Hi Raj,
S9 = 50 uV across 50 ohms. In the wild we rarely (if ever) have 50 Ohms at the antenna terminals. So there goes the baby along with the bath water. I do not know how to have a QSO a while the radio is connected to a set of lab equipment in a lab. I have to operate in the 'wild'.
73,
Bill KU8H
bark less - wag more
toggle quoted message
Show quoted text
On 10/29/20 7:48 AM, Raj vu2zap wrote: On S meter readings on 80's rigs:
I would generalize from my years of fixing and aligning rigs that S9 = 50uV at the antenna.
S8 = -6db of 50uV and S7 = -12db of 50 uV... below S7 the readings are approx.
S9+20/40/60 are usually correct although some rigs were slightly different at +60.
50uV is my first check for S9, if not then a retune and alignment would follow.
Raj
At 29/10/2020, you wrote:
Hi Bob,
The 'S' value in the RST does have some value but an estimate is good enough (and really all we can do). It is hard enough to pin down a number in a well equipped lab. A radio operating 'in the wild' (meaning outside of lab conditions) is just too uncertain. It is not a *hard* value. "Ten feet" is a good example of a hard value. There are no conditions where a ten foot pole can fit in a nine foot space.
I have pulled the cans off or partially off my ears for the same reasons as you and those old people (whoever they are). How do you do that with "earbuds"? A two-diode limiter works with those too. Use the volume control to keep out of the distortion levels. That's why it is called a volume *control*. Or just let your ears bleed. It can literally happen.
73,
Bill KU8H
bark less - wag more
On 10/28/20 5:40 PM, Bob Lunsford via groups.io wrote:
Everything is relative. One's S-meter reading depends on the receiver AND the antenna. One too many variables. A Volume Unit reading is based on voltage across a standard resister value. The VU reading may be more accurate but still has too many variables.
Personally, I do not need an S-meter and unless someone asks me, I do not give a Signal Strength report. It means little to me when we are talking about readability.
I can come up with a circuit that may warm someone's heart but my V6 does not need an S-meter. HOWEVER, the same circuit can be an operator for the AGC circuit. Old time operators used to pull the "cans" off the ears and put them over the temple to either adjust the audio level or keep excessive volume from waking them up. Been there, done that...
Bob ¡ª KK5R
|
Hi Bob,
It's back to that volume control again. Earbuds allow me to run at a much lower volume. A strict interpretation of what you said about damage from using earbuds means that earbuds would damage our hearing even if they were never plugged in and merely in our ears. I will always challenge that. And my earbuds do not 'seal' my ear canal. They are not the expensive kind so maybe that explains the lack of a seal. On the other hand, my cans do seal my entire ear including my ear canal. Except for the cheapest ones I have.
73,
Bill KU8H
bark less - wag more
toggle quoted message
Show quoted text
On 10/29/20 7:10 AM, Bob Lunsford via groups.io wrote: Bill, first of all, earbuds are a no-no. They damage the ears. Any device that is so perfect a seal to outside sounds damages the ears. First to go are the high frequencies thus the need for "old" hams to turn up the treble and turn down the bass.
I use over-the-ear earphones. My favorite is one I got from Radio Shack about 1970. The earpads wore out and were replaced with foam rubber squares that I found that had a 3/4-in round hole in the center. Problem is it has a 1/4-in plug so use it on my FT-890 but use other of like manufacture for other radios.
The RST for one person is not necessarily going to be the same number for another person since as taste is in a person's mouth, the hearing is in each individual's ears and is not normally a group thing. As different people see a diamond in different shades of color, different people hear a concert with varying shades of meaning.
I go the contest route: If a guy has a good sounding, loud enough signal, he gets a 5X9 but if it's in the mud, it then gets a 5X5.
Bob ¡ª KK5R
On Thursday, October 29, 2020, 6:52:14 AM EDT, Bill Cromwell <wrcromwell@...> wrote:
Hi Bob,
The 'S' value in the RST does have some value but an estimate is good
enough (and really all we can do). It is hard enough to pin down a
number in a well equipped lab. A radio operating 'in the wild' (meaning
outside of lab conditions) is just too uncertain. It is not a *hard*
value. "Ten feet" is a good example of a hard value. There are no
conditions where a ten foot pole can fit in a nine foot space.
