Overview
The BRIDZA STW-FS725 is a high-performance rubidium clock source with GNSS disciplining capability, delivering exceptional phase noise and stability. Supporting up to 22 simultaneous outputs and multiple frequency options up to 2.5GHz, this instrument is ideal for distributed timing systems, radar arrays, and clock ensembles requiring the highest level of synchronization.
Supported Models
| Model |
Outputs |
Frequency Options |
Stability (1s) |
| ------- |
--------- |
------------------- |
---------------- |
| STW-FS725-H1-10M |
1 |
10MHz |
≤1.5×10⁻¹³ |
| STW-FS725-H1-100M |
1 |
100MHz |
≤1.5×10⁻¹³ |
| STW-FS725-H2-10M |
2 |
10MHz |
≤1.5×10⁻¹³ |
| STW-FS725-H-10-1000M |
1 |
10/100/1000MHz |
≤1.5×10⁻¹³ |
Front Panel Layout
┌────────────────────────────────────────────────────────────────┐
│ BRIDZA STW-FS725 GNSS DISCIPLINED RUBIDIUM CLOCK │
│ │
│ ┌──────┐ ┌──────┐ ┌──────┐ ┌──────┐ ┌──────┐ ┌──────┐ │
│ │ PWR │ │ GNSS │ │ LOCK │ │ ALM │ │ HOLD │ │ SYNC │ │
│ │ ● │ │ ● │ │ ● │ │ ○ │ │ ○ │ │ ● │ │
│ └──────┘ └──────┘ └──────┘ └──────┘ └──────┘ └──────┘ │
│ │
│ GNSS ANTENNA 10MHz OUTPUTS 1PPS OUTPUTS │
│ ┌──────┐ ┌────┐ ┌────┐ ┌────┐ ┌────┐ ┌────┐ │
│ │ ANT │ │ 01 │ │ 02 │ │ 03 │ │ 01 │ │ 02 │ │
│ │ ● │ └──○─┘ └──○─┘ └──○─┘ └──○─┘ └──○─┘ │
│ └──○───┘ SMA female BNC female │
│ │
│ ┌──────────────────────────────────────────────────────────┐ │
│ │ ETHERNET RS232 DC INPUT OPTIONAL │ │
│ │ ┌────┐ ┌────┐ ┌────┐ ┌────┐ │ │
│ │ │RJ45│ │DB9 │ │ ○- │ │ │ │ │
│ │ └────┘ └────┘ └────┘ └────┘ │ │
│ └──────────────────────────────────────────────────────────┘ │
│ │
│ MODEL: STW-FS725-H S/N: __________ REV: 2.1 │
└────────────────────────────────────────────────────────────────┘
Interface Definitions
| Parameter |
Specification |
| ----------- |
--------------- |
| Connector |
SMA female |
| Supported Systems |
GPS L1 (1575.42MHz), BeiDou B1 (1561.098MHz), GLONASS L1 |
| DC Power |
5V @ 100mA (antenna LNA bias) |
| Input Impedance |
50Ω |
| VSWR |
≤1.5:1 |
| Cable Loss Compensation |
Up to 15dB |
| Return Loss |
≥10dB |
Antenna Requirements:
- Active antenna with LNA
- Gain: 30-40dB (including cable loss)
- Noise figure: ≤1.5dB
2. 10MHz Reference Outputs
| Parameter |
Specification |
| ----------- |
--------------- |
| Connectors |
SMA female (×N, varies by model) |
| Frequency |
10MHz (standard), 100MHz, 125MHz, 250MHz (optional) |
| Signal Level |
13dBm ±2dB |
| Impedance |
50Ω |
| Harmonics |
≤-40dBc |
| Phase Noise |
≤-180dBc/Hz @ 10kHz (100MHz) |
| Isolation |
≥80dB between channels |
3. 1PPS Outputs
| Parameter |
Specification |
| ----------- |
--------------- |
| Connectors |
BNC female (×2 standard) |
| Signal Level |
TTL / LVPECL (configurable) |
| Pulse Width |
1ms / 5ms / 10ms (configurable) |
| Rise Time |
≤10ns |
| Accuracy |
≤±50ns to GNSS time |
| Jitter |
≤500ps RMS |
| Impedance |
50Ω |
4. Ethernet Interface
| Parameter |
Specification |
| ----------- |
--------------- |
| Connector |
RJ45, 10/100/1000BASE-T |
| Protocols |
NTP, SNTP, SNMP, HTTP (Web UI) |
| NTP Accuracy |
≤25μs to UTC |
| NTP Queries |
>140,000 responses/sec |
5. Serial Monitor Interface
| Parameter |
Specification |
| ----------- |
--------------- |
| Connector |
DB9 female |
| Protocol |
RS232 |
| Baud Rate |
9600 (default), 19200, 115200 |
| Data Bits |
8 |
| Parity |
None |
| Stop Bits |
1 |
TOD (Time of Day) Format:
$GPGGA,123519,3958.5446,N,11628.3456,E,1,08,0.9,545.4,M,46.9,M,,*47
Format: NMEA GPGGA
Fields: Time, Lat, N/S, Lon, E/W, Quality, Sats, HDOP, Alt, ...
