We’ve had a few emails to GadgetGuy lately regarding disappointing results with the picture quality of some no-name LCD televisions. In industry-speak, they’re what’s known as ‘yum cha’ brands – basically you get in touch with someone in China, choose from a shopping list of panel sizes and resolutions, components and cases, and slap your own badge on it.

Not all of them are bad, some provide decent results for a very modest price. But there are pitfalls.

The one coming to our attention involves the frequency at which the TV natively operates, its associated term of measurement – hertz – and its application in the world’s two major video systems, PAL and NTSC.

Now, to some broad definitions of these terms.

PAL (Phase Alternating Line) is the television coding system used in Australia and Europe, while NTSC (National Television System Committee) is used by much of the rest of the world, with the USA being the biggest member of the NTSC club. Hertz, as applies to TVs, is the frequency with which the video frames – and half frames – that comprise an image are presented to the screen.

The difference between these two technologies, and the focus of this article, is that the NTSC system updates the onscreen image 30 times per second, or at frequency of 60Hz, while PAL updates at 25 times per second, or at 50Hz. In short, NTSC video is made to display optimally on 60Hz screen, and PAL video on a 50Hz screen.

To press the point, you’ll notice that when big companies extol the virtues of ‘hertz’ technology in Australia that it’s always a multiple of fifty -100Hz was once the buzz, now 200Hz is the cutting edge of LCD TV tech. These TVs are optimised for the Australian market and its PAL video system.

But some budget TVs being sold locally are optimised for the NSTC world. These may be surplus stock from an order intended for the huge US market that were picked cheaply by a local distributor, or just the only stock available to an importer. Whatever the case, they operate internally at 60Hz. This means that they have to turn a 50Hz video signal from a PAL TV broadcast – or DVD or Blu-ray – into a 60Hz signal. To do this they have to repeat every fifth frame of video, with the result being a jumpy, jerky stuttering image.

Now, there will typically be nothing on the television set itself to indicate if it operates internally at 60Hz, not 50Hz, so if you’re contemplating a house-brand television be sure to ask your retailer the question. If they can’t give you the answer – the correct answer – then you don’t want to be buying that TV.

The second thing you can do is audition the TV. Ask to watch some broadcast TV or, even better, take along a DVD or Blu-ray disc with lots of slow panning shots, or watch the credits of a film. Look for stuttering in the image, or jerkiness.

These type of sets will almost certainly be cheaper than those from the big brands, but that saving will be probably be of small comfort when you’re living with a cruddy picture.