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#132979 - 11/04/01 06:51 PM TV Technicalities  
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
I know there are at least a couple of you here involved with TV, telephones, etc., so I thought a brief overview of the TV system in the U.K. might be of interest, as we don't use the U.S. standard.

The original monochrome-only standard was 405 lines at a field frequency of 50 Hz. (as opposed to U.S. 525/60). Broadcast was on 13 VHF channels. Video modulation was positive with an AM sound carrier.

In the 1960s a new system at 625 lines on UHF channels opened, with negative video mod. and FM sound (as in N. America). Color was introduced in 1967 using the German-devloped PAL (Phase Alternation by Line) system.

The old 405/VHF network broadcast programs (B&W only) in parallel with the new 625/UHF until its closure in 1985, so everything is now solely UHF.

Cable is really only just catching on in the U.K., and so far is available in just a few of the large towns. Direct broadcast satellite was pushed heavily in the late 1980s, so many homes now sport an 18-inch satellite dish.

F-connectors are common on cable & satellite, but the standard for terrestrial antennas is the Belling & Lee coaxial plug, developed many, many years ago (and so far as I'm aware, practically unknown in the U.S.A.).

Both terrestrial & satellite are going to digital in a big way now, with the govt. pushing for a closedown of existing analog services within the next few years.


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#132980 - 11/09/01 12:41 PM Re: TV Technicalities  
Scott35  Offline

Broom Pusher and
Member
Joined: Oct 2000
Posts: 2,707
Anaheim, CA. USA
Paul,

You most likely know this already, but I'll post it anyway, just to add to your message.

Our Air Broadcast VHF - UHF stuff for Television and Commercial FM radio goes as follows:

VHF Lo Band [54 to 108 MHz]:

54-60 MHz = TV Channel 2,
60-66 MHz = TV Channel 3,
66-72 MHz = TV Channel 4,
72-76 MHz = Special Services [VHF service, possibly Police, Fire, Railroads, Etc.],
76-82 MHz = TV Channel 5,
82-88 MHz = TV Channel 6,
88-108 MHz = Commercial FM Radio Broadcasts.

VHF High Band [174 to 216 MHz]:
174-180 MHz = TV Channel 7,
180-186 MHz = TV Channel 8,
186-192 MHz = TV Channel 9,
192-198 MHz = TV Channel 10,
198-204 MHZ = TV Channel 11,
204-210 MHz = TV Channel 12,
210-216 MHz = TV Channel 13.

UHF band range is 470 MHz for beginning of TV Channel 14, to 890 MHz for end of TV Channel 83. Each UHF Channel occupies a typical 6 MHz bandwith.

For a typical TV Channel listed above, the AM Video Signal's carrier frequency is 1.25 MHz from just past the "Channel's Edge". It covers about 4.0 MHz of bandwidth. The FM Audio Signal's carrier frequency is about 0.25 MHz from the other "Channel Edge". The FM Carrier is 4.5 MHz from the AM Carrier. FM covers aproximately 200 KHZ [0.20 MHZ] in total sidebands, so the entire Audio Envelope has a good 200K of sound area.
The real bandwidth hog is the AM Video signal envelope!

In the receiver, for Monochrome [Black and White], the composite video signal at the RF amp [RF signal and Oscillator signal heterodyned] = 45.75 MHz.
Scanning at the CRT =
525 lines horizontal [212.5 for odd, 212.5 for even - common interlace] Horizontal frequency = 15,750 Hz [525 lines x 30 Hz].
Vertical oscillator frequency = 60 Hz.

Vertical = Sawtooth waves, Horizontal = Square waves or pulses.

In a Color set, the Horizontal Frequency is less than 15,750 Hz. It's been a long time since I covered TV stuff - especially Composite RGB [Color], so I'll need to grab the books and do some refreshing!!!

The Commercial FM Radio Channels Data is something like:
IF Frequency = 10.7 MHz [both Mono and FM Stereo],
Bandwidth = 30 Khz [Mono], 150 Khz [Stereo]
Spectrum = 88-108 MHz [VHF low band].

And just for the heck of it, Commercial AM Radio is:
Spectrum = 540 Khz to 1600 Khz,
IF Frequency = 262 Khz or 455 Khz,
Bandwidth = 10 Khz.
My dislikes of AM broadcasts are the extremely limited bandwidth [10 K for sound is too dang midrange for me!], and the way receivers love to pick up Atmospheric, Natural and Man-Made noise big time and deliver those signals to the RF Amp as info!

Not sure of DBS, CATV type Commercial Cable TV Broadcasts, or the newer "XM" DBS Audio, so I'll do some searching here and there.
Got any leads???

