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I have set up the S Meter in the CEC firmware using the s meter output from the AGC board.? I think I have the calibration values to where it reads to my satisfaction other than it appears to max out at S9 regardless of the signal strength.? I strong signal gives an S9 while a super strong signal also gives an S9.? Is this normal or do I need to keep fiddling with the calibration numbers?
73,
Justin B.
KI5GKD
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When I was using the S-meter provided in the main CEC sketch (not the outboard processor and -s version) I found the original values for calibration in the Memory Manager were pretty far off. They gave an indication, but not 6db/S unit and not really close to another rig that has very good S-meter calibration. I modified the numbers such that each reading was about 2x the voltage of the other (hence 4X power or 6db) and set the values such that they tracked a commercial radio pretty well. So, yes you can fiddle a bit and certainly get it above S9, but the scale isn't actually very linear and the display isn't that clear with only 8 divisions, so it isn't something to get too excited about. Here are the settings I used:  =Vic=
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Vic - I'll plug these values in and see what happens.? Not really that big of a deal but more curiosity as to if this was the "nature of the beast."
73,
Justin B.
KI5GKD
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Hi,
I calibrated it, played with the values and have same challenge - Meter will not go over 9.
Not sure if it is the sw or the Nextion file.
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Zvika?
4Z1ZV
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Vic - I have the same results with your cal values as I did mine - they were pretty close except for last two.? I guess maybe this is what we have unless a different sensor is used like Ian's sensor on his page.? At least I know it's not just me!
Zvika - not sure what to do at this point other than changing to Ian's LM358 based sensor or going to a second Nano.? I may just live with it!
73,
Justin B.
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Justin, If you have a Nextion display, have you tried monitoring the ADC as Ian (KD8CEC) does in this blog: It might give you some more information to figure out if it is a sensor or software issue. I did the LM358 sensor modification for a friend on a v6 ?BITX.? Since all of the audio signals and controls are on the mainboard, the audio header is open.? I used that to mount a small board with the LM358 opamp as in this picture:  Just a suggestion and some more information. 73 Evan AC9TU
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Just a thought. The audio level is tapped off from the output of the agc board. Meaning that the agc will be attuniating a signal over S9 therefore it tops off at S9. If you want to read the real signal strength then you should tap the signal off at the input to the agc board. I have not yet experiment with this idee yet. J van der Merwe
Justin,
If you have a Nextion display, have you tried monitoring the ADC as Ian (KD8CEC) does in this blog:
It might give you some more information to figure out if it is a sensor or software issue.
I did the LM358 sensor modification for a friend on a v6 ?BITX.? Since all of the audio signals and controls are on the mainboard, the audio header is open.? I used that to mount a small board with the LM358 opamp as in this picture:
Just a suggestion and some more information.
73
Evan
AC9TU
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J,
What you are measuring is the voltage needed to bias the RF input MOSFETs to keep a given signal at the audio volume control.? This will vary with signal strength so that an S9+10 signal should take a higher AGC voltage to keep a given signal strength at the volume control.? It is measuring the feedback signal level, not the actual input signal.? This is how most level meters work as far as I know.
My testing of the AGC with both the Kit-Projects and the LM358 as input says that the scaling is what will drive the signal level.? The 2 setting for the low and the 200 for the highest seems too large of a spread.? I believe that it was more like 10 to 120 as the max in the implementation that I did.? Again, the ADC monitoring function of the Nextion display is the best way to verify what is going on for a specific implementation.? Just be sure to take into account the scaling that the software is doing (divide by 4).
73
Evan
AC9TU??
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You may have something there, Kobus. I wondered if the AGC operating back in the IF stages would limit things such that an S-meter reading audio level would always drop back to something lower, especially on strong signals. In my case I used an audio AGC that followed the high-side volume control tap and it and the S-meter read the same voltage such that the input voltage is not reduced by the AGC action. I bet that's it!
=Vic=
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All the AGC schemes for the uBitx I've seen thus far have audio derived detection of the signal level.
to create a control voltage, that control voltage is then used to attenuate the signal at some point prior to detection.
Measuring the control voltage tells us the signal strength.
Scaling that measurement to accurately show 6dB steps per S-unit across a large range
is generally more bother than it's worth.? Signal strength on any meter
will also be dependent on things like your antenna design and local geography.
S-meters usually aren't very accurate, even on commercial gear.
An accurately calibrated S-meter might be used as a tool for evaluating antennas.
But most of us just use S-meter readings when reporting the other guy's signal strength.
For that, you may as well just pick a number based on what it sounds like.
My advice:? Pick high, let the other guy feel good about his signal.
Jerry, KE7ER
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On Fri, Apr 2, 2021 at 02:27 AM, Vic WA4THR wrote:
You may have something there, Kobus. I wondered if the AGC operating back in the IF stages would limit things such that an S-meter reading audio level would always drop back to something lower, especially on strong signals. In my case I used an audio AGC that followed the high-side volume control tap and it and the S-meter read the same voltage such that the input voltage is not reduced by the AGC action. I bet that's it!
=Vic=
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I ordered some LM358 chips so we'll see what happens.
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Huh. ?Guess you missed the JackAl board and the other Hycas circuits discussed here. ?In all fairness most people only need an automatic volume control because they will not discriminate between the radios rf chain overloading versus distortion in the audio amp from over driving it. ?So using the simpler is better theory, just an audio driven AGC is best for them. ?
