background image

DXD/PTP/GPS User Manual (rev 2.10)

Page 7

5. GPS Receiver 

The GPS menus will only appear if the optional GPS receiver (model DXD/GPS) is installed in your DXD-8. Otherwise the 
following message will appear: 

The DXD/GPS is a small board that installs easily inside the DXD-8 or DXD-16. See Appendix A for installation instructions. 

5.1 WHY GPS? 

In addition to longitude, latitude and altitude, GPS and other Global Navigation Satellite Systems (GNSS) provide time. In 
fact, the reason why these systems can provide very precise position is because the satellites and the ground control stations 
have extremely accurate atomic clocks. 

In the world of PTP, GPS is particularly useful for the DXD Universal clock because a clock locked to GPS is much more stable 
and will be in a better position to be selected by the BMCA to be the PTP Grandmaster. 

Another important reason for GPS is that, in addition to providing an extremely accurate clock, GPS (or GNSS) allows units 
located in remote locations to have their outputs in phase with one another when they are locked to GPS (or GNSS). 

5.2 DXD/GPS RECEIVER 

The DXD/GPS is a high-stability, high-accuracy timing Multi-GNSS receiver that supports concurrent reception of GPS (US), 
GLONASS (Russia), Galileo (Europe), QZSS (Japan - Quasi-Zenith Satellite System) and SBAS (Satellite Based Augmentation 
System). 

Using multiple satellites constellations concurrently increases the number of satellites in view and improves accuracy. 
Simultaneously, using different frequency bands improves robustness against interferences. 

5.3 ANTENNA  

Once the GPS receiver is installed in your DXD, an antenna will need to be connected to the receiver’s SMA connector 
(an antenna is not included with the DXD/GPS). The cable needs an SMA-Male connector on the DXD side. 

Ideally the antenna should be mounted on the roof for better view of the satellites. However, the DXD/GPS incorporates 
Dynamic Satellite Selection™, a new satellite signal selection algorithm developed by NTT that permits GNSS antennas to be 
mounted more freely than ever before. Experimenting will be required to determine the optimal location of your antenna. 

Active antennas are recommended and 5v power is provided by the DXD. For detailed antenna recommendations, please see 
Appendix C. 

5.4 ANTENNA CABLE 

It is useful to know the distance in advance between the antenna and the receiver so that the proper cable solution can be 
implemented. There are 2 aspects to consider: signal loss and cable delay. 

Signal loss

: Since the GPS signal is very weak, the antenna usually amplifies the signal. But the antenna cable offers some 

resistance and the GPS signal strength will attenuate as it travels down the cable. Therefore the maximum cable length depends 
on the gain of the antenna and the quality of the coax cable. Keep in mind that splitters and connectors will further induce 
losses. The general recommendation is that after all system losses there should be 10-15dB of gain left (see appendix C). 

As an example, when using a coaxial cable with a loss of 5.2dB per 100 feet at 1575MHz (GPS) and an antenna with 40dB 
gain, the cable length could be about 400 feet. 

Cable delay

: Signal propagation will cause delay but most likely in the nanoseconds range. If required, the DXD provides 

a way to compensate for these delays in menu 6.2 (see below). 

DXD/GPS NOT INSTALLED 

The GPS Receiver is required for these menus.

Содержание DXD/GPS

Страница 1: ...k DXD OCXO OCXO option for the DXD Universal Clock Operations manual Version 2 10 January 2021 All materials herein Brainstorm Electronics Inc Brainstorm Electronics reserves the right to change or mo...

Страница 2: ...6 GPS Menus 8 6 1 SATELLITES SELECTION MENU 6 1 8 6 2 GPS SETTINGS MENU 6 2 8 6 3 ADVANCED GPS SETTINGS MENU 6 3 8 7 DXD OCXO 9 8 Time of Day 9 8 1 RTC Real Time Clock 10 8 2 Time Jam 10 8 2 1 TIME JA...

Страница 3: ...9 15 Typical PTP use 20 15 1 HYBRID SYNC GENERATOR ACCEPTING MULTIPLE REFERENCES 20 15 2 DISTRIBUTED PTP VS INDIVIDUAL GRANDMASTERS WITH GNSS 21 16 Guidelines for con fi guring PTP Precision Time Prot...

Страница 4: ...a series of 4 numbers separated by periods This key is only valid for the DXD 8 with the serial number used when you placed the order Note that PTP is optional on the DXD 8 only A feature key is not r...

Страница 5: ...ng LOCAL REF WHEN GM When PTP Mode is selected if GPS is available this fields enables GPS to be set as the reference when the DXD 8 is the Grandmaster Enabling this field will announce the DXD 8 as G...

