Codan 6924 Mk 2 project

[VK3ZYZ]

Here is another Codan project that I'm going to attempt.
It is a Codan 6924 Mk2 "portable" HF set.

This comes in a neat carry case.


with basic controls that include an antenna tuner built in.

The transmitter

and the other side has a fold out section with the receiver and crystals.

It looks like there may bave been some attempts to change a couple of frequencies.
The fitted ones are listed as.
1 3995
2 5455
3 8022
4 11612
5 14977
6 5925
7 8093
8 10007
9 nc
10 nc

7 is not working and 8 is 4001

I think I will try to replace the speaker grill with a 3D printed part that will house a new narrow speaker and the frequency display so as to not harm the original.
The Clarifier position will be for the rotary encoder.
At the moment, the LSB/USB/AM&TUNE switch is mechanically limited to the last 2 but I hope that is an easy fix to get the LSB position working as my synth can add that function.

Here too are some pic from the net, and a service manual.
EDIT: The service manual is for the 6924, NOT the 6924 Mk2 version. I've been unable to find the Mk2 anywhere. If you have it, please let me know.

Watch here for updates.

 

[VK3ZYZ]

I've rescued a couple of coils from a Codan 7727 and placed them in Chan 10 position.

Hopefully I can just feed the VFO into the points shown.

Unfortunately, the speaker grill is not an add-on that I can remove, but just pressed from the front panel.

So I think the OLED display will mount on the ALARM position for now.

 

[VK3ZYZ]

I have hacked together some code from the last PCM Hawk I did to try out.
The original crystals will be replaced with the Si5351 signal, as will the "BFO" crystal.
Only channel 10 will be variable at this time, on 80M LSB. The code has quite a few build options that will probably not be used.

 

[VK3ZYZ]

I have it sort off going. The RX seems ok but I am not getting power out even though I can hear it on a local receiver so the low level stuff is working, at least partly. The coils I added for channel 10 are not tuning in the correct spot sinI'll mod the code to allow wide tuning to find where they peak.

The OLED is mounted in the ALARM button position.

Here is the BFO feed in place of the 1.650Mhz crystal.

I took some other pics but hey were out of focus so later.....

Here now.

 

[VK3ZYZ]

At the moment, channel 1 is in use for the 80M as channel 10 did not work. The caps were probably wrong and to just top it off, I broke a slug
To get channel 1 to tune, I added 120p across the existing 680p caps.

 

[VK3ZYZ]

A string of 2K2 resistors is added to the spare switch wafer (that existing spare made it easier) to give a variable voltage indicating the channel switch position. The wiper goes to A6 and the ends of the string is between 0V and 5V. There is an extra R on each end so if one was to read 0V or 5V, that would be an error. Dividing the ADC reading by 86 gives the channel number.

The cable clamp pushed hard against the ADC connector so the board mounting would be better out from the case side a bit.

And here is the latest code. It works ok but still using channel 1 as the 80M band. When I can figure out the coils needed, channels 9 and 10 can be pressed into service and channel 1 returned o the original VK band.

Some WD-40 spray on the tuning controls helped fix noisy operation.

 

[VK3ZYZ]

Here is the VFO circuit.