Noise blankers tend to work best if the noise gate is derived from a
broadband signal, separate to the wanted signal. No amount of DSP magic
will help if the signal is already bandlimited
The Linrad page at http://www.nitehawk.com/sm5bsz/linuxdsp/linrad.htm

discusses this in detail.

R

Tom Holden wrote:
There are some good demos at
http://www.radio.bhinstrumentation.c...nstration.html . I have a
cheap Radio Shack DSP40 that performs at the lower end of the scale as far
as these go. It does a remarkable job of multiple heterodyne reduction and
selectable audio passband but its noise blanker is next to useless and it
does not do noise reduction other than through selectivity.

Tom

"straydog" wrote in message
.org...

A ham friend told me that he heard that DSPs really work at least a little
bit. He doesn't have one and neither do I (although many of the newer and
more expensive rigs have them, and there are one or two outboard DSPs that
are available that can be added to older rigs in some ways). I don't know
all that they can do (auto null heterodynes? auto noise reduction [what
kind of noise reduction?]? audio enhancement [or audio bandpass shaping]
of some kind?) but if static crashes can be really removed or attenuated,
that would be of use to me. Auto null of heterodynes would be nice on
those
occassions when tuner-uppers decide to tune up on my frequency in which I
am already in two way contact with others (on ssb phone). And, maybe there
are some other useful characteristics I don't know about. But, are these
really effective? For example, a 20 db heterodyne null is not much. Nulls
have to be about 50-60 db to be useful.

I'll take any kind of comments, suggestions, refernces to testing, or
personal experience, pro & con recomendations, ...anything...

Art, W4PON

In-band noise blankers can do a pretty good job at lower cost and less
complexity if they are designed properly. The book "HF Radio Systems and
Circuits" from Noble Publishing, also available from ARRL as item 7253, has
some material and references on this subject.

Bill W0IYH

"Richard Hosking" wrote in message
...
Noise blankers tend to work best if the noise gate is derived from a
broadband signal, separate to the wanted signal. No amount of DSP magic
will help if the signal is already bandlimited
The Linrad page at http://www.nitehawk.com/sm5bsz/linuxdsp/linrad.htm

discusses this in detail.

R

Tom Holden wrote:
There are some good demos at
http://www.radio.bhinstrumentation.c...nstration.html . I have
a cheap Radio Shack DSP40 that performs at the lower end of the scale as
far as these go. It does a remarkable job of multiple heterodyne
reduction and selectable audio passband but its noise blanker is next to
useless and it does not do noise reduction other than through
selectivity.

Tom

"straydog" wrote in message
.org...

A ham friend told me that he heard that DSPs really work at least a
little bit. He doesn't have one and neither do I (although many of the
newer and more expensive rigs have them, and there are one or two
outboard DSPs that are available that can be added to older rigs in some
ways). I don't know all that they can do (auto null heterodynes? auto
noise reduction [what kind of noise reduction?]? audio enhancement [or
audio bandpass shaping] of some kind?) but if static crashes can be
really removed or attenuated,
that would be of use to me. Auto null of heterodynes would be nice on
those
occassions when tuner-uppers decide to tune up on my frequency in which I
am already in two way contact with others (on ssb phone). And, maybe
there are some other useful characteristics I don't know about. But, are
these really effective? For example, a 20 db heterodyne null is not much.
Nulls have to be about 50-60 db to be useful.

I'll take any kind of comments, suggestions, refernces to testing, or
personal experience, pro & con recomendations, ...anything...

Art, W4PON