Aerial for DAB Reception

strobo

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After a bit of recent re-jigging, I now have a single 52-element aerial in the loft, feeding two TV's, two Freeview boxes, and two FM tuners. Our signal strength isn't as good as I'd like (direct feed to a TV/STB reaches little more than 70% - with the whole network plugged in, it dips to mid-50's percent).

Because of this I'm planning on investing in a masthead signal amplifier. But looking into what I need has opened up a can of worms really. I see that some of the amplifiers have FM/DAB inputs as well as the usual UHF inputs, and this got me thinking I might well be glad of a dedicated FM aerial integrated into my aerial network, ready for my addition of a DAB tuner to my stereo setup sometime soon.

But then I wonder whether the 52-element aerial would give a good enough signal once it's been amplified anyway. The wall sockets have seperate TV/FM sockets, so the signal is being split there. Would this be sufficient for DAB? Is it generally accepted that a good DVB signal means a good DAB signal, or is that not the case? If you have access to a good quality (albeit amplified) signal, does a DAB tuner need a dedicated DAB/FM signal, or will a standard signal suffice?

I would say our FM signal isn't all that bad, but there are a couple of stations I can receive in the car when it's on the drive that I can't get indoors. Switching from the simple bundled FM aerial to the roof/loft aerial in the past has never offered an improvement in quality or more stations either.

Any advice/suggestions?
 

Sorreltiger

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A DAB aerial is totally different to an FM aerial. The polarity is different - put simply, I believe that an FM aerial will work best horizontally and a DAB vertically. I'm not an expert, so maybe someone with more expertise will put me right if I'm wrong! I did try my rooftop FM aerial with my DAB tuner and it was a little better than a ribbon aerial, but wasn't really satisfactory. You need to buy a specialist DAB aerial for a DAB signal, I'm afraid.

Furthermore, there's no doubt that the biggest improvement would come about if you were able to mount all of your aerials OUTSIDE instead of in the loft. Isn't that possible?
 

strobo

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Cheers for the reply Sorreltiger. The aerial(s) could be mounted outside, but it's an old hosue and a number of factors have resulted in us deciding to have the least number of things passing through the external walls as is possible. We also live on top of a hill where we get VERY strong winds all year round, and aerials don't stay in alignment for very long. The local pigeon population don't help in this respect either...

I'd wondered whether FM and DAB aerials might be identical, seeing as a lot of the wall socket face-plates have an FM/DAB label on them, suggesting the feed might be suitable for both. A lot of the signal amplifiers also have this label, so again, it supported my idea that they were the same. Obviously not.

It's unfortunate that I don't have a DAB tuner with a proper coax input on the rear that I can play with.

I wonder whether DAB does use the same transmitters as DVB. If it does, then this http://www.ukfree.tv/fullstory.php?storyid=1107051475 makes for interesting reading. You have to wonder whether the signal and sound quality of DAB (yep, I've seen the debates) will improve a lot when the switchover finally takes place.
 

8009514

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The FM type aerial is not the best at picking up DAB signals, unless the signal strength is extremely high. This type of aerial is looking for frequencies between 88 - 108Mhz. Dab signals are much higher than that, about 280Mhz or so. However, you stand a good chance of your TV aerial being able to pick them up. TV aerials are generally pretty wideband so I wouldn't envisage a problem using it. You need to take a split or direct feed from the TV aerial cable and feed it direct to your DAB receiver.

Works just fine for me, really good reception in Bristol area anyway.

Hope this helps.
 

strobo

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Cheers gents.

Good site there Chebby. Even better considering I live in Sheffield, so I might pop over to them tomorrow and sort something out (I've already sorted a temporary shopping list
emotion-4.gif
).
 
A

Anonymous

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I put up a 4 way UHF/DAB mast head amp to cover a weak Freeview signal. I noticed that I could get a decent DAB signal using the UHF (sometines it is has a greater signal strength).

Only downside is that recently the whole amp was destroyed due to the EMP created by a lightning strike 200 m away costing £150 to replace.
 

strobo

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The words "Law" and "Sod's" spring to mind Dave.

Well I popped into ATV earlier today (I live in Sheffield), and bought a UHF/VHF amplifier (I'd already installed a splitter in the loft), and an FM 1/2 wave dipole. The dipole is supposedly good for DAB reception too, so it'll suffice until I get my mitts on a new DAB tuner, and hopefully beyond. But for now the FM signal is perfect, so I'm a happy bunny. The TV signal is vastly improved too, though the living room has room for improvement, but that lies in the naff cable that currently feeds it, so that's my next job.

I'm definitely giving a big thumbs up to ATV. The chaps I spoke to were helpful and seemed to know their stuff. The aerials on view also showed just how ropey my Ebay bargain Bacofoil aerial really is.

I'll be back there for some decent cable in the next few weeks, as after reading their website I've decided that making sure the whole house is wired up with good stuff is the way forward, especially if HD is likely to appear on Freeview anytime soon.
 
A

Anonymous

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Not totally different, they both do the same job -i.e. DAB uses FM to transmit and receive digital pulses, but operates at a higher frequency. Because of the higher frequency used by DAB a shorter antenna than the ideal is usually required to get the best reception. You are quite right in that DAB is vertically polarized, however FM is usually universally polarized so a laying your DAB antenna flat wont make much difference to FM reception, whereas aligning an FM antenna vertically may well improve DAB reception. I read an article where under tests FM dipoles worked very well as DAB antenna if cut down to 38cm per section.
 

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