question about ceramic resonator


Posted on Feb 7, 2014

It looks as if they are highly prone to harmonics meaning in this case, that if the resonator is 455KHz, it will also allow 910Hz and 1820KHz and 3. 640MHz which seems to be dominant and on up. But the frequency around 3MHz seems to be prevalent and one or two multiple of that. It first I thought I was getting intermod so I changed my mixer to a double


question about ceramic resonator
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balanced passive mixer and reduced the gain of the front end. I see now why certain frequencies reoccur. It is not intermod it is the harmonics. So my question is this. Is it common practice or taboo to use a ceramic resonator as a 1st IF filter Maybe there are better ones then the cheap one I bought but I am very dissatisfied with it`s performance since my intention was to use it in a single conversion receiver design. In fact I even used two of them. One after the post mixer amp then a single stage amplifier followed by another. It helped but I still had the same harmonic responses. The use of 455 kHz I. F. depends on the RF frequency. Usually you want RF to IF ratio of 5 to 7. Too high RF will require too much RF filtering to reduce mixer image. Too high an I. F. will be subject to A-B (Able-Baker) spurs. Most new receivers are direct conversion. The mixer is very precise to avoid D. C. offsets and 2nd order crossmodulation. There is usually a automated self calibration within the direct conversion I. C. The use of 455 kHz I. F. depends on the RF frequency. Usually you want RF to IF ratio of 5 to 7. Too high RF will require too much RF filtering to reduce mixer image. Too high an I. F. will be subject to A-B (Able-Baker) spurs. Most new receivers are direct conversion. The mixer is very precise to avoid D. C. offsets and 2nd order crossmodulation. There is usually a automated self calibration within the direct...




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