I must agree with Jim on every point. The noise blanker does work but
only on impulse signals. It does little to nothing on broad band noise
and in fact, as Jim stated, can be degrading to the decoding of signals
if used with broad band noise.
And I agree that reducing BW or changing SHIFT is not an ideal means,
but do use 2.7 kHz to 2.8 kHz for better receiver performance. Just let
the software do its job. With wider bandwidths as opposed to filtering
to lesser bandwidths, with wider BW's there is less impact on the
decoding success of the software. The software is designed to operate
within the normal SSB bandwidth of the spectrum. If there are signals
higher in frequency or lower in frequency there is nothing wrong with
using the "big knob" on the radio to change frequency slightly to
receive those signals. And again, the software knows what to do when
it comes time to transmit.
And I find the use of slow AGC is really a must. The electronics is
much better than I am for determining if gain needs to be adjusted.
Just let the superior electronics and software do the job.
73
Bob, K4TAX
On 5/13/2019 12:18 PM, Jim Brown wrote:
On 5/13/2019 2:53 AM, Richard Lamont wrote:
The WSJT-X decoder has huge dynamic range (16-bit 48000 samples/sec
input decimated to 12000 samples/sec, so over 90 dB), so it's best to
use the RX as a dumb converter and let the decoder deal with it. It's
the right tool for the job.
Yes, BUT -- while the theoretical range of a 16 bit system is 96 dB,
non-linearities at the lower end of the dynamic range limit it to
about 90 dB. That's still a lot, and it's why I recommend setting the
audio level as high as possible at the input of the A/D.
This means keeping the bandwidth of the RX at least as wide as the band
displayed on the waterfall and avoiding the use of anything in the K3
that might improve the signal for aural CW/SSB reception such as notch
filtering, equalisation, noise blanking and noise reduction.
I will offer an alternative view on use of the NB. Yesterday, AG6EE
was in a rare grid in northern NV on 6M, and there was VERY strong
impulse noise coming from his direction. Without the NB, WSJT-X could
not decode him. WITH the NB, it did, and I made the QSO. I would NOT
recommend general use of the NB, because it generates IMD that results
in multiple decodes of the same signal, but there are exceptions to
every rule. :)
AGC should be avoided because the level of every FT8 signal in the
passband will be modulated by fading on the strongest signal, which
makes the decoder's job harder.
I find that this is not a problem with AGC-S, primarily because in my
situation, the very strong signals are locals, not subject to QSB.
73, Jim K9YC
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[email protected]
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[email protected]
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
