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Old 21st Feb 2020, 12:53 pm   #21
Panrock
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Default Re: British Heritage Television

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At the moment its mounted for horizontal polarization but could be mounted for vertical if required.
One thing I can say is our transmissions will be vertically polarised. This is because our project is not only about transmitting a radio signal but also concerned with heritage. All the early high power BBC Band I stations were vertically polarised and the vertical H and X aerials came to be seen as (for want of a better word) "iconic".

Steve
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Old 21st Feb 2020, 5:21 pm   #22
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Default Re: British Heritage Television

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At the moment its mounted for horizontal polarization but could be mounted for vertical if required.
One thing I can say is our transmissions will be vertically polarised. This is because our project is not only about transmitting a radio signal but also concerned with heritage. All the early high power BBC Band I stations were vertically polarised and the vertical H and X aerials came to be seen as (for want of a better word) "iconic".

Steve
Was that originally done for signal propagation reasons (which is odd as horizontal polarisation was chosen for VHF radio), or because horizontal 41- 45 MHz antennas were a bit unwieldy?
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Old 21st Feb 2020, 7:16 pm   #23
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Was that originally done for signal propagation reasons (which is odd as horizontal polarisation was chosen for VHF radio), or because horizontal 41- 45 MHz antennas were a bit unwieldy?
To ask why vertical polarisation was used for the first television stations in the UK (but not necessarily elsewhere) makes a very interesting question - perhaps justifying a new thread and comments from the historians here.

We read HERE that despite interference results (and propensity for 'ghosting' too?) to the contrary, vertical polarisation was chosen to avoid 'inconvenience'. Certainly, the horizontal 10 ft-odd long aerials needed for Channel B1 would have very droopy.

Steve
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Old 21st Feb 2020, 7:47 pm   #24
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I know this from personal experience as they were used by our local fill-in transmitter around 1965. Quite a bit bigger than channel 3 which was our normal.
Happy days sitting on a roof with the snow swirling through the wind fixing the lashings.
Three or four element band 1 were great fun.
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Old 21st Feb 2020, 10:27 pm   #25
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In the North-East of England the BBC1 Weardale 405 line relay transmitter operated on channel 1 with horizontal polarising. In use from 1966 to 1985.
Never seen any Ch1 aerials later and it's likely never will now.

DFWB.
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Old 21st Feb 2020, 10:56 pm   #26
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Perth still has loads of channel 3 aerials, why I don’t know since as you say they have been redundant since 1985. Some of these have been up since Kirk of Shotts started and must be a bit dangerous now.
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Old 22nd Feb 2020, 1:43 am   #27
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We ended up with a fairly even mix of V & H BI Tx's
https://www.bvws.org.uk/405alive/info/tx_list.html
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Old 22nd Feb 2020, 9:04 am   #28
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Default Re: British Heritage Television

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Perth still has loads of channel 3 aerials, why I donít know since as you say they have been redundant since 1985.
Assuming you mean Band III aerials, I wonder whether some may be getting used (albeit less than optimally) for reception of Band II FM radio reception.
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Old 22nd Feb 2020, 10:29 am   #29
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Perth still has loads of channel 3 aerials, why I donít know since as you say they have been redundant since 1985.
Assuming you mean Band III aerials, I wonder whether some may be getting used (albeit less than optimally) for reception of Band II FM radio reception.
No these are band 1 channel 3, mostly three element jobs.
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Old 22nd Feb 2020, 10:34 am   #30
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Perth still has loads of channel 3 aerials, why I donít know since as you say they have been redundant since 1985.
Assuming you mean Band III aerials, I wonder whether some may be getting used (albeit less than optimally) for reception of Band II FM radio reception.
Band 3 aerials can be repurposed for DAB. They work well if vertical.
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Old 23rd Feb 2020, 12:33 am   #31
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Default Re: British Heritage Television

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Perth still has loads of channel 3 aerials, why I donít know since as you say they have been redundant since 1985.
Assuming you mean Band III aerials, I wonder whether some may be getting used (albeit less than optimally) for reception of Band II FM radio reception.
No these are band 1 channel 3, mostly three element jobs.
I took this lot in and around Perth in May 2016

https://photos.app.goo.gl/CZ972EaUxhXcjj2t7

Would most of these BI arrays be on Kirk o'Shotts on Ch3?
looks like there was a local low power relay on Ch4 vertical from 1964.
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Old 23rd Feb 2020, 11:34 am   #32
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Yes I would say almost all band1 channel 3. The local band1 low power would likely have been horizontal if it was channel4 band 1 surely. There is a block of tenement type housing in Jeanfield Road in Perth which still has over half a dozen big channel3 aerials.
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Old 23rd Feb 2020, 12:43 pm   #33
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Default Re: British Heritage Television

Anyway, as stated, British Heritage Television is going to be vertical.

Another couple of snippets. Our signal will not be double-sideband but have a vestigial upper sideband (vsb) and the vision modulation of the carrier will be clamped, meaning the sync bottoms will be zero carrier, irrespective of picture content.

Steve
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Old 23rd Feb 2020, 2:44 pm   #34
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I am sat here on a low power Band 3 405 lines transmitter and monitor receiver. Repaired it a few years ago, might fire it up some time, though not convinced it is much more than a pantry transmitter.

Piece of history anyway.
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Old 23rd Feb 2020, 3:09 pm   #35
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Default Re: British Heritage Television

And a third thing, while it occurs to me. There'll be no equalising pulses.

Steve
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Old 24th Feb 2020, 12:50 am   #36
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And a third thing, while it occurs to me. There'll be no equalising pulses.

Steve
Mr Blumlein would have approved.
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Old 26th Feb 2020, 12:34 pm   #37
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Default Re: British Heritage Television

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At the moment its mounted for horizontal polarization but could be mounted for vertical if required.
One thing I can say is our transmissions will be vertically polarised. This is because our project is not only about transmitting a radio signal but also concerned with heritage. All the early high power BBC Band I stations were vertically polarised and the vertical H and X aerials came to be seen as (for want of a better word) "iconic".

Steve
Some of the medium powered channel 1 BBC1 transmitters, such as Redruth and Divis, did use horizontal polarization to reduce the effects of co channel interference from Crystal Palace particularly during certain weather conditions. The effects of electrical interference, on band 1 reception has reduced over the years especially from auto ignition systems but the levels of noise and interference from electronic devices has sadly increased. Most of this comes from the cheap and nasty electronic gismo's that we surround ourselves with these days including plug in switch mode psu's, LED lamps, wi fi routers to name but a few. The answer as always is to use an aerial mounted as high as possible and using good quality coaxial feeder cable.
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Last edited by Hybrid tellies; 26th Feb 2020 at 12:42 pm.
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