|
All the AGC circuits I found doesn't have a way to set the response time to fast or slow attack. Has anyone designed a circuit or know of a circuit that will satisfy my requirement for an AGC function? TIA...
73, Chuck K3VPZ
|
Chuck, ? I am very interested in an AGC circuit for the BITX40. I have already installed a new audio output amp - LM386 - that works substantially better but on strong signals and a good antenna there is distortion from some point onboard. Having to ride the volume is a pain in the you know what. I was looking at my radio-engineer handbook and one of the AGC circuits they show uses the Plessy Sl621 AGC chip. I doubt it is still available but if it was it would make things very simple. Google it, the PDF data is still out there. This uses audio to establish AGC that could be applied in some way to probably Q1 on the BITX board.
|
Somewhen in the past there was a version of the SL621 AGC circuit
made with individual transistors.? Try searching the RSGB handbook
or tech topics.
Cheers,
William
On 03/09/2017 08:38 AM, Doug - via
Groups.Io wrote:
toggle quoted message
Show quoted text
Chuck,
? I am very interested in an AGC circuit for the BITX40. I have
already installed a new audio output amp - LM386 - that works
substantially better but on strong signals and a good antenna
there is distortion from some point onboard. Having to ride the
volume is a pain in the you know what. I was looking at my
radio-engineer handbook and one of the AGC circuits they show
uses the Plessy Sl621 AGC chip. I doubt it is still available
but if it was it would make things very simple. Google it, the
PDF data is still out there. This uses audio to establish AGC
that could be applied in some way to probably Q1 on the BITX
board.
|
Folks,
I made simulations on a "discrete version" of the SL611
(component values from the Plessey 1975 data book) using LTSPICE
and then upon success with teh simulaiton I also made a pcb
layout. There is also a discrete version of the SL621 as a layout
(I am using EASY PC). For unknown reasons I can not upload the pdf
files into my folder (DK5LVs stuff)
Can somebody advise how to upload?
Henning
DK5LV
Am 08.03.2017 um 21:33 schrieb William
Kimber:
toggle quoted message
Show quoted text
Somewhen in the past there was a version of the SL621 AGC
circuit made with individual transistors.? Try searching the
RSGB handbook or tech topics.
Cheers,
William
On 03/09/2017 08:38 AM, Doug - via
Groups.Io wrote:
Chuck,
? I am very interested in an AGC circuit for the BITX40. I
have already installed a new audio output amp - LM386 - that
works substantially better but on strong signals and a good
antenna there is distortion from some point onboard. Having to
ride the volume is a pain in the you know what. I was looking
at my radio-engineer handbook and one of the AGC circuits they
show uses the Plessy Sl621 AGC chip. I doubt it is still
available but if it was it would make things very simple.
Google it, the PDF data is still out there. This uses audio to
establish AGC that could be applied in some way to probably Q1
on the BITX board.
|
I found the following most interesting articles in a Google search - I did not see anything about the discrete equiv. for the SL621.
I have not had a chance to go through them yet. I also need to look at my many ARRL handbooks. There are discrete AGC circuits defined. The circuit is not as much the problem as how to apply the AGC to the BITX. For ease of use I would use audio AGC so two connections to the existing board would be all that is needed.? Not looking for perfect just a lot better than it is now.
I also don't want to reinvent the wheel. If this has already been done or anyone has any ideas please pass it on. I emailed a ham who apparently used the Plessy SL621 in a recent homebrew receiver design. I suspect he had it in his junkbox but if this is still an available chip somewhere it would make things a lot easier.
|
Why not use a NE570 compressor as a AGC ..??
Regards?
On Wed, 8 Mar 2017 at 21:34, Doug - via Groups.Io <dsc3507@...> wrote: I found the following most interesting articles in a Google search - I did not see anything about the discrete equiv. for the SL621.
I have not had a chance to go through them yet. I also need to look at my many ARRL handbooks. There are discrete AGC circuits defined. The circuit is not as much the problem as how to apply the AGC to the BITX. For ease of use I would use audio AGC so two connections to the existing board would be all that is needed.? Not looking for perfect just a lot better than it is now.
I also don't want to reinvent the wheel. If this has already been done or anyone has any ideas please pass it on. I emailed a ham who apparently used the Plessy SL621 in a recent homebrew receiver design. I suspect he had it in his junkbox but if this is still an available chip somewhere it would make things a lot easier.
|
Hi, On most discreet AGC circuits tis a Diode that feeds a resistor capacitor pair, it is the time constant (t = R * C ) that determines how fast or slow the AGC will work, it would be easy to replace the fixed resistor with a pot and experiment , if you can not get it slow enough increase teh capacitor value.
Cheers
On Wed, Mar 8, 2017 at 5:02 PM Marc Jones via Groups.Io <gw0wvl= [email protected]> wrote: Why not use a NE570 compressor as a AGC ..??
