455khz Ceramic Filter Oscillator

This is then fed through a third bjt where the 455khz is mixed in from a ceramic resonator.

455khz ceramic filter oscillator. Lt455fu cfu455f murata equiv filter 12 khz total bw 455khz 3 leg. The circuit consists of a classic relaxation oscillator using a pair of bjts with c r timing circuits to create an audible tone at around 450hz. Now i m searching a schematic for a tunable 455khz bfo without any. Simplest 455 khz oscillator uses only three parts negative resistance ceramic filter oscillator ceramic resonator oscillator rf oscillator with three parts the simplest oscillator ever if anyone can successfully disprove this claim i ll gladly retract it.

Nand gate u2b buffers the original unmodulated signal and its propagation delay ensures that its output is in phase with the output of u2a. For a 4093 oscillator without the filter the frequency 2 7 r c so if the resistor is 3k then c 2 7 3k 470k 19nf. The local oscillator is set to 100 455khz and when the mixer mix the rf 100mhz with the osc 100 455mhz the product will be 455khz and lots of other frequency products. Murata makes the cerafil r line of ceramic filters some of which are designed for use at 455khz and 450khz.

Murata ceramic filters 455 khz signal conditioning are available at mouser electronics. For example the sfpla450kd1a b0 has a 6db bandwidth of 10khz designed for use with am stereo receivers. A search of ebay for filter if 455 turns up units like the avx kyocera kbf455r which may be suitable for your project. Also see that the ceramic filter is connected to 5v in that schematic but my ceramic filter only has 1 input 1 output and 3 ground pins.

What we want is only the 455khz signal. The local oscillator is set to 100 455khz and when the mixer mix the rf 100mhz with the osc 100 455mhz the product will be 455khz and lots of other frequency products. Lt455gw cfw455g murata equiv filter 15 khz total bw 455khz 5 leg. What we want is only the 455khz signal.

Lt455eu cfu455e murata equiv filter 15 khz total bw 455khz 3 leg h149. Lt455hw cfw455h murata equivalent filter 6 khz total bw 455khz 5 leg h148. Mouser offers inventory pricing datasheets for murata ceramic filters 455 khz signal conditioning. The ceramic resonator is a fairly common part often used in remote controls.

Nand gate u2a is the modulator and provides a 100 square wave modulated signal.