Ceramic filter question!

[radio freak]

Hello,
I do not have much experience in working with coils and ceramics, I just wanted to know
whether the part shown in the picture below would work as a ceramic filter on my rc receiver
which uses a MC3361 FM chip from motorola.
Thanks! :confused:

[vintage1]

What part would that be?

[radio freak]

sorry, but I am having problems while uploadin the image but I can give u a detailed description. The number printed on the part is SFU455B,it is orange in colour and has three pins at the base.

[radio freak]

http://www.dgseg.com/Product/ProductDetail.aspx?ProductID=10002197 this is a link where u can have a look at the pic.

[vintage1]

i will work..but I think the B range is quite wide band..likely to get hits from channels next door....

[radio freak]

Thanks for your reply,
but then which part would you suggest would be a replacement for SFU455B
in the same size and package.

[bob_nj]

Can one of you sum up in a sentence or two what function the filter/resonator has in our hobby?

I read a little on it here -> Resonator (http://hem.passagen.se/communication/ceramic.html)
but a few laymans terms wouldn't hurt.

Thanks, and Happy Holidays_bob

[vintage1]

All the resonator is is a filter that operates at 455Khz and has a bandwih of hopefully about 5-10Khz.

Its the main tining element..the crystal oscillator mixes with the incoming signal to give a difference frequency of about 455Khz and that goes into the next sage which has the ceramic fillter..that in charge of selceting your model out of other transmitters..

Best receivers use two filters or at least a single 6 pole one to give best rejection of nearby frequencies. Cheap recievers use just one 4 pole (Hitech Feather anyone?)

Getting ceramic filtres in less than 1000 off quantities is hard..ebay, radio spares shops, or stripped out of old AM radios or baby alarms is the best bet.

Ive still got a few 4 polers around I think.

[dleroi]

Can one of you sum up in a sentence or two what function the filter/resonator has in our hobby?

I read a little on it here -> Resonator (http://hem.passagen.se/communication/ceramic.html)
but a few laymans terms wouldn't hurt.

Thanks, and Happy Holidays_bob

In a nutshell, they vibrate at a fairly precise frequency, so are used in filter and oscillator circuits to achieve stable operation around the frequencies for which they were designed.

In this case, they are filtering the if output of a radio's mixer circuit, to eliminate all but the desired signal.

In oscillator circuits, such as the clock of a microprocessor, they stabilize the clock's "tick" frequency so that events that require timing, like producing a pulse for a servo motor, can be achieved with a degree of precision.

[radio freak]

BOY! you get ciramic filters at a very high price at your place vintag1. I buy a filter at 3 rs. locally, thats about 16 filters for 1$!!!!