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Channel number sequence on VHF dials

 
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Re: Channel number sequence on VHF dials

Post by Synchrodyne » Sun Jul 17, 2016 9:22 am

colly0410 wrote:If ITV had used (with a bit more power maybe) the BBC Holme Moss mast would it have covered more or less the same areas east & west of the Pennines of the north with one transmitter? Just that most other BBC/ITV masts are usually co-sited..


Apparently not, according to this Wireless World item.

WW 195507 p.308.gif


Cheers,

Steve

 
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Re: Channel number sequence on VHF dials

Post by nuvistor » Sun Jul 17, 2016 9:26 am

colly0410 wrote:If ITV had used (with a bit more power maybe) the BBC Holme Moss mast would it have covered more or less the same areas east & west of the Pennines of the north with one transmitter? Just that most other BBC/ITV masts are usually co-sited..


It's possible that the mast at Holme Moss would not have coped with extra loading, that just a suggestion, the other point is all the transmitting equipment was still at Emley Moor. I would have thought that that the site owners would have wanted to put a signal back ASAP, a small mast and aerial could be connected to the transmitter on reduced power reasonably quickly.

There could have been some contractual or legal reasons for a quick return to transmission, even with less coverage, another item to research.

Frank

 
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Re: Channel number sequence on VHF dials

Post by Synchrodyne » Sun Jul 17, 2016 9:46 am

Here is a bit more on that topic.

WW 195503 p.120.gif

WW 195503 p.121.gif

WW 195503 p.122.gif


and:

WW 195611 p.522 ITA Emley Moor.gif


As a rough guide, one needs about 3 times the effected radiated power at Band III to get about the same coverage as a Band I transmitter at the same site, and even then the Band I signal will likely go further, depending upon the topography.

In the US, low band transmitters were allowed up to 100 kW erp, whereas high band transmitters were allowed up to 316 kW erp. I think these numbers were intended to match outer service area signal strength with likely signal reach as limited by the curvature of the earth, but without “overkill”.

Here in NZ, the main Band I transmitters were 100 kW erp, and the main Band III transmitters were 300 kW erp.

In Australia though, 100 kW was used across Bands I, II and III for the main transmitters; the apparent objective was to avoid giving the Band III users any signal strength advantage over the Band I users in the inner service areas, at the expense of reduced overall service areas. On the other hand, here in NZ the objective was to equalize, to the extent reasonably possible, the service areas of co-sited Band I and Band III transmitters.

In the UK, it looked as if ITA used some rather high erps by Band III norms.

Cheers,

Steve

 
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Re: Channel number sequence on VHF dials

Post by nuvistor » Sun Jul 17, 2016 9:57 am

Hi Colly,
I misunderstood your post by the look of it, I thought you meant as a temporary arrangement.
Steve has provided lots of info on your post, reading for later, the gardening beckons.

Frank

 
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Re: Channel number sequence on VHF dials

Post by Terrykc » Sun Jul 17, 2016 11:09 am

nuvistor wrote:Hi Colly,
I misunderstood your post by the look of it, I thought you meant as a temporary arrangement.
Yes, Frank, I believe you did. My understanding of Colly's comment "Just that most other BBC/ITV masts are usually co-sited" is that he was referring to the original ITV roll-out, when there is no way that an ITA aerial would have been permitted on a BBC mast!

The use of 'co-sited' is probably the cause of the confusion - it certainly doesn't mean mast sharing but does imply two masts on the same site, which is not correct! Adjacent siting might have been a better choice.

The ITA did, however, try, as far as possible, to site their transmitters as close to BBC sites as possible so that it simplified matters for the majority of viewers using directional aerials for both bands. Thus, although the BBC was still using Alexandra Palace when London ITV started in 1955, they chose Beulah Hill (aka Croydon) for their transmitter as it was close to the Crystal Palace site that the BBC were adopting from 1956.

Other geographical pairings include Rowridge/Chillerton Down and Sutton Coldfield/Lichfield and there will be many more ...

