When designing an IRS not only do we need to ensure good signal reception at all subscriber outlets, we also need to consider our IRS power requirements.
Devices that will draw current include:
- Launch Amplifiers
- dSCR Multiswitches
- Other active hardware (such as fibre receivers)
Although Whyte Taps and Splitters can provide a convenient DC injection point, they do not draw current themselves, but allow voltage and current to pass.
A DC group should only ever contain one PSU. If we were to have two PSUs in the same DC group, one of the PSU’s often ends up being disproportionately loaded which reduces its lifespan and then ultimately causes the other to fail.
The Whyte WPSU-2.5A power supply provides 18V DC and are already derated to 2.5A. This means that the WPSU-2.5A will deliver up to 2.5A under continuous load conditions.
We need to create our DC group when we are approaching 2.5A of load. Don’t forget if you are powering a masthead amplifier that will draw an additional load of 0.1A (100mA typical).
DC blocks are inline devices provide the physical method of creating DC groups. Once we’ve created a DC group, we can then continue our calculation afresh with the remaining IRS hardware until we approach 2.5A load, and again require another set of DC blocks and a PSU for that DC group, and so on until we’ve planned out all the DC groups for the whole system. Often its convenient to introduce the DC blocks at Taps or Splitters to create your DC groups.
In some instances, you may only need power for a relatively small DC group. The WPSU-0.8A (which is also derated) can provide the ideal solution delivering up to 0.8A at 18V DC.
The Whyte technologies website features a useful current calculator to assist you with calculating your DC group loading of active components:
You can always request a system plan free of charge from Whyte Technologies with all these calculations done for you.
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