You will require:
a digital modulator
a digital signal strength meter
some basic knowledge of DVBT antenna systems and distribution
Please note - If you don't have any or all of these, I'd strongly suggest contacting a qualified antenna installer. They'll save you a lot of time and headaches.
Let's take as our base the example in the image below. We've got a Zycast Q4KR1 modulator taking an HDMI input from a pay-tv box. That particular modulator has a local HDMI 4K pass-through to the 4K TV nearby. It outputs RF through the RLRF380 3-in 8-out RF distribution module, which also combines the modulated signal with the antenna RF channels from the local TV tower. From there, each TV has the potential to tune in all the free-to-air stations, as well as the local modulator channel. This example also includes Infra-Red (IR) remote control distribution.
Apart from the physical connections in the diagram to allow the system to work, there are settings within the modulator and general site information that will affect your system.
First - You need to select an output RF channel for the modulator
Out of the box, most Zycast/Resi-Linx mods default to Channel 39 on UHF (606.5MHz). Using your digital signal strength meter, you need to select a channel for the modulator without an existing free-to-air channel, or without local interference. Most mods can use output channels between Channel 6 on VHF (177.5Mhz) to Channel 69 on UHF (816.5MHz), some are UHF-only modulators.
Note: 700MHz and above are used in Australia for LTE mobile signals, so you should only use these higher channels on a modulator if the external antenna signal has had all the LTE signals filtered out.
The government's https://myswitch.digitalready.gov.au/ website is a decent reference to estimate what your local channels should be but it's no substitute for measurements with a digital signal strength meter. Plus, you'll need one of those for the next step anyway!
Second - You need to adjust the output level on the modulator
You need to attenuate the signal from the modulator to match (within a few dBμV) the signal levels from the local free-to-air signals.
Most modulators are designed for distribution, so they launch at high output power levels. For example, the Q4KR1 in the example above produces an 85dBμV. TV-tuners tend to only accept signal levels between about 45-70dBμV. Passing the modulator through a splitter will have some loss, and every metre of coax will also drop the signal a little further.
The modulators have internal -20dBμV attenuators, in most cases. Otherwise, carry a range of in-line attenuators between about 6dB and 18dB, just in case.
If you've only got one modulator in the system, that's really all that you have to change.
Nice things (for the client's ease-of-use) to change are:
- LCN - Logical Channel Number - Default: 101, so the modulator will be the last TV channel seen on the TV list.
- Channel Name - Default: Channel-1. You might want to rename this to "DVD" or "CCTV NVR" or "Foxtel", etc. This makes it easier for the client to distinguish it amongst all the free-to-air channels.
If you have multiple modulators on the same site, there are other settings that have to be changed to make sure the TVs can distinguish one modulator from the next one. There's a separate article covering that here: https://support.radioparts.com.au/hc/en-us/articles/360053162072-Zycast-Resi-Linx-Using-multiple-modulators-on-a-single-site-multi-stacking-