[CQ-Contest] YAESU DSP vs. CW Filters

Guy Olinger, K2AV k2av at contesting.com
Mon Jul 3 13:34:42 EDT 2000

Yeah, you might think the 400's a bit tight, I do as well.

But a walk in a major contest with a wider bandwidth pair in line, and
you realize that you have to decide to either HEAR up and down there or
NOT HEAR up and down there. Personally, if  I DON'T hear, I last a lot
longer. W2CS can listen all weekend to stuff that gives me brain
damage -- it's an individual choice.

With the passband matching DSP of the MV, the stuff just a tiny bit up
and down the passband will drop off the planet. Not sure I would want
that for CQing on CW. With  the IF shift I make use of those little
ranges up and down where the skirts start to drop. (DSP on SSB might be
quite another matter. Dunno.)

The cascaded filters eliminate key clicks generated in the IF stages,
and make it possible to work close to a REALLY loud cw station up or
down 500 Hz. The DSP will not substitute for the benefit of the loud
station getting really attenuated in the 8 MHz IF.

For the day when DSP substitutes for essentially perfected crystal
filters, we still need another three or four orders of magnitude
improvement in the speed and bandwidth of DSP processors to hit the dirt
cheap fabrication level.

I say this because it will have to run cleanly at low levels at the
8/9/10 MHz IF's to approach the effectiveness had now by cascaded INRAD
filters. And it's the "low level" part that will be the hardest to come
by. The best DSP setup for a while will still be some kind of hybrid,
where we STILL push stuff through a sharp filter at 8 MHz.

There's just no affordable DSP out there that can unassisted pick out a
weak wanted CW signal with an unwanted +60 db CW signal up 200 Hz.

I already can, right now, with my already paid for MP + INRAD's. Switch
to cascaded 250's, IF shift, the wanted signal tuned to the edge of the
skirt, and the unwanted way down the side. AFTER the crystals, the DSP
can slice the remaining audio if the filter between the ears needs help,
that's an existing assist in the MP.

However, given recent progress in computer speeds et al,  it maybe
killer DSP isn't too far off.

Just don't spend a fortune for anything current and depend on just the
DSP to do it for you in the next major CW contest, especially if you're
used to cascaded INRAD's. The MV needs 'em just as much as the MP. For
the moment, the INRAD's are the killer setup, no new whiz-bang yet to
replace king crystal.

- - . . .   . . . - -     .   . . .     - - .   . - . .

73, Guy
k2av at contesting.com
Apex, NC, USA

----- Original Message -----
From: <ed.miske at kennametal.com>
To: <cq-contest at contesting.com>
Sent: Monday, July 03, 2000 9:32 AM
Subject: [CQ-Contest] YAESU DSP vs. CW Filters

> I'm strongly considering replacing my TS940 with a 1000MP MARK V.
> I'm looking for comments on the operation of the YAESU DSP in a CW
> envorinment.
> I've been running the IRC 400khz filters in my Kenwood for the past
> years and have learned to really like them, (though I think the IRC
400's a
> maybe just a little too tight, but that's another story).
> It  has been suggested to me that I will not need optional CW filters
> the MP due to the DSP.
> My gut tells me that the DSP may be fine in casual operation but I'll
> regret not getting the filters when SS CW rolls around.
> Comments?
> Thanks
> --
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