 
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Re: Channel number sequence on VHF dials

Post by nuvistor » Sun Jul 17, 2016 11:26 am

Pilkington report 1962. section 49
http://filestore.nationalarchives.gov.u ... 62-102.pdf

49. Existing V.H.F. sites and masts will be used to the fullest possible extent, but many new U.H.F. stations will need to be built. All U.H.F. programmes for the same area will be transmitted from the same sites and masts, as indeed the Committee recommend.

Surprising what's available on line. Yes apologies to Colly.

Frank
Edit. good information about the concrete mast and the extra relays required due to its lower height than the tubular mast that fell down
http://ieeexplore.ieee.org/xpl/login.js ... %3D5262336

 
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Re: Channel number sequence on VHF dials

Post by nuvistor » Sun Jul 17, 2016 11:54 am


 
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Re: Channel number sequence on VHF dials

Post by Focus 2 » Sun Jul 17, 2016 12:13 pm

CrustyTV wrote:Here's a BRC 1400 VHF tuner from stock with its allocations.

vhf2.jpg


Was a bit awkward in Devon with North Hessary Tor on ch2 and Stockland Hill being on ch9.

To get to the two quickly meant a quick 625 change over and back!

A 1400 I had originated in Devon. The middle (grey) lead had been cut at the microswitch to prevent this from happening!

Brian

 
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Re: Channel number sequence on VHF dials

Post by Synchrodyne » Tue Aug 02, 2016 6:29 am

Returning to the Holme Moss issue, of course it could have provided closely similar coverage for two VHF channels if both had been in Band I. Had the channel planning been done differently, without the initial (mis)use of Band III for non-broadcasting purposes, one could make the case that two Band I channels should have been allocated to Holme Moss, with perhaps some of the second-level transmitters moved from Band I to Band III for the 1st programme.

Holme Moss is somewhat analogous to Te Aroha here in NZ, although the latter is atop a mountain peak in rugged country. But neither is located in a major population area, but rather both broadcast to lower-lying populated areas either side of the divide upon which they were sited, in the Te Aroha case the Waikato, including Hamilton, to the west, and the Bay of Plenty, including Tauranga, to the east. Te Aroha was the only one of the seven main transmitters to use Band I for both channels, namely channel NZ1 for TV1 and channel NZ3 for TV2. The other six used a Band I channel for TV1 and a Band III channel for TV2. So when the channel allocations were made, the special needs of the Te Aroha transmitter, which had a larger footprint than the other main transmitters, were evidently taken into account. As I recall, second-level transmitters tended to use Band III channels for both TV1 and TV2.

Nonetheless, early BBC planning for two-programme national VHF TV coverage did include a Band III transmitter at Holme Moss, as shown in this excerpt from WW 1953 June. I imagine that the coverage from such a transmitter would have fallen noticeably short of that obtained with the channel B2 transmitter.

WW 195306 p.291.gif


And the following shows that for its 1st programme, the BBC originally envisaged using two Band III channels for some of the second-level transmitters. But it had to rework these to use Band I channels, and so Band I ended up being over-subscribed.

WW 195308 p.365 TAC.gif
WW 195308 p.366 TAC.gif


Then this item suggests that co-siting and even co-masting of the ITA and BBC VHF transmitters was considered in the early days. The BBC had included provision for Band II FM radiators on its masts/towers from Sutton Coldfield onwards, and I think (not 100% sure) for Band III TV radiators from Pontop Pike onwards.

WW 195410 p.471 ITA.gif


colly0410 wrote:I suppose we were the only Country that had channel out of sequence rotary VHF tuners, unless someone knows different..


I have never come across any information to suggest that non-sequential VHF tuners were used elsewhere, but that does mean that they were not. The UK situation may have been unusual in terms of expected programme availability back in the VHF-only days, coupled with a high proportion of rented rather than owned receivers, such rented receivers probably not moving between districts with their renters, and maybe a lowish level of population mobility anyway. With owned receivers and highish mobility, as say in the USA, being able to receive all available channels in any district would have been a key requirement.

Cheers,

Steve

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