TBH one of the things I've wondered about in the days since I long-ceased ever doing any tuner fiddling is how reliable bench measurements are with a stereo gen when real transmissions may get passed though a bandwidth limiting filter at the TX - which can mean they are distorted at TX. You can get some idea of why this matters when you recall that tuners that have switchable IF filters tend to show higher distortion in 'narrow' mode. Older tuners may have LC IF filters and these can alter if you're unlucky.įor the RF stages, the filters are wider, but there the problem is to ensure they 'track' the change in LO to ensure you get the filter centered well onto whatever input FM signal you're tuning to. ![]() But in many 'modern' FM tuners will probably be ceramic or similar, so pretty well defined. These filters tend to be the 'sharpest' so need careful alignment. Can also make the tuner more prone to multipath or pops and clicks.įor the IF stages this is mainly a matter of getting the best filter shape, centered on the actual IF freqency. This matters because poor alignment can foul up stereo performance and degrade both distortion and noise performance. Click to expand.It can mean checking that the bandpass filters in both the RF and IF stages are set up correctly.
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