My method for determining the 60 db drop was to use the Orion S meter. I
used an old crystal calibrator as a constant source signal. And yes, I did
have the roofing filter set to 20 khz.
Carl Moreschi N4PY
Franklinton, NC
----- Original Message -----
From: "Bill Tippett" <btippett@alum.mit.edu>
To: <tentec@contesting.com>
Sent: Monday, September 27, 2004 5:18 PM
Subject: [TenTec] Orions SO2R in CQ WW RTTY
> Hi Bob,
>
> Nice job in the contest! Your comment below raises a
> question I've had for some time. Maybe N4PY has some ideas.
>
> 5B4AGN wrote:
> >2. Filter shape factor is really the only significant concern I had
over
> the weekend. With b/w down at around 250 Hz the DSP shape factor is not
far
> short of 3:1 which really isn't good enough. As a consequence, folks
could
> sidle up real close to Orion's beautifully clean signal and sit there
inside
> my passband causing me grief. I spent way too much time over the weekend
> inching up or down in frequency to avoid QRM from folks alongside. This
> leads me to the following conclusion:
> FOR TOP NOTCH CONTEST GRADE RTTY USE, ORION'S DSP NEEDS TIGHTER SKIRTS.
>
> Carl N4PY measured the following in May 2003:
>
> Filter 6 DB width 60 DB width Shape Factor
>
> 100 150 440 2.9:1
> 250 240 470 1.95:1
> 500 510 820 1.6:1
> 1000 980 1160 1.2:1
> 1600 1580 1880 1.2:1
> 2400 2360 2500 1.06:1
> 3000 2930 3270 1.12:1
> 4000 3960 4280 1.08:1
>
> Source:
http://dayton.akorn.net/pipermail/tentec/2003-May/033783.html
>
> But G3SJX of RSGB reported the following:
>
> 100 131 623 4.8:1
> 250 225 682 3.0:1
> 500 444 843 1.9:1
> 1000 965 1338 1.4:1
> 1800 1766 2151 1.2:1
> 2400 2364 2746 1.16:1
> 4000 3974 4362 1.1:1
> 6000 5236 6322 1.2:1
>
> Source: June 2004 RadCom review of Orion
>
> I've wondered about the large difference in shape factors
> for narrow DSP filters and wonder if Carl has any ideas why.
> I'm assuming both Carl and G3SJX set the roofing filter to
> one much broader than the DSP so that they were not measuring
> the cascaded effect.
>
> BTW, when someone sidles up close to me, I usually return
> the favor by moving closer to them, just to make sure they can
> hear me better. ;-) I normally out-hear them and they usually
> go away after awhile.
>
> 73, Bill W4ZV
>
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