John Huffman-3 wrote:
>
>
> My K3 has the 400hz 8-pole filter and the latest firmware. I've noticed
> that the difference between running the DSP filter at 100hz and 150hz is
> greatly increased volume at 150hz. With the NR on (F2-4) easy listening
> at 100hz will bow your ears out at 150hz. Is this just me? I run AF
> gain at 9 o'clock and RF gain at 12 o'clock.
>
> I have a second question. I liked to run my Orion on CW with the AF gain
> up, RF gain down, narrow filter and NR on. That way it listening to the
> other station was like listening to a code practice oscillator. On the
> K3 I still get background hiss with the noise reduction on. Are there
> better settings to use to get the sound I want with no background noise?
>
NR is actually not doing much to improve S/N at low BW settings. The same
was true for Orion (which I used for 4 years). While NR might be useful at
SSB bandwidths, it's probably just fooling you at narrow CW bandwidths.
Read from the horse's mouth below and especially note #6.
73, Bill
http://www.zerobeat.net/mediawiki/index.php/K3_DSP
NR explained by Lyle Johnson KK7P
I think there is a fundamental misunderstanding of what NR is and how it
works, at least in the context of the K3.
1) NR is better named SE (signal enhancer).
2) It is a "short" FIR filter whose coefficients are continuously being
recalculated.
3) It defaults to suppressing everything.
4) When it senses that there is something that correlates (i.e., has a
pattern that doesn't seem to be entirely random), it attempts to build a
filter around those frequencies that seem less random.
5) Because the FIR filter that is being implemented is short, the filter
being built is less selective than the normal DSP filters in the radio.
6) NR is rarely useful if the bandwidth is narrow. If you set your CW width
to 400 Hz or less, for example, there is no point in running NR *unless* you
want to use it as a sort-of "smart squelch."
7) The narrower you set your WIDTH, the more that noise appears like a
signal, and the worse the NR will perform. And the less noise there is
anyway, assuming there is a signal present. NR cannot compete with a narrow
filter, and was not designed to.
8) I find NR most useful during CW operation with the 2.8 kHz roofing filter
NORM'ed so the Rx bandwidth is wide. Assuming band activity is low, the Rx
is quiet. If a CW station comes on within the Rx passband, a filter will be
built around the station and I can hear it.
9) Similarly, I find NR in SSB is mostly useful as a sort of squelch when
tuning around, or monitoring a frequency you are expecting a call on
(probably a net or a sked). I use NR1-1 or NR1-2 for this. Mild suppression,
not too much impact on fidelity, and lets me hear weak signals, too.
I hope this is helpful in better understanding how NR is implemented in the
K3.
--
View this message in context:
http://n2.nabble.com/K3-Narrow-CW-Filter-tp2258338p2258733.html
Sent from the Elecraft mailing list archive at Nabble.com.
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
