[TenTec] Roofing Filters

Ken Brown ken.d.brown at hawaiiantel.net
Mon May 29 18:05:30 EDT 2006


Hi Carl,

That is a pretty broad definition. Every filter in my receiver from the 
frontend bandpass filters to the first IF and second IF filters limit 
bandwidth before the final audio filtering. So there is virtually no 
filter, by that definition, that is not a roofing filter. I'm not 
intending to be argumentative. I am just trying to find out what people 
really mean by the term "roofing filter". I suspect that without a clear 
definition, the term is being used slightly differently by every one who 
uses it.

It seems that most of the time people are referring to a filter after 
the first mixer (regardless of whether it is a up conversion to a higher 
frequency IF or to a mid HF IF). Yet the term may also apply to narrow 
tuning range (typically QRP rig) receivers that have a crystal filter 
before any mixer stage. I have not heard anyone call an LC BPF a roofing 
filter. So does it have to be a crystal filter to be "roofing"?

N6KB

Carl Moreschi wrote:
> The term roofing filter means a filter that limits bandwidth before the
> final stage of filtering.  Because of this, roofing filters do not have to
> have sharp shape factors.
>   
>   



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