Radio Road

Which tuner to get and getting the most from it. Thank God, for the radio!

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RE: Any plans for alignment? (nt)

Posted by Steve O on August 15, 2011 at 20:02:18:
Thanks for sticking with me on this. My filter theory is very rusty.

I have two basic "questions"

1. Has it been established that the 10B IF section is indeed a series of cascaded, "non-resonant" bandpass filters providing an overall Butterworth response as the 10B promotional lit seems to imply? The schematic is drawn such that it looks like a series of buffered passive filters. Or is it just a fancy conventional resonant topology? Something else?

2. If this is indeed a series of cascaded bandpass filters, to achieve max flatness within the passband (as advertised) won't the individual filter pole frequencies and Qs be staggered in some manner to achieve the desired overall response characteristic. If this is the case, it's the frequency staggering of each section that I'd be trying to reverse engineer knowing that the overall filter characteristic was Butterworth of X order with a center frequency of 10.7 MHz and a bandwidth of say 200KHz. By knowing the frequencies for each section, one could then align each section individually to produce the desired overall response characteristic.

I don't own a network analyzer and if I did I wouldn't know how to use it in an FM IF alignment procedure. Is there info on this process? I'm not planning on getting an analyzer but I'm curious about the principles behind it.