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µBITX ... AGC or AVC? an interesting article by Curt WB8YYY ... maybe that's the solution to my troubles ! #ubitx #bitx40 #bitx20 #v6 #ubitxv6


 

On the CCARC (Carroll County Amateur Radio Club, Inc.) website I found a very interesting article on automatic gain control that is worth reading!
Without many frills Carol makes us understand that an AGC (automatic gain control) on the IF of the uBITX, due to the nature of the amps used (bidirectional), is very complex to make at this level of the circuit ...
therefore ? ...
Much better and less invasive to act directly on the volume control, implementing a simple but effective automatic volume control (AVC)!
Think man ... think ...
A little less software and a little more electronic experimentation and, with much less effort, very complex problems can be solved!
Think man ... think !
Greetings to all, Loris IW4AJR


LAKSH MUTHU
 

On Wed, Oct 28, 2020 at 04:06 AM, IW4AJR Loris wrote:
On the CCARC (Carroll County Amateur Radio Club, Inc.) website I found a very interesting article on automatic gain control that is worth reading!
Without many frills Carol makes us understand that an AGC (automatic gain control) on the IF of the uBITX, due to the nature of the amps used (bidirectional), is very complex to make at this level of the circuit ...
DEAR LORIS,
     GOOD DAY . Thank you very much for sharing such a valuable information. I will try this with certain modification and post the result.
 Thank you & Regard,
                   73
                     MUTHU
                     VU2LMN


Bob Lunsford
 

This again is offered to show an S-meter circuit borrowed from the transceiver circuit being sold from Indonesia. It is apparently attachable to the volume control and since it's in the receive system, it does not affect the transmit system. It can be "rubbered" here and there since the component values may be the best for this considering that they are what is available to the builders in Indonesia, the FET and transistor can work equally well when using substitutes. Attaching to the high end of the uBITX's volume control and making the 47K variable in the circuit below a set resistor for calibration purposes results in making this a usable circuit. The meter, of course, can be substituted with an LED barcode circuit OR merely provide a source signal for an on-screen display of received signal level. The circuit as shown is relatively simple, however.

Bob — KKR

Inline image


On Wednesday, October 28, 2020, 7:06:58 AM EDT, IW4AJR Loris <lorisbollina@...> wrote:


On the CCARC (Carroll County Amateur Radio Club, Inc.) website I found a very interesting article on automatic gain control that is worth reading!
Without many frills Carol makes us understand that an AGC (automatic gain control) on the IF of the uBITX, due to the nature of the amps used (bidirectional), is very complex to make at this level of the circuit ...
therefore ? ...
Much better and less invasive to act directly on the volume control, implementing a simple but effective automatic volume control (AVC)!
Think man ... think ...
A little less software and a little more electronic experimentation and, with much less effort, very complex problems can be solved!
Think man ... think !
Greetings to all, Loris IW4AJR


 

The circuit you show is not an S-meter, but a VU-meter, it is proportional to the quadratic law of the diodes used, quite similar to the logarithmic law of dBV (mostly referred to an impedance of a few hundred Ω) to l output from circuit BF, responding poorly to RF levels received in the antenna.
An S-meter is a substantially different circuit, it is proportional to precise RF levels (defined by the IARU as in the table below for the HF) at the antenna input and varies in steps of 6 dBm referred to the µV levels on an impedance of 50Ω.
If you want to see a needle that moves it's fine, if you want to give reports that make sense it's useless!
Regards, Loris IW4AJR.


Bob Lunsford
 

You are right, Loris. If meter has a VU readings on meter face and calibrated as such, it would be accurate at one point on the meter ... per the calibration.

The circuit was "borrowed" from the schematic of a radio produced in Indonesia ... and labeled as such. I put it out there for anyone who might want to play with it. Nothing more.

Bob — KK5R

On Wednesday, October 28, 2020, 5:53:31 PM EDT, IW4AJR Loris <lorisbollina@...> wrote:


The circuit you show is not an S-meter, but a VU-meter, it is proportional to the quadratic law of the diodes used, quite similar to the logarithmic law of dBV (mostly referred to an impedance of a few hundred Ω) to l output from circuit BF, responding poorly to RF levels received in the antenna.
An S-meter is a substantially different circuit, it is proportional to precise RF levels (defined by the IARU as in the table below for the HF) at the antenna input and varies in steps of 6 dBm referred to the µV levels on an impedance of 50Ω.
If you want to see a needle that moves it's fine, if you want to give reports that make sense it's useless!
Regards, Loris IW4AJR.


