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RAPCO Type 1804
L25E8A GPS Precision Frequency Source
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Front Panel |
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| Rear Panel |
 | USES SIGNALS FROM THE GPS SATELLITE CONSTELLATION AVAILABLE WORLDWIDE. |
| VOLTAGE-CONTROLLED QUARTZ OR RUBIDIUM OSCILLATOR CONSTANTLY DRIFT-CORRECTED WITH RESPECT TO THE GPS TRANSMISSION. |
| VERY-LONG-TERM ACCURACY OF THE OUTPUT APPROACHES THAT OF THE SATELLITES' ATOMIC REFERENCE OSCILLATORS. |
| UNITS DO NOT REQUIRE CALIBRATION OF INTERNAL OSCILLATORS IN ORDER TO MAINTAIN FULL PERFORMANCE. |
| RELATIONSHIP BETWEEN 1HZ TIMING OUTPUT AND UTC IS MAINTAINED SO THAT PRECISE RELATIVE TIMING CAN BE ACHIEVED BETWEEN DISTANT INSTALLATIONS. |
Designed and manufactured under strict quality
control conditions, the 1804 can be used with confidence as a frequency
reference for both analogue and digital T.V. & radio transmission, in
Cellular networks and for Telecommunications timing. Other applications include
military communication systems, satellite ground stations and
calibration-laboratory systems, particularly in connection with the development
and manufacture of high-technology products. With over 1,400 installations
worldwide, the 1804, now in its third-generation, continues to offer an
unmatched combination of accuracy, functionality and reliability.
PRODUCT IDENTIFICATION
Products in this family are divided into two main groups, which are:
1804L25xxx - Quartz referenced units
1804L26xxx - Rubidium referenced units
The 1804 is available with a wide range of options;
identified by a two or three-character suffix in the type number [xxx in the
above examples]
The 1804L25E8A, described below has become virtually an industry standard for
numerous broadcast applications, In particular it has been successful for
Digital Audio Broadcast (DAB) and Digital Video Broadcast (DVB) in Single
Frequency Networks where the control of both Frequency and Timing is crucial.
The Rubidium-reference 1804L26xxx versions offer exceptional accuracy for
calibration-standard work or as a Master clock for satellite control centres or
Telecommunications Timing. The 'stand-alone' accuracy of the reference
oscillator is more than two orders-of-magnitude higher than a Quartz-referenced
unit.
SPECIFICATION 1804L25E8A
FREQUENCY OUTPUT
| Reference Frequency | 10 MHz |
| Number of Outputs | 1x Sinewave on (BNC) |
| Amplitude, Sine output | +10dBm in 50 ohm. factory setting, (+7 to +13dB available) |
| Type | Square wave, +ve edge on-time 1Hz, derived from the internal drift-corrected oscillator and phase-locked to the average position of the GPS 1pps (UTC). |
| Number of Outputs | 1 x BNC |
| Signal Level | TTL >+4V o/c, >+2.4V into 50 ohm |
| Accuracy (uncalibrated) | Leading edge on-time to UTC-UNSO to within ±300 nanosecond. |
| Stability | ±100nS typical, 95% probability. |
Two operating modes are available:
(a) Terminal Mode - Unit powers up in this mode
Data are formatted to directly drive a 'dumb' terminal, or a PC running a terminal emulator. This provides a continuous, rolling display of Date and Time plus Position and Satellite-acquisition data.
(b) Remote Mode
A range of commands is available providing comprehensive control and interrogation of the unit’s functions
and status.
ALARM OUTPUT
| Provides an alarm
indication in the event of:
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Loss
of GPS lock Oscillator control loss Power supply failure |
| Relay Contacts | Normally-closed, Voltage-free (but BNC connector shell grounded) |
| Contact rating | 30V 0.5A d.c. max. |
| Alarm | Hold-off delay user
programmable 1 sec to 18 hours for GPS and Control Alarms (Separate settings) Immediate alarm on power failure. |
GPS RECEIVER
Double conversion/8 Ch Correlator
GPS ANTENNA
A weatherproof GPS Antenna assembly is supplied
with each unit.
