Q-Lite Satellite Modem Installation and Operating Handbook
6-7
•
Receive Doppler buffer usage
. This indicates how full the receive Doppler buffer
is. This is displayed only when a receive Doppler buffer is being used to
compensate for movements in the satellite (i.e. when the Rx clock source is set to
something other than
Satellite)
.
•
Number of Doppler buffer overflows and underflows.
These represent the number
of times the receive buffer has slipped as a result of overflows and underflows.
These counts are reset to zero when the demodulator goes out of lock. They can
also be cleared using the front-panel menus.
•
Receive DVB-S2 baseband frames and errors
. These indicate the number of
DVB-S2/S2X baseband frames and baseband frame errors, respectively, that
have been received since the Rx service was started and give an indication of the
quality of the service. The
Reset baseband counts
button can be used to set these
counts back to zero.
6.2.2.3 Status Paired Carrier™
The
Paired Carrier™
section of the
Status
screen is displayed and continually updated
with the following information while
Paired Carrier™
is enabled:
•
Paired Carrier™
status
. This is shown as
Locked
when
Paired Carrier™
has
locked to one of the two overlapping carriers and is shown as
Unlocked
when
Paired Carrier™
is attempting to acquire the carrier (refer to
Section 6.2.3
for
potential causes).
•
Paired Carrier™
frequency offset
. This is the measured offset between the
expected centre frequency for the wanted carrier and the actual centre frequency.
An unexpectedly large offset may indicate a false lock, where
Paired Carrier™
is
locked to something other than the wanted carrier.
•
Paired Carrier™
satellite delay
. This is the measured round-trip delay to the
satellite. Once this value has been established then the carrier acquisition time can
be optimised by setting the
Paired Carrier™
minimum and maximum satellite
delays accordingly. It is recommended that these are set to the measured delay -
/+0.5ms respectively (via the
Edit->Paired Carrier
menu).
•
Paired Carrier™
near/far power ratio
. This indicates the power spectral density
ratio of the two overlapped carriers. It may be useful during deployment and
whenever degraded performance is being experienced to check that the power ratio
is as expected in relation to the level of power asymmetry. The power ratio should
be in the range -10dB to 10dB for normal operation.
6.2.2.4 Status ACM
The
Adaptive Coding and Modulation
(
ACM)
section of the
Status
screen is displayed and
continually updated with the following while ACM is active:
•
Remote modem Es/No
(energy per symbol to spectral noise density ratio).
•
Transmit data rate
. This is the instantaneous transmit data rate, which varies with
modcod
(modcod is the term used to describe the combination of modulation and
FEC rate).
•
Transmit modcod
. This is the current transmit modulation and FEC rate, which
vary with remote Es/No.
