inexpensive 45 MHZ crystal filter

L. inexpensive 45 MHz crystal filter A receiver with an intermediate frequency, IF, which is higher than the highest received frequency, fc, has the great advantage that the sep- aration between the received fre- quency and the image frequencies, fc ± 21F, is large. A filter with a high centre frequency and narrow pass-band which is eminently suit- 1 1 * T50-12 1 1 1 50n 1 8 Wdg 27005 MHz ai- 27015 7-74 ~ 2 Wd9 1 1 1 8Wd9 Y" T50-12 20, 1 son~ see text F X1...X5 =27 MHz L5 L1A=8wdg L1B=8wdg L1 = Eerrite bead able for SSB reception can be built from relatively few components. Oscillator crystals often have one or more spurious resonances and this makes their application in filters undesirable because of the risk of unwanted pass-bands. The broader the filter response, the greater this risk becomes. It is possible to use 27 MHz third-over- tone crystals (standard in most CB equipment) in their fifth overtone mode. Figure 1 shows the circuit of a coarse 45 MHz filter using two 27 MHz...