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

Sun, 5 May 2002 16:47:36 -0500

DSP works!

----- Original Message -----
From: "John L Merrill" <[email protected]>
To: <[email protected]>
Sent: Sunday, May 05, 2002 2:53 PM
Subject: RE: [Icom] FW: A DSP IF filtering test any IC-756Pro/Pro2 owner can
perform

> get what?
>
> -----Original Message-----
> From: [email protected] [mailto:[email protected]]On
> Behalf Of Matt Erickson
> Sent: Sunday, May 05, 2002 10:08 AM
> To: [email protected]
> Subject: Re: [Icom] FW: A DSP IF filtering test any IC-756Pro/Pro2 owner
> can perform
>
>
> Some guys STILL don't get it.
>
>
> At 08:30 PM 5/5/02 +1000, you wrote:
> >g'day all on the icom reflector
> >
> >this is a useful and demostrative test
> >i would not dispute that dsp has a role to play in a quality
communications
> >receiver
> >
> >but only as a post filter beyond a couple of good tight xtal filters
which
> >determine the
> >close in two tone third order intermodulation dynamic range
> >
> >the test proves conclusively that the dsp has a dynamic range in excess
of
> >60db - big deal,
> >so does a typical radio shack "communications receiver" (sic), as hams we
> >should be getting 100dB
> >from the big name manufacturers rather than the 70dB to 80dB currently
> being
> >thrust upon us.
> >it is not all that difficult to achieve in a mass production environment
> >
> >again, we should be clear in voicing this to icom, yaesu & kenwood :
> >
> >(1) we are prepared to pay the extra for high dynamic range 1st mixers,
> >       which almost entirely determine the intermodulation dynamic range
> >achieved -
> >       if the rest of the package is of similarly high quality
> >
> >(2) dsp is a useful adjunct & can entirely replace all the VBT, PBT, twin
> >PBT stuff
> >       that we grew addicted to before we understood much about
> >intermodulation
> >      dynamic range, but don't fob this stuff upon us at the expense of
> >dynamic range
> >
> >(3) if you can't give us at least an option of tight narrow bandwidth at
> >first IFs in the 70MHz region
> >      then we can live without absolutely continuous coverage from 100kHz
> to
> >60MHz; give us a 1st IF around
> >      9MHz where quality discrete lattice xtal filters are cost effective
> (if
> >costly) and leave a gap in coverage
> >      around the first IF freq  (or in the top end rxs with
sub-receivers,
> >let the main & sub have different
> >      non-overlapping coverage gaps). with cpu control & DDS as standard
> now,
> >mixing and matching
> >     of multiple local oscillators & IFs is a trivial exercise
> >
> >just my 2 cents worth
> >
> >73s gd dx de sam dellit vk4zss
>
>
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