Topics

AGC kits

 

It has come to my attention after the fact that the AGC kits I sold a few weeks back do not match the schem with the parts placement. I am very sorry about the mix up, If memory serves you should still have all the right values to match the schem. Taking the 100k from the input and adding just after the .1uf cap after the 2n3904, use the 10k on the input.

 If anyone has any questions or needs parts please e-mail me directly, I will ship any parts missing or needed free of charge to help make up for the mistake.

 Again sorry about the mix up this was my 1st run of any type of kit and have learned a few lessons to say the least.

dherron at live dot com
--
David

 N8DAH
Kit-Projects.com

Joe Puma
 

Can you show us a diagram of what we have to do. Using a pic of the actual board itself.  





On Feb 8, 2018, at 2:57 PM, N8DAH <Dherron@...> wrote:

It has come to my attention after the fact that the AGC kits I sold a few weeks back do not match the schem with the parts placement. I am very sorry about the mix up, If memory serves you should still have all the right values to match the schem. Taking the 100k from the input and adding just after the .1uf cap after the 2n3904, use the 10k on the input.

 If anyone has any questions or needs parts please e-mail me directly, I will ship any parts missing or needed free of charge to help make up for the mistake.

 Again sorry about the mix up this was my 1st run of any type of kit and have learned a few lessons to say the least.

dherron at live dot com
--
David

 N8DAH
Kit-Projects.com

 

I would love to show you the real board but I sold them all

As posted in the original sale thread here is the site where all this came from: AGC

10k is on the IN 100k to GND right after the .1uf cap next to the 2n3904.

 

 


--
David

 N8DAH
Kit-Projects.com

Vic WA4THR
 

Just about to work with the assembled board you supplied. Are there any issues with that?

=Vic=
WA4THR

Ed Kelley
 

Do you have a list of the components by designation Ex: R1, R2, C1, C2.
The pcb does not show values only designations.

On 2/8/2018 8:31 PM, N8DAH wrote:

I would love to show you the real board but I sold them all

As posted in the original sale thread here is the site where all this came from: AGC

10k is on the IN 100k to GND right after the .1uf cap next to the 2n3904.

 

 


--
David

 N8DAH
Kit-Projects.com


 

read the link




From: BITX20@groups.io <BITX20@groups.io> on behalf of Ed Kelley via Groups.Io <ekelley946@...>
Sent: Friday, February 9, 2018 4:15 PM
To: BITX20@groups.io
Subject: Re: [BITX20] AGC kits
 
Do you have a list of the components by designation Ex: R1, R2, C1, C2.
The pcb does not show values only designations.

On 2/8/2018 8:31 PM, N8DAH wrote:

I would love to show you the real board but I sold them all

As posted in the original sale thread here is the site where all this came from: AGC

10k is on the IN 100k to GND right after the .1uf cap next to the 2n3904.

 

 


--
David

 N8DAH
Kit-Projects.com



--
David

 N8DAH
Kit-Projects.com

Joe Puma
 


image1.jpeg


On Feb 9, 2018, at 5:17 PM, N8DAH <Dherron@...> wrote:

read the link




From: BITX20@groups.io <BITX20@groups.io> on behalf of Ed Kelley via Groups.Io <ekelley946@...>
Sent: Friday, February 9, 2018 4:15 PM
To: BITX20@groups.io
Subject: Re: [BITX20] AGC kits
 
Do you have a list of the components by designation Ex: R1, R2, C1, C2.
The pcb does not show values only designations.

On 2/8/2018 8:31 PM, N8DAH wrote:

I would love to show you the real board but I sold them all

As posted in the original sale thread here is the site where all this came from: AGC

10k is on the IN 100k to GND right after the .1uf cap next to the 2n3904.

 

 

<agc.png>
--
David

 N8DAH
Kit-Projects.com



--
David

 N8DAH
Kit-Projects.com

Tim Gorman
 

So there shouldn't be a 10K between the diode and the gate of the fet?

There isn't one on the original schematic and there aren't any pads on the circuit boards for one either.

tim ab0wr

ekelley
 

Is this the board?



On 2/8/2018 8:31 PM, N8DAH wrote:

I would love to show you the real board but I sold them all

As posted in the original sale thread here is the site where all this came from: AGC

10k is on the IN 100k to GND right after the .1uf cap next to the 2n3904.

 

 


--
David

 N8DAH
Kit-Projects.com


Tim Gorman
 

Does anyone know what the typical output level of the first AF amp should be for a strong signal? I built the AGC amp shown in the message by Joe Puma and the AF output begins to distort with an input of 300mv to 350mv RMS. I haven't yet built a spreadsheet to see how much AGC action is provided as the AF level goes up. Maybe I can get to that tomorrow. I don't have any way to sweep the amplitude of the input AF, only the frequency. So I'll have to build everything up manually a point at a time in order to see what compression is provided. 

