Console Signal meter reading


michel soldevila
 

Hi folks,
I performed a simple test with my RSP2 receiver and my Marconi 2022D RF generator:
The RF signal was fed to SMA antenna port A via a short 50 ohms coax cable.
The Console settings were as follow:
-RF gain = 0 
-AGC On
-Visual gain = 0
-Mode = CW
-Bandwidth = 200 Hz
I noticed a difference of 20 dB between the generator output level and the signal meter reading; this difference is almost constant from1 to 50 MHz, for signal levels between -100 dBm and -50 dBm. The difference is smaller at -40 dBm level (only 10 dB). The Console signal meter reading is above the generator output level.
My question:
Should I use the "Visual gain" setting to compensate for that diffrence?
 73, Michel (F1GOC)


Larry Dodd
 

Michel,
First, I suggest you turn AGC OFF to get anywhere near an accurate reading. 
Larry K4LED 

On Jan 25, 2022, at 11:39 AM, michel soldevila <michel.soldevila@...> wrote:

Hi folks,
I performed a simple test with my RSP2 receiver and my Marconi 2022D RF generator:
The RF signal was fed to SMA antenna port A via a short 50 ohms coax cable.
The Console settings were as follow:
-RF gain = 0 
-AGC On
-Visual gain = 0
-Mode = CW
-Bandwidth = 200 Hz
I noticed a difference of 20 dB between the generator output level and the signal meter reading; this difference is almost constant from1 to 50 MHz, for signal levels between -100 dBm and -50 dBm. The difference is smaller at -40 dBm level (only 10 dB). The Console signal meter reading is above the generator output level.
My question:
Should I use the "Visual gain" setting to compensate for that diffrence?
 73, Michel (F1GOC)


Allan Isaacs
 

Hi Michael

There may be a problem here?

It depends on how the output from your signal generator is measured. Some will regulate the input into the generators attenuator to say 0dBm then rely on the attenuator to define the output at its socket.

If you connect a high impedance load to the signal generator its output will equate to the level indicated by the attenuator setting but, if a 50 ohm load is connected directly, this reading at the output socket will not be valid.

My Marconi TF2008 is marked to show this anomaly.

You could test this hypothesis with a high impedance scope?

73 Allan G3PIY


From: main@SDR-Radio.groups.io [mailto:main@SDR-Radio.groups.io] On Behalf Of michel soldevila
Sent: 25 January 2022 16:39
To: main@SDR-Radio.groups.io
Subject: [SDR-Radio] Console Signal meter reading

 

Hi folks,
I performed a simple test with my RSP2 receiver and my Marconi 2022D RF generator:
The RF signal was fed to SMA antenna port A via a short 50 ohms coax cable.
The Console settings were as follow:
-RF gain = 0 
-AGC On
-Visual gain = 0
-Mode = CW
-Bandwidth = 200 Hz
I noticed a difference of 20 dB between the generator output level and the signal meter reading; this difference is almost constant from1 to 50 MHz, for signal levels between -100 dBm and -50 dBm. The difference is smaller at -40 dBm level (only 10 dB). The Console signal meter reading is above the generator output level.
My question:
Should I use the "Visual gain" setting to compensate for that diffrence?
 73, Michel (F1GOC)

 


Gedas
 

pse see below:

https://www.youtube.com/watch?v=qHJE6wa9dVw

Gedas, W8BYA EN70JT

Gallery at http://w8bya.com
Light travels faster than sound....
This is why some people appear bright until you hear them speak.
On 1/25/2022 11:39 AM, michel soldevila wrote:

Hi folks,
I performed a simple test with my RSP2 receiver and my Marconi 2022D RF generator:
The RF signal was fed to SMA antenna port A via a short 50 ohms coax cable.
The Console settings were as follow:
-RF gain = 0 
-AGC On
-Visual gain = 0
-Mode = CW
-Bandwidth = 200 Hz
I noticed a difference of 20 dB between the generator output level and the signal meter reading; this difference is almost constant from1 to 50 MHz, for signal levels between -100 dBm and -50 dBm. The difference is smaller at -40 dBm level (only 10 dB). The Console signal meter reading is above the generator output level.
My question:
Should I use the "Visual gain" setting to compensate for that diffrence?
 73, Michel (F1GOC)


michel soldevila
 

Hi Allan,
Test setup
RF generator on 15 MHz, output level set to 13 dBm or 1Vrms :
- ~ 6 Vcc measured (2.1 V rms) on my Tek 454 scope in case of direct connexion
- ~ 3 Vcc measured (1.05 V rms) on the scope when the generator is loaded with a 50 ohms resistive load 
The displayed output level of the generator is thus correct if the generator is loaded with its internal impedance, which is the case of the SDR antenna port A.
Do you agree ?
73, Michel (F1GOC)


Allan Isaacs
 

Hi Michel

Yes, I agree.

I just watched the W8BYA video and you can see the SDR Play can be set up to indicate precise signal levels by trial and error and of course within realistic limits.

My receivers are an early SDR Play, an old Lime and a repaired Andrus. The available console settings are completely different for each of these and obviously I need to follow the calibration procedure suggested by Gedas to get correlation between true and indicated RF levels if indeed this is possible.

  

For example the Andrus has only a basic gain setting 0, -12, -24 and -30dBm with no IF gain or video gain settings.

 

As an example.

My Andrus sees a broadcast station on 198KHz, with no antenna connection, at -102dBm with gain 0dB and base noise visually at less than -145dBm but reading -136dBm and b/w +/-6KHz. If I change the gain to minus 30dB I see the base noise rise visually to minus 127dBm with a reading of minus 112dBm or visually minus 122dBm at +/-1KHz b/w. The broadcast station reads minus 108dBm but I can hear no audio. Changing the gain to -24dB provides a reading of minus 103dBm with very noisy audio; minus 12dB gives me the same reading of minus 102dBm with noisy audio. Finally reverting to 0dB gain I see the same minus 102dBm with clear audio.

What is changing with gain setting is the signal to noise ratio.

For weak signals the console setting is easy.. set the gain to 0dB. For strong signals I need to use a gain setting between -12 and -30dB. These tests had AGC off and because the signal level was so weak turning AGC on had no effect.

73 Allan G3PIY


From: main@SDR-Radio.groups.io [mailto:main@SDR-Radio.groups.io] On Behalf Of michel soldevila
Sent: 25 January 2022 19:53
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] Console Signal meter reading

 

Hi Allan,
Test setup
RF generator on 15 MHz, output level set to 13 dBm or 1Vrms :
- ~ 6 Vcc measured (2.1 V rms) on my Tek 454 scope in case of direct connexion
- ~ 3 Vcc measured (1.05 V rms) on the scope when the generator is loaded with a 50 ohms resistive load 
The displayed output level of the generator is thus correct if the generator is loaded with its internal impedance, which is the case of the SDR antenna port A.
Do you agree ?
73, Michel (F1GOC)

_._,_._,_

 


Roger Need
 

SDR Console does not use the correction tables for signal levels provided by SDRplay for S meter calibration so the readings are way off.  SDRuno does use these tables and readings are accurate to +/-1 dBm.  I have verified this with my signal generator using both programs.

Another related issue. There was a long debate a while ago in this group about whether the S  meter should indicate the total average power in the selected bandwidth or the power of the strongest signal (like the carrier for AM reception).  I believe SDR Console measures the latter and SDRuno measures the former. 

Roger


Simon Brown
 

Roger,

 

You are correct on both counts.

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of Roger Need via groups.io
Sent: 27 January 2022 19:04
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] Console Signal meter reading

 

SDR Console does not use the correction tables for signal levels provided by SDRplay for S meter calibration so the readings are way off.  SDRuno does use these tables and readings are accurate to +/-1 dBm.  I have verified this with my signal generator using both programs.

Another related issue. There was a long debate a while ago in this group about whether the S  meter should indicate the total average power in the selected bandwidth or the power of the strongest signal (like the carrier for AM reception).  I believe SDR Console measures the latter and SDRuno measures the former. 

Roger


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Please use https://forum.sdr-radio.com:4499/ when posting questions or problems.


Mag loop Simon
 

Simon

Will there be away to “adjust” the relative s meter reading on sdrc ever?

