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#140185 01/31/04 09:46 AM
Joined: Jul 2002
Posts: 8,423
Likes: 3
Trumpy Offline OP
Sorry Paul,
But this is not directly related to Electrical Work, but.
I was reading an article in a local paper that said that Australia and New Zealand have the best Interference free environment to recieve radio signals, because of their distance from large transmitters and other sources of Electrical noise.
Well someone want's to tell my 2 metre Transciever and the Dreco AM radio that I have here, the reception is full of hash and so forth.
Anyone else still listen to AM Radio?.
But the point of this is, what are your interference loevels like?. [Linked Image]

Joined: Aug 2001
Posts: 7,520
Interference levels have certainly increased over the years here, and with Britain being such a crowded island (the part that is England especially so), it's becoming more of a problem.

It's no so bad where I live, as this is a comparatively rural area, but in any decent sized town you'll hear no hear of assorted howls, clicks, rasps, and other interference.

Since the 1980s the number of broadcast stations has increased tremendously as local and "Ethnic" stations have sprung up, so after dark reception of all but the strongest local transmitters is often marred by interference.

I read an article a while back about a ham operator who had taken a trip to Tristan da Cunha , a tiny remote island in the South Atlantic. He was amazed at how the background noise on his receivers was suddenly so quiet again.

Joined: May 2001
Posts: 717
Heck, ya'd figure with all the listening posts we have down there, they'd keep it quiet. [Linked Image]

I don't have it too bad here, and of course I listen (and transmit) in AM, but guys that don't live too far from me get lots of interference, mostly from power lines with poor insulators, or connections at xfrmrs.

Notice with the digital revolution, the filtering is the part most often improved on the radios, there's gotta be a reason.

Joined: Dec 2002
Posts: 1,253
djk Offline
Paul, other than RTE services on MW/AM here other AM reception is really poor here in Cork, Ireland.

I'm not sure if it's just my house but it's full of howls, buzzes and clicks. Although I think perhaps we're just too far from the BBC's transmitters and on the wrong side of various mountain ranges.

We've also got a big problem in this city and elsewhere with "leaky cable"

Our cable TV systems carry FM radio signals. So if you have a HiFi with a coax cable connection you can plug it in and directly tune into to a number of non-local radio stations fed from the cable company's headend on FM e.g. BBC Radio 1-6 and various propriatary audio services.

However, the system is very old in places and over the past few years has started to leak FM signals that interfere with normal FM received off air.

e.g. you could be driving along in your car listening to the classical music on Lyric FM and suddenly for a few seconds you get a blast of BBC Radio 1 or while listening or in the middle of your favourite alternative rock on 2FM suddenly get a blast of BBC radio 4!!!

The cable company's also in severe financial difficulties so I don't think their maintenence is anything like it used to be.

Irish cities got cable TV VERY early as it was a means of watching UK terrestrial tv. Some of the systems date from as early the 1950s and 60s! with most being 1970s. As time went on they added satellite services etc.

The older parts (most) of the network is simply single or double heavy coax which is often run from house to house along the facia boards or along the back walls of gardens. There is a junction and socket at each house and their feed is just plugged in and either enters through the attic, a window frame or straight through the wall into a simple coax socket that has filters to prevent any signals being sent back to the network (e.g. VCR outputs)

Many of the networks don't even bother with encryption for the 20-40 basic channels.. all you need is a tv with "hyperband" tuning that can handle VHF Band I/II/III and UHF.

Cork employs a horrible 1970s scrambling (encryption would imply it was more technical than it is) system similar to many old US cable systems. It's identical other than it's tweeked to handle PAL and 220V AC

The analogue Settop box:
[Linked Image from]
(the previous version has wood panels!!!)

Older descrambler/convertor:
[Linked Image from]

This is gradually being replaced by digital cable which is far better..

[Linked Image from]
Chorus (Cork Cable) on-screen guides ... much like Sky Digital based on OpenTV.

Sagem Cable and DTV boxes used (for Cable and MMDS respectively)

[This message has been edited by djk (edited 01-31-2004).]

