Codan 8727 info (And 7727)

V

VK3ZYZ

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The filter looks a lot better made on a bit of Vero Board!
1.65MhxFilterTop.JPG
1.65MhxFilterBtm.JPG
And here it is installed.
1.65MhxFilterInstalled.JPG
The resonance is a bit high , 1.8Mhz, as I used 470pF caps in stead of 510pF.
But it goes ok.
 
V

VK3ZYZ

Guest
Codan8727VFO_Delux3.png

Here is a 3D printed front for the Codan 8727, fitted with the VFO-Delux board.
This is not all wired up and the pushbuttons still need to get here.
Also, there is the aux meter code to do, as well as a general code build. Still, this is what it will look like.

Codan8727Front.png

Another thing to do is an interface to give pushbutton volume control in place of the original pot.
AND, band switching.....
Lots more to do.
 
V

VK3ZYZ

Guest
As I'm trying to get this going for tomorrow's ham meeting, a pot and various switches have been added. It is pretty rough, but I hope it will work enough.
(A quick trip yesterday to Jaycar for parts)
Codan8727VFO_Delux3_1.png


Codan8727VFO_Delux3_2.png


Most of the push buttons will not be used.
It looks like a bit of black tape over the ESP32 board LED may be a good addition too.
But, eventually, the front will be in black plastic.

EDIT:
I changed to an S meter as a VU meter is not what a radio really needs :)
Codan8727VFO_Delux3_3.png
 
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VK3ZYZ

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I am still plodding along with this every so often.
Here is the code so far, using a PCF8574 as the band select outputs.

PCF8574 Board.jpg

A board originally for driving an LCD has been pressed into service as that was what I had on hand. The top address link is installed to change the address from 0x27 to 0x23.
One of the first 5 outputs go high as the channel is selected. This will be used to drive optos as level shifters from 5V to 10V switching. Only the first 5 are used, but 8 are available if the code is changed to allow it. And if you need more outputs (or inputs), additional PCF8574 chips can be added with different addresses selected.

Ihave found when running the VFO in the Codan 8727, the 1000 step size was way too high.
I've changed it...
unsigned long step_size = 10; // default tuning increment (Hz) was 1000

That is better.
But, the calibration factor is not working so will have to talk to my son and ask him to have a look at the code.
 

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VK3ZYZ

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Photo on 20-12-2022 at 8.57 PM.jpg

I hope to try this out on the net tomorrow.
There is still some work to do on the tuning for all the bands but a couple are working.

EDIT: (Tomorrow now) I just had a contact with VK2QA on 7.110Mhz. It works :)
Well, there was a 3kHz offset earlier but that was because I had programmed the USB offset to the VFO instead of the LSB!!!!
All better now. So, in a couple of ours, it should be up on the 3.630Mhz net :) Also, the S Meter now works. Needs a cal pot still.
The fixed code is below.
 

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VK3ZYZ

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I have given up on trying to get the band selected via the ESP32 ADC and band select rotary switch.
Now the band is switched from the ESP32 driving a PCF8574A I2C port expander and an MIC2981 Source Driver. I tried optos but the ones used dropped too much voltage.
Photo on 3-01-2023 at 9.28 PM.jpg
I2C Band Select.jpg

A hacked together board plugs onto the 8727 band select header. This works fine!
 

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VK3ZYZ

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Here is the full synth circuit showing the add-ons for the Codan 8727
8727_VFO_Delux.jpg


And this has the new front panel connections, along with the bans switching again.
8727Front.jpg
 

VK3ZYZ

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The new front print is not quite as good quality as I'd hoped.
Codan8727Blackfront.png

Still, it will have to do until I can get my better quality 3D printer working reliably again.
 

VK3ZYZ

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Here is a board for the Codan 8727 band select drive.
See post #26. This also has other used as there are optional terminals so it is not just for the Codan. The board mounts upside down onto the Codan header.
Codan 8727 BandSelect.jpg

I hope to get some boards made soon. This board could be a handy add-on for quite a few things.
See the MIC2981 data sheet for the chip.
 

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VK3ZYZ

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I've been having problems with bumping the encoder knob so shifting the frequency.
So, here is a mod.
Photo on 12-1-23 at 5.11 pm #2.jpg


Photo on 12-1-23 at 5.11 pm.jpg

Now, a front panel button toggles the LOCK/TUNE, and another toggles the USB/LSB selection.

An easy way to lock the encoder is to ...
step_size = 0; // LOCK
or..
step_size = 2; // TUNE

Originally, the step_size was 1000. I had 10 but now 2.
For some reason, a step size of 1 does not work correctly?????

If the encoder knob it turned rapidly, it still changes the tuning as the acceleration is still working, but this will do I think.
The LOCK/TUNE label may be moved to the top left, under the frequency display when I figure out just how the display positioning has be set up, but I may just keep it where it is.
FYI, here is the code.
 

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