Like many terms in Ham rigs today, "roofing filters" have taken on a whole
new identity that, in this case, has very little to do with their original
function. But there's a tenuous connection, just the same. 

As you probably know, "roofing filter" referred to a filter in the VHF
(typically 60 to 100 MHz) range for an H.F. rig that allowed a very high
I.F. to avoid image issues in an "all H.F. band" rig.

In the Elecraft rigs, people applied it to the 8 MHz I.F. filter. As bizarre
as that sounds, it was apparently in an attempt to show that the xtal filter
set the bandpass ahead of the 15 kHz DSP filters. 

Similarly, in the KX3 the name "roofing filter" is used to indicate the
filter in the audio range that comes ahead of the audio DSP filters. 

73 Ron AC7AC

-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Fred Jensen
Sent: Saturday, April 13, 2013 4:53 PM
To: [email protected]
Subject: Re: [Elecraft] Benefits of Buying a Factory Assembled KX3

On 4/13/2013 4:49 PM, Walter Underwood wrote:

> I got a kit, partly because I did not get the roofing filters.
> Without those, a kit KX3 is fully aligned at the factory.

How do roofing filters work on a direct conversion radio?  That's not a
snarky question, I don't know and would like to.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2013 Cal QSO Party 5-6 Oct 2013
- www.cqp.org

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