Disciplining Modes
| Mode |
Description |
Holdover Performance |
| ------ |
------------- |
--------------------- |
| GNSS Lock |
Full GNSS disciplining |
±50ns to UTC |
| Holdover |
GNSS signal lost |
±1μs/24h |
| Free-run |
Internal rubidium only |
Refer to spec |
| External |
External 1PPS reference |
Depends on ref |
Power Supply
| Parameter |
Specification |
| ----------- |
--------------- |
| Voltage |
+12VDC or +24VDC (selectable) |
| Current |
≤3A @ 24V, ≤5A @ 12V |
| Power Consumption |
≤30W |
| Connector |
Circular 4-pin or terminal block |
Mechanical Dimensions
482mm (19" rack width)
┌─────────────────────────────────────┐
│ │ 44mm (1U)
│ STW-FS725 │
│ GNSS DISCIPLINED RUBIDIUM │
│ │
│ [ANT] [===10MHz===] [===1PPS===] │
│ │
└─────────────────────────────────────┘
└── 450mm ──┘
Typical Application
┌────────────────────────────────────────────────────────────────┐
│ DISTRIBUTED TIMING SYSTEM │
│ │
│ ┌──────────┐ │
│ │ GNSS │ │
│ │ Antenna │ │
│ │ (Roof) │ │
│ └────┬─────┘ │
│ │ │
│ ├──────────────────┐ │
│ │ │ │
│ ▼ ▼ │
│ ┌─────────┐ ┌─────────┐ │
│ │STW-FS725│ │STW-FS725│ │
│ │ (Main) │ │(Backup) │ │
│ └────┬────┘ └────┬────┘ │
│ │ │ │
│ Coaxial Distribution via STZ-PF-xx │
│ │ │ │
│ ├──────────┬───────┤ │
│ │ │ │ │
│ ▼ ▼ ▼ │
│ ┌────────┐ ┌────────┐ ┌────────┐ │
│ │ Radar │ │Com. │ │ Data │ │
│ │ Array │ │Base Sta│ │Center │ │
│ └────────┘ └────────┘ └────────┘ │
│ │
└────────────────────────────────────────────────────────────────┘
SCPI Command Set
*IDN? ; Read identification
:FREQ ; Query output frequency
:FREQ ; Set frequency (Hz)
:OUTP:STAT 1 ; Enable outputs
:OUTP:STAT 0 ; Disable outputs
:SYNC:MODE ; Set sync mode (GNSS/EXT/HOLD)
:SYNC:STAT? ; Query lock status
:SYNC:OFFS? ; Query offset to reference
:SYST:TIME? ; Query current time
:GPS:QUAL? ; Query GNSS fix quality
:GPS: satellites? ; Query visible satellites
:GPS:SNR? ; Query signal levels
Troubleshooting
| Symptom |
Cause |
Solution |
| --------- |
------- |
---------- |
| GNSS LED off |
Antenna disconnected |
Check SMA connection |
| - |
No satellite visibility |
Reposition antenna |
| - |
Cable too long |
Use amplifer or shorter cable |
| Lock LED flashing |
Searching for satellites |
Wait, check antenna position |
| Holdover LED on |
GNSS signal lost |
Check antenna/cable |
| NTP not responding |
Network config error |
Check IP settings |
| - |
Firewall blocking |
Open UDP 123 |
Download Resources
Document Version: 1.0
Last Updated: 2026-05-24
BRIDZA Technologies