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Kit-Projects ND6T Ubitx AGC

 

More posted tonight.

https://shop.kit-projects.com/index.php?route=product/product&product_id=101
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David

 N8DAH
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dseyler@...
 

It appears that you have changed the layout of the solder pads for the switch wires. It does not match the board that I have. Is this a newer design?

Doug WB5TKI

KE2GKB
 

The version you have is the production design. The photos on the website are the prototype revision. After installing it in my own uBitx I realized it was harder then it needed to be so I adjusted the solder pads to make everyone else's life's easier. The only changes are to the pad layout.

73

Tim Keller - KE2GKB https://shop.kit-projects.com

dseyler@...
 

OK, Tim, thanks for the clarification.

Doug WB5TKI

EI4GNB
 

Installed mine last night..
Clear improvement in good conditions. 80m FT8 went from being a horrible mess to visually and audibly tidy.
FAST setting will reassure You of it's speed with some audible pumping after periods of FT8, and on some loud broadcast stations - fairly hard knee stuff.
I tried to cut corners by not installing the supplied switch, this was a mistake - You really will want the option to change between FAST/SLOW/OFF if You intend on doing anything other then digimodes IMHO.
I had a previous s-meter mod, so a simple move of A7 from that to the pad on the board kept it running without any drama, as long as it's in FAST or SLOW mode.
All-in-all, this was worth doing. Looks well 'borg' too sitting as it does on the motherboard :)

 

Just put more on the site.
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David

 N8DAH
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digger AB3XU
 

Hey,

I've installed the uBITX AGC board per the instructions and it just doesn't seem like its working correctly. I feel like I've gone round circles trying to make sense of it all.

In part I wonder if some kits were shiped with a lot of switches that are configured differently? I've attached a drawing of continuity checks of the supplied switch and it doesn't seem to make sense with the documentation.

I've also tried to understand the logic of the switch based on schematics I've found on ND6T's website and can't figure it out. Is there a schematic available for this particular board? I think a lot of my questions would be answered with a schematic.

Without going too far down the rabbit hole, here are two points to begin with:

* AGC is off with the switch in the up position (NOT down). This was determined by measuring the voltage on the S-METER Output; it drops to 0.0 volts with the switch in the up position.

* The voltage measurement at S-METER Output on the AGC board is very low:
    -73dBm (S9):    0.02V
    -53dBm (S9+10): 0.25
    -63dbm (S9+20):  0.78

    This is using a Sark-110 for an input; the level was verified with a Siglent SSA 3021X. The Sark's lowest output is -73dBm. All measurements were made with S-METER Output attached to A7 of the Raduino.

Also attached is a drawing of how it's all wired up.

73, digger AB3XU

KE2GKB
 

Hey Digger, Thanks for the feed back. So you are actually the second person to reach out to us about this. We realized this afternoon that the documentation was in error. I supplied david with the wiring information incorrectly. I had the switch upside down in my install DOH!

The simple fix is to flip the switch over, It is correct with the notch facing down. The directions being supplied going forward have the information fixed. With an adjusted wire up to solve the issue. Our sincerest apologies.

As for the low S-Meter issue. What version uBitx do you have? Is it a v4? It was brought to my attention after production started that the v4 has a lower audio drive then the v3 models. The original circuit this was based off of is tuned for the v3's I am actively working on a fix for this. Your numbers are actually super helpful.

KE2GKB

-- Tim Keller - KE2GKB https://shop.kit-projects.com

KE2GKB
 

Sorry missed the questions in the photograph.

1) Off and Ground are the same. To turn the circuit off you need to ground common. This removes the audio input to the circuit, and thusly turns off the AGC. This was marked this way in part due to what is in answer 3. 2) The official Wire up instructions say that Yellow is VolHigh, That is what our documentation is based on. 3) the D designations are in that single photo as it is a clip out of the schematic. The prefix was used for clarity when reading the schematic. The image was copied from the schematic and used with out editing. Yes D_Com and Common are on the same Net.

-- Tim Keller - KE2GKB https://shop.kit-projects.com

Adrian Chadd
 

Hi!

Thanks to everyone for digging into this. I just added the AGC mod to my board and wondered about this behaviour. I'd love to know how to tweak the board to work on a v4 bitx.

Thanks!


-adrian

digger AB3XU
 

Thanks also, Tim, for these explanations. With the correct wiring instructions most of these questions didn't need to be answered.

