Tricks to fix pixelation (published in 'The Sydney Morning Herald' 16July2010)

Sally Garden of Deeper Image with a diplexer connector. (Now called 'Wilkgard Technology Group Pty. Ltd)

While many viewers might blame bad weather, there are other reasons for pixelation. And in many cases, they can be fixed.

Last year, the federal government estimated there were 17 million televisions in private homes and Commercial Radio Australia estimates 50 million radios are in domestic use.

The perfection promised by digital transmission has a downside. Because it is digital technology, if the signal strength falls below a certain threshold, there will be no sound and pictures will break up and pixelate.

"There is no snow or ghosting on digital, as it is either on or off — you either get reception, or you don't," says Sally Garden, founder and manager of Deeper Image Television.

Garden, who is writing a book, Guide to Installing a TV Antenna, says: "Digital television or radio needs far less of the signal than analog but it needs to be clean.

"Radio reception only has a tiny bandwidth of information, a fraction of what TV needs. You don't need as much of the signal. It's a lot easier to solve radio reception than TV reception."

But before you throw out another television, consider the antenna. Do you need a new one or can you adjust the position of the one you have? And have you looked at what cables are needed?

"High-definition digital is here and the high-volume use of combination antennas is unfortunate, as users suffer from pixelation, often on one channel, and in some cases it can be each channel," Ms Garden says.

"This is often a direct result of combination antennas. A diplex antenna is the better way to do the job."

A combination antenna incorporates both VHF and UHF signals. A diplex antenna installation has two antennas that operate at their own frequency, yet can be on the one boom.

"Even the best antennas are a compromise, as they are asked to perform across a range of channels, which all have different frequencies. You can liken this to asking logs in a river to flow in an even line — not likely," Garden says.

The usual tip to position an antenna correctly is to point it towards the nearest transmitter. Avoid trees and high buildings in the signal path from the transmitter to the antenna. If there are too many trees or buildings in the way, you could try pointing the antenna in the direction of another transmitter. Websites such as Deeper Image Television display the locations of transmitters for any suburb.

Mounting the antenna is where many people go wrong, Garden says.

"They look at their roof and say, 'Ah, the chimney would be good.' But you need to mount it where the best position for signal is. The height in most situations is not as vital. There are a range of mounts and brackets that will suit almost any situation."

Digital televisions have their own set-up menus where you scan the frequencies to get the maximum signal strength for each channel. However, Garden says, the greatest percentage of problems in upgrades to digital is due to poor cabling and connections.

She says it is important to buy a quality lead from the plate to the TV, as this will reduce the likelihood of pixelation.

"When people only have poor SBS pictures, it's not necessarily the antenna but, in many instances, poor cable," she says. "Many poor signal conditions can be overcome by replacing your old copper cables with a RG6 DUO or quad-shield cable. Professionals should use quad but in my experience the DUO for the do-it-yourself person is adequate. I prefer it because fittings are available without the use of professional tools to make a professional termination."

Garden recommends F-connectors for shielding to keep the impulse noise down. Impulse noise interference can be generated by electrical equipment such as fridges and microwaves. Garden says more than 50 per cent of mild pixelation problems can be fixed by replacing an outlet plate and connectors with F types.

"This termination provides superior shielding, which keeps noise out of your system and is a major reason for pixelation," she says.
For people living in apartments, typically there is one antenna for all residences, a booster and lots of cable to get into the apartments. The signal is amplified and distributed to all residences.

"This set-up is OK for analog but digital is more complex. Digital equipment needs less signal but it is sensitive to noise and will start to pixelate. Usually, the cable is inadequate. It must not generate noise if it is used for a digital signal."

What about improving your radio reception? Many old television antennas can be used for FM radio, Garden says.

"Most of the time, particularly in capital cities, FM radios can be improved by plugging in to a regular television antenna socket."

All commercial FM stations are simulcast on digital radio. "Even the old antenna you have been using for years is likely to improve your FM reception, whether broadcast in digital or analog," Garden says.

"Of course, if you want to listen to digital radio you have to invest in new radios. AM radio is a different matter. The kids that used to build crystal sets (simple radio receivers) understood that you needed long lengths of copper wire with an insulator on each end. We have discovered electric fence insulators are something you can use for this job. We are looking at making a DIY kit for this, as there are many restrictions in homes as to where you can string out a 35-metre length of copper wire."

Garden says apartments need to have their systems checked to establish whether the amplification and cabling is suitable.

In good signal strength areas, the antennas supplied with digital radios are "more than adequate", says Graeme Redman, the managing director of PURE Australasia, a subsidiary of British digital radio developer PURE. Some digital radio models also have the provision for an external antenna connection, he says.

"Where poor signal strength is an issue, the use of an external antenna can dramatically improve reception. In fringe reception areas, it is desirable to get a digital radio with an external antenna connection and install an external antenna."

Redman discovered it was possible to get quality and reliable reception "well outside the designated coverage area" when he installed a $66 off-the-shelf digital antenna on a roof at a friend's house to pick up digital radio in country Victoria.

Quality of reception depends on a number of factors, he says, including the power of the transmitter, distance from the transmitter, atmospheric conditions, topography of the land and obstacles such as mountains and large buildings that can create "shadows" in the coverage area.

"Construction of the buildings can also be an issue, giving poor or no in-building reception in areas that would otherwise have acceptable signal strength," Redman says.

"These factors lead to variable signal reception in what may otherwise be classified as a good signal strength area.

"In mobile phone parlance, such areas are commonly called black spots. Other factors that can affect good reception are electrical interference that can make listening or viewing untenable. This can come from a wide range of sources, from other electrical or electronic equipment, atmospheric sources or just insufficient signal strength to rise above the basic radio frequency clutter.

"Where the signal is weak, a better antenna will provide more signal to the radio."

Read more: https://www.smh.com.au/digital-life/hometech/tricks-to-fix-pixelation-20100715-10c40.html#ixzz3xZhs9Ber 


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