Ceramic filter pinout and help with a 455khz BFO

[Richard9025]

Hi !
I salvaged a 455khz ceramic filter from a CB radio , but I cant find any datasheets or relevant info on the internet
Some photos :







If you can't determine which pin is which , I can take some photos of the radio that it was extracted from (eurocb micro 2) , maybe a schematic and the photos will get the answer .
Now with the BFO (it is based on the model from IK1ZYW http://spazioinwind.libero.it/ik1zyw/hardware/osc455.html)
In the following schematic I assumed that pin 1 is output , pin 2 ground and pin 3 input :



The votage regulator works , from an input of 9V i get 5.1V
Now , to test if it works , I connected it to an SDR , but I can't see the oscillation on 455khz :
With it connected , I dont see anything , no change
But if I rotate R2 (a multiturn , 10 turns , pot) or I just get near the bfo , look at what happens , if I get away , it dissapears :



Yeaa , messy stuff

Thanks !

 

[davenn]

I assumed that pin 1 is output , pin 2 ground and pin 3 input :

always dangerous to assume

confirm it from the radio you took the filter out of

 

[Richard9025]

I forgot to connect C3 to ground , now it works perfectly , thanks !

 

[davenn]

I forgot to connect C3 to ground , now it works perfectly , thanks !

good to hear

 

[73's de Edd]

Sir Richard9025


There would be two uses for a BFO . . . one would be for the use of the reception of upper and lower SSB VOICE communications .

The other would be for the reception of code signals .... . .-.. .-.. --- --- ---.

If the former, can you tolerate the audio rate modulating square wave frequency that the '14 is generating in order to "BANG" the ceramic filter into shocked state operation, in order to generate its 455khz signal.

As for using it on the latter situation of receiving a code signal, that might be permissible, if it doesn't heterodyne with the converted audio signal.

Most people typically will use an already on hand or easily locatable 455 khz IF transformer in a conventional oscillator circuit to get their pure sine BFO signal..

DIFFERENT SITUATION NOW . . . .

If that is your signal above . . . . . that situation is now being different, as you are banging the unit with a 22.8 khz driving signal, which would be up on in the ultrasonic range.
No problems.


73's de Edd