 

Hello Bob
I do not agree with you, a VU-meter will never be able to give a reading that is responsive to µV levels in the antenna, you will never be able to calibrate it correctly over the entire range of signals! if it suits you it will indicate signals from S6 or S7 upwards and in any case certainly not related to the signals in the antenna, I did it with an ILER-40 and I assure you that the withdrawal from the BF is only used to swing a needle on the indicator instrument.
Not for nothing, all the rigs that are respected, take the signal in MF (directly proportional to the signal received in the antenna) and convert it in various ways.
Have you ever observed what the RSSI is out of some MF chips? (eg NE614) ... well, read the data sheet a bit and maybe you will understand what I mean by S-Meter that is useful for something!
Instead of working on various software and having two computers connect to each other and then saying that we did a DX, it would be better if we reviewed what it means is "learning and experimenting with wireless communications" and what data we exchange, don't you think?
Ciao de  IW4AJR Loris


Bob Lunsford
 

Notice that I said that if "calibrated" that it would be accurate at one point, the point where it was calibrated. Therefore, you are right that: "you will never be able to calibrate it correctly over the entire range."

HOWEVER, it would possibly be useful for the engine behind an AGC circuit. Also, who cares (I don't...) if a signal is S7, S9 or 40 over S9. I don't unless someone asks about his/her signal — which is rare. An AGC circuit would be more useful, anyway.  The label for the diagram, that it an S-Meter circuit, was the label from the Indonesian designers. I wonder if you paid notice to this.

Bob — KK5R

On Wednesday, October 28, 2020, 6:56:51 PM EDT, IW4AJR Loris <lorisbollina@...> wrote:


Hello Bob
I do not agree with you, a VU-meter will never be able to give a reading that is responsive to µV levels in the antenna, you will never be able to calibrate it correctly over the entire range of signals! if it suits you it will indicate signals from S6 or S7 upwards and in any case certainly not related to the signals in the antenna, I did it with an ILER-40 and I assure you that the withdrawal from the BF is only used to swing a needle on the indicator instrument.
Not for nothing, all the rigs that are respected, take the signal in MF (directly proportional to the signal received in the antenna) and convert it in various ways.
Have you ever observed what the RSSI is out of some MF chips? (eg NE614) ... well, read the data sheet a bit and maybe you will understand what I mean by S-Meter that is useful for something!
Instead of working on various software and having two computers connect to each other and then saying that we did a DX, it would be better if we reviewed what it means is "learning and experimenting with wireless communications" and what data we exchange, don't you think?
Ciao de  IW4AJR Loris


Dean Souleles
 

The LED solutions always seemed too fussy for me - too component dependent so I took a different approach,  I recently built a new audio module for my not-a-biTx "Furlough 40" SSB transceiver which you can read about and see demonstrations of on the KK4DAS Blog  This circuit includes and audio AGC and relative strength signal sensor (S-Meter).  It would be fairly easy to adapt to the uBitx but I haven't done so.  I haven't done a post of the new audio module yet - but it will go something like this.....

The audio AGC works by sampling the audio output of the LM-386 audio amp (in parallel with the speaker jack) - and feeding it back through a simple diode/capacitor peak detector that drives a BS170 MOSFET which is used as a voltage controlled variable resistor that forms 1/2 of a voltage divider with the other half being the volume pot wiper.  The AGC level is controlled by a 10K trimmer at the output of the LM386.   To adjust it I set the volume pot to about 50% and adjust the trimmer until both weak and strong signal sound good.  It attenuates the very strong signals sufficiently that I no longer jump out of my chair when they come on and I have plenty of volume control for weak signals.  Hint - use a multi-turn trimmer for finer adjustment.  Many thanks to uber-Elmer N6QW, Pete Juliano for this sub-circuit.

The relative signal strength meter works by sampling the output of the audio pre-amp through an op-amp to another diode/capacitor peak detector.  The voltage on the cap is sampled by an Arduino analog input pin and a simple look up table conversion is used to translate sampled voltage into an "S level" on the display.  Attentive readers will recognize the signal strength sensor as the same one the Ian Lee KD8CEC proposed some time ago and is well documented on his blog. So my circuit should work just fine with the KD8CEC firmware if you decide to use it. Just plug the output of the sensor into Arduino pin A7 and you should be golden.  Similar to KD8CE, my sketch uses a look up table of sampled voltage to convert to "S levels". I calibrated it by adjusting the lookup table until the S display matched what I saw on my Kenwood transceiver for the same signal.  Not scientific, nor precise - but it matches my commercial rig and allow me to say "You are S9+20 OM, Fine Business, indeed."  No, it does not measure µV at the antenna and convert it to a log scale - but it's output matches my commercial rig. And it makes a nice bouncy display to impress all of your friends and family. If you follow the reviews in QST you will know that event the "best" commercial rig S-meters vary a lot and don't do much better than this simple circuit, despite the IARU S-level specification.

