[TenTec] WIDER FILTER FOR WEAK CW DXING?

[Bill Cotter]

Jerry,

Taking your point regarding filter response shape (ideally, rounded 
edges, steep slopes, and flat passband), and looking at the 
response curves for the Inrad CW filters, they look pretty incredible.

         http://www.qth.com/inrad/graphs/759.gif

         http://www.qth.com/inrad/graphs/750.gif

         http://www.qth.com/inrad/graphs/763.gif

I don't know if these are actual plots of sampled 400Hz filters, or 
'marketing' plots. But, using these filters, I can say that they 
are very, very good for weak signal listening in noisy conditions. 
They don't have the incessant roaring (noise power) in the passband 
like the TT 500Hz filter.

73 bill n4lg


At 03:25 PM 6/16/2007, you wrote:

>It is possible to have sharp corners, flat frequency response, steep
>skirts, and a good time response but that is ungodly expensive in
>hardware because the design has to use many extra resonators to 
>correct
>the phase response. In a digital filter it is handier to have the 
>extra
>poles to achieve both goals, at the cost of total time delay.
>
> >
> > > I almost always have easier and clearer copy on weak cw signals
> > > when I use the 1.8 kHz filter vs. the .5 or .25 kHz filters 
> in my
> > > 6.3 MHz IF. I've got nothing in the N1 position. Is this the 
> way
> > > it's supposed to be?
> >
> > --
> > 73 DE N7WIM / G8UDP
> > Kevin Purcell
> > kevinpurcell at pobox.com
> >
>
>--
>73, Jerry, K0CQ,
>All content copyright Dr. Gerald N. Johnson, electrical engineer
>