Joe Puma
 

I posted the board before. Can we use this as diagram?

image1.jpeg

On Feb 10, 2018, at 3:15 PM, ekelley <ekelley828@...> wrote:

Is this the board?



On 2/8/2018 8:31 PM, N8DAH wrote:

I would love to show you the real board but I sold them all

As posted in the original sale thread here is the site where all this came from: AGC

10k is on the IN 100k to GND right after the .1uf cap next to the 2n3904.

 

 

<agc.png>
--
David

 N8DAH
Kit-Projects.com


Paul KL7FLR
 

the board layout and other documentation can be found at https://www.dropbox.com/sh/og5oifvqprldp7j/AACpE5Wqs1kmKePrfw825ONDa?dl=0

73,
Paul
KL7FLR

Henning Weddig
 

Tim, please have a look on my folder (DK5LV) subfolder "LTSPICE XVII" in the BITX 20 group. I have made simulations of the AF preamp, the gain ist 46 dB.  I can confirm that the LTSPICE simulations comply with measurements I made using my BITX40.

In the subfolder "BITX40 level diagramme" You can find my level diagramme. I can confirm that my assumptions on the gain of the stages in the BITX 40 comply with the measurements of my BITX 40.

This means that the AF preamp is momentarily the stage which limits the distortion free dynamic range of the complete BITX40. The high gain of the audio string is necessary to get a suitable overlal audio power. To put an AGC system between the output of the AF preamp and the LM386 does not improve the ability of the BITX 40 for  a maximum distortionless RF antenna input signal. 

Henning Weddig
DK5LV


Am 10.02.2018 um 22:18 schrieb Tim Gorman:

Does anyone know what the typical output level of the first AF amp should be for a strong signal? I built the AGC amp shown in the message by Joe Puma and the AF output begins to distort with an input of 300mv to 350mv RMS. I haven't yet built a spreadsheet to see how much AGC action is provided as the AF level goes up. Maybe I can get to that tomorrow. I don't have any way to sweep the amplitude of the input AF, only the frequency. So I'll have to build everything up manually a point at a time in order to see what compression is provided. 

Tim Gorman
 

Henning,

Thank you for the information. Your data is quite informative. I have bookmarked your link.

I don't have an actual radio to test against. I am hoping my ubitx will ship in the next few days. 

In measuring the agc board itself, using a 1K resistor as a load, a 100mvPP input results in an 18mvPP output across the 1K resistor. Since I don't know the load resistance of the volume pot and the final AF amp I just picked 1Kohm as a representative value. If this is true the volume will have to be turned up significantly in order to get the same speaker output. The AGC board seems to provide a gain of 5 (18mv to 90mv) while the gain of the input is about 12 (100mvPP to 1200mvPP) so it does seem to provide significant gain compression as the output of the AF preamp goes up. 

I look forward to actually measuring the AGC boards functionality when I get my ubitx put together. 

tim ab0wr

Henning Weddig
 

Tim,

the AF potentiometer deliverd by HF Signals with the BITX40 kit has a value of 10k.


Am 11.02.2018 um 15:39 schrieb Tim Gorman:

Henning,

Thank you for the information. Your data is quite informative. I have bookmarked your link.

I don't have an actual radio to test against. I am hoping my ubitx will ship in the next few days. 

In measuring the agc board itself, using a 1K resistor as a load, a 100mvPP input results in an 18mvPP output across the 1K resistor. Since I don't know the load resistance of the volume pot and the final AF amp I just picked 1Kohm as a representative value. If this is true the volume will have to be turned up significantly in order to get the same speaker output. The AGC board seems to provide a gain of 5 (18mv to 90mv) while the gain of the input is about 12 (100mvPP to 1200mvPP) so it does seem to provide significant gain compression as the output of the AF preamp goes up. 

I look forward to actually measuring the AGC boards functionality when I get my ubitx put together. 

tim ab0wr

Tim Gorman
 

The actual resistance will also depend on the input resistance of the final amplifier. For instance, if the volume pot is set to maximum you would have the 10K pot in parallel with the input resistance of the final amp. 

I will try a 10K resistor and rerun the test in the next couple of days. 

Joe Puma
 

Okay I spent some time trying to understand the change. You sent 10k (103) resistor tapped to the paper.  Replace that with the 100k (1000) near the input and that’s it right. Okay I will make the change soon

Thanks,
Joe
KD2NFC 



On Feb 8, 2018, at 9:31 PM, N8DAH <Dherron@...> wrote:

I would love to show you the real board but I sold them all

As posted in the original sale thread here is the site where all this came from: AGC

10k is on the IN 100k to GND right after the .1uf cap next to the 2n3904.

 

 

<agc.png>
--
David

 N8DAH
Kit-Projects.com