I have pulled the cans off or partially off my ears for the same reasons
as you and those old people (whoever they are). How do you do that with
"earbuds"? A two-diode limiter works with those too. Use the volume
control to keep out of the distortion levels. That's why it is called a
volume *control*. Or just let your ears bleed. It can literally happen.
73,
Bill? KU8H
bark less - wag more
On 10/28/20 5:40 PM, Bob Lunsford via groups.io wrote:
> Everything is relative. One's S-meter reading depends on the receiver
> AND the antenna. One too many variables. A Volume Unit reading is based
> on voltage across a standard resister value. The VU reading may be more
> accurate but still has too many variables.
>
> Personally, I do not need an S-meter and unless someone asks me, I do
> not give a Signal Strength report. It means little to me when we are
> talking about readability.
>
> I can come up with a circuit that may warm someone's heart but my V6
> does not need an S-meter. HOWEVER, the same circuit can be an operator
> for the AGC circuit. Old time operators used to pull the "cans" off the
> ears and put them over the temple to either adjust the audio level or
> keep excessive volume from waking them up. Been there, done that...
>
> Bob ¡ª KK5R
|
Re: A strange thing about calibration!!
hello bob, thank you for your answer, but this does not solve my problem and I do not have an explanation on these 2 parameters in the ubitx manager. 
|
hello, I will do some tests later this that: Noise reducteur and some AGC noise reducrer + 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 for AGC see here: /g/BITX20/topic/4103085#8877try to adapt that,?I think there have already been topics on this? lees 5€ orders placed cdt
|
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 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
|
Re: A strange thing about calibration!!
I was not talking about "calibrating" the V6, I call that something else. I was talking about "calibration" of the S-Meter/VU Meter at one point (volume level) and not assuming that it it correct for other volume levels.
I used to have a job at a calibration unit for the government and one item I calibrated was an audiometer. I used the Technical Manual for this and it was to check it at different levels represented by numbers on the unit's meter. Modern technology has not changed so much but military nomenclature and standards do not without being intensely documented. Therefore, proceed.
Bob ¡ª KK5R
On Thursday, October 29, 2020, 8:03:41 AM EDT, Gerard <kabupos@...> wrote:
Curt,
I don¡¯t think you understood what I meant.
Calibration is one thing, setting the BFO is another.
what I mean, when you do.calibration, you look for the zero beat.Then you validate
and have to reboot the Ubitx for this .
And that¡¯s where it¡¯s weird, your BF signal is good to the ear, but in fact it is modulated at the frequency of 16.6 Khtz. (60 micro second of pulsation). You don¡¯t hear it, but that¡¯s the reality. You can try to calibrate in all directions, you¡¯ll always get that result.
Plug an oscilloscope into the speaker and you¡¯ll see.
BFO setting has nothing to do with this.
Now, I have another question, does anyone know these settings
and their implications.
cdt
|
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 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
|
Re: A strange thing about calibration!!
Curt,
I don¡¯t think you understood what I meant.
Calibration is one thing, setting the BFO is another.
what I mean, when you do.calibration, you look for the zero beat.Then you validate
and have to reboot the Ubitx for this .
And that¡¯s where it¡¯s weird, your BF signal is good to the ear, but in fact it is modulated at the frequency of 16.6 Khtz. (60 micro second of pulsation). You don¡¯t hear it, but that¡¯s the reality. You can try to calibrate in all directions, you¡¯ll always get that result.
Plug an oscilloscope into the speaker and you¡¯ll see.
BFO setting has nothing to do with this.
Now, I have another question, does anyone know these settings
and their implications.
cdt
|
On S meter readings on 80's rigs:
I would generalize from my years of fixing and aligning rigs that S9 = 50uV at the antenna.
S8 = -6db of 50uV and S7 = -12db of 50 uV... below S7 the readings are approx.
S9+20/40/60 are usually correct although some rigs were slightly different at +60.
50uV is my first check for S9, if not then a retune and alignment would follow.
Raj
toggle quoted message
Show quoted text
At 29/10/2020, you wrote: Hi Bob,
The 'S' value in the RST does have some value but an estimate is good enough (and really all we can do). It is hard enough to pin down a number in a well equipped lab. A radio operating 'in the wild' (meaning outside of lab conditions) is just too uncertain. It is not a *hard* value. "Ten feet" is a good example of a hard value. There are no conditions where a ten foot pole can fit in a nine foot space.
