Basic Arduino VFO for crystal replacement

VK3ZYZ

Moderator
Ray has some Si5351 boards...
Thanks Ray.
Si5351_Fitted.jpg

It works :)


ItWorks.jpg
(Ignore the actual frequency please. I have the program half 2M and half 70cm bands. Oops!)
 
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VK3ZYZ

Moderator
This code is better!
I just noticed the board is in TX mode with no input on the TRX line. but the code starts up in RX until the encoder is turned. That will be an easy fix, but maybe tomorrow. Or better still, someone else fix it and post the updated code.
Please feel free to play as much as you want.
 

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VK3YNV

Moderator
Hi Denys,

Compiled ok and runs without any problems, still haven't found the encoders, and tested the CTCSS output, but it all looks ok so far.
Congratulations Denys Nice job!

IMG_3632.JPG
IMG_3633.JPG
IMG_3634.JPG

Next job will be to modify the software to generate the frequencies to suit the Philips FM828.
 

VK3ZYZ

Moderator
I have started on an FM828A.
FM828FrontChassisCutout.jpg
Front panel cut out to fit an OLED display.

A slot needs to be filed into the chassis to fit the encoder.
EncoderSlot.JPG

And the power switch mount cut, removing the AUX switch. The 2 brown wires of the AUX are cut off, soldered together and insulated.
PowerSwitchMod.JPG

Then, the encoder is wired. I 3D printed a mounting bush.
EncoderWiresAndBush.JPG

It fits pretty well.
EncoderMountedFront.JPG EncoderMountedBack.JPG

To mount the VFO board, it turns out there are a couple of holes just in the right place. A M/F M3 pillar for each. Make sure the thread is not too long to short the boards under. 2 nuts seem to be a good length.

Pillars.JPG
And the board fits :)
ItFits.JPG

On the TX exciter board, remove the black wire..
TX_RemoveBlack35-3.JPG
and add the VFO signal coax, with a coupling cap. Braid to 3 and cap from center to 41.
TX_Coax.JPG

Similarly, on the RX, remove the black wire..

RX_RemoveBlack.JPG
and add the coax as shown. there is a cap on board that can be used but the value may need increasing. Edit: I added a 150pF on the back of the PCB.

RX_Coax.JPG

This is as far as I have got for now...
EncoderAndCoax.JPG

Something to eat sound good!

Edit:....
Almost Alive.jpg

I am having problems with the code. It looks like a RX divisor of 3 is too low. It may be a maths problem or a limitation of the si5351.
A divisor of 6 looks ok.
And I need a knob for the encoder in the AUX position.

EDIT: The receiver tunes up ok, no mods needed. In fact I did it and listened to the club meeting on it.
 
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VK3ZYZ

Moderator
Here is the code so far. This is using an OLED display, based on the SSD1306 chip.
You can use a white one, but I like the yellow/blue. This one has the top 1/3 in yellow, and the lower 2/3 as blue.
EDIT: I fixed the TX multiplier as it should be 8, not 12.
ModifiedUSB.jpg
And this is how I modified a USB plug to fit. All I beed to do now is 3D print a nice replacement 90 degree headshell for it.
The extra cut in the lead sheath was there already!
 

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VK3ZYZ

Moderator
To fix the USB plug as above, I 3D printed a housing and with a couple of bits of dual wall heat shrink, made a good fix.
USB_MiniPlug6.jpg
USB_MiniPlug1.jpg USB_MiniPlug2.jpg USB_MiniPlug3.jpg USB_MiniPlug4.jpg USB_MiniPlug5.jpg
 

VK3ZYZ

Moderator
The CTCSS resistors are wrong. Use the SIP R2R pack. It works.
There is another artwork error that does not really matter too much. Pin 7 is connected to the CTCSS resistors/SIP and that needs to be cut. The SIP pin now will be linked to the other 3 that are connected together.
BoardCut.jpeg


Here is a view of the "finished" VFO.
CTCSS.jpg
A 100nF cap is connected from the gnd pin to the top of the resistor as shown. This smooths the side wave.


