P300H
P300 Series Modem Installation and Operating Handbook
Page 117
6.12.11 Change, BUC/LNB, Tune Ref Menu
This screen is only shown if a tuneable internal reference is fitted (ie something other than the default
1PPM reference).
Tune Reference:[50]%
to nudge
YES to accept, NO to cancel
Change, BUC/LNB, Tune Ref Menu
This screen allows the internal reference oscillator to be calibrated up to about +/- 1PPM (the actual range
depends on the exact oscillator option chosen) to compensate for ageing of the quartz crystal.
To calibrate the internal oscillator, either monitor the 10MHz reference if set to be output up the coax, OR,
(OFF SATELLITE) set the Tx carrier to the highest possible frequency, engage
ÝÉ
(Carrier Wave) from
the test menu, and measure the carrier centre frequency itself.
Needless to say
. Ensure whatever you are measuring the frequency with is itself calibrated, warmed up,
and significantly exceeds the stability of the reference option fitted to the modem (viewable under
ײº±
,
̸·- ˲·¬
)
6.13 MONITOR MENU
Monitor: 1:Demod performance 2:Terrestrial BER
3:Carrier IDs 4:Distant Eb/No & BER 5:AUPC 6:BUC
Monitor Menu
Each of these options is now discussed in turn
.
6.13.1 Monitor, DEMOD PERFORMANCE Menu
Eb/No:10.3dB, To FEC:6.8E-4, To RS:7.8E-7
FAW BER:<1.0E-12, Final BER:<1.0E-12 (RS)
Monitor, Demod Performance Menu
This screen which is regularly updated provides the following information:
Demod Eb/No
This is the effective `signal to noise ratio` the USER sees, (ie Ebi/No, the energy
per information bit). This is also shown on several of the
ͬ¿¬«-
screens.
To FEC
This is the measured uncorrected BER before any FEC. It is the raw
uncorrected bit error rate
into
the FEC and it is not representative of the User
BER after forward error correction. Displayed only if the inner FEC is active, ie
not operating uncoded.
To RS
This is the measured error rate into the Reed-Solomon decoder (from the FEC,
unless operating uncoded). The difference between this and the
To FEC
figure
shows the improvement due to the Inner FEC.