Monday, November 09, 2015

Airband receiver kit + Si5351

Got one airband receiver kit from a popular an auction site,

(kit's are cheaper now from what I've seen)

Kit includes everything and even some extra components (better more than less).
It worked first time after assembly. Already with that in mind (or as standalone in case of failure) decided to convert it to use the Si5351 clock generator IC, re-using the airband VFO box I made to convert the PAE receiver from single channel to VFO. The Park Air Electronics receiver conversion wasn't successful because of the low range of the internal VFO without manually retuning the coil so the box and the inner Arduino was kind of redundant:

The PAE airband receiver, single channel selection by dip switch's. for what the air band vfo box project was initial intended:
The airband VFO box was supposed to remotely change the DIP switch settings of the PLL, it worked as I programmed but the VFO tuning range was short so I only got 2Mhz excursion from the main frequency before the PLL unlocking... it was kid of bitter taste of a failure in the middle of a success.

So for the Airband kit I place the Si5351 (and the kit itself) inside the airband vfo box and changed the code from the DIP connections to the clock programming of the Si5351. The connection to the airband receiver kit mixer from the Si5351 is strait forward and worked first time:

For the in place kit connection on the PCB what needs to be changed is the connection to NE602 on pin 6 and pin 7, applying the VFO signal on pin 6 of the NE602, the oscillator part (in the kit) is removed by means of disconnecting pin 6 and 7 to the main board..

..using a simple adapter to be inserted inline without modifications on the PCB :

you see the two "missing" pins on the underside that will no connect pin 6 and 7 of the NE602 to the kit PCB
They are never the less connected on the top part of the adapter board and connected then to the VFO (si5351)

The kit without adapter

Final product with adapter in place and connected to the Si5351:
From left to right, back panel, airband kit, arduino and the si5351 module on top, and on the right the from panel with the LCD display and frequency selection buttons.

Still no external squelch and volume on the box (mid and right pot's) because I don't have a drill around....

The power will be provided from the Park Air electronics receiver, that will remain single channel, so when I power it on will get that channel and another one I can select on the new airband kit.

Here's the schematic for the push buttons by popular request:

Have a nice week!


Povilas said...

Great work - thanks.
Components are on the way... :)

Ricardo - CT2GQV said...

Hello Povilas,

Thank you for the comment.

Have fun!

Marci Harci said...

Good job
the sourche code public??
if you send me
am happy

Marci Harci said...

Good receive
i build if you send code

Ricardo - CT2GQV said...

Hello Marci,

Thank you for the comment.
Drop me an email and I will send you the code.
email is: my_call_sign @

Ricardo / CT2GQV

Marci Harci said...

I send a mail

Ricardo - CT2GQV said...

Hello Marci,

Please do send email.


ORMO said...

Hello Ricardo!

Ive trying the same way as You.

Ive bought this kit, disconnected pin 6 and 7 of NE602, connected the SI5351 and... nothing.
There was a lot of noises from speaker.

The Si5351 DO have a lot of signal on output. Did You use some kind of ATT on the output of SI?

New airband receiver kit has been delivered to me, so I ll try again... The 8.33 step will be beautiful...
Can you send me and email with your code ?

73! SP7EZG form Poland!!

Ricardo - CT2GQV said...

Hello Artur,

Will send code.
In regards to the connection:

1 - Was it working before with the inboard VFO ? I find it easier to tune to a "volmet" station since it's normally a continuous transmission.
2 - Is the si5351 on the correct frequency?
3 - Output level of the si5351 worked fine to the ne602 without att, only dc blocking capacitor
4 - Code will be sent by email.


Ping said...

Hi Ricardo !

I'm sorry if my question is stupid, and most likely it is because everybody else manage to solve the problem on their own :D
My understanding of your modification is :
- disconnect the pins 6 and 7 of NE602 from the main's board varicap VFO;
- reconnect every pin but 6 and 7 of the NE602 to the main board via piggyback socket;
- connect NE602's pin6 to CLK1 of the Si5351 through the coax core and a 1pF cap;
- connect Si535 to NE602's GND (pin3) through the coax sleeve.
From the explanations, pictures and comments, I could not sort out what to do with NE602's pin7...
So my noob question is : where do I connect NE602's pin7 for this mod ?

Thank you ;)

Ricardo - CT2GQV said...

Hello Ping,

As for the change, do like this:

Pin 6 and 7 of the NE602 will _not_ connect to the base board (the airband receiver pcb)
Inject VFO signal from the si5351 to pin 6 of the NE602 (base of the internal NE602 oscillator circuit) trough a 1pF dc blocking capacitor.
Again: pin 7 on NE602 is left "free running" no connection to anywhere.
Ground is common to the Si5351, arduino and air band receiver pcb so I left't floating on the NE602 pcb adapter board side but connected on the Si5351 side to avoid any ground loop.
I will try to improve the schematic in the future, even I got confused with my writing.

Hope it helps!

Ping said...

Hi Ricardo,

It's crystal clear !
Thank you very much :)

Toshihiko JR6JAE said...

Hello, I am from Japan
I read your article very interestingly.
It's a wonderful completion.
I am also making an air band receiver with the same circuit.
I made a code with nano but it does not work well
Will you tell me the code

Ricardo - CT2GQV said...

Hello Toshihiko,

Thank you for the comment.
Send me an email to: "my callsign" @ and I will reply back.


Anonymous said...

I have folled your steps and used my selve written code for the Arduino. but every time I connect the si5351 to the other parts the receiver jamms it seleve, it only receives the signal of the si5351.
I have tried to shield everything but it doesn't work.
How can I fix this issue?



Ricardo - CT2GQV said...

Hello Philipp,

Some troubleshooting steps:
- check the circuit works without the changes on the vfo part, that is if you have any reception with original vfo circuit.
- check the si5351 is outputting on the right frequency, some one reported some fake/not working ones some time ago.
- check that when changes were made on the circuit, the original connection of the ne602 vfo are not there in parallel
- check if the cap of 1pF is in series withe the vfo.

Good luck.
Ricardo / CT2GQV