High-environment double-filtered type.
Downlead cables should be ordered separately. Non-standard lengths available to
order.
(See Technical page for antenna installation notes)
GPS ANTENNA DOWNLEAD CABLE TYPE
Two types of antenna downlead cable are available, to cater for differing
installation requirements.
Types E43 and E44 are supplied in standard lengths of 20 metres (E43) and 50 metres (E44).
TYPE E43
Length
20 metres
Cable type URM43. O/D 5mm nominal
N-type connectors supplied fitted both ends.
TYPE E44
Length
50 metres
Cable type BELDEN 9913. O/D 10.3mm
or WESTLAKE 103 O/D 10.4mm
N-type connector supplied fitted both ends.
TYPE E44x Maximum length 70 metres
NOTE :
Where the user
prefers to supply their own cable, the following
parameters must be met. Rapco cannot accept liability for the
correct performance of cables not supplied by them.
a) The cable must be
compatible with N-Types
(straight entry) co-axial connectors (21mm O/D type)
b) Cable impedance (Zo) must be 50 ohm.
c) Maximum cable loss must not exceed 9dB at 1575MHz.
d) Total `round trip'
d.c. resistance of the cable must not exceed
1 ohm.
e) The VSWR of the complete cable assembly must not exceed 1.8:1.
OSCILLATOR TYPE
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FREQUENCY ACCURACY 7 days min. continuous power up and GPS. Averaging Period 24 hours min. Temperature Quasi-Constant, Range 26°C ± 10°C |
1804L25E8A SC-Quartz OCXO |
1804L26A Rubidium |
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Absolute Frequency Error, Ref: USNO |
±5E-11 |
±1E-11 |
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Short Term Stability (Allan Variance 1 sec) |
1E-11 |
3E-11 |
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REFERENCE OSCILLATOR stand alone performance (without GPS) |
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Long Term Stability (drift rate, ageing) |
<±2E-10/day |
±5E-11/month |
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Frequency vs. Temperature (25°C ± 10°C) |
±5E- 10 |
±2E-10 |
1804L25E8 series GPS/Qz UNIT ---- TYPICAL PHASE NOISE PLOT
POWER SUPPLY
| Voltage | 220/230/240V ac ±10% 45 to 66 Hz. |
| Power loading | 15VA typical up to 40VA dependent on options fitted. |
| Connector | 3 pin IEC, 2 m LSF cable & connector supplier |
| dc option is fitted to many models | |
FRONT PANEL INDICATORS
ac, dc (power), Alarm1,
Alarm2, GPS, Control, Status, Antenna Fault,
plus others depending on options fitted.
DC INPUT for
external battery support eg RAPCO 1811
+24V nominal (18-32V d.c. range)
DC OUTPUT
Supply for RAPCO ACU/Distribution Units
DIMENSIONS
Width 483mm standard 19" rack mount format
Height 43.6mm (Standard 1U)
Depth 350mm excluding connectors
Weight 3.5kg approx.
Note: Rack support brackets must be used
CONSTRUCTION
Fully enclosed aluminium alloy case finished
Alocrom 1000.
Front panel painted Parchment White with black legends.
SAFETY
The 1804 Series is compliant with
European Directive 73/23/EEC
Standard :
EN 61010-1
SAFETY & EMC
The 1804 Series is
compliant with European
Directive 89/336/EEC,
Standards:
EN50081-1 (Emissions)
EN50082-1 (Immunity)
TEMPERATURE RANGE
1804 unit
Operating :
0 to +50oC RH 90% non-condensing
Storage :
-40 to + 70oC RH 30%
Aerial Assembly
Operating :
-40 to + 70oC RH 100%
Storage :
-55 to + 85oC RH 30%
OPTIONAL FEATURES
A number of optional features are
available for the 1804 series. With a few exceptions, these are factory-fit
items
(specify at time of order) and are supplied at extra-cost. Further details
available on request.
REFER TO 1804 / 1814 OPTIONS PAGE
for additional information.REFER TO ACCESSORIES & SPARES PAGE for additional information.
Rapco's policy is one of continual improvement. We therefore reserve the right to change this specification without notice
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