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On Apr 2, 2021, at 9:31 AM, Jerry Gaffke via groups.io <jgaffke@...> wrote:
?All the AGC schemes for the uBitx I've seen thus far have audio derived detection of the signal level. to create a control voltage, that control voltage is then used to attenuate the signal at some point prior to detection. Measuring the control voltage tells us the signal strength. Scaling that measurement to accurately show 6dB steps per S-unit across a large range is generally more bother than it's worth.? Signal strength on any meter will also be dependent on things like your antenna design and local geography. S-meters usually aren't very accurate, even on commercial gear. An accurately calibrated S-meter might be used as a tool for evaluating antennas. But most of us just use S-meter readings when reporting the other guy's signal strength. For that, you may as well just pick a number based on what it sounds like. My advice:? Pick high, let the other guy feel good about his signal. Jerry, KE7ER On Fri, Apr 2, 2021 at 02:27 AM, Vic WA4THR wrote:
You may have something there, Kobus. I wondered if the AGC operating back in the IF stages would limit things such that an S-meter reading audio level would always drop back to something lower, especially on strong signals. In my case I used an audio AGC that followed the high-side volume control tap and it and the S-meter read the same voltage such that the input voltage is not reduced by the AGC action. I bet that's it!
=Vic=
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¡_. _._
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The HyCas is a fine IF amp, but I wouldn't consider using it on a uBitx.
The primary charm of the uBitx is simplicity.
Patching in a HyCas would double the parts count of the radio.
If I was building a no-compromise radio, the HyCas may well be in it.
On the uBitx, it seems absurd.
Didn't realize the JackAl board included the HyCas IF strip for use in the uBitx.
Jerry, KE7ER
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On Fri, Apr 2, 2021 at 11:46 PM, MadRadioModder wrote:
Huh. ?Guess you missed the JackAl board and the other Hycas circuits discussed here. ?In all fairness most people only need an automatic volume control because they will not discriminate between the radios rf chain overloading versus distortion in the audio amp from over driving it. ?So using the simpler is better theory, just an audio driven AGC is best for them. ?
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Poking through the forum, the JackAl board gets high marks.
I had been ignoring it mostly because I prefer the simplicity of a stock uBitx with the 16x2 display.
I'm not really keen on the TFT screen of the v6 either.
Likely a minority opinion here.
Jerry, KE7ER
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On Sat, Apr 3, 2021 at 06:34 AM, Jerry Gaffke wrote:
The HyCas is a fine IF amp, but I wouldn't consider using it on a uBitx.
The primary charm of the uBitx is simplicity.
Patching in a HyCas would double the parts count of the radio.
If I was building a no-compromise radio, the HyCas may well be in it.
On the uBitx, it seems absurd.
Didn't realize the JackAl board included the HyCas IF strip for use in the uBitx.
Jerry, KE7ER
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I¡¯m sure an audio AGC and a 16x2 display works fine for you. ?The 510¡¯s in the output too. ?Its ultimate in simplicity. ?For me, i prefer a little technology and am not so concerned about hobo costs. ?Im also in an area where the IF chain can easily overload from all of the radio activity so a decent AGC is key to making it useful. Ive even considered using a preselector (which i have ?incorporated on other radios ive built).?
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On Apr 3, 2021, at 8:45 AM, Jerry Gaffke via groups.io <jgaffke@...> wrote:
?Poking through the forum, the JackAl board gets high marks. I had been ignoring it mostly because I prefer the simplicity of a stock uBitx with the 16x2 display. I'm not really keen on the TFT screen of the v6 either. Likely a minority opinion here. Jerry, KE7ER On Sat, Apr 3, 2021 at 06:34 AM, Jerry Gaffke wrote:
The HyCas is a fine IF amp, but I wouldn't consider using it on a uBitx.
The primary charm of the uBitx is simplicity.
Patching in a HyCas would double the parts count of the radio.
If I was building a no-compromise radio, the HyCas may well be in it.
On the uBitx, it seems absurd.
Didn't realize the JackAl board included the HyCas IF strip for use in the uBitx.
Jerry, KE7ER
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A fully audio AGC scheme (with attenuation also in audio) allows strong signals to
overload the audio preamp at Q70, so not ideal for some environments.
I think the ND6T AGC scheme is a good choice for the uBitx.
It uses simple audio detection, but attenuation occurs at the RF input.
The attack would be delayed more than the HyCas AGC, so some pops would
get through.??I am curious what other advantages the HyCas might have.
The HyCas must detect signal levels after the crystal filter without seeing the BFO,
that is inherently difficult to do well.
The front end of the uBitx is wide open till you get to the 45mhz crystal filter,
an optional preselector strikes me as an very good idea.
Jerry, KE7ER
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On Sat, Apr 3, 2021 at 07:32 AM, MadRadioModder wrote:
I¡¯m sure an audio AGC and a 16x2 display works fine for you. ?The 510¡¯s in the output too. ?Its ultimate in simplicity. ?For me, i prefer a little technology and am not so concerned about hobo costs. ?Im also in an area where the IF chain can easily overload from all of the radio activity so a decent AGC is key to making it useful. Ive even considered using a preselector (which i have ?incorporated on other radios ive built).?
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Vic WA4THR
Zvi Segal
Kobus ZS6CHK
MadRadioModder