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#134497 - 11/16/02 11:46 PM Radio Telephones  
Trumpy  Offline


Member
Joined: Jul 2002
Posts: 8,211
SI,New Zealand
Just want to know if Radio Telephones are still used in your country.
We still use UHF Trunked Networks, VHF Land Mobile nets, and still use a system of VHF-FM
Digital for our Emergency Services.
Could anyone please tell me what type of recieving equipment is required to decode the Digital signal, to Voice?.
Your input please!!


Let's face it, these days if you're not young, you're old - Red Green grin

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#134498 - 11/17/02 05:49 AM Re: Radio Telephones  
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
Still plenty of use in the U.K. Low and high-band VHF is in widespread use for PMR (Private Mobile Radio), used extensively by taxis, breakdown services, utility company vehicles, local authorities, etc. Extra frequencies were allocated to these in the late 1980s after the closure of our old 405-line VHF TV network.

UHF has also been widely employed for shorter range. A lot of police systems around the country used UHF links for the pocket radios, direct to the station for the local "bobby on the beat." I'm not sure if any such systems are still in use, but at one time there was a UHF-VHF relay built into the patrol cars. The cop could therefore use his UHF pocket radio while out on a call somewhere and still benefit from the better range of the VHF car system.

I know there has been a gradual move toward trunked UHF systems and digital, but to be honest I've not bothered to keep up with all the developments here in recent years.

As for decoding, it will depend upon the type of system in use. Some of the latest digital trunked systems being used in the U.S. are quite complex and require a considerable amount of equipment and programming to monitor effectively.


A lot of the emergency services have been moving toward trunked UHF networks, and digital.


#134499 - 11/18/02 10:07 AM Re: Radio Telephones  
Texas_Ranger  Offline
Member
Joined: Dec 2001
Posts: 2,396
Vienna, Austria
In the good old days police radio in Austria used to be on 86 MHZ FM and could be scanned with any old radio going down to this frequency range. (These radios were outlawed when too many people discovered this, after that all radios went only down to 88 MHZ)

Edited due to typos

[This message has been edited by Texas_Ranger (edited 11-23-2002).]


#134500 - 11/18/02 03:04 PM Re: Radio Telephones  
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
In the U.K. the original broadcast allocation was 88 to 100MHz with receivers designed accordingly.

The portion from 100 to 104MHz or thereabouts was widely used by police departments around the country, and many people discovered they could listen-in when imported Japanese receivers that went right up to 108MHz became readily available. The police were gradually moved on to other frequencies during the 1980s so that the broadcast band could be extended right up to 108 MHz.

In the U.S. & Canada, the sound carrier for TV channel 6 lies just below the FM band, and it's possible to tune it in on some receivers.


#134501 - 11/19/02 01:48 AM Re: Radio Telephones  
Trumpy  Offline


Member
Joined: Jul 2002
Posts: 8,211
SI,New Zealand
Our Radio Frequencies over here, were all over the place until a few years ago.
In 1985, the old P&T department of the Post Office gave up the admin of Radio Services, thank God for that, they just issued licences in a frequency that they thought fit, it was a real mess, more emphasis on cash, than management of the Spectrum, you wan't to ask a few Ham's in this country what they thought of the old P&T.
But now we have a structured frequency spectrum, complying to ITU standards, glad that I did not have to sort that mess out, it took them 2years, a lot of licences were also revoked, from people that should never have had a licence in the first place.
[Linked Image]


Let's face it, these days if you're not young, you're old - Red Green grin

#134502 - 11/20/02 02:32 AM Re: Radio Telephones  
Trumpy  Offline


Member
Joined: Jul 2002
Posts: 8,211
SI,New Zealand
Paul, who administrates the Radio frequencies
in the UK?.
Do you ever have a cross-interference problem with the more western parts of Europe?, in the UK, with respect to TV and Radio frequencies.
Your help please.