I ask as it would be nice to have it adjustable ( say the scale on the side of waterfall/ spectrum) so as to read the same as main rx.

To explain I use the elad duo as a second rx and panadapter on my ftdx3000. The s meter readings are often well out mainly below s7. ( ie 3000 says s3..sdrc says s5 or 6)
As i use phasers against noise antennas here, it would be very very useful to see the decrease in general noise floor when adjusting. The 3000 s meter shows this but not the sdrc s meter.( when fine tuning.it just stays the same.)

Hopefully i have explained this to your understanding? ?

By the way house for sale in 3 months!! Cornwall here we come..looking at properties between truro and helston..will take bribes to move nearer bude..

Simon g0zen


Mag loop Simon
 

Hi again

Thinking about this..I wonder if the duo with sdrc is “ not seeing “ what the 3000 is..ie duo is “ seeing “ the whole rx spectrum and hence not adjusting its signal level when the phaser is in operation? Sorry for poor explanation, but qro amps, antennas etc are my thing..still much to learn about sdr’s..

I do use antenna out to drive the duo, maybe i should use if out( with suitable if offset settings on sdrc)

Ps the Cornwall 160-40m special amp is coming along nicely..

Re s meter on sdrc vs 3000.. s1 on 3000= s3.5 on sdrc…s5 on 3000 =s4 on sdrc, would be nice to be able to adjust s meter or linearity on spectrum to match.


Thanks Other Simon


Simon Brown
 

DUO is very probably not seeing the same signal level as the 3000.

I do agree that a per-radio signal calibration is needed.

Simon Brown, G4ELI
https://www.sdr-radio.com

-----Original Message-----
From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of Mag loop Simon
Sent: 27 January 2022 20:50
To: main@sdr-radio.groups.io
Subject: Re: [SDR-Radio] Console Signal meter reading

Hi again

Thinking about this..I wonder if the duo with sdrc is “ not seeing “ what the 3000 is..ie duo is “ seeing “ the whole rx spectrum and hence not adjusting its signal level when the phaser is in operation? Sorry for poor explanation, but qro amps, antennas etc are my thing..still much to learn about sdr’s..

I do use antenna out to drive the duo, maybe i should use if out( with suitable if offset settings on sdrc)

Ps the Cornwall 160-40m special amp is coming along nicely..

Re s meter on sdrc vs 3000.. s1 on 3000= s3.5 on sdrc…s5 on 3000 =s4 on sdrc, would be nice to be able to adjust s meter or linearity on spectrum to match.


Thanks Other Simon








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Please use https://forum.sdr-radio.com:4499/ when posting questions or problems.


Conrad, PA5Y
 

Hello Simon, I would certainly welcome the ability to calibrate the S-meter on a single tone for each of my transverter set-ups. I use a Perseus, LAN IP and occasionally a Afedri-AFE822x.

Regards

Conrad PA5Y

-----Original Message-----
From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of Simon Brown via groups.io
Sent: 27 January 2022 22:00
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] Console Signal meter reading

DUO is very probably not seeing the same signal level as the 3000.

I do agree that a per-radio signal calibration is needed.

Simon Brown, G4ELI
https://www.sdr-radio.com

-----Original Message-----
From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of Mag loop Simon
Sent: 27 January 2022 20:50
To: main@sdr-radio.groups.io
Subject: Re: [SDR-Radio] Console Signal meter reading

Hi again

Thinking about this..I wonder if the duo with sdrc is “ not seeing “ what the 3000 is..ie duo is “ seeing “ the whole rx spectrum and hence not adjusting its signal level when the phaser is in operation? Sorry for poor explanation, but qro amps, antennas etc are my thing..still much to learn about sdr’s..

I do use antenna out to drive the duo, maybe i should use if out( with suitable if offset settings on sdrc)

Ps the Cornwall 160-40m special amp is coming along nicely..

Re s meter on sdrc vs 3000.. s1 on 3000= s3.5 on sdrc…s5 on 3000 =s4 on sdrc, would be nice to be able to adjust s meter or linearity on spectrum to match.


Thanks Other Simon








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Please use https://forum.sdr-radio.com:4499/ when posting questions or problems.