Regards?
On Wed, 8 Mar 2017 at 21:34, Doug - via Groups.Io I found the following most interesting articles in a Google search - I did not see anything about the discrete equiv. for the SL621.
I have not had a chance to go through them yet. I also need to look at my many ARRL handbooks. There are discrete AGC circuits defined. The circuit is not as much the problem as how to apply the AGC to the BITX. For ease of use I would use audio AGC so two connections to the existing board would be all that is needed.? Not looking for perfect just a lot better than it is now.
I also don't want to reinvent the wheel. If this has already been done or anyone has any ideas please pass it on. I emailed a ham who apparently used the Plessy SL621 in a recent homebrew receiver design. I suspect he had it in his junkbox but if this is still an available chip somewhere it would make things a lot easier.
|
hi all,
The SL621 works from the audio but controls the RF/IF. It has
fast attack, to reduce the signal, a longish hang time to cope
with inter-word/sentence gaps and then rapid decay to rapidly
bring gain back up to full.
Personally I would prefer to control IF and/or RF rather than
detected audio.? Controlling AF creates risk of overload in
IF/detector.?
Cheers,
Will?
On 03/09/2017 11:21 AM, John Baggott
wrote:
toggle quoted message
Show quoted text
Hi,
On most discreet AGC circuits tis a Diode that feeds a resistor
capacitor pair, it is the time constant (t = R * C ) that
determines how fast or slow the AGC will work, it would be easy
to replace the fixed resistor with a pot and experiment , if you
can not get it slow enough increase teh capacitor value.
Cheers
On Wed, Mar 8, 2017 at 5:02 PM Marc Jones via
Groups.Io <gw0wvl= [email protected]>
wrote:
Why not use
a NE570 compressor as a AGC ..??
Regards?
On Wed, 8 Mar 2017 at 21:34, Doug -
via Groups.Io
I found the following most
interesting articles in a Google search -
I did not see anything about the
discrete equiv. for the SL621.
I have not had a chance to go
through them yet. I also need to look at my many ARRL
handbooks. There are discrete AGC circuits defined.
The circuit is not as much the problem as how to apply
the AGC to the BITX. For ease of use I would use audio
AGC so two connections to the existing board would be
all that is needed.? Not looking for perfect just a
lot better than it is now.
I also don't want to reinvent the
wheel. If this has already been done or anyone has any
ideas please pass it on.
I emailed a ham who apparently used
the Plessy SL621 in a recent homebrew receiver design.
I suspect he had it in his junkbox but if this is
still an available chip somewhere it would make things
a lot easier.
--
|
The audio amp with AGC as seen in the uBitx could be a good addition to the Bitx40. ?That amp will have less distortion than the LM386. ? If you want to know what's involved for really good AGC, follow the link in this post: ?/g/BITX20/message/22670??
|
or you could do
worse than check out the IF AGC (and S Meter) approach used by
Eamon Skelton EI9GQ in his various rig designs. A google
seatrch will find them. I intend to use one of his designs,
which are all generally similar and also echo the "epitome" IF
AGC design that Ashar champions.
Bill, VK7MX
On 9/03/2017 7:33 AM, William Kimber
wrote:
toggle quoted message
Show quoted text
Somewhen in the past there was a version of the SL621 AGC
circuit made with individual transistors.? Try searching the
RSGB handbook or tech topics.
Cheers,
William
On 03/09/2017 08:38 AM, Doug - via
Groups.Io wrote:
Chuck,
? I am very interested in an AGC circuit for the BITX40. I
have already installed a new audio output amp - LM386 - that
works substantially better but on strong signals and a good
antenna there is distortion from some point onboard. Having to
ride the volume is a pain in the you know what. I was looking
at my radio-engineer handbook and one of the AGC circuits they
show uses the Plessy Sl621 AGC chip. I doubt it is still
available but if it was it would make things very simple.
Google it, the PDF data is still out there. This uses audio to
establish AGC that could be applied in some way to probably Q1
on the BITX board.
|
Found this on? eBay item number:?271695585529
10 available from Isreal-free shipping Hope this helps 73 WA9DOH GEC PLESSEY SL611C, RF/IF Amplifier, Wide AGC Range: 50dB
On Wed, Mar 8, 2017 at 3:25 PM, Henning Weddig via Groups.Io <hweddig@...> wrote:
Folks,
I made simulations on a "discrete version" of the SL611
(component values from the Plessey 1975 data book) using LTSPICE
and then upon success with teh simulaiton I also made a pcb
layout. There is also a discrete version of the SL621 as a layout
(I am using EASY PC). For unknown reasons I can not upload the pdf
files into my folder (DK5LVs stuff)
Can somebody advise how to upload?
