[Icom] FW: A DSP IF filtering test any IC-756Pro/Pro2 owner can perform

Sun, 5 May 2002 12:51:35 -0400

Thanks for the post...that states the best example of DSP and just how
important and helpful it is to have it in the Pro II I own....as much as I
love my FT1000D the bottom line is what few times I operate it now..I can
not block and filter QRM and dig signals out like I can with the Pro II. The
Kenwood TS870 and MP and Mark V series are not bad...but they are all way
too much of a pain to menu through to accomplish the same thing and on the
MP and Mark V...you need to buy a truckload of filters and Nrad modes to get
close to this kind of performance. I for one thought I would never own an
Icom HF radio after buying and selling a IC746 in three weeks due to the
poor receive performance on 2 and 6 meters. But I am glad I did and I am
excited about the direction DSP is headed. It will only get better and
better and the prices cheaper and cheaper as the chips in computers have! If
this post is offensive to you..please hit the delete button as it is based
on my personal experience with the gear mentioned here and my own research.
73, Steve, NX1G

----- Original Message -----
From: "Julio" <[email protected]>
To: <[email protected]>
Sent: Sunday, May 05, 2002 11:57 AM
Subject: Re: [Icom] FW: A DSP IF filtering test any IC-756Pro/Pro2 owner can
perform

> Warren have you tried this out? I don't think I understand it.
>
> Julio
> ----- Original Message -----
> From: "Adam Farson" <[email protected]>
> To: "Icom Reflector" <[email protected]>
> Cc: "GEORGE T. BAKER" <[email protected]>; <[email protected]>
> Sent: Sunday, May 05, 2002 1:13 AM
> Subject: [Icom] FW: A DSP IF filtering test any IC-756Pro/Pro2 owner can
> perform
>
>
> > I am posting this test procedure to the reflector on behalf of, and by
> kind
> > permission of, Rob Peebles, W8LX. The test procedure can also be found
on
> my
> > Icom page:
> >
> > http://www.qsl.net/ab4oj/icom/w8lx.html
> >
> > Best 73,
> > Adam, VA7OJ/AB4OJ
> > North Vancouver, BC, Canada
> > http://www.qsl.net/ab4oj/
> > Note new e-mail address:
> > mailto:[email protected]
> >
> >
> > Good evening gentlemen.
> >
> > "Perhaps these are not what you would call "narrow filters" but they are
> > adequately narrow to ultimately prevent overload of the DSP A/D
> > converter(s) and that is all that is required." (Excerpt from George,
> W5YR's
> > posting of 5/1/2002)
> >
> > Try this test to convince yourself the above is true.
> >
> > Take your PRO and set up in the CW mode with a bandwidth of 50 Hz (with
> BPF
> > illuminated).  Tune in WWV at a time when the signal is strong
(currently
> 20
> > over S9 @ 15 MHz).  When you are zero beat perfectly (i.e. sidetone
pitch
> > matches beat note from the WWV carrier) all you hear is the carrier (no
> > modulation, voice etc.).  Now tune up 100 Hz (due to calibration errors
it
> > might be easier for you to just move up with the RIT instead of the main
> VFO
> > after you find the true zero beat) and listen to the BCD time code.
Notice
> > how well you can hear the bit pattern of the time code (and how you
don't
> > hear much of anything else).  Set the AGC to fast and watch the digital
S
> > meter paying particular attention at the top of the minute when there is
> no
> > 100 Hz tone transmitted.  Pretty impressive for being 100 Hz away from
> that
> > strong carrier!
> >
> > Now go up to 150 Hz above the WWV carrier....don't hear a thing.  See
how
> > low the noise floor is?
> >
> > At 200 Hz above the WWV carrier  we see the harmonic of the 100 Hz BCD.
> >
> > At 250 Hz above it is spooky how much of the signal you don't hear!
> >
> > Now, go up to 500 Hz (even minutes) or 600 Hz (odd minutes) and listen
to
> > the standard audio frequencies.  Pay attention to the ramp of the tone
> > coming and going in conjunction with the ticks (during the period of the
> > tick the 500 or 600 Hz tone is briefly muted).
> >
> > 1000 Hz is the fundamental frequency of the ticks.  At that offset you
see
> > the ticks very nicely but nothing else - well unless it is an even
minute
> > then you hear the harmonic of the 500 Hz tone being transmitted!
> >
> > When you tune through WWV in such a manner and see how you can pick
apart
> > and separate the various components of their transmission without
overload
> > from the main carrier you get a pretty good feel for what kind of
> "close-in"
> > ultimate selectivity and noise floor that can be achieved with DSP
> > filtering.
> >
> > Hopefully you can make enough sense out of my ramblings to try this at
> home
> > (I'm tired and just about to go to bed).  I've just re-convinced myself
I
> > don't want to go back to life before DSP.
> >
> > 73,
> >
> > Rob Peebles, W8LX
> > Dublin, Ohio
> >
> > Postscript:
> > Tuning 10 MHz now I can barely hear WWVH in the background.  WWVH's top
of
> the
> > minute tone
> > is 1200 Hz, and yes I can isolate it in the passband too (it is so weak
it
> > doesn't move the s meter).  I hear it much better on 15 MHz (where WWVH
is
> > stronger), and on 20 MHz (where I can't hear WWVH) it's gone.
> >
> > ----
> > Your Moderator: Dick Flanagan W6OLD, [email protected]
> > Icom FAQ: http://www.qsl.net/icom/
> >
>
>
> ----
> Your Moderator: Dick Flanagan W6OLD, [email protected]
> Icom FAQ: http://www.qsl.net/icom/
>