[INRAD] Filter Board

[Dick Powers]

So it's kind of like a funnel right in the front end to eliminate the
unwanted stuff right off the bat I guess, huh?
Thanks Steve (Boy I haven't seen the term "kc" used in awhile.)
Dick WB9PWQ 73

On Tue, 25 Oct 2005 20:37:46 -0400 <steve.root at culligan4water.com>
writes:
> A "Roofing filter" is a crytal filter that is used in the 
> first IF.  My understanding of the problem is that the 
> decision to include general coverage reception dictated a 
> first IF frequency in the VHF range, like 70 Mc.  Until 
> fairly recently it was difficult to make a narrow filter that 
> operated at these frequencies.  The first IF stage was pretty 
> broad, on the order of 12 Kc wide.
> 
> I have a lot of time in with both the FT-1000MP and the FT-
> 1000D before and after adding the roofing filters.  The 
> differences are immediately apparent.  The MP in particular 
> was much improved.  During periods of heavy activity like a 
> CW contest I usually ran the MP with the pre-amp off and 6 or 
> 12 db of attenuation in line to keep the receiver 
> from "crunching".  After adding the roofing filter the 
> attenuation wasn't necessary as stong signals outside the 
> passband were eliminated by the filter.  In a word, it's 
> great!
> 
> 73 Steve K0SR 
> 
> 


Dick