Author: Anthony Dunnett
MATV – Master Antenna Television – The process of distributing incoming signals from antenna(s) to multiple outlets, whilst maintaining even, strong signal throughout a single dwelling.
Ever since television needed to be distributed, coaxial cable has been the distribution conduit of choice. Although analog VHF has given way to digital UHF, coaxial distribution methods have not changed very much.
Digital Terrestrial Television
Since December of 2013 digital television services have been available to many parts of New Zealand .The need for good quality incoming UHF digital signals is a fundamental requirement. Digital TV will load and lock with a third of the signal required for analog reception.
The difference between analog and digital reception is that with analog reception, as the signal gets weaker it generates noise “Snow” . With digital reception once the signal drops to threshold it will pixelate and become unstable.
Signal distribution around a house using existing RG59 cabling and saddle and clamp splitters very rarely provides a satisfactory distribution network as RG59 proves to attenuate the digital signals dramatically. Originally designed for VHF use, using frequencies ranging from 45 MHz to 250MHz, the UHF television broadcast (specifically DTT ) spectrum starts at 400 MHz and extends to 860MHz.
RG6 is spec’d from 45MHz to well over 2 GHz and is ideal as feeder cables from the aerial to splitter and from a splitter to each outlet point. While newer shielding techniques have allowed us to cut signal loss to a minimum, there is always some signal loss. Here’s the breakdown of signal loss (attenuation) in decibels for 100 ft. of cable. Just remember, the longer your cable runs are, the more signal loss you will experience. That’s why it’s best to keep installation lengths as short as possible.
Digital UHF aerials are designed with F connector output connections instead of saddle and clamp. The current range of UHF aerials feature gain figures as follows.
1: 23 element used for prime signal areas “line of sight “ approximately 10 dB gain.
2: 47 element used for secondary signal areas “line of sight “outside that of prime signal areas approximately 12dB gain.
3: 91 element used for fringe or difficult signal areas approximately 16dB gain.
The key to successful home distribution “MATV”systems relies on incoming signal strengths that can be split providing outlet signals at each point which exceed the threshold figure by several dB. Much has been written about DTT reception and the amount of signal required to operate a single television and multiple televisions. Based upon over 500 installations around the Auckland region using a variety of reception equipment ranging from set top boxes and Free View recorders to integrated Free View Televisions the results are very close in all instances.
Minimum signal required for stable reception on a single Free View television = 45dBuV
Maximum signal required for stable reception on a single Free View television = 78dBuV
Any less than 40dBuV (although the threshold point on many receivers may vary a little, down as low as 35dBuV), the result can be loss of signal or pixelation.
Any more signal than 80 dBuV and the front end “Tuner” can overload and the result is pixelation and poor picture which is often mistaken for insufficient signal. It is most important that a suitable aerial is selected and quality feeder cable used.
Home Distribution System
Given the information as presented above, several rooms can be connected to the MASTER ANTENNA. However if older RG59 stranded cable is present then it will need to be replaced.
RG11 RG6 RG59
In some single story homes it is possible to hide the new cable behind overflow down pipes. If the home is fitted with a wooden floor the splitter can be placed under the floor and feeder cables laid to each room. Some homes have enough room between the wall cavities to attach the new RG6 to the existing feeder cables and run them to each outlet point from a central point in the attic.
Other homes with concrete floors and no wall access require the new cables to be externally laid from a central point. Most eventualities can be addressed without the feeder cables looking intrusive.
It is important (due to signal losses though the splitter, which can be as high as 4 db per port and a further db or so cable attenuation) that the signal for distribution is in the region of 70 dBuV or higher from the aerial, as this will provide (once the cable and splitter attenuation is taken into consideration) 45dBuV to 55dBuV at each outlet .
Mast head amplifiers should be avoided if possible as the amplified signal can be in excess of the devices maximum input signal. The use of mast head amplifiers to combat the losses in older RG59 cable and saddle and clamp splitters should also be avoided.
Example of masthead amp.
If in doubt contact us or a suitably qualified Installer who should be able to advise on the best possible solution for quality digital reception.