Terrestrial Switchoff - sorry to labour the point but...
 

"Ian Jackson" wrote in
message ...
In message , Stephen
writes

wrote in message
. ..
For those who haven't yet seen the Ofcom consultation on
future mobile
broadband spectrum.

"The 694-790 MHz band is expected to become a key band for
mobile
broadband"

and references to studies at 470 - 694 MHz.

http://stakeholders.ofcom.org.uk/bin...fi-mobile-bb/s
ummary/cfi-mobile-bb.pdf


If they sold off the whole of UHF, we could go back using VHF
for TV if we
just forgot about the regional news. Freeview only needs 6
channels for
single frequency networks and these 6 should be available on
VHF Bands I and
III.

Only the regional TV variations need to be relegated to
satellite, cable &
internet.

The VHF bands are much less attractive to mobile phone
operators because of
the much longer aerials required (particularly for Band I) but
they are
perfectly good for terrestrial TV, and a new VHF TV aerial
would be cheaper
than a dish, and much easier to align. We might return to the
days of H
aerials, X aerials and Band III Yagis, but with digital TV on
VHF instead of
405 lines.

VHF (especially Band 1) is not best suited to off-air
multi-channel TV.

For a start, Band 1 is very prone to long-range sporadic-E
interference in the late spring and early summer. Even well
before the advent of digital transmissions, many European
countries had ceased TV on Band 1 because of such problems.

Then there's the problem of designing aerials with sufficient
bandwidth vs gain. OK, the Americans have such things, but they
are generally used for the reception of relatively strong
downtown transmissions. I'm not sure how good those used in
Europe are (or used to be). I can't remember if (for example)
Band 3 aerials, covering the whole of 175 to 230MHz, were very
common.

There are only eight or nine 8MHz VHF TV channels available (3
in Band 1 and 6 or 7 in Band 3) - and it would be extremely
difficult comprehensively to provide the whole of UK with 6
digital MUXes in the same way as the two analogue channels were
provided. At best, the full 6 MUXes could probably only be
provided in well-separated centres of large populations.
Elsewhere, the number of channels would have to be reduced.
Although this is not dissimilar to what happens at present, I
feel that the situation would be much more marked than we have
at UHF.
--



\pedant mode on

There were five channels in Band 1 and eight channels in Band
III. They were only about 6.5MHz wide as against 8MHz used today.

\pedant mode off


--
Woody

harrogate three at ntlworld dot com

Terrestrial Switchoff - sorry to labour the point but...
 

In message , Woody
writes
"Ian Jackson" wrote in
message ...
In message , Stephen
writes

wrote in message
...
For those who haven't yet seen the Ofcom consultation on
future mobile
broadband spectrum.

"The 694-790 MHz band is expected to become a key band for
mobile
broadband"

and references to studies at 470 - 694 MHz.

http://stakeholders.ofcom.org.uk/bin...fi-mobile-bb/s
ummary/cfi-mobile-bb.pdf


If they sold off the whole of UHF, we could go back using VHF
for TV if we
just forgot about the regional news. Freeview only needs 6
channels for
single frequency networks and these 6 should be available on
VHF Bands I and
III.

Only the regional TV variations need to be relegated to
satellite, cable &
internet.

The VHF bands are much less attractive to mobile phone
operators because of
the much longer aerials required (particularly for Band I) but
they are
perfectly good for terrestrial TV, and a new VHF TV aerial
would be cheaper
than a dish, and much easier to align. We might return to the
days of H
aerials, X aerials and Band III Yagis, but with digital TV on
VHF instead of
405 lines.

VHF (especially Band 1) is not best suited to off-air
multi-channel TV.

For a start, Band 1 is very prone to long-range sporadic-E
interference in the late spring and early summer. Even well
before the advent of digital transmissions, many European
countries had ceased TV on Band 1 because of such problems.

Then there's the problem of designing aerials with sufficient
bandwidth vs gain. OK, the Americans have such things, but they
are generally used for the reception of relatively strong
downtown transmissions. I'm not sure how good those used in
Europe are (or used to be). I can't remember if (for example)
Band 3 aerials, covering the whole of 175 to 230MHz, were very
common.

There are only eight or nine 8MHz VHF TV channels available (3
in Band 1 and 6 or 7 in Band 3) - and it would be extremely
difficult comprehensively to provide the whole of UK with 6
digital MUXes in the same way as the two analogue channels were
provided. At best, the full 6 MUXes could probably only be
provided in well-separated centres of large populations.
Elsewhere, the number of channels would have to be reduced.
Although this is not dissimilar to what happens at present, I
feel that the situation would be much more marked than we have
at UHF.
--



\pedant mode on

There were five channels in Band 1 and eight channels in Band
III. They were only about 6.5MHz wide as against 8MHz used today.

\pedant mode off

I'm talking about the potential channel capacity of Bands 1 and 3 for
carrying standard UK 8MHz digital MUXes (based on standard UK and Irish
analogue 625-line cable TV practice, and also off-air broadcasting in
Ireland), so what relevance does your admittedly pedantic statement have
to what I said?

\pedant mode on

The UK, the System A channel width was 5MHz (sound-vision spacing
3.5MHz), with Ch1 being a bit of an oddity because it originally started
life as full DSB vision (later being changed to the standard VSB
format).

\pedant mode off
--
Ian

Terrestrial Switchoff - sorry to labour the point but...
 

