Why is the bandwidth of the RF filter is wider compared to that of an IF Filter?

AI Thread Summary
The discussion highlights the significance of the 'Q' factor in understanding filter bandwidths, noting that a high 'Q' leads to increased sensitivity to component variations. This sensitivity makes it challenging to construct reliable RF filters, prompting the use of intermediate frequency (IF) filters in superheterodyne receivers for better practicality. IF filters enhance receiver selectivity and can utilize sharp-sided crystal designs. RF filters serve to prevent overload and mitigate spurious responses, operating across various frequencies. Overall, the conversation emphasizes the balance between filter performance and practical construction in radio technology.
detski
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Look up filter 'Q'.
http://en.wikipedia.org/wiki/Q_factor#Physical_interpretation_of_Q
When the bandwidth of the filter is forced to be very small relative to the filters center frequency (f0), i.e. it has a high 'Q', the filter's BW and f0 become very sensitive to slight variations in the components. Parasitic inductance and capacitance of the components and their connections become significant. Thus the practicality of the superhetrodyne radio receivers in which the the RF is first mixed down to some lower IF frequency where the tuning filters can be constructed reliably and easily.
 
As said above that is the point of having superhets..

The IF filter defines the selectivity of the receiver and can be a sharp sided crystal filter. RF filters may be needed at a variety of frequencies and may be tunable and are only required to prevent overload and reduce spurious responses such as the image frequency.
 
detski said:
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LOL The easiest way to learn is to do the math for yourself if you can here is a link to my rf filter http://www.oscilent.com/catalog/Category/rf_saw_filter.htm" page let me know if you find what you are looking for... Good luck
 
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