I have seen "digital" tv areals on sale and before I go round telling people they are no different to "analogue" areals could someone confirm please ?

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As far as I can tell they seem to be higher gain and more directional.

I need a whopping great big one here to get a reasonable signal when its attic mounted.

When the weather sorts itself out I'll probably stick it up outside.

 

to me they look just like the analog ones there are different gain analog areals too I do know that digital requires a good signal but to label an areal digital specific I think is a con its like the VHF / UHF thing

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It's still UHF, digital or analog (encoding), the signal is still a radio frequency, with a carrier and FM modulated. I doubt there is any significant difference.

I haven't gone out and bought the converter box yet, but got the coupons last week. I get pretty good UHF with a little bow-tie type on top my TV, but not too picky about detail. Will see if it's good enough in a week or two (not a high priority, still have a couple of weeks on the coupons).

 

Most of the 'digital antennas' I've seen are all Yagi's. Problem is if all the TV stations in your area aren't in the same spot (are they ever?) You'd need a remote control rotating coupling on the antenna to get the full set of channels in your area.

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There is no difference in the aerial itself, analogue and digital signals are picked up equally well - both are just modulated RF carriers.

Where the difference falls is that some UK transmitters have digital multiplexes in a different band to the main analogue channels - and the vast majority of UK aerials are channelised (either group A, B or C/D). In order to cover the wider spread of the channels you need a wideband aerial - these are lower gain than channelised ones, so you often need a larger aerial to give similar signal strength.

But the entire 'digital aerial' lark is just a scam to sell you a new aerial, like wise some companies are now advertising 'digital coax' to go with your 'digital aerial'.

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http://www.farnell.com/datasheets/98473.pdf is a 75 ohm cable, 6.1mm diameter that gives 37.8 dB/100m at 800 MHz

http://www.farnell.com/datasheets/98486.pdf is a 75 ohm cable, 6.8mm diameter that gives 18.0 dB/100m at 800 MHz

If you have a 20m run of cable from your aerial to the reciever, the difference is 4dB, so you get more than twice the signal with the better cable.

Analog TV works badly with a poor signal. Digital TV does not work at all with a poor signal, so in poor signal areas a better aerial and better cable can make a huge difference. In a good signal areas you can use any old rubbish.

It is always worth giving it a try. A new aerial and cable costs a lot to install, and a digital reciever is £20, so you might as well try it, and then buy a better aerial if you need it, and look at better cable if the run is long.

 

Not to be too picky, but in the U.S. the digital TV signal uses 8-VSB vestigial sideband modulation, which is a modified form of single-sideband AM modulation.

But as you note the signal or modulation type has little effect on the type of antenna required. That's mainly determined by the bandwidth required (channel width and how many channels are to be received) and the available signal strength.

 

You also might need to point it in a slightly differrent direction as the transmitter which provides digital TV might be in a different location.

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This is extremely rare though, almost always they are on the same mast - there are a few exceptions, where space wasn't available though.

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In US it seemed (but may not be entirely true) that many or all VHF TV stations were moving to all UHF frequencies. Similarly, antennas aimed at the "digital" marketplace seemed to be UHF only. I don't know if the plan is to abandon or re-assign the VHF channels.

The traditional TV antenna in the US is/was VHF and UHF - the longer elements being for VHF. A UHF antenna elements are substantially shorter and a higher gain seems possible in a moderate boom length. If digital TV is UHF only then a "digital" antenna would be different in that VHF would be eliminated.

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Well it all seems to add up..

For Digital TV (as in Norway where I live). Its all on UHF so most of the old aerals can be used as the are "dual band" but its correctly as some one said that digital TV needs a better signal than analog. With analog TV you can have "snow" on the picture and have a BW signal because of the low signal level. There is also a lot to gain signal level vise with a better coaxcable. Im used to trying and failing (althou with analog signals, beeing a radioamateur).

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Here in the UK TV has all been UHF since the mid 1980s - the last VHF transmissions were turned off back in about 86 but Nigel will know more about this than me.

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I can't remember when it was, by the time it was turned off almost no one was using it.

Just checked Wikipedia, it was beginning of January 1985.

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