[Elecraft] Re: roofing filter loss and method of compensation

[wayne burdick]

Like other roofing filters, the narrower the passband, the more loss. 
In general the loss is similar to those shown for the FT-1000 8.215 MHz 
filters shown on the INRAD web site. Our 5 pole filters in some cases 
have a little less loss.

The loss at this point in the radio (the first I.F.) has very little 
impact on MDS or other characteristics, because the noise figure is 
established in earlier stages.

When you install any roofing filter, you use the menu to tell the 
firmware what the filter's bandwidth is, any small offset from 8.215 
MHz, and what the relative loss of the filter is. The DSP adjusts the 
15-kHz I.F. gain based on the entered loss amount, so all filters have 
the same overall gain.

Once a filter is installed, you can specify which modes it is available 
in (or all modes).

73,
Wayne
N6KR


On Apr 29, 2007, at 3:57 AM, DOUGLAS ZWIEBEL wrote:

> Can you discuss the loss of the "narrow" roofing filters and elaborate
> on "how" you compensate for that?  How does that compensation impact
> rx peformance specs (ie, do some "get worse)?
>
> Thanks,
> de Doug KR2Q
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