TV and radio aerials on one mast?

[Rafal]

Hi, I know that aerial installs were covered here on "few" occasions but I did not find answers via searching news groups and net. Planning to install two new aerials for TV /incl freeview/ and fm radio. /Streatham, London, about 1-2 miles from Crystal Palace transmitter/. I would like to install both aerials on one mast. I vaguely remember that in that case there should be a certain distance between them / something to do with the wavelength they operate?/ Or is it just not good practice to put them together? What about the distance from other aerials? How to calculate the signal strength? /my Naim Audio tuner need min 600mV for 'full quieting'/ Your opinions on omni circular fm aerial

normal one.

Thank you in advance Rafal

[Andy Hall]

Generally the more the better but try to keep them at least half the wavelength of the VHF antenna apart. If you can manage at least 2m, that would be a good idea.

As above. The issue that you are more likely to run into is having too much signal and picking up reflected signals in an area of high signal strength

I presume that that is 600 microvolts, not millivolts.

At any rate, for where you are located, even a piece of wet string should give more than enough signal/

Normally I would say that these are junk, but again because of high signal strength and because you probably have transmitters in different directions but locally to where you are then not a bad idea.

.andy

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[Scott M]

The instructions that came with my Maxview FM aerial said it should be at least 1m from the TV aerial if they're going on the same pole.

[Dave Plowman]

They are rubbish. If all the stations you want to receive are broadcast from CP/Croydon, a simple dipole or two element will do.

The further they can be separated, the better. But the VHF aerial should be mounted vertically these days which can make things more tricky.

You'll probably need to attenuate the UHF signal, especially if feeding a distribution amp - I do, and I'm in Balham, with line of sight to CP.

[Mortimer]

Both aerials on one mast should be OK, keep them at least 1 metre verticaly apart.For digital TV (Freeview) get a good quality high gain aerial although as you are close to transmitter signal strength should be fine. FM radio is on 88 to 108 mHz (wavelength in order of 3 metres) whilst TV is on about 650 mHz (wavelength in region of 0.5 metres) the elements of the different aerials are cut to a length probably about one quarter of the wavelength they are designed to receive. Hence a TV directional aerial has shorter elements than an FM radio directional aerial.For good radio reception use a directional aerial and point it at local FM broadcast transmitter, not necessesarily the same place as TV transmitter. Ask at local TV shop or look on BBC web site or phone BBC advice line. Omni directional aerial OK but as it suggests it will receive all FM equally from 360 dgrees around so may present weaker signal to your receiver or may introduce interference.Avoid sighting your aerials so they are blocked by any others between you and transmitter. Hope that helps. Mark.

[Christian McArdle]

Quite frankly, I'd give it a go with the TV aeriel inside the loft. Then you can put just the FM aeriel on the mast. 2 miles from Crystal Palace will have amazing signal strength, easily enough to overcome a tile/slate roof, provided you don't get any nasty reflections.

You can easily try it out cheaply to see if you get good reception before commiting to an external aeriel.

Christian.

[Ian Stirling]

If you want to recieve stations at a distance, it can make an incredible difference. For example, the typical portable radio will pick up some 10 stations. With a proper omni antenna (made from bamboo and copper wire) it went up to some 80+.

[Dave Plowman]

More to the point they'll allow multi-path reception which is death to decent sound quality off FM. I don't know what Streatham is like in this respect, but I'm not that far away and it matters here - Sauf Lunnun is full of hills.

[Rafal]

Thanks a lot.

That is exactly the info I was looking for. I want to try omni due to the number of independent radio stations in London, but that could kill good reception of BBC3 & 4

[Andy Hall]

Probably not.

You are also relatively close to Wrotham, which carries the national BBC channels and has a much higher power level than the local stations.

.andy

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[Dave Plowman]

There are 'fill in' transmitters for the national stations at CP. Before these reception in my part of London was more akin to parts of Wales.

I used to drive to work via Trinity Road which runs from Wandsworth Bridge to Tooting Bec, crossing Wandsworth Common. And in the traffic jam crossing the common in the morning, R4 would cancel so completely due to multipath that you couldn't understand speech. Sometime in the late '80s, John Birt the then DG of the BBC bought a house just off Trinity Road - which never sprouted an external VHF aerial

- so either he had a line feed of the main BBC stations, or he never listened to them on FM, as portable radio reception was near impossible. Then shortly afterwards these 'fill in' transmitters appeared with R4 being the first.

Before this I had experimented with an 8 element VHF on every chimney stack in the house trying for best results from Wrotham, but never got

100% satisfactory results.

However, IIRC these transmitters are vertically polarised only, and since all the others are mixed polarisation it makes sense to have the aerial vertically mounted - which non of the riggers round here seem to have cottoned on to...

[Andy Luckman (AJL Electronics)]

NO NO NO, not if he wants it to work properly, assuming you are talking about an aerial.

[Christian McArdle]

Obviously normally you wouldn't even think about it. However, 2 miles from CP must be worth a shot. I've had excellent reception from a reasonable quality aeriel inside a loft 20 miles from Hannington.

If it doesn't work, then you haven't lost anything. The aeriel just goes on the mast.

Christian.

[Dave Plowman]

The signal strengths from CP are very high, and it might well work fine, depending on the roofing materials. It could be easy enough to try - certainly not the same as fiddling about on a roof.

[Ric]

Then you would be a fiddler on the roof!

[Dave Plowman]

But if only I were a rich man...

[Andy Luckman (AJL Electronics)]

It is irrelevant that the signal strength is high. The reflection are the killer. BTW it is an AERIAL.

[Christian McArdle]

Indeed, as I stated in my first reply. I've also had excellent reception from a loft aerial before. I'm not saying that it will work in every (or even many) cases, but as it is a free bet, you might as well try it.

I knew it didn't look quite right...

Christian.

[Dave Plowman]

In practice it's still worth a try. As I'm sure you know, UHF is funny stuff that has rules of its own. Whether you'll get refections off anything inside a roof void is anybody's guess.

[Nick Finnigan]

I've got a new Freeview box connected using ancient brown cable and several connectors.to a 20 quid (ish) aerial from CPC inside my loft, pointed at Winter Hill about 20 miles away. How should I tell if it is not working properly?