Installing a TV antenna inside the roof cavity - Page 1
Forum section: electronics / general

author: Halcyon
author_rank: Unknown
timestamp: July 16, 2015, 09:14:35 am
content: I think I know what the response will be but I'd like to hear your opinions anyway.I need to install a TV antenna on my house. I'd rather not put it on top of the roof as I think they are bloody ugly. I have a huge area in the roof cavity and ideally I'd like it installed in there for aesthetics, protection from the elements/birds and one less thing for lighting to hit.I'm situated on top of a mountain >50KM line-of-sight to the main transmitter towers in Sydney @ 50kW ERP (the same facility that Dave toured inthis video). The roof itself is made of Colorbond (steel) sheeting, which I realise is going to significantly attenuate the received signal and increase bit error rate. But has anyone actually tried and tested this type of installation anyway? What were your results?

author: babysitter
author_rank: Frequent Contributor
timestamp: July 16, 2015, 09:22:03 am
content: Frequency? Polarisation? I think there is a method of using a tiny (300/frequency meter) antenna using you steel sheating for ground plane, being tiny and robust and not ugly.

author: Halcyon
author_rank: Unknown
timestamp: July 16, 2015, 09:25:16 am
content: Quote from: babysitter on July 16, 2015, 09:22:03 amBetween 177MHz to 226MHz for most stuff. Horizontally polarised. There are two alternative towers which are a bit closer but are much lower output and in the 600-odd MHz range.

author: Muttley Snickers
author_rank: Unknown
timestamp: July 16, 2015, 10:13:28 am
content: GDay halcyon,It wont work under a tin roof at all and even older cement and mossy terracotta tiles will affect the reception when damp or wet, I was an installer for many years and got bored with it and went out on my own in a different field, still have all my test gear from 30 years ago and occasionally still do the odd one, mainly telescopic towers to 50 feet.Muttley

author: Halcyon
author_rank: Unknown
timestamp: July 16, 2015, 10:21:41 am
content: Cheers Muttley,I suspected this was going to be the case. Plus I'd imagine heavy rainfall between me and the tower will also have quite an effect. I might just attach it to an "L" type pole to the side of the house. I just don't like the idea of making holes in the roof if I can help it.I don't have any test gear so I'll have to rely on the signal info on the TV itself (which should do an alright job). Unless you're offering to climb up a gum tree and install it for me there?

author: Muttley Snickers
author_rank: Unknown
timestamp: July 16, 2015, 10:48:04 am
content: If this is your new house which I virtually installed that rack into the other day then dont make any penetrations through the roof at all, the plumber will be pissed off and you could void any guarantee. In addition if not done correctly they can resonate in certain conditions and drive you and yours completely bonkers not to mention the chance of leaks.You can use a facia mount (hockey stick) or an adjustable iron roof mount, neither are damaging.Muttley

author: Halcyon
author_rank: Unknown
timestamp: July 16, 2015, 10:52:48 am
content: Quote from: Muttley Snickers on July 16, 2015, 10:48:04 amYep, same house. I'm a 'planner', so I like to research and arrange things months in advance :-)

author: Muttley Snickers
author_rank: Unknown
timestamp: July 16, 2015, 10:54:07 am
content: Invoice Sent.........

author: Halcyon
author_rank: Unknown
timestamp: July 16, 2015, 10:56:32 am
content: Quote from: Muttley Snickers on July 16, 2015, 10:54:07 amI have a full 48 RU Hallam rack if you're interested? ;-)

author: Muttley Snickers
author_rank: Unknown
timestamp: July 16, 2015, 11:00:39 am
content: Thanks for the offer but I'm all racked already........

author: Ian.M
author_rank: Super Contributor
timestamp: July 16, 2015, 11:48:51 am
content: If you had a gable end directly facing a local transmitter, I'd say try it, but I think Muttley has almost certainly pegged it. However, in the interests of science, if you are DIYing the aerial installation and have half an hour spare, do try a temporary hookup in the roof space and report back exactly how bad it is!

author: Fraser
author_rank: Super Contributor
timestamp: July 16, 2015, 12:07:42 pm
content: In the UK we use only UHF but there are many Aerial options to choose from. Some are designed to be discrete. I am not a fan of active aerials for TV as I like to start with adequate signal at the physical elements before adding amplification. The caravan fraternity have a good range of active TV aerials to choose from though. They seem to work but prices are high for decent types. Boats also have active TV aerials of good quality these days. Maybe worth Investigating if you really cannot tolerate the usual bird perch YagiSome of the Caravan aerials are quite attractive. These will be exterior to your home but compact.In the UK we also have compact active aerials for houses. The better types use a Log Periodic inside a plastic Radome. Cheap ones offering massive gains from a simple loop are usually junk.On using a TV inside a metal clad roof. It's a non starter if you have to aim through the metal sheets.Aurora

author: Ian.M
author_rank: Super Contributor
timestamp: July 16, 2015, 12:24:55 pm
content: Quote from: Aurora on July 16, 2015, 12:07:42 pm50Km to the transmitter is nearly fringe reception. Most active aerials wont do well at all in fringe areas, and those that are sufficiently directional and have a low enough noise threshold to work tend to be large and $expensive$. IMHO start with the best all metal directional aerial you can afford and add a masthead amp if the signal level is inadequate. Be prepared to move the antennae several wavelengths in any direction to get it out of multi-path reflection nulls caused by the roof or by horizontal metal structures near to the line of sight to the transmitter.Quote... or if aiming through concrete with mesh reinforcing or foil backed insulation. You may be able to pick up a reflected signal coming in from some random direction but it will almost certainly fade every time a truck goes past.

author: Muttley Snickers
author_rank: Unknown
timestamp: July 16, 2015, 12:31:02 pm
content: Ian.M is correct in regards to the pitched gable end but you will find that the builders will line it with Sisalation which is a sheet foil insulation, some brands of antennas are better than others and see if you can get one with drawn elements without a folded seam, also although unsightly uncut black cable ties facing up every 120mm along each element help keep the birds off.Some customers that use and drink the rain water prefer this approach, birds still land but not as many.Muttley