VHF-antFirst of all, stating the obvious, a television antenna is needed to receive signals, so let’s run through the components needed for digital reception.

An outdoor antenna offers the best solution by far, but an indoor antenna may be a viable option in some good reception areas.

The signal is carried by cable to a decoder which is inside the television. If the television is non digital, then a ‘set top box’ decoder is needed to provide sound & pictures.

If there are multiple outlet points in the building, then the cable will run from the antenna to a splitter, where other cables will be sent out to the various outlets.

More complicated ‘head end’ or distribution systems are installed in multi story buildings, motels, nursing homes etc.

Signal is horizontal in the Brisbane broadcast area. There are areas around Australia where signal is vertical and areas where there is a mixture of both horizontal and vertical.

If travelling you may need an antenna which is designed to cope with these variances.

Since the switch over to digital signal only there are now four common types. Older, pre digital antennas will be replaced over time with new antennas designed for digital signal. These are often much smaller than the old VHF and combination antennas shown below.

So let’s tackle the various types of antennas found around the Brisbane area.

 

VHF only

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UHF only

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 Combination VHF & UHFAE21

 

 

 

Prior to the introduction of SBS and Community television Briz31 which were UHF, all signal was broadcast on VHF, therefore there are quite a lot of VHF only antennas on homes and unit blocks. Notable areas are Keperra and The Gap for instance.

These antennas are easily identified, in that they are quite large and have elements (arms) which are all roughly the same length. Channel coverage is generally 0-12.

UHF antennas were used in conjunction with VHF antennas to include SBS and Briz31 in the channels available in the home. Again, this is common on homes in areas such as those mentioned above and some unit blocks.

These antennas are generally horizontal with short elements (arms) and no long elements.

An alternative design can be described as a vertical panel wire grill.

Channel coverage is generally 28-36 or 28-69.

UHF antennas are used exclusively in areas such as the Gold and Sunshine Coasts, where channels are broadcast in UHF only.

Traditional style combination antennas are the most common type around Brisbane, offering the possibility of receiving all channels in the one antenna. There are many brands, sizes and styles of these antennas with anything from 7 to 54 elements. These antennas have long elements (arms) at the rear and short elements at the front.

Channel coverage is generally 2-12 & 28-36 or 2-12 & 28-69.

The longest of these elements are for ABC analog (Ch2), which brings us to what has become the new antenna of choice for installers.

Analog signal will be discontinued as of 2013, so a shift has been made to log periodic antennas which are combination VHF & UHF but without the long elements. These antennas are lighter, smaller in size, and offer better signal quality than the older antennas. The channel coverage is from 6-12 & 28-40 or 6-12 & 28-69.

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So, do you really have to change your antenna to receive digital television?

Not necessarily, though it may be one of the factors effecting poor reception.

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If you have not yet switched to a digital tv or set top box and your picture is poor, then the chances of getting digital pictures successfully are not good.

Poor digital signal will, at worst give you ‘No Signal’ messages or at best, pixelisation, in which case the picture breaks up or stalls along with sound distortion or loss.

Though digital sound and picture quality is much improved over analog, good strength and quality of the received signal is essential for interruption free viewing.

The next component to look at is the cable used to carry the signal.

There are two types which have been used extensively, and these are:

Twin feeder ribbon cable

Coaxial cable

Ribbon cable may still exist in older unit blocks and homes. Although it may have been ‘state of the art’ at the time of installation, it is not well insulated and is prone to break, especially where exposed to the weather. In some circumstances and in good condition it may work for digital, but is unreliable and upgrading to coaxial cable is recommended.

Coaxial cable for television is available in several sizes and grades; RG59, RG6 & RG11.

RG59 was the next step in replacing ribbon cable and offered better shielding from electrical interference. It may be cream, brown or black in colour and was fine for analog reception. This type of cable is now used extensively for CCTV security cabling.

RG6 is a heavier (thicker) cable than RG59 and comes in a variety of shielding options.

Single shield, Duo-shield, Tri-shield & Quad-shield.

As indicated by their names, the level of shielding offers increased protection from outside interference, with Quad-shield being the current cable most used by installers for both free to air (FTA) and Pay TV connection.

 

RG11 is a heavy coaxial cable used as a backbone supply cable in high rise and other large installations, where multiple residences are supplied signal from a central point.

 

To come…Splitters, wall plates etc

 

The splitter.

As the name suggests, this item is used to take the signal from the antenna and distribute it to more than one point. Splitters are available for 2, 3, 4, 6 & 8 points.

There are different splitter types for free to air (FTA) and satellite, FTA having one leg (path) for passing power, whereas satellite splitters have all legs power pass.

Power pass for FTA is needed in cases where a signal amplifier is installed to boost weak signal and we’ll come to amplifiers further on.