As far as vol-high I'm taking it from the via hole at R70 which is just a few inches from the agc board.

73, digger

KE2GKB
 

I am under the impression the documentation has been fixed.
That aside. R70 is a good place to be taking the audio from no issues there.
I am fairly confident the issue stems from the drive level on the v4's being lower then the agc expects. I think the simple solution is going to be add another amplifier stage before the audio in on the AGC but not having a board my self it is hard to test this.
Digger could I get the measurements of Vol-High with those same measurements?

-- Tim Keller - KE2GKB https://shop.kit-projects.com

digger AB3XU
 

Tim, here's what I got this evening. Hopefully the numbers are good. They are similar to what I posted yesterday. The Vol-Hi measures are p-p done on an o-scope. There was a fair amount of noise at Vol-Hi maybe about 10mVp-p. It was tough getting a good connection.

Input       ADC     A7(Vdc)    Vol-hi(Vp-p)

-73dBm        2     0.02        20mV
-63dBm       59     0.303       72mV
-53dBm      158     0.795       240mV
-43dBm      196     0.981       660mV

I had to do the Vol-Hi measurements a second time after I realized it wouldn't work with the ADC on. (My turn to say, DOH)

--digger AB3XU

 

I have restocked mic's, paddles and AGC's. The AGC doc's have been updated with the correction for the DP3T.

73
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David

 N8DAH
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Lee Weifenbach <wb3acc@...>
 

Hi David, would you please email me the updated switch diagram for my agc I just received from you a week or two ago.  I did question the supplied diagram.  thanks  Lee   wb3acc@...    73


On April 14, 2019 at 11:55 PM N8DAH <Dherron@...> wrote:

I have restocked mic's, paddles and AGC's. The AGC doc's have been updated with the correction for the DP3T.

73
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David

 N8DAH
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Lee I sent it over. The updated instructions are in the same download area on the kit-projects website.
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David

 N8DAH
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KE2GKB
 

Digger do you have any other uBitxs? I currently do not have a good known noise source (Working on it! but alas the day job has its priority :( ) So it is currently out of my capability to make comparison measurements. I do know that those numbers are on the order of about 3x lower then they should be based on the non scientific measurements I have taken on my unit.

-- Tim Keller - KE2GKB https://shop.kit-projects.com

Adrian Chadd
 

i have a ubitx v4 with your AGC board installed. I also live in an amusingly noisy environment and I have relevant testing kit. :-P

Let me know what you'd like and I'll go see if I can take some measurements for you.


-adrian


On Tue, 16 Apr 2019 at 09:26, KE2GKB via Groups.Io <tkeller=keepdream.in@groups.io> wrote:

Digger do you have any other uBitxs? I currently do not have a good known noise source (Working on it! but alas the day job has its priority :( ) So it is currently out of my capability to make comparison measurements. I do know that those numbers are on the order of about 3x lower then they should be based on the non scientific measurements I have taken on my unit.

-- Tim Keller - KE2GKB https://shop.kit-projects.com

KE2GKB
 

If I could ask for the same measurements that digger took that would be great. 
The solution here is going to be either modding the ubitx to fix the audio issue or adding an amp for the boards that need it.  The attenuation range is based on how much af drive is given to the circuit. If you read nd6t's original articles you can see why the values reported by digger are just not cutting it!


I'm personally just fustrated that some of you will have issues with our product. While it is a kit it's meant to just work. So thank you all for the support!

On Tue, Apr 16, 2019, 1:10 PM Adrian Chadd <adrian@...> wrote:
i have a ubitx v4 with your AGC board installed. I also live in an amusingly noisy environment and I have relevant testing kit. :-P

Let me know what you'd like and I'll go see if I can take some measurements for you.


-adrian


On Tue, 16 Apr 2019 at 09:26, KE2GKB via Groups.Io <tkeller=keepdream.in@groups.io> wrote:

Digger do you have any other uBitxs? I currently do not have a good known noise source (Working on it! but alas the day job has its priority :( ) So it is currently out of my capability to make comparison measurements. I do know that those numbers are on the order of about 3x lower then they should be based on the non scientific measurements I have taken on my unit.

-- Tim Keller - KE2GKB https://shop.kit-projects.com


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Tim Keller - KE2GKB
https://shop.kit-projects.com