I've used an external audio filter on most of my receivers. Both DSP and
passive (http://www.geraldj.networkiowa.com/papers/speakerfilter.pdf).
The passive filter leaves no artifacts behind. I haven't found the DSP
59+ can dig a signal out of the noise, but if the signal is near the
noise level it can improve S/N. And bandpass filtering is very good,
50Hz bandwidth only rings on 35 wpm + CW speeds. Bandpass filtering
after the AGC loop can have strong rejected signals pumping the AGC and
so varying the signal you want, but it also has an AGC mode that levels
audio and tends to bring back noise after noise reduction.
CW with my passive filter set to cutoff about 450 Hz with a suitable low
pitch beat note is kind of eerie. No noise, just signal.
73, Jerry, K0CQ
On 2/26/2011 11:13 AM, kc9cdt@aol.com wrote:
Ray,
Yep for CW I use the manual notch IF I ant to make one go away.....
The NR is, well not so good...usually I just leave it off. Occationally
it works OK..
To tell the truth, I have several boat achor RX's that do much beter in
noise.
The best is probably the Hallicrafters SX-117...it's audio PB is on the
low side...so it is MUCH quieter to listen to...rather nice I might
add. As you tune...signals just seem to jump out of the noise.
I think a external audio filter setup would work pretty well on OII...
Any one try one yet?
73,
Lee
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