I memorized the VHF - UHF Spectrums from countless custom Parasitic Yagi Antennas projects, plus bandpass filters to block neighboring HAM Radios from stepping so hard on our signals, they would get cross modulated horribly - sometimes the video signal got pushed away completely!
Most of the time, the interference was just simple Herringbone on TV 2, 4 and 5.
But when the guy next door fired up the 10 KW 30 MHz Radio set, that's when watching any TV Channel was futile!

This was kind of fun! [what a life I lead when this is fun stuff, huh [Linked Image]]. Glad you posted this topic!

Scott SET


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

#132981 - 11/09/01 12:55 PM Re: TV Technicalities  
Scott35  Offline

Broom Pusher and
Member
Joined: Oct 2000
Posts: 2,707
Anaheim, CA. USA
Oh, forgot to add POTS [Plain Old Telephone Systems / Service] stuff:

On-Hook voltage = 30-55 VDC,
off-hook voltage = 1-5 VDC
Ringer voltage = 90-130 VAC [something like 20 - 30 Hz],
Loop currents = 10 ma to 25 ma.
Bandwidth = 3Khz [330 Hz to 3.3 Khz].

Touch Tone signals = DTMF [Dual Tone Multi Frequency].
Full Duplex at user end[s] of loops [at sets], 2 to 4 wire at C.O. [Central Offices] or within local hubs.
The 2 to 4 wire conversion is responsible for the transmitted sound "Reflected" back to the speaker - such as when a person speaks into the microphone [of the typical landline handset], the sound can also be heard in the handset's speaker.

Can't recall the DTMF base frequencies, so I'll find that info and post later.

Scott SET


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

#132982 - 11/09/01 05:59 PM Re: TV Technicalities  
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
Yep, I've got most of the data on this in my reference books.

The U.K. 405-line system used 10,125 Hz line scan, which on older sets was often quite audible. The original VHF carriers when BBC-TV started were 45 MHz video, 41.5 MHz sound, later to become known as channel 1. Ch. 1 thru 5 were low VHF, called Band I here, ch. 6 thru 13 high VHF or Band III. I haven't got the exact allocations to hand at the moment, but they were in roughly the same area of the spectrum as U.S. channels.

The 625-line transmissions still in use today are UHF band IV and band V. Channels are numbered 21 thru 69, running approx. 470 to 860 MHz. Audio carrier is 6MHz above vision, and we also have a 1.25MHz vestigial sideband. Line scan is 15,625 Hz and PAL color sub-carrier at 4.43 MHz approx.

For a large part of the 1960s and into the early 1970s, manufacturers made dual-standard sets. These had a monster changeover switch which not only swapped from the VHF to UHF tuners, but also adjusted the scan frequency, switched in the appropriate filters, routed sound IF to AM or FM demod., changed video demod. polarity, etc.

I have quite a collection of 1950s/1960s journals, and the were a lot of experiments carried out to decide on the best color (UK "colour") system. The BBC did some trials with the American NTSC system adapted to 405-lines, but by the early 1960s the decision to adopt 625-lines was made, so I guess it was inevitable that PAL would be used. The phase-locked color means that our sets don't need a "hue" control.

*
VHF/FM radio started here in 1955, initially using just the 88 to 100 MHz range. When stereo was introduced, we adopted the same Zenith 19kHz pilot-tone system as in America. FM IF is standardized at 10.7 MHz, but our pre/de-emphasis is different - 50uS vs. 75uS. FM was only extended to 108MHz a few years ago; the 100 to 108 section was previously used for police radio, much to the joy of those with imported Japanese sets which would tune above 100MHz! FM radio is Band II, by the way.

AM broadcast is pretty much the same, except we have 9kHz spacing and thus an audio bandwidth of a glorious 4.5kHz! There was an eventual push to standardize the IF at 470 kHz, but older sets often used 455, 460, 465, etc.

Britain (and Europe) also use an AM broadcast band called "long wave" running approx. 150 to 300 kHz. Standard AM 540 to 1600 kHz is often called "medium wave.
Up until the 1970s, most radios made for domestic use actually calibrated the AM scale(s) by wavelength instead of frequency, so standard MW ran approx. 550 to 190 meters (UK "metres") on the dial.

(Hence the slogan of our most famous "pirate" station: "On one-nine-nine, it's Radio Caroline.")

We have digital radio in operation now, using some of the vacated old Band III TV spectrum. I'm not sure of the details, because I'm not that interested in it myself; I'm more of an "old-time" radio enthusiast.

