[Lowfer] narrow filters

[John Andrews]

Doug,

I'll agree with Jay on the FFT programs, never having seen a situation 
where playing with audio levels, contrast or color couldn't produce the 
same results.

But for copying regular-speed CW signals such as NDBs, an external audio 
filter can be a big help. I picked up an HP 3581A from eBay, and its 30 
Hz or even 10 Hz positions do make a difference. That said, watching the 
CW signal on Spectran accomplishes about the same thing, with similar 
minimum thresholds. But it's fun to exercise your ears and brain, and to 
be able to make an audio recording. The audio filter may help.

John, W1TAG

On 10/31/2010 8:06 AM, Douglas D. Williams wrote:
> Since LF activity really seems to be picking up, I went ahead and
> ordered the 250Hz 455kHz IF filter for my R75. This, combined with my
> current 500Hz, 9MHz IF filter, should give the receiver good
> selectivity. In your opinions, would I see any additional benefit in
> getting an even narrower external audio filter? Some of the DSP units
> can provide selectivity down to 20Hz! I'm not sure if this amount of
> selectivity would help when trying for QRSS signals. I suppose it
> could be of benefit when listening for NDBs. Opinions?
>
> -Doug KB4OER
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