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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Alarms, Phones, Aerials, CCTV & Datacomms >> Loft aerial https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1248689385 Message started by Zambezi on Jul 27^th, 2009, 11:09am

Title: Loft aerial
Post by Zambezi on Jul 27^th, 2009, 11:09am

Somebody has asked me to put a loft aerial in their loft as a temporary measure until they decide what they want to do regarding Sky or Freesat or BT vision etc.
The trouble is they have foil insulation between the rafters and the roof tiles.
Will an aerial work under the foil, I highly doubt it but I thought I would ask anyway?

Title: Re: Loft aerial
Post by plugwash on Jul 27^th, 2009, 5:36pm

I would think it would depend on how strong the signal is and how thick the foil is.

Title: Re: Loft aerial
Post by Zambezi on Jul 27^th, 2009, 5:40pm

There are quite a few layers of foil (I did not count then but I would guess about 3).

Title: Re: Loft aerial
Post by Lectrician on Jul 27^th, 2009, 8:30pm

You can but try.

What do neighbouring properties have? If their aerials are smallish, the signal will be good, and a loft aerial will likely be fine in the short term (you may need to go larger than the neighbours).

Size = elements. How many cross pieces or X pieces do the neighbours have?

Title: Re: Loft aerial
Post by CWatters on Jul 27^th, 2009, 9:02pm

I put a loft aerial in my selfbuild. The roof insulation between the rafters is two layers of celotex so four layers of foil in all. With the insulation in place the signal levels were exceptionally poor as I expected (my background is in electronics). Some multiplexes were totally missing.

Before climbing on the roof to fix it to the chimney I removed just the one rafter bay of insulation in line with the aerial as an experiment. I was surprised to find I got a usable signal. Not full strength, but usable. This is pure luck though. You might cut a hole in the insulation and find you still don't get a signal.

If you are reasonably close to a main transmitter almost any "digital" aerial might work after a fashion but it may not be the best aerial to use. Aerials sold as "Digital" aerials are generally wide band aerials but not everyone needs a wide band aerial. Narrow band or "Grouped" aerials can sometimes work better because they have more gain. It depends where they are and what transmitters they can see. They might have to use a wideband to get both digital and analogue.

Perhaps bash the postcode into here..

Digital
http://www.wolfbane.com/cgi-bin/tvd.exe?

Analogue
http://www.wolfbane.com/cgi-bin/tva.exe?

If in doubt tell us their postcode and we can give some idea how difficult reception will be in that area.

Title: Re: Loft aerial
Post by Zambezi on Jul 28^th, 2009, 7:28am

That web check thingy said it needs an amplified extra hi-gain aerial. I did not check the neighbours aerials but the signal is not great around here (customer lives 2 blocks away from me).
I did say to him that his best bet would be to use an aerial man but he wants to use me (because I am too cheap!).

At some stage he is going to get a Loftbox type distribution amp but he has not decided what he wants yet. He currently has an aerial on the other end of the house, with a mast head amp on it, which picks up pretty much everything on Freeview. He was not keen on me running a cable all the way around his house from the other aerial. Slightly odd customer, who likes things to be done his way but not always the best way ::)

Title: Re: Loft aerial
Post by Lectrician on Jul 28^th, 2009, 7:44am

wrote on Jul 28^th, 2009, 7:28am:

He currently has an aerial on the other end of the house, with a mast head amp on it, which picks up pretty much everything on Freeview.

As soon as you say masthead amp you kind of know the strength is going to be poor.

Title: Re: Loft aerial
Post by Zambezi on Jul 28^th, 2009, 9:24am

Mast head amps are common around here, we have one on our place and it is still iffy sometimes.

Title: Re: Loft aerial
Post by CWatters on Jul 28^th, 2009, 4:36pm

I think if his area needs a big aerial and a mast head amp he'd be advised not to waste money on a loft aerial. Thing it is so unpredictable. Perhaps worth a read...

http://www.aerialsandtv.com/loftaerials.html

Is there a reason why you can't run a wire from the existing aerial through the loft? I would persuade him to install a distribution amp immediatly below the existing aerial in the loft and run an output around in the loft to where he wants the new TV point.

The only issue is to check how the existing mast head amp is powered. Some are powered up the UHF down lead so cutting that and inserting a distribution amp would be more complicated. I think some Blake distribution amps provide power for a mast head amp up the UHF aerial input but you would have to find out what the mast head amp needed.

Title: Re: Loft aerial
Post by Zambezi on Jul 28^th, 2009, 8:55pm

I want to fit a distribution amp and do it once but he wants to think about what he wants where and what he will use Sky/Freesat, BT Vision etc.
The new aerial point is in a granny flat, that is not going to be used (not as far as I can see anyway).

The mast head amp has a plug in power sully that is fitted to the feed of one of the TVs. If you switch the power supply off, you loose signal everywhere.

Title: Re: Loft aerial
Post by Lectrician on Jul 29^th, 2009, 8:34am

wrote on Jul 28^th, 2009, 8:55pm:

The mast head amp has a plug in power sully that is fitted to the feed of one of the TVs. If you switch the power supply off, you loose signal everywhere.

That indicates a distribution amp of some kind is already fitted.

Can you not just use that?

Title: Re: Loft aerial
Post by Zambezi on Jul 29^th, 2009, 8:38am

AFAIK it is the amp on the aerial that distributes it to the various points in the house (3 points that I know of).

Title: Re: Loft aerial
Post by CWatters on Jul 29^th, 2009, 10:09am

That's possible. Some mast head amps have multiple outputs. How many wires can you see coming out of it? If there are three then there might be a spare one.

Title: Re: Loft aerial
Post by Zambezi on Jul 29^th, 2009, 12:40pm

I only saw three but did not really pay too much attention, it was a Saturday and I was on my way home after a hard days work ::)
He was not too keen on cables going all over the place but I will go and have a proper look when I am next there and hopefully get him to do the job once rather than a bit now and a bit in a couple of months time. It would mean 1 trip into the fluffy itchy stuff, not 2 ;D