Why do some cabinets have TV aerials beside them?

Has anyone noticed this where they live? Some, but not all of the cabinets in my area have aerials beside them, pointing at the nearest Freeview transmitter. I haven't read anything about this kind of thing before. What do they need an aerial for? Is it something to do with BT Vision?

Edited by haggismn (Sat 16-Feb-13 18:00:06)

Any chance of a photo or two uploaded somewhere please?

In reply to a post by haggismn:

Has anyone noticed this where they live? Some, but not all of the cabinets in my area have aerials beside them, pointing at the nearest Freeview transmitter. I haven't read anything about this kind of thing before. What do they need an aerial for? Is it something to do with BT Vision?

Sounds like a mobile phone mast

In reply to a post by robertcrowther:

Sounds like a mobile phone mast

I would expect mobile phone masts to point upwards, not towards a TV transmitter.

Suspect what you are seeing are the cabinets associated with a mobile mast, some of the smaller units have cabinets which look very similar to some forms of the FTTC ones.

Probably Remote Reporting and/or Control.

Sounds similar to that on Meteorological Stations.

Also keep in mind that in the 1980s and 1990s that Teletext ("Ceefax") was used to remotely control Norwich BBC Studio Transmissions etc from London.

Teletext was also used to update some Supermarket Chains Price Lists, in the Teletext Pages 700 series.

Monitoring is done over the fibre link. Susspect the OP is mistaken .

Here's one
and another

There are a few more, although not within walking distance. They seem to point in the general direction of Divis Mountain or Black Mountain transmitters - Black Mountain's freeview transponders are vertically polarised, Divis on the other hand has a much stronger signal. Its freeview transponders are horizontally polarised, but perhaps there is another vertically polarised transponder on it for BT usage? On the first image, there is a mobile mast on the other side of the road, the aerial isn't pointing directly at it. All of the aerials and cabinets have been recently installed, before there was nothing there.

Edited by haggismn (Sat 16-Feb-13 17:31:52)

In the 1st picture, is the fibre cabinet out of view?

The cabinet in that picture is not an Openreach FTTC one

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)

I agree that most WiFi applications are based on omni-directional (convoluted) aerials/antennae, but Directional WiFi aerials are available as shown here-

http://www.wifi-shop24.com/en/WiFi-Antennas?gclid=CK...

There was a recent thread on this forum about getting WiFi to a garden shed, obstructed by a thick line of conifer trees, two of those directional aerials may have produced a solution.

I am aware of co=linear arrays of dipoles, in excess of 100, operating in the 10 GHz / 3 cm band, producing extremely narrow beams.

most likely water company infrastructure - sewage pumping etc.

Another possibility is that it is for a local Cable TV system; and that the cabinets may have been there for some years.

With the change-over to Digital Terrestial TV, a more directional but broad (TV) band aerial is required to cover the range from about 400 MHz to 800 Mhz, so has become obvious with a newish pole/standard; and a more sensitive (longer) aerial at the top.

I understand that there were/are quite a few in the Valleys area, in-filling "shadow" areas.

====================

A465 Head of the Valleys road, as originally built - rather like doing "circuits and bumps" in a small plane.

Take off from one roundabout, climb up to the summit, then dive down to land at the next roundabout, "taxi" through it to take off again ... .

In reply to a post by eckiedoo:

I agree that most WiFi applications are based on omni-directional (convoluted) aerials/antennae, but Directional WiFi aerials are available as shown here-

http://www.wifi-shop24.com/en/WiFi-Antennas?gclid=CK...

There was a recent thread on this forum about getting WiFi to a garden shed, obstructed by a thick line of conifer trees, two of those directional aerials may have produced a solution.

I am aware of co=linear arrays of dipoles, in excess of 100, operating in the 10 GHz / 3 cm band, producing extremely narrow beams.

Interesting, I stand corrected.

They would never use a Yagi aerial (wideband or not) for wi-fi though, would they?

Edited by deleted (Mon 18-Feb-13 01:52:47)

Agreed that a Yagi aerial would be unlikely for WiFi, difficult to produce the physical parts and assemble them etc.

There is a fair chance though that a slot aerial design might be considered, and the convoluted "bent piece of metal" found inside Modem/Routers etc may reflect this-

http://www.antenna-theory.com/antennas/aperture/slot...

With the Laptops & Netbooks I have seen opened up, the WiFi aerials seem to be built in to the hinges.

The 100+ dipole aerials I am aware of, were of extremely robust design, for various reasons.

Regarding WiFi and its Broadband aspects, you may find the involvement of Hedy Lamarr (Hollywood Film/Movie Star 1940s) of interest, as WiFi uses similar Frequency-Hopping techniques-

http://en.wikipedia.org/wiki/Hedy_Lamarr

They would never use a Yagi aerial (wideband or not) for wi-fi though, would they?

yes, ideal for a client end pointing at an omni base station. Sometimes they live in a plastic tube so don't look like a yagi.

But not on the scale we're talking about here, i.e. the photos. To be big enough to incorporate the reflector, that's a massive plastic tube which wouldn't fare too well once the wind got up a little bit. It would be so impractical to incorporate a Yagi aerial into a modern wi-fi receiver, unless we're talking about home-made solutions with whatever resources can be gathered.

I think the point is that this is clearly a water cabinet, and tens of thousands of water and electricity "stations" use a vertically aligned Yagi pointing at the nearest (usually mainly TV) transmitter. Relatively close to me, but a bit out in the country, there are at least two electricity poles with switchgear on them, which have the same Yagis - presumably to set an alarm off somewhere in the event of a failure, or if an engineer has unlocked the massive padlocked lever and thrown it.

None of this is anything to do with fibre, or related "wi-fi" as we principally know it, and that was my point. It has been interesting though, I assume the Yagis in tubes you're talking about are smaller than usual?

indeed the aerial pictured is not wifi frequency as its was too big and somewhere in the UHF area by the look of it.

Here's a wifi example

In reply to a post by gazzyk1ns:

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.

That's right. In fact the utility companies use a part of the UHF band just below TV, about 410 MHz I think, the yagis you see will therefore have slightly longer elements, than the ones that are designed for TV reception, as well as being mechanically more roust than domestic models..