User's Manual

CSM System Time – GPS & LFR/HSO Verification

68P09258A31–A

Oct 2003

1X SCt 4812T BTS Optimization/ATP

3-44

Low Frequency Receiver/High Stability Oscillator (LFR/HSO)

The CSM and the LFR/HSO – The CSM performs the overall

configuration and status monitoring functions for the LFR/HSO. In the

event of GPS failure, the LFR/HSO is capable of maintaining

synchronization initially established by the GPS reference signal.

LFR – The LFR requires an active external antenna to receive

LORAN–C RF signals. Timing pulses are derived from this signal,

which is synchronized to Universal Time Coordinates (UTC) and GPS

time. The LFR can maintain system time indefinitely after initial GPS

lock.

HSO – The HSO is a high stability 10 MHz oscillator with the necessary

interface to the CSMs. The HSO is typically installed in those

geographical areas not covered by the LORAN–C system. Since the

HSO is a free–standing oscillator, system time can only be maintained

for 24 hours after 24 hours of GPS lock

Upgrades and Expansions: LFR2/HSO2/HSOX

LFR2/HSO2 (second generation cards) both export a timing signal to the

expansion or logical BTS frames. The associated expansion or logical

frames require an HSO–expansion (HSOX) whether the starter frame has

an LFR2 or an HSO2. The HSOX accepts input from the starter frame

and interfaces with the CSM cards in the expansion frame. LFR and

LFR2 use the same source code in source selection (see Table 3-19).

HSO, HSO2, and HSOX use the same source code in source selection

(see Table 3-19).

NOTE

Allow the base site and test equipment to warm up for 60

minutes after any interruption in oscillator power. CSM board

warm-up allows the oscillator oven temperature and oscillator

frequency to stabilize prior to test. Test equipment warm-up

allows the Rubidium standard timebase to stabilize in frequency

before any measurements are made.