Henning
DK5LV
Am 08.03.2017 um 21:33 schrieb William
Kimber:
Somewhen in the past there was a version of the SL621 AGC
circuit made with individual transistors.? Try searching the
RSGB handbook or tech topics.
Cheers,
William
On 03/09/2017 08:38 AM, Doug - via
Groups.Io wrote:
Chuck,
? I am very interested in an AGC circuit for the BITX40. I
have already installed a new audio output amp - LM386 - that
works substantially better but on strong signals and a good
antenna there is distortion from some point onboard. Having to
ride the volume is a pain in the you know what. I was looking
at my radio-engineer handbook and one of the AGC circuits they
show uses the Plessy Sl621 AGC chip. I doubt it is still
available but if it was it would make things very simple.
Google it, the PDF data is still out there. This uses audio to
establish AGC that could be applied in some way to probably Q1
on the BITX board.
|
If anyone wants to play with an SL621 I have a few for the cost of the postage from VK. Email offline to callsign at tpg com au They haven't been tested since 1980 when I built a 20m ssb trx but that still works ok. Google "Plessey SL600 application" for all the application booklets. There was a discreet component version of the SL621 in Radcom, probably in the late 1970's. It used a lot of components.
Brian vk4bap
|
Actually, come to
think of it,? the Plessey VOGAD chip from that series might be
an interesting experiment for anybody wanting to try speech
processing in the BITX?
Bill, VK7MX
toggle quoted message
Show quoted text
If anyone wants to play with an SL621 I have a few for the cost
of the postage from VK. Email offline to callsign at tpg com au
They haven't been tested since 1980 when I built a 20m ssb trx
but that still works ok.
Google "Plessey SL600 application" for all the application
booklets. There was a discreet component version of the SL621 in
Radcom, probably in the late 1970's. It used a lot of
components.
Brian vk4bap
|
Jerry, Is there a schematic of the ubitx anywhere I can download?? In my mind the issue would be more how to modify the Bitx40 to actually apply the AGC. DEriving it owuld e much easier than applying it. Does anyone have ideas on applying it? I suspect it would need to be done at Q1 or before? Altering the bias on Q1? Putting another controlled stage before Q1?
|
Folks,
Following on the idea of using VOGAD chips for "speech proceesing", the Plessey SL6270 was used on NorCal Cascade kit and the Howes kits ASP3.
It is not a compressor, but a "gain controlled microphone preamplifier" or "voice operated gain adjusting device"? (VOGAD):
No matter how far or close are you with respect to the mike, the output is the same.
Someone revamped it recently and got a bunch of them made, subsequently sold via E..ay.
I hope it helps.
jon, ea2sn
|
Doug,?
We have been discussing the ubitx schematic for teh last ten days ?on this llist. See the previous post about ubitx
- f
On Fri, Mar 10, 2017 at 1:08 PM, Doug - via Groups.Io <dsc3507@...> wrote: Jerry, Is there a schematic of the ubitx anywhere I can download?? In my mind the issue would be more how to modify the Bitx40 to actually apply the AGC. DEriving it owuld e much easier than applying it. Does anyone have ideas on applying it? I suspect it would need to be done at Q1 or before? Altering the bias on Q1? Putting another controlled stage before Q1?
|
Schematic is a web link immediately under the picture: ? ?
On Thu, Mar 9, 2017 at 11:38 pm, Doug - wrote:
Is there a schematic of the ubitx anywhere I can download? ?
|
In reviewing the ubitx schematic I don't see any AGC. Am I missing something?
|
Doug, ? It is the second section of the audio amp (TDA2822).? It is described in the written section “AGC” at:
? 73, Dale? K9NN ?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of Doug - via Groups.Io
Sent: Thursday, March 23, 2017 10:36 AM
To: [email protected]
Subject: Re: [BITX20] Finding an AGC circuit with fast/slow attack ? In reviewing the ubitx schematic I don't see any AGC. Am I missing something?
|
|
This email has been checked for viruses by Avast antivirus software.
|
|
Hi Chuck There is this circuit that I have not yet built, but I intend from the PY2OHH Site. The operation is simple, the audio signal taken out of the volume potentiometer is amplified by the 2N2222 (2N3904) to a voltage doubler (2.2μF capacitor and two 1N4148 diodes), where a DC voltage is generated Proportional to the audio signal. This audio signal is integrated by the 10k and 100k resistor set and the 47μF capacitor, and the 100k (and capacitor) resistor value determines whether AGC is slow (100k higher) or fast 100k lower). This accumulated dc signal goes to the 2N7000 which functions as a variable resistor, acting at the output of the audio signal, to the potentiometer (and to the LM386 power amplifier in the case). The 2k2 trimpot should be adjusted in such a way that when the AGC acts it should be smooth. I hope it helps.
73 from Junior PY2ADA
|
Marc Jones
K2BAG
Júnior PY2ADA