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bw41101 · 25-09-2007, 16:28

Having not seen your aerial, I will assume that it is of (what they call) a Yagi design, I.e. load of element arranged in a rows, something like this?:

Attachment 14966

Now if you look at the elements, you should see (I've drawn) an elipse around them. This indicates the bandwidth of the aerial, the more elements you have the more gain (recieve power) it has. However the down side, is the narrower the bandwidth - this concept is referred to as the Capture Effect. To compare, it's like looking at an object through a telescope, I.e. you see the object close up but within a very narrow field of vision, whereas binoculars you see a smaller object but with a wider field of vision - make sense?

Taking this into account, you have a very powerful recieve capability but at the expence of a very narrow field of view. In order to get the best out of your aerial you're going to have to adjust it's position very carefully in order that it can see the signal coming in.

Unfortunately (being loft mounted) you will (no doubt) recieve some signal degredation (attenuation) due to the roofing materials within the close proximity.

Apologies for the techno speak, but (I hope) I've been able to clarify the problems you're having. The proffesionals use a field strength meter in order to read the signal strength directly from the transmitter. As you've (probably) not got access to one of these. The only way (I can recommend) is that you take a portable TV set up into the loft with you, fit a plug on to the cable (from the aerial) then connect the aerial to the TV. You should then (standing behind the aerial) gently adjust the position of same in order to get the best picture.

Channels 4/5 are usually the weakest signals, so if you can get these, then all of the others should be okay too. Look for pictures without any shadows (ghosting) and a good clean audio without any hiss.

Once you get what you're looking for, you can then lock the aerial in place and attach the main cable via a socket (should be okay for a loft installation) and (hopefully) you're in business

Good luck and Si thee

25-09-2007, 16:28	#4
bw41101 Inactive Join Date: Mar 2007 Location: Blackpool Services: Broadband XL TV XL Phone - A device with buttons that makes a funny noise when it rings! Posts: 929	Re: ariel fitting Having not seen your aerial, I will assume that it is of (what they call) a Yagi design, I.e. load of element arranged in a rows, something like this?: Attachment 14966 Now if you look at the elements, you should see (I've drawn) an elipse around them. This indicates the bandwidth of the aerial, the more elements you have the more gain (recieve power) it has. However the down side, is the narrower the bandwidth - this concept is referred to as the Capture Effect. To compare, it's like looking at an object through a telescope, I.e. you see the object close up but within a very narrow field of vision, whereas binoculars you see a smaller object but with a wider field of vision - make sense? Taking this into account, you have a very powerful recieve capability but at the expence of a very narrow field of view. In order to get the best out of your aerial you're going to have to adjust it's position very carefully in order that it can see the signal coming in. Unfortunately (being loft mounted) you will (no doubt) recieve some signal degredation (attenuation) due to the roofing materials within the close proximity. Apologies for the techno speak, but (I hope) I've been able to clarify the problems you're having. The proffesionals use a field strength meter in order to read the signal strength directly from the transmitter. As you've (probably) not got access to one of these. The only way (I can recommend) is that you take a portable TV set up into the loft with you, fit a plug on to the cable (from the aerial) then connect the aerial to the TV. You should then (standing behind the aerial) gently adjust the position of same in order to get the best picture. Channels 4/5 are usually the weakest signals, so if you can get these, then all of the others should be okay too. Look for pictures without any shadows (ghosting) and a good clean audio without any hiss. Once you get what you're looking for, you can then lock the aerial in place and attach the main cable via a socket (should be okay for a loft installation) and (hopefully) you're in business Good luck and Si thee