Local oscillator with SA612 doesn't oscillate

[halunke86]

Hello,

for my receiver I want to use an SA612 as a mixer, but the test of the 1. mixer-part does'nt work, so I decided to test only the local oscillator.
The problem is in the simulation (I was so happy that I found a SA612 spice model) everything works fine, but in reality doesn't oscillate anything.
Is it possible to test only the local oscillator or is there a problem because I have no "input signal"?
Or is there a problem with the dimension of the parts?

Thanks for help

yours sincerly

halunke

 

[Takeshi-san]

try this way

 

[halunke86]

I don't want to use a crystal because i want to tune the frequency (16,x Mhz)....

 

[Takeshi-san]

or this way from datasheet

---------- Post added at 22:28 ---------- Previous post was at 22:27 ----------

with XTAL you can also tune the frequency little bit

 

[halunke86]

@takeshi-san: i'm using the colpitt-l/c-tank modell from the datasheet.... and i want to tune it more than i can tune with a crystal...

 

[Takeshi-san]

let me guess... breadboard?

 

[halunke86]

yes.... but i want to test the circuit before designing the layout and see no other possibility to do this... any suggestions?

 

[Takeshi-san]

your wires around breadboard have capacitance, so oscillator might not start. easyiest way to "design layout" is use universal board http://www.piclist.com/images/www/hobby_elec/picture/pic6_6420.jpg

 

[lab7@owl-inc.com]

Hello Halunke86, A little over a year ago you mentioned you found a spice model for the SA/602/SA/612?
I found one also. It seems I only have the symbol and not the spice code.

Could I trouble you to get a copy of your model for the 602 sent via email.

I would be deeply grateful.

Regards,
Rob

 

[rohitkhanna]

The oscillator section of '602/612 works fine without need for any external signal. You must be making some other mistake in your setup - there ARE some tricky aspects which need attention.

So DO post an exact schematic of your physical setup, that'll help in isolating the problem spot quicker.

Which point are you probing the oscillations at ? Pin7 is good. If you want oscillations out of pin 4 or 5, then pin 1 & 2 need to have caps/ resistors attached in a certain way.

oops... just now noticed how old the post is