Have fun - and if anyone decides to build this please drop me a line.  Happy to share the s-meter code from my sketch if anyone is interested.

73,
Dean
KK4DAS


 

On Thu, Oct 29, 2020 at 03:33 AM, Dean Souleles wrote:
The LED solutions ...
Hi Dean
all beautiful and interesting but, if your purpose is also partially commercial, you could save a lot of money on the circuit by using only one chip (eg AD8307 or NE604) taking the RF signal in Medium Frequency and obtaining a reading consistent with the µV in the antenna! !!! look at my post for the old CA3089 (sadly now obsolete) ... replace it with an integrated in production and "that's all folks" ... it's easier than you think!
Let's stop being poor HAM ... electronics, telecommunications and practice can be learned, it is our ITU service, just is necessary a lot of patience, a lot of passion and a great desire to learn !!! we are OM, technicians and experimenters !!! not users of screwdrivers !!!!
The alternative is to lose our privileges and see disappear in the future in "Amateur Radio service"!
Greetings to all ... Loris IW4AJR


Dean Souleles
 

On Thu, Oct 29, 2020 at 05:44 AM, IW4AJR Loris wrote:
AD8307

Hi Loris - 

Let's see - one AD8307 from DigiKey is $14 - my handful of parts is about $3 - so if you want to save "a lot of money" use my design :)!    In fact the entire  Furlough-40 can be built for less than $100 in parts - only about a dozen active parts for an SSB transceiver.

My purpose was not commercial - it was to lean basic electronics and RF theory and practice.  I'm not an EE and had very little electronics experience before building the Furlough-40.   The Furlough-40 is based on a brilliantly simple design by N6QW, Pete Juliano that uses only about a dozen active parts for an exceptional performing  scratch-built  QRP SSB rig.  Pete calls it the SimpleSSB and he presented it to enthusiastic response at the GQRP club conference two months ago.  

At this point in my learning curve an "integrated, that's all folks" approach isn't for me.   built the F-40 from scratch because I didn't learn much from the simple uBitx kit build.   I built it during quarantine (thus the name "Furlough-40") earlier this year and have since worked "around the world" of 5 watts SSB phone and digital.  I could not be more pleased with how well the rig works and what I have learned. There is something to be said for simplicity,. Following Pete's advice I built my own Manhattan style boards, built one module at a time so I could really understand and learn how the circuit works.  So, when I wanted to add AGC and S-Meter I kept in mind the simplicity of design and low cost of components.  (Although adding a transistor and Op-Amp increases the active component count by 20%!) The great thing about this hobby is that there are continual learning opportunities.   And if you don't like it one way - you can have it your way! 


Thanks for the note and 73,

Dean
KK4DAS


Jack, W8TEE
 

Dean:

You're absolutely correct about the work done by Pete. Stick him in a jungle with a penknife and some matches and he'd come out a month later with a 1KW xcvr...he does amazing stuff.

Also, if you want to see some absolutely beautiful Manhattan style construction, look at work by Dave Richards, AA7EE. This is a series of photos of one of his builds:


There's a lot to be learned from both guys!

Jack, W8TEE

On Thursday, October 29, 2020, 8:34:04 AM EDT, Dean Souleles <dsouleles@...> wrote:


On Thu, Oct 29, 2020 at 05:44 AM, IW4AJR Loris wrote:
AD8307

Hi Loris - 

Let's see - one AD8307 from DigiKey is $14 - my handful of parts is about $3 - so if you want to save "a lot of money" use my design :)!    In fact the entire  Furlough-40 can be built for less than $100 in parts - only about a dozen active parts for an SSB transceiver.

My purpose was not commercial - it was to lean basic electronics and RF theory and practice.  I'm not an EE and had very little electronics experience before building the Furlough-40.   The Furlough-40 is based on a brilliantly simple design by N6QW, Pete Juliano that uses only about a dozen active parts for an exceptional performing  scratch-built  QRP SSB rig.  Pete calls it the SimpleSSB and he presented it to enthusiastic response at the GQRP club conference two months ago.  

