Freeview via outdoor or loft aerial? Crystal Palace

[michaelwalker]

Until last Thursday we had access to all Freeview channels via a large aerial mounted on a long pole on our chimney, professionally installed just over a year ago. The wind got hold of the aerial in the storms last week and used it to rip our chimney off its moorings and spead it out all over our roof.

I'm worried that if we have the chimney rebuilt and an identical aerial fitted the same thing will just happen again sooner or later so I'm wondering if a suitably high gain loft aerial might be an alternative. I'm using a cheapo Homebase loft aerial and signal amplifier at the moment and getting the Mux 1 channels (BBC) but none of the others plus poor-to-atrocious analogue pictures.

Our local transmitter - Tunbridge Wells, about 7 miles away - is only rated for the channels I'm getting according to the DTT web site referenced in the Freeview Bible, but our outdoor aerial was able to bring in the whole lot, radio stations and all, so I know it's possible. The further problem we have is that there's a large evergreen oak right opposite the house, between us and the transmitter, hence the long pole (it was at least 7-ft) and large aerial (a Triax model I think, like the 'Unix' models on the SatCure shop site; the whole installation cost a fortune).

So the question is, given all this, is there any hope at all of getting an adequate signal out of a loft aerial in these circumstances? Given that I'm getting some channels out of a cheapo DIY aerial and bog standard coax cable, would a better aerial/amplifier/cable do the job, even allowing for the signal loss from an indoor aerial location? There's a usable space in the loft at the front of the house, where it's easy to point the aerial in the right direction and I already have a mounting pole in there.

[SatCure]

The chimney was probably in poor condition if a properly lashed mast took it down.

Try the (suitable) aerial in the loft. Just run a temporary cable through the hatch to try it. A variable gain masthead amplifier might help.
www.SatCure.co.uk/tech/amps.htm#masthead
www.SatCure.co.uk/tech/logperiodic.htm
(The log-periodic aerial is unlikely to have a high enough gain).

If it's no good, you'll have to get it mounted on the new chimney or gable end (if you have one). Tell the builder that the chimney must support it. Bear in mind that the mortar will remain "green" for a few weeks. You can get the builder to make a suitable (sealed) entry hole for the cable to go into the loft. Better than running it down the tiles.

[michaelwalker]

Martin

Thanks for this. Just so I'm absolutely clear and don't go and order the wrong things, would the Pro-Vision V10-030 aerial and Vision C12554 Mastamp 4-way variable gain amplifier be a combination worth trying?

If it does wind up having to go outside, would it need to be mounted as high as the previous aerial (the rigger was trying to get it above the tree opposite us) or could it go a bit lower down? A gable-end is available but I don't want to have to bolt an even longer mast to this if I can avoid it, especially as it would have to go round the projecting eaves and would be quite an eyesore.

Thanks again.

[SatCure]

1. The log-periodic aerial is unlikely to have a high enough gain.

2. Impossible to guess.

[michaelwalker]

So what would be a better type of aerial to try? The highest gain possible like the DAT45 or even 75? I don't mind spending some time on alignment or even buying the meter if necessary.

Fitting it outside if inside doesn't work isn't quite such an issue as it wouldn't be me doing it anyway so I'd get advice from the rigger. Just like the idea of a visually unobtrusive (ie invisible) solution that's weatherproof, won't wreck my house and which I can install myself.

[SatCure]

Well, I'd personally be interested to know if the log-periodic does work. Normally it would be fine if it's only 7 miles from the transmitter. Unfortunately, you'd have the expense of returning to to us if it doesn't. But if you'd like to try it, why not order the Pro-Vision V10-030 and also the DAT45 or DAT75. If you report back to me on the results (with photos if possible), I will personally refund your return postage.

One problem I foresee is that, if your trees grow leaves in summer, they could reduce the signal, so you won't be certain until then.

Edited by: SatCure at: 28/3/07 3:38 pm

[michaelwalker]

Can't say fairer than that. I'm happy to try them, take photos, report results, etc, and return whichever isn't needed for refund. If the smaller aerial does the job I won't even open the larger one. should I get one of the masthead amps as well or just go for the DAT75 for maximum gain?

