[TenTec] Orions SO2R in CQ WW RTTY

[Carl Moreschi]

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 at alum.mit.edu>
To: <tentec at 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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