No, that is the only cabinet there, but the mobile phone mast across the road has 2 or 3 cabinets at it. Is it not a fibre one? What kind is it, and why might it need an aerial?

Edited by haggismn (Sat 16-Feb-13 17:43:46)

All the cabinets I've seen usually have a contact in case of emergency/damage sticker on them

Sorry, I had wrongly assumed that because these were new cabinets, that they were Openreach fibre based (this isn't a VM area either so I thought everything was BT). I will check again later for a sticker and also pass another cabinet with an aerial, which I believe is a different type to the 2 shown here. If you think it is not relevant to fibre discussion then please move it elsewhere.

Edited by haggismn (Sat 16-Feb-13 17:52:09)

May not even be a telco's cabinet . Have seen water companies use similar

The antenna is a reasonably high gain UHF Yagi i.e. close to the same freqs as used for TV broadcasting.

The cabinet will be used for control and monitoring for a utility (water, gas, etc).

The antenna is pointing at Divis/Black Mountain as that is the high point over Belfast which can see the surrounding area. The owners of the cabinet installation may even have their base station antennas installed on the TV masts as part of a sharing agreement with Arqiva (owner of the UK's broadcast masts) or have a separate mast of their own positioned on the mountain.

Thank you for the info.

It is very interesting they have used this method for communication. Would it not be more cost effective and reliable to use the BT network, rather than paying the costs for planning, installing and maintaining antennae at each cabinet, and also the cost of setting up a base station? There must also be an added risk that planning permission might be refused, as the aerials are quite noticeable and may be considered unsightly by some.

Regarding the location of the base station, one of the cabinets is in an area in Newtownabbey which can't receive Freeview from Divis/Black Mountain due to there being no line of sight. Everyone uses the Carnmoney Hill relay for terrestrial TV. The cabinet aerial here however still points towards Divis/Black Mountain, in spite of a hospital building in the way. You can see here on Google street view (the cabinet is somewhere near the postbox). Surely they must have substantial reliability issues here with communication, with the change of weather and whatnot?

Take a look at the multitude of secondary aerials mounted on Black Mountain TV Mast-

http://www.thebigtower.com/live/Black%20Mountain/91P...

Others have similar collections.

Are there any signs of trenching and in-fill between the cabinets and the mounting posts/standards?

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The two photos you have posted are apparently Yagi Arrays with a Reflector and several Directors (9?), which will have relatively narrow beam widths ("Half-Power Points" about -6db if I remember correctly), so will be aimed relatively accurately at the corresponding aerials at the other end of their respective link/s.

If they are using the same master tower, then you should be able to triangulate and locate relatively accurately, particularly if you find at least one more, resulting in a "Cocked Hat" around the master, by plotting the respective sighting lines on a map.

If you are deploying many remote cabinets - it is more cost effective to have these radio linked back to 1 main base station than pay for dedicated leased lines from each cabinet.

Good project management would ensure that planning permission was granted before buying all of the necessary radio equipment, masts and antennas.

Whilst good line of sight is required for TV reception, a narrow band data link can tolerate a less perfect path. Alternatively, the utility may be using another closer mast on the mountaintop, other than the ones used for TV transmissions. Radio links are tested for fade margin to ensure suitability in poor weather.

I am very familiar with the Carnmoney Relay as I installed the Freeview transmitters there prior to NI switchover.

Edited by ToneDeaf (Sat 16-Feb-13 20:23:31)

In reply to a post by Ribble:

May not even be a telco's cabinet . Have seen water companies use similar

It's most likely a water company remote monitoring setup.

In reply to a post by simon194:

In reply to a post by Ribble:

May not even be a telco's cabinet . Have seen water companies use similar

It's most likely a water company remote monitoring setup.

Yes, a vertically aligned Yagi aerial is almost always water or electricity monitoring. In this case, from the fact that it's a small street cabinet, it would be water. The Yagi aerials will usually point to the nearest TV transmitter or relay, because that's where the water/electricity companies have sensibly placed their receivers.

The first photo at least, is a water cabinet which monitors flow and no doubt several things I don't know about. They often have a blue plate on them with white text and a simple diagram, giving the most basic (to a water engineer) details of its location and route.

Electricity sub-stations use the same Yagi vertical alignment and usually point at the same "TV" mast (although sometimes to receivers on water towers or mobile masts if they're close and high enough), but they're easily identified - i.e. they'll have a fence and danger of death sign around them.

Wi-Fi would never use a Yagi aerial, because Wi-Fi needs to be omni-directional, whereas Yagi and all other types of "TV" aerial are directional and dependent on either a vertical or horizontal alignment.

Edited by deleted (Sun 17-Feb-13 04:19:23)