Sources of pixilation in the Digital Antenna Installation

Technical Bulletin

When solving any television signal problem it is essential to have a clear understanding of the component parts.

We have the receiving device.  Signal in its simplicity is an energy.  The antenna is the thing that captures the energy.   So the question is: is it functioning as well as it should be according to recommended standards?   For the technician it is easy – he has a meter but the home handyman has to rely on his observation skills.  Are the connections all clean and solid in appearance?  Is the antenna pointing in the right direction?  This is a common fault as they are often positioned behind a tree which effects results when the wind blows.  Another question to ask is “ if I move the antenna could a find a clearer path to the transmitters”?

The next component part that is doing some work is the cable.  Mountings and masting simply hold the antenna up and play no part in the actual delivery of signal beyond making it possible for the antenna to work.

connec1Cable however is a vital piece.   What happens if you use a poor quality hose?  They develop leaks, the fittings on the tap or gun leak water.   It is exactly the same with poor cable and fittings.  Digital television signal demands quality cable and cable terminations.   F connectors have to be used if the shield (outer foil and wire and often up to 4 layers) is to be properly protected from interference.

Old devices like pal connections (push in fittings found still on the back of TV’s (for reasons I do not understand) are unacceptable when terminating your cable from the antenna.  You must use an F connector outlet plate.  This is the single biggest cause of pixilation in TV pictures.  The most fundamental repair is to change the outlet plate and install a quality connection cable from the outlet to the TV.   DIY kits are available. This solves some 70% of problems.

The splitters installed in homes are another source.   The Pal or saddle and screw variety (still sold and used by untrained people) are another No No!    Today splitters are available with twist on quality F connectors which home handyman can install if unable to call a technician to replace it for you.

The cable itself is another source of pixilation as cable deteriorates over time.  Solid soft copper inner conductors are useable in good condition where vhf frequencies are used.  UHF frequencies it is totally unsuitable.     VHF is any broadcast between 6 and 12.     Professional installers should always recommend that it is replaced as it will fail – it is a question of when.

I have seen it many times since the inception of digital television antenna installations.    It has on at least one occasion caused considerable upset with a customer.    We changed the outlet and short lead and suddenly pictures are good.  Customer delighted.  Simple fix and inexpensive.  Technician strongly recommends cable be changed as his meter told him something the customer could not see which was quite high errors in the signal packets and he had observed soft copper inner on the cable.   Customer said no that is fine and Technician did not insist a bit harder.    Pictures failed 3 months later (a bit more degradation of the cable) and now customer wants the job done but expects some sort of financial discount.   I mention this because it can look all good but it will fail with this type of cable – it is only a matter of time.

A copper inner is soft and bends easily.  Do not confuse with copper coated steel conductors which are very hard to the touch.   This is the preferred type of cable.  Known as RG6Quad but care should be taken that the cable being purchased is genuine and not a copy.

So if you are deciding on a solution you would start with:

Change the outlet and fly lead if inferior.   Even for the professional this is vital as it gives him a window to look at the performance of the antenna and the antenna system, if there are many outlets.   The professional technician would then check levels and bit error rates.   Then recommend what is needed as a result of his finding

Home handymen can do this step without a problem as it requires no roof climbing and no special tools are needed.

Sally Garden