-Meter!!!

N6OIL

The other day I had my TS-830S un-hooked and had about an S-7 reading.

John - AI4FR

Let's also remember that many "S" meters on older equipment is user adjustable.

James Del Principe

So help me out here. If I short out the input and it still reads S3 or so and I have a pronounced hiss, then isn't this internally generated noise??? And doesn't this serve to mask weak signals?  If not internal, then this speaks of poor shielding.
My analog radios like the FT2000 and FT 847 and quite quite when the antenna terminals are shorted and, of course, the S meter reads zero since there is no AGC voltage generated.
Respectfully, Jim     KD1I

Jay Nation

James

And that shorted input was intended to have a 50 ohm load across it, so may not be near as accurate when reading a short. A 50 ohm short will probably give you a different measurement. 

But neither reading, will be a signal measurement.

Noise just IS, it's never 0.

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Bill -VA3WTB

James,,In the case of the Flex, the internal noise is created by the receiver bins being sampled, Direct sampling....this sampling is working all the time. So without an antenna the bin samples are registered. In any radio there is no such thing as 0 RF in the receiver, a non SDR radio can not measure the small voltages and display them.

On your Flex as you increase the pass band width, you see the S meter signal rise. And if you drag the pass band narrow to very thin the S meter should say S1.

The FT2000 is not a direct sampling radio and works much differently then a Flex.
As you know, a Flex hears weak signals really well because of the technology it uses.

James Del Principe

Jay, thanks for the reply but I did use my own 51 Ohm, non-reactive load as well as a short.  Still has internally generated noise to what I consider unacceptable levels.....   Noise, like any other signal, is additive.... so any source adds to the total.
Whether the "S" meter reads S3 or S2 or S4, it still comes from internal sources.

Best 73, Jim

Bill -VA3WTB

That true Jame,,internal, in a direct sampling radio and the way Flex samples the bins this is very normal.

James Del Principe

Maybe then, and I'm going way out on a limb here, what is needed for operator comfort, is a form of downward compandering like the Flex transmit audio has. That way an operator would not have to listen to that background sound. The level could be adjustable to just clip the unwanted background noise perhaps at the "audio stage" rather that at the frontend. I know the AGC-T can be lowered or even the volume but this is not the same. Those will affect weak signal reception.   Just a thought.    Jim

K6OZY

You mean a squelch?   That has been a LONG requested feature on this radio for non-FM modes.   I would love that added.

James Del Principe

Well, yes, you could call it a squelch. I think of a squelch as all or nothing with a threshold but that could work....if someone would do it.  I 'spose a hardware squelch could be made external to the Flex too but this is an awfully expensive radio not to have one built in.   Jim

James Whiteway

Rumor has it, that someone designed, in software, a squelch that could detect speech only. And ignore all other noise sources that could not be identified as human speech. Thereby, keeping the audio off until such time as a human voice is detected. Pretty cool idea if true. (and it may be)

Bill -VA3WTB

Jim, the tiny voltage sampled in the receiver bins are not effecting the receive audio.
You may have a good idea there how ever. I find by adjusting the AGC-T on an ongoing basses I can make the receiver very quiet. Also by narrowing the pass band down a bit works well as also.
In order to keep the receiver very open and hearing weak stations I don't know about turning down the front end.

Bye the way, The AGC-T is a more complicated device then some realize. It works just like the DEXP only in reverse if you can get you head around that..lol

So it keeps the noise out when there is little signal, then when a signal is is heard it opens up. This setting is in relation to the AGC setting,,slow,,med..and fast.
Many times if you want to make thing quieter setting the AGC to slow helps and carefully adjust the AGC-T so it does not pump....

Bill -VA3WTB

I just use the  squelch in RFSTACKS when I want it.

Rick WN2C

Rex why in the world would you want an inaccurate S meter? You can always tell your contacts that you have a dutch meter and tell them their signal is 10 to 20 over anyway.

Bill -VA3WTB

Rick, oh no..don't start all over again.

James Del Principe

Bill, thanks for the further input.   Yes, you are correct that the AGC-T can be adjusted downward to make the background quieter but must then be readjusted for weaker signals which then is noisier between contacts. I am on a morning roundtable where some stations are 20 over 9 and others just above the noise level. To optimize, I would need to slide the AGC-T up and down..... bummer. Also, it needs to be reset for different band conditions. I don't want to be a whiner here. It is a great radio but could profit from just one more feature.... squelch or clip or what ever the background sound. There is no excuse for internally generated noise with this. We are not listening to shot noise on our vacuum tubes. HI HI  Should not be too difficult.... just need the will to do it.   I will try the AGC on slow. I usually use medium.      Best 73, Jim

James Del Principe

Bill, I am not familiar with RFSTACKS.    Can you elaborate, please?   Jim

James Del Principe

James, I don't know if it needs to be so sophisticated as to detect a human voice but just clipping at the noise level should not be too difficult.     Jim

Jay Nation

Jim

http://mkcmsoftware.com/Flex/Index 

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John - K3MA

I bet Dr. Kelvin if he was alive would disagree with your 0 RF statement.

Rick WN2C

I'm sorry


Jay Nation

I've got a 50 ohm BNC terminator **** onto my XVTR connector.
I set a 500 Hz RX filter width.
And all I got was this crazy picture showing SmartSDR reading S-0.
No internal noise visible. No signals either.

Hard to argue with reality.


BTW when I switch it to read as dBm it reads as low as -135 dBm. There is always noise in this reality. It can be measured.


The level varies 2-3 dBm very slowly, but it won't read any lower than S-0.


When I turn off the 20 dB preamp it does read S-1 @ -120 dBm.

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James Del Principe

Jay, I'm curious why you chose the xverter input and not the normal antenna?   Some advantage to that?    What would your results have been using Ant 1 and a reasonable SSB bandwidth like 5.6 KHZ?     Under your present conditions, what does the noise level sound like in headphones?    Regards, Jim

Jay Nation

Jim

They would have been higher, of course!

The dummy load I have is a cantenna type it hears signals and noise, The BNC terminator is quieter. 

My point was more about SmartSDR can read lower than S-4, if you feed it with S-0 or less.

The IARU S meter specs state values for S1, -121 dBm to S9 +10 dB, -63 dBM, my guess at an S-0 level which isn't spec'd would be  -127 dBm. I'm unable to get the actual measurement lower than -135 dBm. Which since the IARU didn't spec any negative S meter signal level values below S-1, -121 dBm will just have to do.

I don't have a signal generator that can output an S-1, -121 dBm, 0.2 microvolt signal so I can't test for the lowest IARU spec'd reading. 

SmartSDR probably meets the IARU Specifications.

And the noise sounds like noise in the headphones and gets quite loud if I turn the volume up all the way.


So yes, noise still sounds noisy.

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Jay Nation

https://en.wikipedia.org/wiki/S_meter#IARU_Region_1_Technical_Recommendation_R.1 


YMMV.

And so may your S meter readings.

http://www.seed-solutions.com/gregordy/Amateur%20Radio/Experimentation/SMeterBlues.htm#The Measurements

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James Del Principe

Jay, it is possible to make attenuators for very low measurements. You are probably already familiar with this but I have made 40 DB (100:1) pads with three resistors in a Pi network. The two legs are 50 Ohms and the "bridge" between the legs is 2500 ohms. You can easily make any ratio you wish this way.      Jim

Jay Nation

Jim

Yes I could do that, or I could just accept the SmartSDR S meter is accurate the way it is.
 
I've never given anyone a 599, S-1 signal report, my antenna always seems to have plenty of signals I can actually hear. 

I'm more interested in working those before they disappear.

But I'll think about it.

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Robert Hicks

Against my better judgement I will enter the fray to make a few comments. These will all relate to Collins receivers. To my knowledge and recollection, there were no Collins receivers for Amateur use at least that contained a preamp. The Collins specification for s9 was 100uV as read on the signal generator which provided 50uV across the “50 ohm” input impedance. The signal generators at least in those archaic days were calibrated in open circuit voltage at the output of the generator. Great care was taken in the design to attempt to provide as linear AGC as possible in order to have accurate S meter readings as possible. Adjustments were provided to make the S meter read 0 when no signal was applied and S-9 at 100uV on the generator. Since the receiver was not without noise at no input that necessarily implies some non-linearity at that end of meter reading. So to say the S meter was inaccurate could be both correct and incorrect since it was clearly calibrated at S9 but uncalibrated at at no input just to make meter read S0. Further, since the meter depended on the AGC buss for it’s reading, the receiver bandwidth noise differences were not taken into account since these noise differences were small compared to the S9 calibration signal. Different manufactures took more or less pain to provide a measure of the received signal. Hallicrafters was known as providing generous S meter readings. Put several of the receivers mentioned in this thread and you will probable see differences between them for the same signal at the input. So what’s the point? If you like to see the meter wiggle on SSB put a VU meter on the audio and you can make it read whatever you wish and for a given RF gain setting it might be relatively accurate. With the FRS products vs “conventional” radios we are comparing apples and oranges. Thoughts from a Collins Engineer of 32 yrs, and retired (1991) when Direct Sampled radios were just a gleam in someone’s eye. History lesson ended. Bob W5TX