Let's face it, these days if you're not young, you're old - Red Green grin

#134503 - 11/21/02 11:02 AM Re: Radio Telephones  
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
For many years (decades, in fact!) it was administered by the Radio Regulatory Dept. of the Home Office (HQ was Waterloo Bridge House for anyone who knows London). They were basically under the ultimate control of the Postmaster General, who was also in charge of GPO Telephones.

Like many other well-established govt. bodies, it all changed in the 1980s and radio got passed around like a grenade with the pin removed!

Control finally settled with the Radiocommunications Agency, which was set up as a new branch of the DTI (Dept. of Trade & Industry). Don't you just love the alphabet soup of government? [Linked Image] Anyway, they have a website: www.radio.gov.uk

There has long been cooperation between the U.K. and neighboring countries on frequency allocations, under various international agreements with the Intl. Telecommunications Union and the European Broadcasting Union. (By the way, the latter is nothing to do with the EU or the EC Commission, although like everything else I don't doubt that that bunch of undemocratic bureaucrats would try to take credit for it!)

We do occasionally get some interference from the Continent, even up in the UHF range. Here on the east coast I can sometimes receive UHF TV signals from The Netherlands, and co-channel interference appears on shared channels, but it usually doesn't last long. I should add that under such conditions we also get co-channel signals from other UK transmitters.

Tne south coast can occasionally get similar co-channel signals from northern France, although because the French system is incompatible with ours most people wouldn't actually realize the source of the signals.


#134504 - 11/23/02 12:18 PM Re: Radio Telephones  
classicsat  Offline
Member
Joined: Nov 2002
Posts: 456
RadioTelephones, as in point to point
radio is still in Canada, although mobile
phones have cut the growth in the two way
radio buisness. Most of the two-way radio busnesses are rather large, side buisnesses, or sell more than just 2-way radio.


#134505 - 11/23/02 01:11 PM Re: Radio Telephones  
Texas_Ranger  Offline
Member
Joined: Dec 2001
Posts: 2,396
Vienna, Austria
In Austria (at least in Vienna) it's possible to receive czech TV in perfect quality. (VHF band I think), in some parts of Austria you can receive german, italian, hungarian and probably swiss signals as well.
Worst problem: Our ORF 2 channel (2nd national TV station) interferes with many Video recorders, because they operate pretty much on the same frequency band. This can lead to nasty cross-interference. (Shadow images,...)


#134506 - 11/23/02 04:11 PM Re: Radio Telephones  
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
Ranger,
Austria uses PAL (Phase Alternation by Line) systems B/G (B on VHF, G on UHF). This is the closest that there is to a common European standard, being used in Germany, Switzerland, Sweden, The Netherlands, and many other places. Even the channel assignments are the same in many countries, e.g. Austrian ch. 2 is the same as German ch. 2. There are a few exceptions, e.g. Italy had its own peculiar channel assignments.

The most notable exception to the PAL B/G system is France, which uses SECAM system L (SEquential Couleur A Memoire). Apart from the different color-encoding method, system L differs from B/G in having positive video modulation and AM sound instead of the more usual negative video and FM sound.

A lot of the former Iron-Curtain countries also used SECAM but with systems D and K, which have different bandwidths and carrier spacings. I believe some of those countries have since adopted PAL B/G since the fall of the USSR, which also used SECAM D/K (and presumably still does?).

The UK and Ireland use PAL system I, which is similar to G but with a different video bandwidth and video/audio spacing. Hence when the Dutch signals roll in on tropospheric ducting here, we don't get any sound.

A similar problem with VCRs occurred here a few years ago with the opening of a new network (confusingly called "Channel 5", although it is not and is never likly to be on the real ch.5 - VHF TV closed here in 1985!).

When our UHF TV network was planned in the 1960s, a small section in the middle was left unallocated. As a result, practically all VCRs (and video games, satellite boxes etc.) are factory preset to ch. 36. The new "5" network was assigned ch. 36 in some parts of the country, and a condition of the licensing was that if anyone reported problems they were obliged to send somebody around to the house, for free, to re-tune the affected equipment.


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