 

Modern splitters vary in design from older types in looks and the way cables connect to them. Older ‘box’ styles have saddle & screw connections which are more susceptible to corrosion and poor connection than newer ‘F’ connector types. ‘F’ connector connections are more robust, as the cable is terminated and screwed onto the splitter, forming a more secure bond. ‘F’ connectors have become standard on components from antennas through to wall plates.

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The diplexer

Diplexers are used when the signal from two antennas is to be fed down through one cable. This is the case where separate VHF & UHF antennas are installed on the same mount, or where FTA and satellite are to be combined.

There are different diplexers available for FTA & satellite use and, as with splitters, newer FTA diplexers will be ‘F’ type, while older ones may have saddle and screw connections.

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Wall plates

There are a host of different wall plates available to suit not only tv connection, but also telephone, data and home theatre or a combination of these. Some wall plates may take 2,3,4 or 6 inserts, but we will just deal with those for direct connection for television.

There are three types commonly used, and these are:

  • Free to air
  • Freeview
  • Pay TV
  • Combination of FTA, Freeview & Pay TV

FTA wall plates can be recognised by the fact that the lead to the set top box, DVD recorder or tv plugs directly into the socket of the wall plate.

Older wall plates may have a printed circuit with saddle and screw connections, where newer ones or replacements will be ‘F’ type in the main.

Pay TV will be ‘F’ type back and front, requiring the cable to the decoder to be screwed onto the wall plate. Depending on the installation, pay tv installations may require two cable connections on a wall plate.

FTA and Pay TV can also be available in a single wall plate.

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Skirting mounts

These mounts are usually used where a cable is brought up from below a timber floor. There are types for FTA & Pay TV and versions with ‘F’ type or saddle & screw connections.WP2U

 

 

And now we come to signal amplifiers, commonly called boosters.

Several types and output sizes are available, but a booster is not necessarily the answer to bad reception.

If the signal is ‘clean’ but weak, fine; but if the signal is ‘dirty’, an amplifier could actually make the reception worse.

In short, all other areas of interference should be eliminated first, making sure the antenna, cable, connections, splitter and wall plates are in good condition. Where possible, using multiple splitters should be avoided.

Older, poorly shielded cable may pick up electrical interference where it has been run near power cable, and may have to be replaced or relocated.

There are amplifiers available which can be installed at an outlet point which will deliver a small boost to one, or possibly two tvs. These have the advantage of being portable, so may be an answer in some situations. ie units, caravans, etc.

Mast head amplifiers are available for VHF, UHF or combination types with either saddle & screw or ‘F’ type connections.

These amplifiers are the preferred type for installers as they give the best results. The amplifier itself is mounted on the pole under the antenna and the power supply is installed to one of the antenna outlets in the home. This power supply feeds a small electrical current through the coaxial cable to the amplifier which boosts the signal to all the outlet points connected to it.

When we talked about splitters above, mention was made of power pass for FTA splitters.

The power supply must be installed at the point which allows power to pass, otherwise the amplifier will not work. ie If the installer has connected the splitter with power pass to the lounge room, then that is where the power supply must be. Relocating it to another room for instance, will cut off power to the amplifier unless the cables are changed around at the splitter as well.

Not covered so far…. locating the antenna & antenna mounts

One of the most important factors impacting reception is the location of the antenna.

Any decent installer will use a digital meter to locate the best spot for signal prior to a new install, or a relocation at an existing installation.

Once the antenna is mounted, it is aligned precisely with the meter. The days of someone inside shouting “left a bit, right a bit” are long gone!

Where possible, for aesthetic reasons, the antenna would not be a feature at the front of a house, which is sometimes the case on older properties.

Other considerations are the close proximity of trees or taller buildings which may either damage or block signal to the antenna.

There are two or three common antenna mounts, and some other alternatives for industrial steel roofs or for difficult signal locations.

The first of these is simply a wall stand off mount which has been bent to compensate for the roof pitch it is being used on. This type of mount has a very small footprint and is the cheapest option an installer could use. Generally used on steel roofs and about 1m in height, Brisbane Antenna Specialists does not use this type of mount as we consider it inadequate.

A more robust mount is the tripod roof mount, which has a base plate roughly 200mm square and support for a separate 1.2m pole. There are versions for steel or tiled roofs, the tile roof version having a kick down in it where it overlaps the front of the tile it is mounted on.

All house roof mounts are attached by screws through the roof material, (steel or tile), into the batten below and holes are sealed with silicone sealer.

A third type is the fascia mount, or ‘J’ mount, which as the name suggests, mounts on a fascia timber with a bend out around the gutter to the vertical pole. Various lengths are available and they can also be attached to brick or concrete walls

There are also mounts for flat steel roof styles, as well as bracing and other options for taller masts if required.

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