I just sent this, in part, over to the LDM users list:
Short: Our NOAAport system was down between 14:25Z and 15:35Z for cable
replacement and checking. It is back online now...and you shouldn't have
seen any issues.
Long: We replaced the 120' length of RG-6 coax cable from the dish to the
Novra S-200 receiver with 120' of RG-11 dual-shielded cable from
Starcomm. By doing so, we also didn't need three inline barrel conectors
which added to the signal loss. Before we started this, our signal
strength at the dish was 92%, and 76% at the Novra S-200 receiver. After
the replacement, it was 92% at both the receiver and at the dish. Two
engineers and myself, based on the cable loss rating, believe we got an
additional 8 dB of signal gained to the receiver by this replacement.
Furthermore, checking/unchecking the "long line" option (long cable run,
adds 1 volt to the system) only slightly improved the carrier to noise
(C/N) ratio. Speaking of which, that increased from ~11.5 to around 12.5
after the cable replacement, until a fairly thick high cirrus shield came
over and dropped it down to around 10-11. I have no idea yet what's
supposed to be a "good" C/N with this setup.
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I have a couple of more things to add to this. First of all, I got an
email response back from the Chief Engineer of Weigel Broadcasting in
Chicago. He responded simply:
For most QPSK feeds, anything over 8db is good C/N.
So if you decide to use the Novra S-200, or another device that displays
C/N, now you know what to shoot for.
Secondly, do use RG-11 for anything longer than 50' coax runs for
NOAAport. You won't regret it. You can use up to 100' of RG-6 and probably
be good, but with a rain fade situation, every db counts! If your signal
is mission-critical like mine is, the extra expense is worth it.
*******************************************************************************
Gilbert Sebenste ********
(My opinions only!) ******
Staff Meteorologist, Northern Illinois University ****
E-mail: sebenste@xxxxxxxxxxxxxxxxxxxxx ***
web: http://weather.admin.niu.edu **
*******************************************************************************