*
One thing you all might find odd: TV sets here are required to have a license. At the moment, it costs just over £100 per year (about $150). Radios had a license at one time, but this was abolished in 1971.

Go here for some interesting TV stuff: http://www.meldrum.co.uk/mhp/


P.S. Scott: The scan freq. you're looking for is 15,734 Hz for 525/NTSC color, directly related to the sub-carrier freq. of 3.57-something MHz.


[This message has been edited by pauluk (edited 11-09-2001).]


#132983 - 11/09/01 06:14 PM Re: TV Technicalities  
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
Telephones:

All the basic characteristics are similar, although the specified sound levels vary by a few dBm.

I don't have a list of the DTMF tones handy either, but we use the same frequencies (DTMF dialing didn't arrive here until the 1980s).

Modern house station wire follows the white-blue, blue-white, white-orange orange-white etc. pattern, but older wire was just plain blue, orange, green, brown.

The cords on the phones are diferent again: red, blue, green, white. Tip is white (green in U.S.), ring is red. Green and blue are/were in various ways before and after the introducton of modular jacks in about 1982 (different to U.S. types).

Standard tones are a little different here, e.g. busy tone is just a single 400Hz tone instead of a double frequency, and with slightly different on/off timing. There's also the famous British double-ring cadence as well, well known to any Brtish movie buffs no doubt. (The ring timing is actually 0.4 sec on, 0.2 off, 0.4 on, 2.0 secs. off).

Lots of other minor differences as you might expect, e.g. the long-distance prefix is 0 instead of 1, and our emergency number is 999 instead of 911.


#132984 - 03/30/03 01:50 AM Re: TV Technicalities  
Trumpy  Offline


Member
Joined: Jul 2002
Posts: 8,211
SI,New Zealand
Scott35,
The International band of Emergency Services
has been at 154MHz, for some years, just below the Marine VHF frequencies
However, with the advent of Digital Comms, this is now all UHF Trunk-line stuff,
What I do know is the Fire Service over here in NZ, uses CTCSS and Cellphones to provide thier communications, were as we used to use Handhelds and Base sets before.
Go figure. [Linked Image]


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

#132985 - 04/13/03 10:54 PM Re: TV Technicalities  
Trumpy  Offline


Member
Joined: Jul 2002
Posts: 8,211
SI,New Zealand
Paul,
When is the proposed Closedown of the Analouge systems, supposed to take place, over in the UK?.
How will people that still only have a Analouge Terrestrial system, get on?
Over here, apparently, we are supposed to be moving to a Digital Terrestrial Platform, with a proposed shutdown of the Analouge systems in 2008.
Don't think so though, they(The Gov't) can't even make thier minds up, as to what format, is going to be implemented yet, and we all know how fast governments act!.
Typical, and I bet that they will choose the one that will be obselete the soonest, too.
They'll try and do it on the cheap. [Linked Image]
Knowing our luck, it'll probably use NTSC.

[This message has been edited by Trumpy (edited 04-13-2003).]


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

#132986 - 04/14/03 04:59 AM Re: TV Technicalities  
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
The last I heard, the shut-down of analog is scheduled for around 2008. There were rumors a year or two ago that the government was pressing for shut-down in 2005, but I've heard nothing more about that.

The govt. here doesn't really give a d*** about the TV service. All they're interested in is the huge amount of money they'll make by auctioning off the cleared parts of the spectrum for yet more mobile phone and other similar services.

The way they seem to be planning it at the moment, we'll be left with digital TV across a very fragmented band with other services slotted haphazardly in between. [Linked Image]


#132987 - 04/14/03 10:33 AM Re: TV Technicalities  
classicsat  Offline
Member
Joined: Nov 2002
Posts: 456
NTSC is not a digital format. However, the digital format used for terrestrial digital
TV in North Amreica, is called ATSC.


#132988 - 04/14/03 06:04 PM Re: TV Technicalities  
Trumpy  Offline


Member
Joined: Jul 2002
Posts: 8,211
SI,New Zealand
classicsat,
Thanks for that reminder, I was just showing that I have about as much of an idea about TV systems, as what our govt over here does!. [Linked Image]
Paul, Over here, there was to be an auction of the 2 and 3GHz bands and quite a few other frequencies, but it was prevented(thankfully!) by the Treaty of Waitangi settlement courts, but there is no way in hxxl, I am going to go there, at all! [Linked Image]
With that in mind, our frequency spectrum over here, would have been an empty cupboard, years ago and nothing to show for it.
I just hope they don't ever start selling the Amateur and HF CB Bands, these have been the source of many hours entertainment for me, from the age of 18 onwards! [Linked Image]


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

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