The leaves won't be any different in summer, it's an evergreen, so if it works now it'll work then.

[SatCure]

I'd suggest the Pro-Vision V10-030 aerial and Vision C12554 Mastamp 4-way variable gain amplifier.

Oh, I should mention that the DAT aerials clip together and they are absolute swines to take apart!

[andybr07]

Michael,

As a fellow sufferer of the storm then I'd be interested to know how you get on. It sounds like I had a very similar set up. The aerial looked like a Triax/Unix model as you describe. The chap said it was a high gain aerial. Mine was mounted on a 10 ft steel pole. I just don't think I can risk the same again up on the other stack even with an aluminium mast to reduce the weight. I'm further away from my transmitter than you but I was rated to (and did) get all the channels. The BBC1 mux was actually the poorest performer. But reception was borderline as it improved moving it from one stack to another (When I had two of course). And it would vary due to seasonal/atmospheric factors. So, I reckon I'd describe my reception as moderate to poor.

So, it may be that the log periodic would not have enough gain. But the DAT ones sound like they need to be securely and accurately mounted (not waving around on the end of a 12 feet mast or higher).

Andy

[michaelwalker]

Andy, I'd be happy if my efforts could help others in similar situations.

I've been doing lots of reading up in the Freeview Bible and other web sources plus some testing with my TV. Although I'm only rated to get mux 1 (BBC channels), using just the cheapo loft aerial with bog-standard UHF cable (ie single screened, and with a connector of unknown provenance in it too) I can also get watchable services on D5 and not-quite watchable on D4, rating 9, 6 and 4-to-5 out of 10 respectively on my TV's signal strength meter. The bad news is that D2, which contains all the ITVs and Channel 4s on my local transmitter, reads 0!

The loft aerial was also aligned years ago by hand using analogue reception and lots of 'better'/'worse' shouting from downstairs...

All in all it seems well worth experimenting as there are plenty of reasons why my current loft setup wouldn't be very good and maybe the previous professional installation was a brute-force solution (as well as being the most profitable for the installer, I suspect).

Martin, are there type E options for any of the aerials you've suggested I try? I've checked my local transmitter channels and I only need to cover 37 to 61 to get everything, analogue and digital. If we could get the digital working we could start at 39 instead of 37 (37 is analogue channel 5; 39 is D5).

Apart from aerial type, I just need to sort out how much cable and what connectors I need then I'll place an order.

Thanks

[SatCure]

Group "E" aerials are somewhat rare beasts. A wideband would be the best compromise. You could even try a log-periodic with a low-noise masthead amp. Although the gain is low, they often win because of useful characteristics that minimise interference from other transmitters.

[michaelwalker]

Hi, I'm slightly going round in circles here trying to get together a list of items to order. I'm looking at the DAT 45 and 75 and reading the notes I see you say that 'Although it is possible to mount these aerials for vertical polarisation (with extra parts - see data sheet*) it is extremely unlikely that you would need to do so. In the UK, vertical polarisation of terrestrial signals is used only by local repeater stations. If the station is local, then you are unlikely to need a high gain aerial!'

My local station is a repeater (from the Heathfield main transmitter) as far as I can tell and it does have vertical polarisation, according to the DTT website. And I already know I need a high-gain (or possibly highly resistant to interference) aerial which is why I'm going to try the log-periodic model as well.

So what extra bits do I need? It seems I can't find out until I've ordered, but I want to get all the bits at once so I can get it all done and stop worrying about it...

[SatCure]

You can download the "DAT" data sheets here:
www.SatCure.co.uk/tech/dat.htm

[michaelwalker]

Martin, thanks for the link. I couldn't find the Televes 3012 vertical mounting support bracket in your shop, though, but I've ordered everything else and put a note about it on the order. I can probably lash something together out of the various existing bits and bobs in the meantime, as it's not going to have to stand up to any wind or rain in the loft. If the pro-log + masthead amp combination does the trick I won't even need it.

[SatCure]

We don't stock the Televes 3012 bracket. I think it's a "special order" item. Judging by previous requests to Televes, I advise you not to hold your breath!