Hey baby, can you demodulate 7MHz channels?

When television was invented, the world divided into two camps. There were the Americans, who invented a system using 525 lines, around 480 of which are active, and a 60Hz refresh rate. This system was adopted in North America, Japan, Taiwan, and a few other places that followed America technology wise. This divided the radio spectrum into chunks that are 6MHz wide.

The rest of the world adopted a system using 625 lines, around 576 of which are active, and a 50Hz refresh rate. VHF systems use channels that are either 7MHz or 8MHz wide, and most UHF systems use channels that are 8MHz wide. However, there are a couple of exceptions. Argentina and Uruguay squeeze this system into 6MHz channels. Australia uses 7MHz channels for both VHF and UHF. Australia is the only country in the world that uses 7MHz channels for UHF. (Systems using wider channels have less interference between adjacent channels, less interference between the pictures and the sound, less interference between the colour signal and the black and white signal, and (sometimes) better horizontal picture resolution).

Most analogue televisions are now multi-standard, and are capable of receiving television signals with any of the three channel widths, and adjusting automatically to work with what they find. (At least, my Toshiba is capable of doing this).

When you upgrade from analogue to digital television, the legacy of the analogue system only matters in one way. Unless you reallocate all your spectrum, you have to retain the same channel width as before. If your analogue television system used 7MHz channels, then that is what you are stuck with. One of these slices of spectrum can now carry a lot more than one channel, but you are restricted to slices this size.

Today, I went looking at set top boxes for digital television. One of these would allow me to receive a much larger number of television channels than is possible with analogue TV. This is nice, but I might not be staying in England too long, and if I am going to pay a little money for one of these boxes, I want one that will hopefully work if I take it back to Australia. Australia uses the same digital television standard as Europe (something called DVB-T), but uses 7MHz channels in the UHF band. The key question is whether one of these set top boxes is capable of demodulating and deconding 7MHz channels. There is no real reason why it shouldn't be able to, as the change is a trivial one, but I want to know.

So, I went into three electronics shops. Each had a range of set top boxes, which were quite inexpensive. What I wanted to know was whether these boxes would work in Australia. Technically, this question was asked as "Can this box demodulate 7MHz channels?". In each shop I asked a salesman if I could look at the technical specification sheet. In each case I was told that the product was in a sealed box that they would not open before it was sold, so no. I was then asked what I wanted to know. I asked whether the boxes could demodulate 7MHz channels. In each case, I might as well have been speaking Aramaic. On a couple of occasions I attempted a little explanation of what the question meant, and that it was about whether the boxes would work in Australia. Despite the fact that the salesmen had not the slightest conception of what the technical questions I was talking about were, two of them had opinions on whether the boxes would work in Australia. One said he thought it would. The other said he thought it wouldn't. The third admited he didn't know.

(An electronics shop had a PCI bus card that could be plugged into a computer. This card had the digital TV decoder electronics on it, so that people who put the card in their computer could then watch digital television on their computer screen. I was able to see the specifications for this card, and the people in the shop actually had some clues. This card was capable of handling 7MHz channels. This makes me think that the set top boxes may be able to do it too, because they are probably made using the same chipsets as the PC cards. However, I simply do not know the answer. And it is close to impossible to find out).

Update: The Internet Ronin comments that maybe I should contact the manufacturer. Well, yes, I should. However, there is a certain art to attempting to draw information out of salesmen, that is interesting, if only from an anthropological point of view. The salesman isn't going to understand the question from a technical perspective, but it is possible that the bundle of facts he knows or has been told about the product could answer the question somehow. Salesmen will also often claim to understand things they don't, and this needs to be edited out. Therefore, I need to figure out what questions I can ask that will get the answer I want, rather than directly asking a question that is too technical. It's an interesting challenge. (Of course if they do not know anything, there is nothing that will help).