8A083X30 Rev.11
APX Series P25 Interface
DVRS
User’s Guide
January 2019
Page 21 of 94
Band Locking
When both the MSU and DVR are configured to operate in the same frequency band,
the DVRS requires a special set of filters including and in-band filter placed at the MSU
antenna port. The special in-band filters are required in order to prevent interference
when the DVR and MSU are activated at the same time. When the in-band filter is not
presen
t (‘MSU RF Bypass switch’ in the Tweaker Hardware setup screen is unchecked),
the Band Lock feature is enabled by default and the Tweaker prevents DVR operation
on MSU channels that are explicitly using the same frequency band as the DVR. On
MSU channels where the frequency band is not explicitly known such as in multi-site
Trunking systems, the MSU will be prevented from using frequencies in the same band
while the DVR is active (i.e. in SYSTEM or LOCAL mode). In this case the MSU will no
longer allow roaming to sites using the locked out band. If the MSU is currently on a
Trunking site that uses the locked out band, the MSU will roam to another site. If no
other sites are available, the MSU will become Out Of Range. When the DVR is inactive
(OFF mode), the MSU frequency band is unlocked.
If Band Locking is disabled in the Tweaker, the MSU is allowed to roam to any site
regardless of the frequency band. A typical in-band application that may require Band
Locking to be disabled is the Fixed DVRS application when the MSU and DVR antennas
are mounted in such way as to provide minimum 70dB of isolation and in-band filtering is
not required.
For MSU conventional channels where the band is known and fixed, the DVR restricts
access to channels using the locked out frequency band.
If Band locking is enabled in the DVR and SCAN is enabled in the MSU, the MSU will
skip over any channels in the scan list that are configured to operate in the same
frequency band as the DVR.
For information on MSU Scan operation and limitations, please refer to the
section of this document.