At this point in my learning curve an "integrated, that's all folks" approach isn't for me.   built the F-40 from scratch because I didn't learn much from the simple uBitx kit build.   I built it during quarantine (thus the name "Furlough-40") earlier this year and have since worked "around the world" of 5 watts SSB phone and digital.  I could not be more pleased with how well the rig works and what I have learned. There is something to be said for simplicity,. Following Pete's advice I built my own Manhattan style boards, built one module at a time so I could really understand and learn how the circuit works.  So, when I wanted to add AGC and S-Meter I kept in mind the simplicity of design and low cost of components.  (Although adding a transistor and Op-Amp increases the active component count by 20%!) The great thing about this hobby is that there are continual learning opportunities.   And if you don't like it one way - you can have it your way! 


Thanks for the note and 73,

Dean
KK4DAS


--
Jack, W8TEE


Gerard
 

hello,
I will do some tests later this that: Noise reducteur and some AGC
noise reducrer
https://www.petervis.com/electronics%20guides/dynamic%20noise%20reduction/dynamic%20noise%20reduction.html
+ Bargraph with leds  kit less 2 euros. See A.....o.
lm 1894 pcb board less 11€  see E..y.
if you what DIY with transistors
https://www.abcelectronique.com/annuaire/montages/cache/787/reducteur-dynamique-de-bruit-le-dnl.html

for AGC see here:
https://groups.io/g/BITX20/topic/4103085#8877

try to adapt that, I think there have already been topics on this 
https://www.amazon.fr/gp/product/B0894PNWTZ/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1
lees 5€
orders placed

cdt


Jerry Gaffke
 


If you buy a bunch, one AD8307 is under $0.50
https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313&_nkw=20pcs+ad8307&_sacat=0

Not clear if those are factory seconds, clones, or got left over at the end of reels.
But as of three years ago, those ebay AD8307's were deemed good enough:
    http://ka7exm.net/emrfd/Messages/thread_14309.htm

It's a wonderful part, worth having $10 worth filed away if you build stuff.

Not that I would bother with an AD8307 on a simple transceiver for an S-Meter.
Even if properly calibrated from uV at the antenna port, it doesn't account for
your antenna system or local geography, and so is not that meaningful for the
station at the far end.
May as well just pick a number somewhere between 9 and 1,
9 if it's the among the strongest signals, 1 if you can't hear it.
Or if you want to promote good feelings, just give everybody you can copy a 9.
There are plenty of other design issues to obsess with first.

But an AD8307 as an RF probe can be extremely valuable.
Buy an AD8307 module if you don't want to spend a day fiddling with tiny parts.
Even the modules are well under $14, including shipping.

Anyways, thanks for the pointer to Pete's 40m SSB transcever.
Is there a complete schematic of it available somewhere?
There's a bunch of links at the bottom of that webpage, but nothing complete and consistent.

For example, these bidi amps are interesting, different from *Bitx* and W7ZOI designs:
    http://www.n6qw.com/Images/Simple%20SSB/Bi%20Lateral%20amp.jpg
and totally different than what's presented in this discussion:
    http://www.n6qw.com/Bi-directional%20Amp%20SSSB.htm
No mention of prior art, or the pros and cons of his somewhat different implementation.

Jerry, KE7ER


On Thu, Oct 29, 2020 at 05:33 AM, Dean Souleles wrote:
Let's see - one AD8307 from DigiKey is $14


 

HELLO TO ALL !
First of all, we all went a bit off topic!
The question was about how to somehow govern the BF level without becoming deaf to any strong signal interfering in the QSO!
The origin was a beautiful article by WB8YYY explaining why using an ALC in the µBITX circuit is less expensive, more efficient and easier to plug into the transceiver than any of the various "AGCs" on the KIT market.
For the S-meter (which is just an extra candy when you work in the mountains) I am attaching a simple simple schematic with a NE604 (now available as SA604 for no more than 3/4 $ from both DIGIKEY and MOUSER) that I used  in the ILER-40.
Speaking of DIY, have you tried to build a simple but efficient spectrum analyzer? ... years ago I tried my hand at a project that only reached 300MHZ, that's where I discovered how important it is to try to get a linear dB detector! also a series of two old QST articles covered the subject and the NE/SA604 chip was already the best in cost and benefit back then!
For the rest of the speeches it seems to me that lately the HAM spirit has somewhat decayed, but it is only a little over forty years that I have been desperately trying to do the OM trying to adapt and align myself to the teachings of W1AW ... unfortunately I have my limits and I hope to become a little better and also include the "new" HAMs ...
Hello everybody ! ... discussion over!
73 de IW4AJR Loris


Jerry Gaffke
 

It's fine to go off topic, that's what a discussion does.

Anyways, the ND6T AGC circuit is about as simple as that from WB8YYY,
and doesn't depend on luck to find the right LED+LDR. 
Unfortunate that WB8YYY couldn't give specific part numbers.
I'd rather have a pot to set the decay time on an AGC circuit
than depend on the characteristics of an LDR (a light dependent resistor).
You may want a different setting for CW than SSB, 
or run into an operator who pauses between sentences.

While ND6T's circuit detects the signal level from the audio exactly as WB8YYY's does,
it attenuates the signal back at RF, not at audio.
Attenuating at RF prevents overloading the two IF amps,
and especially the audio pre-amp at Q70 which saturates first by a wide margin.
Several thousand of these were kitted up a couple years ago by Kees, no longer available.

I think clipping with a couple diodes to prevent ear damage is sufficient on a simple rig,
that and an RF gain pot that you then turn down till the distortion is gone.


Regarding ALC vs AGC, we don't all speak the same language.

Historically, feedback in amplifiers to maintain a somewhat constant output signal
was called ALC (automatic level control).  We're talking tube radios from the 50's.
A google search for ALC finds that it is often a synonym for AGC. but ALC is now
more often used to describe a circuit in transmitters that maintain a somewhat
constant RF output power regardless of audio level going in.

Apparently in a few companies or groups or forums or regions, ALC might refer to
something that adjusts gain in an audio stage instead of an RF or IF stage.
That seems an arbitrary designation, what do we call gain control going into
an ADC that accepts analog signals between zero and 10mhz?

My question is, what is a "BF level"?

Jerry, KE7ER



On Thu, Oct 29, 2020 at 08:08 AM, IW4AJR Loris wrote:
First of all, we all went a bit off topic!
The question was about how to somehow govern the BF level without becoming deaf to any strong signal interfering in the QSO! 
The origin was a beautiful article by WB8YYY explaining why using an ALC in the µBITX circuit is less expensive, more efficient and easier to plug into the transceiver than any of the various "AGCs" on the KIT market.


Vince Vielhaber
 

The S meter isn't intended for the guy at the other end. Band conditions and a whole host of other things will affect the signal strength. The S meter is for the operator, it gives him/her something to compare to other signals. Sharing that reading with the guy on the other end is only useful to him if the two (or more) talk on a regular basis or are making a comparison. "The band really sucks tonite, you're only an S7 where you're usually 20 over". "What's better, antenna A or antenna B?"

Vince - K8ZW.

On 10/29/2020 10:59 AM, Jerry Gaffke via groups.io wrote:

Not that I would bother with an AD8307 on a simple transceiver for an
S-Meter.
Even if properly calibrated from uV at the antenna port, it doesn't
account for
your antenna system or local geography, and so is not that meaningful
for the
station at the far end.
May as well just pick a number somewhere between 9 and 1,
9 if it's the among the strongest signals, 1 if you can't hear it.
Or if you want to promote good feelings, just give everybody you can
copy a 9.
There are plenty of other design issues to obsess with first.


Jerry Gaffke
 

A slight correction, or perhaps amplification:

> Historically, feedback in amplifiers to maintain a somewhat constant output signal
> was called ALC (automatic level control)
> A google search for ALC finds that it is often a synonym for AGC.

AVC (automatic volume control) is another term for this concept,
and that is pretty much synonomous with AGC in my book.
  https://groups.io/g/BITX20/message/68083


ALC is more typically used with regard to transmitters,
though I do seem to recall the term being used on receivers.

There's also "automatic sound control" out there.

What's the correct usage?
I don't care.
It's all auto gain control to me. 

Which doesn't quite scan, but could be a song by Billy Joel.

Jerry, KE7ER


On Thu, Oct 29, 2020 at 09:03 AM, Jerry Gaffke wrote:
Regarding ALC vs AGC, we don't all speak the same language.

Historically, feedback in amplifiers to maintain a somewhat constant output signal
was called ALC (automatic level control).  We're talking tube radios from the 50's.
A google search for ALC finds that it is often a synonym for AGC. but ALC is now
more often used to describe a circuit in transmitters that maintain a somewhat
constant RF output power regardless of audio level going in.

Apparently in a few companies or groups or forums or regions, ALC might refer to
something that adjusts gain in an audio stage instead of an RF or IF stage.
That seems an arbitrary designation, what do we call gain control going into
an ADC that accepts analog signals between zero and 10mhz?


Jack, W8TEE
 

Sometimes S values do suggest "skip" zones when I listen, telling me which section of the country might more likely respond to a QRP-level CQ.

Jack, W8TEE

On Thursday, October 29, 2020, 1:13:29 PM EDT, Vince Vielhaber <vev@...> wrote:



The S meter isn't intended for the guy at the other end.  Band
conditions and a whole host of other things will affect the signal
strength.  The S meter is for the operator, it gives him/her something
to compare to other signals.  Sharing that reading with the guy on the
other end is only useful to him if the two (or more) talk on a regular
basis or are making a comparison.  "The band really sucks tonite, you're
only an S7 where you're usually 20 over".  "What's better, antenna A or
antenna B?"

Vince - K8ZW.


On 10/29/2020 10:59 AM, Jerry Gaffke via groups.io wrote:
>
> Not that I would bother with an AD8307 on a simple transceiver for an
> S-Meter.
> Even if properly calibrated from uV at the antenna port, it doesn't
> account for
> your antenna system or local geography, and so is not that meaningful
> for the
> station at the far end.
> May as well just pick a number somewhere between 9 and 1,
> 9 if it's the among the strongest signals, 1 if you can't hear it.
> Or if you want to promote good feelings, just give everybody you can
> copy a 9.
> There are plenty of other design issues to obsess with first.

--
  K8ZW  http://www.metalworkingfun.com   http://www.hamradio.fun






--
Jack, W8TEE


 

On Thu, Oct 29, 2020 at 05:03 PM, Jerry Gaffke wrote:
It's fine to go off topic, that's what a discussion does.

...

Hi Jerry,
Pay attention, the title does not mention "ALC" but "AVC" Automatic Volume Control, just to clarify.
In reality, the three definitions represent three different methods of regulating a signal, no matter what frequency they are dedicated to, while the regulation mode may be different.
Since gain is the ratio between the level of the output signal and the level of the input signal of a circuit, the first difference is in how you act on this ratio.
An AGC circuit intervenes on the "Gain" of a circuit called amplifier, acting in a negative way on the amplification of the circuit itself, modifying its polarization and consequently the amplification efficiency (this is the way generally used to limit small signal amplifiers).
The ALC generally, on the other hand, intervenes directly on the amplifier input signal (e.g. dynamics compressor with input attenuation resistance) thus acting indirectly on the "Gain" forcing an amplifier with more or less constant gain to amplify smaller signals and therefore output a limited signal.
The AVC can be classified as an ALC, the difference in the name derives from the circuits used for sound reproduction (in which there is an easily accessible volume control) to allow to obtain an "expansion" effect of the compressed signal recorded and played back.
Just to give you a practical example, go and see on the WEB some "old" expander circuit from the 70s / 80s, you will often find a LED / LDR combination that achieves the desired effect.
In amplifiers for large signals (e.g. linear transmission) the use of AGC or ALC is practically indifferent, the latter is often used only because it is easier to make and much cheaper (try to vary the polarization of a final valve and you will notice the problem).
Having said this, we can say that practically 90% of the KITs for processing the signal in a receiver (obviously in the QRP transceivers sold in KIT) are ALCs, i.e. they act as "attenuators" of the input signal to the receiving chain, they have little to do with the AGC circuits of their big brothers.
The advantage of the circuit proposed by WB8YYY lies in the fact that it only controls the volume level in low frequency, without "attenuating" anything in reception and leaving unchanged the excellent original characteristics of the µBITX receiver.
Just to clarify, I found an attenuation of all received signals of at least 10/20 dBµ (from 2 to 3 points S less in reception), inserting in RX a well-known "AGC" sold as an additional module to the µBITX.
Greetings IW4AJR Loris


Dean Souleles
 

Hi Jerry,

The SimpleSSB is a modular rig, so by design there is no overall single schematic.  The IF module that you linked to uses Pllessy amplifier circuits described in EMRFD.  Pete gives the details on his web site.   The modules are the following:

1. Audio amp 
2  Mic amp
3. IF module with filter - relay steered bi-directional IF
4. Arduino and SI-5351 
5. Band pass filter
6. Bi directional amp - RF amp on receive, Tx pre-driver on transmit
7. Tx Driver amp
8. iRF-510 final

Each module is fully described on Pete’s web site.  I built it over about three months at the beginning of the year.  The modular approach makes it straightforward to swap out different designs.  It has been a great experimenters learning platform for me.

73,
Dean
KK4DAS