In message , Bill Wright
writes
Ian Jackson wrote:


Then there's the problem of designing aerials with sufficient
bandwidth vs gain. OK, the Americans have such things, but they are
generally used for the reception of relatively strong downtown
transmissions. I'm not sure how good those used in Europe are (or used
to be). I can't remember if (for example) Band 3 aerials, covering the
whole of 175 to 230MHz, were very common.
Log periodics.

http://www.wrightsaerials.tv/aerialp...ngus/005.shtml

Half a log is better than no log at all:
http://www.wrightsaerials.tv/aerialp...ngus/007.shtml

I've actually got an unused (box unopened) large American multi-element
Band 1-2-3 aerial. I realise now that, one day, it may actually come in
useful.
--
Ian

Terrestrial Switchoff - sorry to labour the point but...
 

"Bill Wright" wrote in message
...
Stephen wrote:

The VHF bands are much less attractive to mobile phone operators because
of the much longer aerials required (particularly for Band I) but they
are perfectly good for terrestrial TV, and a new VHF TV aerial would be
cheaper than a dish, and much easier to align. We might return to the
days of H aerials, X aerials and Band III Yagis, but with digital TV on
VHF instead of 405 lines.


I doubt if the aerials would be that elaborate. With no ghosting to worry
about and the ability of DTT to work with a low s/n ratio I should think
the aerials would mostly be in the loft, and would be simple dual-band
omni types. An SFN would probably be VP.

Isn't that what set-top rabbit ears are for?

--
Max Demian

Terrestrial Switchoff - sorry to labour the point but...
 

Ian Jackson wrote:
In message , Bill Wright

I've actually got an unused (box unopened) large American multi-element
Band 1-2-3 aerial. I realise now that, one day, it may actually come in
useful.
There are some Band III tv aerials in my dad's loft. I'm selling the
house next week. They can stay there.

Bill

Terrestrial Switchoff - sorry to labour the point but...
 

Max Demian wrote:

Isn't that what set-top rabbit ears are for?

Yes but modern sets radiate more RF than the old ones!

Bill

Terrestrial Switchoff - sorry to labour the point but...
 

In message , Woody
writes:
"Ian Jackson" wrote in
message ...
[]
There are only eight or nine 8MHz VHF TV channels available (3
in Band 1 and 6 or 7 in Band 3) - and it would be extremely
[]
\pedant mode on

There were five channels in Band 1 and eight channels in Band
III. They were only about 6.5MHz wide as against 8MHz used today.

\pedant mode off


In UK, yes, under system A. In most of the rest of western Europe, there
were three on I (IIRR numbered 2 to 4) and correspondingly on III, IIRR
numbered 5 to 12 or 13. (Systems B and G if memory serves.)
--
J. P. Gilliver. UMRA: 1960/1985 MB++G()AL-IS-Ch++(p)[email protected]+H+Sh0!:`)DNAf

Can you open your mind without it falling out?

Terrestrial Switchoff - sorry to labour the point but...
 

On 21/03/2013 18:58, Woody wrote:

\pedant mode on

There were five channels in Band 1 and eight channels in Band
III. They were only about 6.5MHz wide as against 8MHz used today.

\pedant mode off

A c t u a l l y , dear pedant, I think you'll find that 405-line system
A used 5 MHz channelling, or perhaps I should say 5 Mc/s.

European 625-line is (or was) System B in the VHF bands and used 7 MHz
channels, not 8. This was never used in the UK of course. 8 MHz
channelling only appears at UHF, System G for the mainland and System I
(with 6 MHz sound and originally a wider VSB) for the UK, also used in
South Africa.

DVB-T (and -T2 AFAIK) have a 7 MHz channel option to allow use in the
VHF bands. Do any countries use this?

--
Andy,

Terrestrial Switchoff - sorry to labour the point but...
 

In message , Andy Wade
writes
On 21/03/2013 18:58, Woody wrote:

\pedant mode on

There were five channels in Band 1 and eight channels in Band
III. They were only about 6.5MHz wide as against 8MHz used today.

\pedant mode off

A c t u a l l y , dear pedant, I think you'll find that 405-line system
A used 5 MHz channelling, or perhaps I should say 5 Mc/s.

European 625-line is (or was) System B in the VHF bands and used 7 MHz
channels, not 8. This was never used in the UK of course.

Some of the 8MHz lettered channels (A to J) were used for 625-line
broadcasts in the Irish Republic, and in Irish and UK cable TV systems.

8 MHz channelling only appears at UHF, System G for the mainland and
System I (with 6 MHz sound and originally a wider VSB) for the UK, also
used in South Africa.

The narrowing of the 1.25MHz VSB to 0.75MHz was first found necessary on
cable TV systems, when NICAM (on vision + 6.552MHz) was added to
channels which were on lower adjacent channels, and got totally
clobbered by the upper adjacent VSB.

DVB-T (and -T2 AFAIK) have a 7 MHz channel option to allow use in the
VHF bands. Do any countries use this?

Just a final point.....
Do any DTV TV sets or STBs tune to Band 1? I think they start much
higher (off the top of my head, around 130MHz?). If so, that's another
reason for not using Band 1 for digital.
--
Ian

Terrestrial Switchoff - sorry to labour the point but...
 

On 3/22/13 8:11 PM, Ian Jackson wrote:
Just a final point.....
Do any DTV TV sets or STBs tune to Band 1? I think they start much
higher (off the top of my head, around 130MHz?). If so, that's another
reason for not using Band 1 for digital.

The ones I have seen start at 174 MHz (or the lower edge of Band III).
If you set them to a country where only UHF is used for DVB-T however
they start at 470 MHz.

gr, hwh