I have pulled the cans off or partially off my ears for the same reasons as you and those old people (whoever they are). How do you do that with "earbuds"? A two-diode limiter works with those too. Use the volume control to keep out of the distortion levels. That's why it is called a volume *control*. Or just let your ears bleed. It can literally happen.
73,
Bill KU8H
bark less - wag more
On 10/28/20 5:40 PM, Bob Lunsford via groups.io wrote:
Everything is relative. One's S-meter reading depends on the receiver AND the antenna. One too many variables. A Volume Unit reading is based on voltage across a standard resister value. The VU reading may be more accurate but still has too many variables.
Personally, I do not need an S-meter and unless someone asks me, I do not give a Signal Strength report. It means little to me when we are talking about readability.
I can come up with a circuit that may warm someone's heart but my V6 does not need an S-meter. HOWEVER, the same circuit can be an operator for the AGC circuit. Old time operators used to pull the "cans" off the ears and put them over the temple to either adjust the audio level or keep excessive volume from waking them up. Been there, done that...
Bob ¡ª KK5R
|
Bill, first of all, earbuds are a no-no. They damage the ears. Any device that is so perfect a seal to outside sounds damages the ears. First to go are the high frequencies thus the need for "old" hams to turn up the treble and turn down the bass.
I use over-the-ear earphones. My favorite is one I got from Radio Shack about 1970. The earpads wore out and were replaced with foam rubber squares that I found that had a 3/4-in round hole in the center. Problem is it has a 1/4-in plug so use it on my FT-890 but use other of like manufacture for other radios.
The RST for one person is not necessarily going to be the same number for another person since as taste is in a person's mouth, the hearing is in each individual's ears and is not normally a group thing. As different people see a diamond in different shades of color, different people hear a concert with varying shades of meaning.
I go the contest route: If a guy has a good sounding, loud enough signal, he gets a 5X9 but if it's in the mud, it then gets a 5X5.
Bob ¡ª KK5R
On Thursday, October 29, 2020, 6:52:14 AM EDT, Bill Cromwell <wrcromwell@...> wrote:
Hi Bob,
The 'S' value in the RST does have some value but an estimate is good
enough (and really all we can do). It is hard enough to pin down a
number in a well equipped lab. A radio operating 'in the wild' (meaning
outside of lab conditions) is just too uncertain. It is not a *hard*
value. "Ten feet" is a good example of a hard value. There are no
conditions where a ten foot pole can fit in a nine foot space.
I have pulled the cans off or partially off my ears for the same reasons
as you and those old people (whoever they are). How do you do that with
"earbuds"? A two-diode limiter works with those too. Use the volume
control to keep out of the distortion levels. That's why it is called a
volume *control*. Or just let your ears bleed. It can literally happen.
73,
Bill? KU8H
bark less - wag more
On 10/28/20 5:40 PM, Bob Lunsford via groups.io wrote:
> Everything is relative. One's S-meter reading depends on the receiver
> AND the antenna. One too many variables. A Volume Unit reading is based
> on voltage across a standard resister value. The VU reading may be more
> accurate but still has too many variables.
>
> Personally, I do not need an S-meter and unless someone asks me, I do
> not give a Signal Strength report. It means little to me when we are
> talking about readability.
>
> I can come up with a circuit that may warm someone's heart but my V6
> does not need an S-meter. HOWEVER, the same circuit can be an operator
> for the AGC circuit. Old time operators used to pull the "cans" off the
> ears and put them over the temple to either adjust the audio level or
> keep excessive volume from waking them up. Been there, done that...
>
> Bob ¡ª KK5R
|
Hi Bob,
The 'S' value in the RST does have some value but an estimate is good enough (and really all we can do). It is hard enough to pin down a number in a well equipped lab. A radio operating 'in the wild' (meaning outside of lab conditions) is just too uncertain. It is not a *hard* value. "Ten feet" is a good example of a hard value. There are no conditions where a ten foot pole can fit in a nine foot space.
I have pulled the cans off or partially off my ears for the same reasons as you and those old people (whoever they are). How do you do that with "earbuds"? A two-diode limiter works with those too. Use the volume control to keep out of the distortion levels. That's why it is called a volume *control*. Or just let your ears bleed. It can literally happen.
