For this post we’ll be referring to Whyte System 5 IRS components and where they are used for a typical ‘5 wire’ installation, in this case for Sky TV in the UK. Let’s take a closer look at the components and note some important references along the way that will help us create a system plan.
From our satellite dish (say an 80cm solid dish) we’d be looking at an ‘Off air’ signal level of 83dBµV keep this figure in mind when planning your IRS systems (‘Off air’ is the signal level measured at the LNB). In this instance were using a Quattro LNB which has an output for each band and polarity:
VL = Vertical Low
HL = Horizontal Low
VH = Vertical High
HH = Horizontal High
DTT (UHF) Antennas (TV aerials):
Use the correct type of DTT antenna for your reception area – your local trade counter will be able to advise you on antennas suitable for use your region. Digital UK has an excellent resource http://www.digitaluk.co.uk/reception_guide for identifying your local DTT transmitter, as does UK Free TV https://ukfree.tv/prediction which has a coverage map feature.
DAB and FM antennas:
For DAB you’ll probably need to consider where the local DAB transmitter is for your district. A list is available via UK Digital Radio http://www.ukdigitalradio.com/coverage/currenttransmitters/ especially if you happen to be in a poor reception area. For FM, in cities you may want to consider an Omni directional antenna (with a halo like appearance), for marginal reception areas a directional FM antenna would be more suitable. Information on UK FM transmitters can be found here https://ukfree.tv/transmitters/locations/AMFM These days the majority of UK FM radio services are also available via Freesat or Freeview.
Combining diplexer: (DTT, DAB and FM)
These (usually masthead mounted) allow us to combine DTT, DAB and FM signals together for input to our IRS system via a single cable. We’ll refer to this combined source as ‘TERR’ from this point.
This device will enable us to set the required signal level for distribution through our IRS system. Extensive IRS systems may require more than one amplifier.
Whyte taps have a low loss trunk of 4dB and come in a choice of 1, 2 or 3 Way with either 10 or 20dB attenuation options. Taps enable us to have attenuated output levels while maintaining a higher trunk level as we continue down the chain that forms our IRS.
Whyte Splitters have a low 4dB loss and enable you to split the SAT & TERR source 2 ways. Although passive devices Whyte Splitters and Taps do have a convenient DC injection input.
Series 5 Whyte Multiswitches have 5 inputs (4 SAT + 1 TERR) that enable us to present signals at their outputs which are appropriate for use with a variety of ‘Legacy’ set top boxes (with the exception of Sky-Q, more about that later). Whyte Multiswitches come in 8, 12, 16, 24 and 32 Way versions. Whyte Multiswitches also have gain control for each source of satellite signal (VL, HL, VH and HH) and TERR. We’ll refer to Satellite as ‘SAT’ from this point on.
Whyte dSCRs enable the use of Sky-Q boxes (and other Unicable II set top boxes that can utilise dSCR mode). These Multiswitches have the benefit of also supporting legacy mode (13/18VDC 22 kHz on/off). Whyte dSCRs make use of user bands to enable multiple viewing and recording options. We’ll be going into details about dSCRs and how they work in future Whyte technical posts.
Good quality cable should always be used. Foam filled, copper core, copper foil and copper braid is a minimum requirement these days. WF100 manufactured by Webro http://www.webro.com/coaxial/tv-satellite/wf100-cable/ is a CAI approved cable with excellent signal characteristics. You can assume a maximum loss of 3dB per 10M at satellite frequencies and 1.5dB per 10M at terrestrial frequencies. These values will be important when creating your system plan.
We’re going to need to power our IRS hardware. By calculating the system load requirements we can plan our DC groups and the number of power supplies required. Whyte IRS equipment can be directly powered through the DC input or via the HL or HH trunk lines. Each ‘active’ Whyte IRS component has a current rating that needs to be taken into account. The load of the LNB and or other IRS system components (made by other manufacturers) will also need to be factored in too. A Quattro LNB is typically rated at 200 mA where as a GTU would be 490mA (always check your manufacturer specifications). Remember: Do not exceed the current rating stated on the power supply for your DC group.
These are used where we are creating our DC groups (of devices) so that our signals pass, but the voltage and current does not. By calculating how much power is required you can add your DC Blocks where needed to create your DC groups. DC Blocks are in-line F-Type devices that are fitted to the trunk of your IRS where required.
75 Ohm Terminators:
It’s the end of the line! No output ports on your IRS should be left unterminated, as this will result in the system performance being degraded. Always terminate unused outputs.
Ensure that everything is fixed in place securely. Whyte Series 5 components push together with ‘Quick F-Connectors’ (where provided) to create a neat mountable solution which will minimise signal losses. All Whyte IRS hardware features standoff corner brackets that allow you to pass cables under the device and include fixing screws. Some system plans can be arranged to show the orientation of devices (where joined by Quick F Types).
In our next technical post were going to make a start on our system plan.