Cascading a Z-Distribution Unit
Every Z-Distribution unit has eight coaxial outbound ports which could be used to cascade other units. The RF output of these coax outbound ports will have a positive slope/tilt. This is to accommodate losses in the coaxial cables across the CATV spectrum. If a distribution unit receives its RF input from a CATV source and its coax outbound ports are being used to feed other units, then this distribution unit is referred to as a Main unit. This is a level 1 device. A main unit can have up to eight cascaded units referred to as Satellite units. These would be level 2 devices.
The Main unit transmits a pilot tone at 240MHz which is used by the satellite units to measure the distance between them and apply necessary signal conditioning adjustments. The 240MHz pilot tone falls in the guard band between the RF Channels 26 and 27. This may cause interference with these adjacent channels on some tuners. In order to prevent the potential interference, GigaBUD 1000s and ZHCs have an option of turning the pilot tone off. However, in the event of a power outage, the GigaBUD 1000 Master units will re-power to a “Tone On” state.
- For a GigaBUD HD 860, the red button on the back of the unit is used to toggle the unit from a Main to a Satellite mode and vice-versa. The unit also has dedicated CATV and Cascade IN coaxial ports in the back. If the unit is set as Main then the RF feed needs to be connected to the CATV port and if the unit is set as a Satellite then the RF feed needs to go into the Cascade IN port.
- GigaBUD Videohub 1000 has a Native mode where all the three LED's on the front panel of the hub are ON. The unit will automatically switch into Main mode when the RF feed from a source is plugged into CATV port and into a Satellite mode when a coax outbound feed from a Main unit is plugged into its Cascade IN port. The button on the back of the unit enables the user to turn the pilot tone signal on/off **
- On the Z-Distribution ZHC, the coax input port is a hybrid CATV/CASC-IN port. The unit will be in Native mode just like the previous generation model and upon plugging the RF feed, it looks for a pilot tone signal at 240MHz and if there is no such tone it configures itself as a Main unit. If it detects a 240MHz pilot tone on the RF feed then it will configure as a Satellite unit. The pilot tone on ZHC main units will automatically turn off after 8 hours. This should give the satellite units enough time to run, lock onto to the main unit, calculate the distances and balance the incoming RF signal.**
Depending on how many cascades a Satellite unit has gone through, it can be a level 2, 3 or 4 device. Each Level 2 device can connect to up to 8 Level 3 devices and each Level 3 device can connect to up to 8 Level 4 devices. If all “Outbound” ports of all Level 1, 2, & 3 devices are used, a single Master can Cascade together 585 units. Cascading of these units must be limited to 4 levels. Please refer to the article Compatibility of Z-Distribution Units Across Different Generations if you have or are planning to use a system with a mix of multiple generations of Z-Distribution units.
Another important consideration when cascading two Z-Distribution units is the length of the cable connecting a main unit to a satellite unit, which is dependent on the type of the coaxial cable used. If using an RG6 cable this length cannot exceed 400ft and for an RG11 cable, the length cannot exceed 600ft. Use of coaxial attenuators between a main and a satellite units is not recommended to bring the levels down. If the two units which need cascading are in the same closet then use a short RG6 cable (approximately 1 meter to reduce RF reflections) to connect the units.
**All the units with fiber input option are configured as fiber only units. If you wish to change the input type of the unit to accept the coax feed and then use it as a Main or a Satellite unit, please contact Z-Band Customer Support and we will provide you the proper software which will let you make these changes to the units.
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