Страница 6: ...a quick set up This menu gives you the option to set the timing values to the pro fi le default values 4 4 PORT TIMING MENU 5 4 Announce Interval 3 to 4 1 8sec 16sec Sets the rate at which the master...

Страница 7: ...in your DXD an antenna will need to be connected to the receiver s SMA connector an antenna is not included with the DXD GPS The cable needs an SMA Male connector on the DXD side Ideally the antenna s...

Страница 8: ...sideration as it can not only impact the signal strength but also cause a delay in the signal Under typical conditions however the expected cable delay is negligible in the nanoseconds range The follo...

Страница 9: ...e reference sources include time and rate information GPS and PTP for example carry precise time and date information as well as frequency However traditional reference signals such as video sync or w...

Страница 10: ...nd wanting all of the cross frame outputs 25 etc to be in correct phase and epoch as well as wordclocks and AES In a primarily legacy application this is the way to increase the number of legacy outpu...

Страница 11: ...to use Local Time instead while others may even prefer different standards for different times Be aware that even though the time source may give Time Of Day it may not correspond to the time indicate...

Страница 12: ...on Jan 1 1970 This process occurs everyday at the same time as set in the DAILY JAM TIME fi eld Daily Jam Time The value entered in the DAILY JAM TIME field is the amount of time after midnight local...

Страница 13: ...to LOCKED GRANDMASTER In case the DXD is or becomes a PTP Salve when locked it changes to LOCKED PTP SLAVE Note that if another source was selected in the reference menu such as Video Sync and the DXD...

Страница 14: ...lock and the Grandmaster in sec Additional times may appear on this page such as Time Code based on the installed options 11 2 2 GPS RECEIVER STATUS PAGE The GPS RECEIVER status page displays the foll...

Страница 15: ...as the ability to clock to a non Dante PTP v2 clock AVB Audio Video Bridging is a set of IEEE standards that facilitate the transport of high performance audio and video on a LAN One of those standard...

Страница 16: ...suited clock is found it will become the Grandmaster 12 6 SYNCHRONIZATION There are several different PTP messages used during synchronization sequenced as follows 1 The grandmaster sends a Sync messa...

Страница 17: ...clocks on a single PTP communication path must use the same method to measure the time delay 12 8 TYPES OF CLOCKS IEEE 1588 de fi nes three different types of clocks Ordinary Clock OC Boundary Clock...

Страница 18: ...ate of the port can change The BMCA determines what unit becomes the Grandmaster If the current Grandmaster disappears or looses GPS another Grandmaster is selected For more on the Grandmaster selecti...

Страница 19: ...it has been set by the operator 14 1 JUMP TO RELOCK When the time difference detected between the external PTP GM and the DXD System Time is above the Jump Threshold value the DXD will jump to the ne...

Страница 20: ...t all equipment could be kept perfectly synchronized But for added fl exibility the DXD s can also be set up to lock to any legacy sync or to PTP as illustrated below These choices are available in th...

Страница 21: ...TP slaves to an external Grandmaster in the second illustration the DXD 8 s are all Grandmaster for their networks and each is locked to GNSS This second solution is particularly useful when distances...

Страница 22: ...ith any other domain number will be ignored menu 5 2 Ports Timing per IEEE 1588 all devices on a PTP domain must have the same value set for these ports timing Announce Interval Announce Receipt Timeo...

Страница 23: ...GMPv2 On larger networks a router is required to manage multicast group membership Switches that support IGMP snooping are also recommended 17 Troubleshooting Error Warning Messages 17 1 PTP NO PORT W...

Страница 24: ...3 Menu 5 1 If PTP was selected TIME JAM BNC INPUT will automatically show in menu 5 1 in blue blue status information The words Time Jam will also appear on the REFERENCE line at the bottom of the ma...

Страница 25: ...the ribbon cable to J23 the GPS connector on the motherboard B J23 is the designator number on both DXD 8 and DXD 16 PCB As always with ribbon cables make sure the connectors are properly oriented do...

Страница 26: ...Including cable loss Low Gain mode FLNA High 3 For best jammer resistance and lower power consumption use 10 dB lower gain than the max gain 18 3 2 RECOMMENDED PASSIVE ANTENNA 1 High Gain mode FLNA Op...

Страница 27: ...TIMEOUT 3 announce intervals SYNC INTERVAL 1 sec log 0 MINIMUM DELAY REQUEST INTERVAL 1 sync interval GLONASS Yes GALLILEO No QZSS LIC A Yes SBAS QZSS LIS SBAS DIF FIX ANTENNA CABLE DELAY 0 ANTENNA H...

Страница 28: ...Page 28 DXD PTP GPS User Manual rev 2 10...

Отзывы: