I'm about to mount a loft aerial for TV...

[MM]

This is a bog-standard 18-element TV aerial from Wilkinsons (£8.99) and I plan to mount it in the loft space, where even a room aerial gives excellent reception via the SLx6 Philex aerial booster.

From my bedroom window I can observe the aerial on the chimney of a neighbouring house. How can I preserve its "angle" as closely as possible when I mount my aerial? Or isn't the position that critical?

I've been thinking of schooldays when we were given the trigometric task of working out a tree's height, but I can't think of any comparable algorithm to transfer the neighbour's aerial's "direction" to mine. I'll just have to "remember" the position as I climb into my loft.

MM

[Frank Erskine]

Get somebody to watch the TV as you point the aerial in different directions. Even easier, attach a short cable to the aerial temporarily and take a TV set into the loft, then simply adjust for the best signal (least grainy and minimal ghosting)(assuming you're still using analogue reception). Remember to check all channels because you may have a compromise a bit. An 18-element will be quite directional.

[Mark Spice]

When I did this I just took a compass bearingoff the neighbour's arial and then replicated it in the loft with mine. A bit of judicious shouting from SWMBO about picture quality led to some fine adjustment and Robert was one's father's brother.

Cheers

Mark

[MM]

At the risk of sounding like a bit of an orienteering virgin, can you explain how to do that with a compass (which I don't have, but I expect they're dirt cheap, the simple ones). Do you mean that I should somehow position myself in the road and orientate with the compass accordingly? I can't get close to the house in question because of fences, but I can see the aerial through my binoculars in much detail!

Thanks! (And thanks, too, to Frank earlier.)

NB: Other houses in the road also have their aerials pointed "pretty much" in the same direction, but the emphasis here is on "pretty much", because I wouldn't say their installers had bothered on position too much, going by the discrepancy between several aerials! Like I said, reception with a tiny room aerial (plugged, though, into the distribution/booster thingy in the loft) is already excellent, and had I known I probably wouldn't have bothered to buy the 18-element aerial anyway. But I've assembled it now, so it's gonna get used!

MM

[Mark Spice]

You only need to get a rough direction as you fine tune it later. What I did was to position myself in line with the arial and line up the body of the compass along that line. You can then turn the bezel of the compass so that the 000 is at the point of the North needle. When you go into your loft just turn the compass so that the North pointer meets back up with the

000 and you are lined up in the same direction again.

'Pretty Much' should be good enough as you will still want to do some fine tuning but getting this far saves a lot of random waving about.

Cheers

Mark

[Vortex]

This is simple.

1. Plug your postcode into this will return the transmitter that applies to your area, and amongst other things the compass bearing to it from your postcode
2. Obtain a compass from Milletts or similar (start at about a fiver)
3. Orient aerial.

[Bob Eager]

What I did was this:

a) Get the location of the transmitter (dtg.org.uk I think) and find it on the OS map. b) Find my house on the OS map. c) get the bearing of the Tx from my house. d) convert this to an angle relative to my road e) since the roof joists are at 90 degrees to the road, add 90 degrees to the angle from d) f) make cardboard template containing that angle g) use template to align aerial relative to joists

Then fine adjust in usual way

[Harry Bloomfield]

MM formulated on Sunday :

If you have a sighting compass, stand at the back or front of the aerial you want to align such that you see it in perfect alignment. Now site your compass on the aerial and note the degrees. Then just transfer that bearing onto your own aerial in the loft. The original may not be spot on, so try a few bearings on several aerials.

[Harry Bloomfield]

Bob Eager brought next idea :

You forgot the correction for magnetic variation.

[Alan]

In message , Bob Eager wrote

You can get the bearing directly by putting your postcode into

[Bob Eager]

Why? No compass involved at any stage (unless this is a wind-up). c) is done with a protractor or simple trigonometry.

[Harry Bloomfield]

Bob Eager laid this down on his screen :

How do you translate the bearing of the transmitter to a bearing from the house without a compass, if you cannot see the transmitter? You at least need a compass to work out the direction the house faces.

[MM]

Thanks for all the wonderful replies!

MM

[Bob Eager]

(sigh)

The bearing of the transmitter to the house is done ON THE MAP (simple trig, or use a protractor). Then (read original post) I measured the bearing corresponding to the run of the (straight) road on which I live. From that, simple addition (or subtraction) gives me the angle between the line to the transmitter, and the front edge of the house (parallel to aforementioned road). Joists are 90 degrees from that. Make template. Done.

[John]

WOW! Brilliant

[Harry Bloomfield]

Bob Eager expressed precisely :

The method does though rely heavily on the road being straight for long enough and your house being aligned to that road. Living on a rather short road with several bends in it and in a house not aligned with the road, I was struggling to grasp your method.

[Bob Eager]

[Mungo "Two Sheds" Toadfoot]

I have a compass on my mobile; you line up the little graphic of the sun to the real sun then you know where you are.

Up in my niece's loft: 'Right then... phone... sun... oh bugger.'

Luckily I'd already played outside so I knew roughly which way to point the aerial! Doesn't seem to matter if you're not too precise either, which is lucky.

Si

[Bob Eager]

I guess one could compensate by using a fairly large scale map - I've always had one of those, wherever I've lived.

After all, high accuracy isn't needed since there's always a final adjustment. I know I'd have pointed in completely the wrong direction otherwise!

(actually, the transmitter recommended by the DTG site turned out to be useless. Another one, about 120 degrees anticlockwise, as it were, turned out to be far better)

[Frank Erskine]

Is this the twirly thing that hangs above your bed?

:-)