Below shows the audio/power supply board in the version worked on. There is a TX timer set for 1 min. Cut the link shown to disable the timer.
AudioVRegBoard.jpg
 

VK3ZYZ

Moderator
The next one is started!
This is an FM828E that will be on 6M.
FM828E_03.png

It is all hooked up, except the CTCSS line, and mods I will do for a 'standard' mic and LS.
After those, the tuning mods will start.
Here is the code too. Just note, this radio has not been tuned as yet, so the code too may need adjusting.
FM828E_01.jpg

I just noticed, it will be an idea to move the frequency display to the right a bit.
 
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VK3ZYZ

Moderator
The code has been fixed to adjust the display position.
FixedDisplay.jpg

Other mods are to replace the sockets on the back with more 'standard' ones.
SocketMods.jpg

Also, the power lead is soldered on as I do not have the original connector. That is ok as I'm making all the power connectors the same anyway. Anderson power pole connectors are the ones to use.
Anderson Power Pole.jpg

The exciter mods were to add some caps..
18pF across the Varactor coupling cap, and 6p8 across the VFO and buffer coils.
ExciterAddedCaps.jpg

As was the receiver...
6p8 across each trimmer. Added to the end of the trimmer caps to the case.
ReceiverCaps.jpg

The PA needs mods but it "works" with all the trim caps fully closed. Not full power, but quite ok.
Full mods will be posted later when I get them done.

Here is the updated code as well.
 

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VK3ZYZ

Moderator
6M_FM828_Front copy.png
I thought it was about time the front was put back on.

Also, I'm in the process of enclosing the VFO in a tin box, and will shield the leads to the encoder and display to see if that gets rid of a couple of birdies.
 

VK3ZYZ

Moderator
I'm working on the second FM828 Low band.
The cables from the display and encoder are now shielded.
FrontCables0.JPG

FrontCables1.JPG

A couple of holes have been drilled at an angle for these cables.
FrontCables2.JPG

FrontCables3.JPG

FrontCables4.JPG

And, for this one, I've added the cap under the PA board.
This is the before...
PA_btm.JPG

And after. The red coloured 1206 SMT caps are 22pF, un-coloured 1206 SMT cap is 10pF, and the leaded ceramic cap is 6.8Pf. It may need to be increased as it should be 10pF.
This is not a SMT cap as the spacing is too wide.

PA_Caps.JPG

So far, these mods have not been tested.
 

VK3ZYZ

Moderator
As I do not really want to run the FM828 sets as remotes, I have designed a 3D printed front.
Front.jpg

There is a knock out place for a front mic socket if needed.
Back.jpg

This is the case that bolts to the FM828 with the 2 bolts.
Frontcase.jpg

And all put together.
Assembled.jpg

I may make it larger, or at least the back of the case bigger to line up with the cover.
 

VK3ZYZ

Moderator
I just took delivery of these encoders...
EncoderPlus.png
They come with the PCB and a knob. All for around $2 so that is a lot better than the bare version!
And they are bread board friendly too!
 

VK3ZYZ

Moderator
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VK3ZYZ

Moderator
I was looking to go to a sine wave generator, and in this case, the AD9833 12Mhz board.

AD9833.png
When they arrived today, (3 only, I ordered 6), I was interested to see how they go,
I am a bit disappointed.
Here are some wave forms...

AD9833_1Mhz.jpg

AD9833_1.65Mhx.jpg
AD9833_2Mhz.jpg
AD9533_5Mhz.jpg

and 10Mhx (my scope read it as 12Mhz because it is actually moving as well as distorted,
AD98333_10Mhz.jpg
The distortion is rippling along the waveform.
A filter will help, but I may as well stick to the Si5351 boards and add a filter there.

These chips will make a good audio and low RF frequency sig gen.
 

BillC

Active member
Might need a LPF. and an impedance/load to work into at the higher end of its frequency range, looks interesting though.
 

VK3ZYZ

Moderator
The AD9954 looks really good!. It can be the basis of a very fine bit of test gear, or transceiver.
The club members could do with a good construction project I think.
Oh, I have been assured by the suppliers of the AD9833 boards that I purchased that they sent 2 packages to be below the postage threshold so the other boards should arrive shortly.
 
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