73,
Bill KU8H
bark less - wag more
toggle quoted message
Show quoted text
On 10/28/20 5:40 PM, Bob Lunsford via groups.io wrote: Everything is relative. One's S-meter reading depends on the receiver AND the antenna. One too many variables. A Volume Unit reading is based on voltage across a standard resister value. The VU reading may be more accurate but still has too many variables.
Personally, I do not need an S-meter and unless someone asks me, I do not give a Signal Strength report. It means little to me when we are talking about readability.
I can come up with a circuit that may warm someone's heart but my V6 does not need an S-meter. HOWEVER, the same circuit can be an operator for the AGC circuit. Old time operators used to pull the "cans" off the ears and put them over the temple to either adjust the audio level or keep excessive volume from waking them up. Been there, done that...
Bob ¡ª KK5R
|
Re: uBITX ... AGC or AVC?
I just did Ooz, some days my hands are not steady..
Raj
At 29/10/2020, you wrote:
toggle quoted message
Show quoted text
Not really sure I got it. If It
works well, please share the added schematics also drawn with a pencil on
paper.
Il gio 29 ott 2020 10:53 AM IW4AJR Loris
<lorisbollina@...>
ha scritto:
- On Thu, Oct 29, 2020 at 07:30 AM, Raj vu2zap wrote:
- Try something else..
- Use a SBL-1 or similar. DBM. it is a BiDi device
- Connect one?? RF port to signal INput and second to OUTput or
other way.
- Feed a DC control voltage through a resistor to the IF port. Try with
1-10K.
- Vary the voltage and see the signal level change. The behavior is
opposite
- of the varicap control voltage.
- We can use this for AGC and ALC in either direction.
- WOW !!! I had never thought about it ! it's almost brilliant! with a
little time, as soon as the job allows me, I could try!
- Thanks Raj ... it's as simple as it is brilliant!
- 73 de IW4AJR Loris
|
Re: uBITX ... AGC or AVC?
At 29/10/2020, you wrote:
Please post the circuit diagram
also with your suggestions, that will helpful to us.
VU2TDD , Biju
On Thu, 29 Oct 2020, 12:00 Raj vu2zap,
<
rajendrakumargg@...> wrote:
- Loris,
- Try something else..
- Use a SBL-1 or similar. DBM. it is a BiDi device
- Connect one?? RF port to signal INput and second to OUTput or
other way.
- Feed a DC control voltage through a resistor to the IF port. Try with
1-10K.
- Vary the voltage and see the signal level change. The behavior is
opposite
- of the varicap control voltage.
- We can use this for AGC and ALC in either direction.
- Raj
|
Re: uBITX ... AGC or AVC?
Not really sure I got it. If It works well, please share the added schematics also drawn with a pencil on paper.
On Thu, Oct 29, 2020 at 07:30 AM, Raj vu2zap wrote:
Try something else..
Use a SBL-1 or similar. DBM. it is a BiDi device
Connect one? RF port to signal INput and second to OUTput or other way.
Feed a DC control voltage through a resistor to the IF port. Try with 1-10K.
Vary the voltage and see the signal level change. The behavior is opposite
of the varicap control voltage.
We can use this for AGC and ALC in either direction.
WOW !!! I had never thought about it ! it's almost brilliant! with a little time, as soon as the job allows me, I could try!
Thanks Raj ... it's as simple as it is brilliant!
73 de IW4AJR Loris
|
Re: uBITX ... AGC or AVC?
On Thu, Oct 29, 2020 at 07:30 AM, Raj vu2zap wrote:
Try something else..
Use a SBL-1 or similar. DBM. it is a BiDi device
Connect one? RF port to signal INput and second to OUTput or other way.
Feed a DC control voltage through a resistor to the IF port. Try with 1-10K.
Vary the voltage and see the signal level change. The behavior is opposite
of the varicap control voltage.
We can use this for AGC and ALC in either direction.
WOW !!! I had never thought about it ! it's almost brilliant! with a little time, as soon as the job allows me, I could try!
Thanks Raj ... it's as simple as it is brilliant!
73 de IW4AJR Loris
|
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 ?V 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
|
Re: uBITX ... AGC or AVC?
Please post the circuit diagram also with your suggestions, that will helpful to us.
VU2TDD , Biju
Loris,
Try something else..
Use a SBL-1 or similar. DBM. it is a BiDi device
Connect one? RF port to signal INput and second to OUTput or other
way.
Feed a DC control voltage through a resistor to the IF port. Try with
1-10K.
Vary the voltage and see the signal level change. The behavior is
opposite
of the varicap control voltage.
We can use this for AGC and ALC in either direction.
Raj
At 28/10/2020, you wrote:
On Wed, Oct 28, 2020 at 12:31
PM, Raj vu2zap wrote:
- I had experimented with a AGC which was very simple. Disconnect R23
and R43 from ground and introduce
- a varicap which I had MV2109. A series resistor to the varicap
through which you varied the capacitance
- and thereby the gain. This method worked very well with both IF
stages and even on the TX branch.
- I wish some members would experiment on this approach.
Hello Raj ...
Interesting solution, if I have some free time I could try it!
I would like to have an explanation from you:
what is the function of AGC? transmission for uBITX? ... perhaps as
a compressor instead of an external speech-processor?
Thank you, 73 Loris - IW4AJR
|
Re: uBITX ... AGC or AVC?
Loris,
Try something else..
Use a SBL-1 or similar. DBM. it is a BiDi device
Connect one? RF port to signal INput and second to OUTput or other
way.
Feed a DC control voltage through a resistor to the IF port. Try with
1-10K.
Vary the voltage and see the signal level change. The behavior is
opposite
of the varicap control voltage.
We can use this for AGC and ALC in either direction.
Raj
At 28/10/2020, you wrote:
toggle quoted message
Show quoted text
On Wed, Oct 28, 2020 at 12:31
PM, Raj vu2zap wrote:
- I had experimented with a AGC which was very simple. Disconnect R23
and R43 from ground and introduce
- a varicap which I had MV2109. A series resistor to the varicap
through which you varied the capacitance
- and thereby the gain. This method worked very well with both IF
stages and even on the TX branch.
- I wish some members would experiment on this approach.
Hello Raj ...
Interesting solution, if I have some free time I could try it!
I would like to have an explanation from you:
what is the function of AGC? transmission for uBITX? ... perhaps as
a compressor instead of an external speech-processor?
Thank you, 73 Loris - IW4AJR
|
Re: ?BITX ... AGC or AVC?
Sorry guys,
On the TX side it is R23/43 on RX side is R13/33. It worked as AGC for RX
and ALC on TX.
On RX I controlled the gain from received audio on TX was a DC gain
control pot.
I can't provide specific circuit details from here as I am holed up at
the farm. All these
experiments were done on a bitxv3 board. To experiment with this idea you
will need
to be knowledgeable on the subject and not for beginners.
Raj
At 28/10/2020, you wrote:
toggle quoted message
Show quoted text
Loris is right, Raj's R23 and
R43 are both on the transmit side of the uBitx bidi amps.
So perhaps not AGC for the receiver, which is what most would be
interested in.
But could also work on the receive side of the bidi amps.
A clear and complete description from Raj would help others to try it,
"introduce a varicap" is not terribly specific.
A search in the forum posts for "Raj AGC" finds no hits on this
AGC scheme.
Don, ND6T, had a couple blog posts about easy hacks to implement manual
RF gain
on the Bitx40, should be possible to make these work on the uBitx.
Dozens of threads in the forum on adding AGC to the Bitx40 and
uBitx.
The "automatic" part of AGC may not be needed, but a simple RF
gain control
to avoid receiver overload would be good.
That and back-to-back diodes in the audio chain somewhere
to prevent blown eardrums when using headphones.
Jerry, KE7ER
On Wed, Oct 28, 2020 at 06:10 AM, IW4AJR Loris wrote:
- On Wed, Oct 28, 2020 at 12:31 PM, Raj vu2zap wrote:
- I had experimented with a AGC which was very simple. Disconnect R23
and R43 from ground and introduce
- a varicap which I had MV2109. A series resistor to the varicap
through which you varied the capacitance
- and thereby the gain. This method worked very well with both IF
stages and even on the TX branch.
- I wish some members would experiment on this approach.
- Hello Raj ...
- Interesting solution, if I have some free time I could try it!
- I would like to have an explanation from you:
- what is the function of AGC? transmission for uBITX? ... perhaps
as a compressor instead of an external speech-processor?
- Thank you, 73 Loris - IW4AJR
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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 ? 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 ?V 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 
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Gerard
Bob Lunsford
Raj vu2zap
Biju Apkrcl