Topband: DSP Summary - FT1000MP, TS870, others

[Iowaguy]

Reflector friends. . .

As promised, I have attempted to put together a summary of sorts regarding
the overall effectiveness of DSP.  My original comment that started all of
this shared my disappointment at the lack of effectiveness of DSP in
the  FT1000MP.  I then put out a follow up comment seeking input from owners
of the TS870, the new IC 756PRO, and others.

I have been flooded with replies!  Like other subjects, many observations
are anecdotal and subjective (we clearly hear things differently).  I will
do my best at summarizing a wide array of responses, comments, and
observations.

First of all. . . to address the original issue of DSP effectiveness on the
FT1000MP.  Roughly 65% of the responses said (in one way or another) that
the DSP was not effective and did not really contribute toward pulling out
weak signals that are near/at/or slightly below the noise floor.  About 35%
felt that the FT1000MP DSP offered a very small contribution toward pulling
out weak signals.  Many people lamented the fact that the DSP (which is at
the audio level) was not in the AGC loop.  However, not one input about the
MP DSP was really very positive.  (hmmm...see P.S. below...de W4ZV)

With regard to the TS870 DSP performance. . . the numbers were significantly
different.  Roughly 70% felt the TS870 made some sort of meaningful
contribution toward pulling out weak signals.  The other 30% indicated that
the DSP helped marginally but did not like the distortion introduced by the
DSP "washing" the noise (I've heard it. . . it does sound different).  Aside
from the DSP issue, several people commented that the Inrad filters
contributed significantly toward helping prevent receiver overload (at which
time the DSP goes "bonkers" and just puts out garbage according to the
owners).  Several people commented positively about the fact that the DSP
was in the AGC loop.  It was interesting that virtually everyone felt, at
the minimum, the DSP helped at least a little.

Two people commented that purchasing the FT1000MP was a mistake, and that MP
owners should be purchasing the Ten Tec Omni VI Plus.  One VI+ owner
commented that the DSP makes the signals "leap out of the noise."  (An
editorial comment. . . we had four VI+ units at our local contest station
and I never experienced anything like that during many hours parked in front
of them).   The other VI+ owner indicated that the DSP helped and was
worthwhile.  Maybe Ten Tec is on to something???

Several people lamented the general problem with L.O. noise generated in
synthesized rigs.  Several people commented they were either hanging on to
their R4Cs (many with Sherwood mods), S Lines, A4's, or wished they had.

It was interesting to find that there are quite a few folks out there
running two or three receivers at the same time.  In this scenario, one
receiver was usually an earlier tube type, non-synthesized rig (R4C, S Line,
A4, etc) but several were running high end Racals.

Several people also commented on the general ineffectiveness of the various
after market (all audio stage) DSP units.  No one commented very positively
about any of them with regard to pulling weak signals out of the noise floor.
However, several people indicated that these units (as well as built-in DSP)
helped with ignition noiseand other impulse type noise.

And lastly, I did get one input from a person who had just sat down for a
few minutes and tried out an IC-756PRO.  He said the receiver DSP looked
fairly promising but didn't really have enough experience to draw much of a
conclusion.

I apologize if I have rambled.  It has been much more difficult to
characterize people's thoughts than I had ever imagined.  Even though
we're dealing with something that is quantifiable and measurable, many of us
don't have means to do that. . .  so we just "use our ears" (which
ultimately tells the bottom line) and try to relate with words what we're
hearing.  That makes quantifying all of this a bit challenging!

I hope this summary has shed a bit of light on what is definitely a very hot
topic!

73 to all. . . Dave
W0FLS

P.S.  I thought I sent this to Dave but maybe he didn't recall it.  I have
found one and only one DSP setting to be effective for very weak signals to 
my ears: Pitch = 350 Hz, both 250 Hz IF filters, Contour full CCW, NR full
CW, both Shift and Width about 1/2 division CW from detent (adjust by ear).
Also, I know K6SE likes Contour to first CCW positon (bandpass) with 
menu 4-5 set to 60 Hz.  So there are at least two of us who have found at
least one setting useful.  Please take further discussion of this to the
1000MP reflector at  http://www.qth.net/archive/1000mp/1000mp.html  de W4ZV
 





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