GPS/GNSS Modules

Multi-GNSS Disciplined Oscillator Model GF-8804/05 NEW


Atomic clock class stability GNSSDO
24-hour holdover performance comparable to Rubidium

GF-88 series is a full-featured multi-GNSS disciplined oscillator (GNSSDO), embedded with multi-GNSS receiver, OCXO, LDO regulator and antenna detection circuit in a compact pin-header module.
It provides outputs of one-second pulse, synchronized with Coordinated Universal Time (UTC) and reference frequency (10MHz) signal.

GF-8805, equipped with a high quality OCXO, has a frequency stability equivalent to that of an atomic oscillator of 1.5 μs / 24 hours, not only during reception of GNSS signals, but also during holdover when GNSS falls into unlock. Another module called GF-8804 shares the same form factor with excellent cost performance. It is recommended either model based on designers request could save significant time and effort during product design.



  • Generates UTC-synchronized 1PPS (pulse per second) and continuously disciplined 10 MHz

  • One-module combining a GNSS receiver, crystal oscillator and peripheral circuits that dramatically reduces design cycle (time-to-market) of wireless system.

    GNSS Receiver manufacturer featured one-package solution (no need external CPU)

  • Extremely high stability of 4.5ns (1sigma) using a single band receiver in comformity with G.8272 PRTC-A, PRTC-B

    FURUNO technology made it possible to achieve 5G performance with 4.5ns (1 sigma) stability by single band receiver. GF-8804 and GF-8805 are both in conformity with G.8272 PRTC-B. This is achieved by an improved and advanced position estimation algorithm. It optimizes position calculations using several different GNSS satellite constellations. It allows users to achieve 5G-required performance without changing existing single band GNSS antennas.

    >> White Paper: High Stability of 4.5ns (1 sigma) using a single band GNSS timing receiver

  • Suitable for various RF・Broadcasting applications. Designed functions aiming to solve usual troubles on site.

    The number of radio stations applied with GNSS time synchronization, ex. PMR, local 5G, and V2X, has been increasing year by year. Especially in urban area, users have to face problems such as urban canyon (signals blocked) and multi-path (signals reflected) etc.

    GF-88 series have embedded solutions against;

    1. Multipath in Urban area
    2. Jamming (interference wave)
    3. Spoofing
    4. Interruption of GNSS signal (holdover)

    In addtion, as a longterm supplier of major mobile base venders, Furuno keeps the same carrier grade quality on GF series as well.

    1.GNSS antennas can be mounted on walls and windows of tall buildings
    The Dynamic Satellite Selection™* minimizes deterioration of time synchronization performance by choosing only the high quality satellite signals
    * a new satellite signal selection algorithm developed by NTT
    >> White Paper: Industry-leading multipath mitigation in urban canyon environments

    * GF-880x : GT-88 + OCXO/TCXO
    2.Jamming (interference wave)

    If GNSS receiver is interfered by jamming signals, it can mitigate the negative impact and prevent GNSS signal loss or failure. It also helps investigate the source by detecting and monitoring frequency and power level from the jamming signals.
    >> White Paper: Measures against GNSS jamming (jamming wave)


    Malicious spoofing signals intentionally mislead the position and timing calculation of the GNSS receiver. Therefore it is designed to detect and cancel such effects and protect the system from spoofing attack.
    >> White Paper: Measures against GNSS spoofing signals

    4.Interruption of GNSS signal (holdover)

    Even if the receiving satellites are all lost due to antenna failure, jamming, signal interruption, the timing function keeps working for a holdover period of time.
    ・In case GNSS positioning is interrupted, it predicts and corrects oscillator performance through exclusive adjusting technology.
    ・Excellent cost performance as replacement for atomic oscillator.
    >> White Paper: "Holdover function" as measures against GNSS reception interruptions

  • A lineup of 2 holdover-highlighted models of "Grande" form factor.

    GF-8804, GF-8805 have same pin assignment and output as GF-8801~03. They are designed for applications that request different holdover ability.

    For size oriented users, GF-8801, GF-8802, GF-8803 are also available as small, low-profile model (i.e. Short form factor).

    Form factor Model 1PPS Accuracy 10MHz Short Term Stability
    (Root Allan variance ( =1s))
    Size (mm)
    Lock State Holdover
    Lock State, Holdover
    Short GF-8801 < ±40ns - < 5×10-10 34×27×11
    GF-8802 < ±40ns < ±50μs/24h < 5×10-11 34×27×15.5
    GF-8803 < ±40ns < ±10μs/24h < 2×10-11 34×27×20
    Grande GF-8804 < ±40ns < ±5μs/24h < 1×10-11 100×52×20
    GF-8805 < ±40ns < ±1.5μs/24h < 1×10-11 100×52×20

    [Test data]
    1PPS Timing Accuracy <± X μs continued from start of holdover.
    * Reference information only, values not guaranteed.
    Form factor MODEL 1PPS Accuracy
    < ±0.1μs < ±0.4μs < ±1.1μs < ±1.5μs < ±5μs < ±10μs
    Short GF-8802 - - 1h 2h 8h 16h
    GF-8803 - 1h 3h 4h 16h -
    Grande GF-8804 - 2h 6h 8h - -
    GF-8805 2h 6h 18h - - -
  • Coherent behavior between time pulse (jitter less 1PPS) and frequency (10 MHz)

  • Single satellite tracking capable operations (except Navigation Mode)

  • Synchronization with external pulse

    Enables synchronizing to time pulse from an external source
    ・Usable to synchronize to time information such as IEEE1588 or SyncE obtained through the network
    ・Improves robustness of the system



GNSS Reception Capability
GNSS Reception
32 channels
Tracking: > -162 dBm
Acquisition: > -148 dBm

Tracking: > -158 dBm
Acquisition: > -144 dBm

Tracking: > -146 dBm
Acquisition: > -136 dBm

Tracking: > -147 dBm
Acquisition: > -131 dBm

*Measurement platform with recommended active antenna
ITU-T Recommendation
in comformity with G.8272 PRTC-A, PRTC-B
Initial Stabilization Time
< 5 minutes (untill lock state)
10 MHz Output
Square pulse, Sine wave
10MHz Output (Lock State)
10MHz Long Term Stability (24h average): < ± 1 × 10-12
10MHz Short Term Stability (Root Allan variance ( =1s)): < 1 × 10-11
1PPS Output (Lock State)
1PPS Accuracy: < ± 40ns (vs UTC)
1PPS Stability: < 4.5ns(1 σ)

*Open sky
10MHz Output (Holdover)
10MHz Long Term Stability (24h average): < ± 1 × 10-10
10MHz Short Term Stability (Root Allan variance ( =1s)): < 1 × 10-11

10MHz Long Term Stability (24h average): < ± 3 × 10-11
10MHz Short Term Stability (Root Allan variance ( =1s)): < 1 × 10-11
1PPS Output (Holdover)
1PPS Accuracy: < ± 5μs/24H
(< ± 400μs/1H(TYP))

1PPS Accuracy: < ± 1.5μs/24H
(< ± 400μs/1H(TYP))
Supply Voltage
5.5 VDC
Power Consumption
400 mA(Typ)

*When supply voltage is stabilized
Operating Temperature
-40°C to +85°C
Antenna Detection
Short and Open Detection
Outer Size
100 mm x 52 mm x 20 mm
eSIP (NMEA 0183 Standard Ver 4.10)
Anti-Jamming (BCW), Multipath Mitigation (Dynamic Satellite Selection™), Anti-Spoofing, T-RAIM, Synchronization with external pulse

Countermeasure for GNSS receiver failure

We provide technical white papers for each of the typical failures caused by GNSS receiver. For each failures, our experts in time synchronization explain details about countermeasures on receiver side, using diagrams to show the effectiveness, and how to select products. If you are considering a GNSS receiver for the first time, please take a look.

  1. Multipath in Urban area
    White Paper: Industry-leading multipath mitigation in urban canyon environments
  2. Jamming (interference wave)
    White Paper: Measures against GNSS jamming (jamming wave)
  3. Spoofing
    White Paper: Measures against GNSS spoofing signals
  4. Interruption of GNSS signal (holdover)
    White Paper: "Holdover function" as measures against GNSS reception interruptions

Download page

Evaluation Kit

P/N VF-84 : Evaluation kit for GF-8804
P/N VF-85 : Evaluation kit for GF-8805

Connect the PC with a USB port to communicate. Output time pulse (1PPS) and 10 MHz reference frequency (selectable) from a SMA terminal.

Contents: GNSS antenna, CD (GNSS Conductor GF), USB cable

Evaluation kit configuration (video)
simple use by connecting the GNSS antenna with the power supply.

User Case

GF-88 series is selected as a core part of Grandmaster Clock (GMC), which plays key role in synchronization of network devices.

Seiko Solutions Grandmaster Clock: calibration system of mechanical watch Grand Seiko (Page in Japanese only)

Documents, Software

Download documents and software related to this product and other GPS/GNSS products (Specifications document, Drivers and Monitor software).

Download page

* Specifications subject to change without notice.