Joined: Jul 2002
Posts: 8,423
Likes: 3
Trumpy Offline OP
Guy's I'm told that the further South you go in the South Island here, the lower the Interference levels get.
And also the longer the propagation paths get too!.
I remember when I was stationed at a Fire Station in Invercargill(Southern tip of NZ) back in the early 90's.
I worked an Amateur station in Canada on 6 metres with really good signals both ways (r-9,s-8)
This was from a hill though, but I was only using 15 watts and it was NOT during any Skip season or through any repeaters.
I had a 13 Element Yagi(self-fabricated) and Rotator unit that I had made to fit the back of my station-wagon at the time.
Have had heaps of contacts on home-brew gear like this over the years!. [Linked Image]

Joined: Aug 2001
Posts: 7,520
suddenly for a few seconds you get a blast of BBC Radio 1
Ugh! What a horrible prospect! [Linked Image]

The main RTE Radio 1 MW transmitter (Tullamore, 567kHz) is receivable fairly well across much of Britain during the daytime, although after dusk it gets swamped out by competing signals from the Continent.

Joined: Dec 2002
Posts: 1,253
djk Offline

As far as I know RTE are going to reuse their transmitter which was broadcasting Longwave Radio Atlantic 252 for years to carry RTE Radio 1.

Wheather that means the MW service will be dropped or not is another question.

It would make sense though as most listeners in Ireland are on FM and LW would give them greater coverage into the UK.

Joined: Aug 2002
Posts: 1,691
Wouldn't make sense to drop the MW transmitters...

I mean...a lot of cheap radios are made without the LW band so what do you do if you're in an area with no RTE FM service and your radio is FM/MW with no LW?

You can't have too many transmitters....I'm a firm believer in redundancy. [Linked Image]

Joined: Aug 2001
Posts: 7,520
I had a quick look at the RTE website and saw their plans for 252kHz. I think Atlantic 252 has been fairly widely listened to in Britain in recent years (although it's not my kind of station).

Good point about LW. It's not used as a broadcast band in many parts of the world (e.g. North America), so many imported Japanese radios don't include it. They have to make specific European versions anyway to cater for the 9kHz channel spacing vs. 10kHz in the Americas, but with PLL tuning that's often just selectable with an internal link.

On the redundancy angle, you would have liked the old set-up in Britain, where the AM/MW and VHF/FM transmitters were simply simulcasts of the same program. In more recent years the MW broadcasts of some stations have been dropped leaving them on FM only, but we still have many local radio stations on both MW and FM.

Joined: Dec 2002
Posts: 1,253
djk Offline
In the case of RTÉ the MW service will continue but I can't see it lasting in the very long term as it has practically no listeners and is relatively expensive to maintain.

RTE MW Services:
Radio 1 Medium Wave Frequencies (Usually mirror of FM service with some opt outs where sports commentary and programmes aimed at immigrant communities in various languages are carried only on MW)

Tullamore 529m (567 kHz) 500 kw
Cork 412m (729 kHz) 10 kw

2FM Medium Wave Frequencies (Mirror of FM service)
612 KHz - Athlone (Nationwide) 100,000 W
1278 KHz - Dublin / Cork 10,000 W

FM coverage is 100% and I've never yet found a spot where I haven't been able to receive any of the RTE Radio services on FM within Ireland.

Radio One on Medium Wave tends to be listened to by Irish people in the UK.

RTE own a fairly large LW transmitter (252KHz) which they broadcast a very sucessful music station, Atlantic 252 from.

Atlantic 252 was a 50:50 joint venture between RTE and RTL.

As UK commercial radio matured the audience for pop music on LW declined so the station eventually shut down. So it makes a lot of sense for RTE to reuse the transmitter to relay RTE Radio one as the 252KHz service provides much better reception in the UK and beyond.

RTE's worldwide services:

ALL RTE frequencies, FM, LW, MW and Satellite

The grizzly details of the 252KHz LW transmitter

[This message has been edited by djk (edited 02-06-2004).]

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