. The service areas of~ the Wenvoe television (Band I) and v.h.f. sound transmitters

Transcription

1 RESEARCH DEPARTMENT. The service areas of~ the Wenvoe television (Band I) and v.h.f. sound transmitters \ TECHNOLOGICAL REPORT No. K /43..,. THE BRITISH BROADCASTING CORPORATION ENGINEERING DIVISION

2 RESEARCH DEPARTMENT THE SERVICE AREAS OF THE WENVOE TELEVISION (BAND I) AND V.H.F. SOUND TRANSMITTERS Technological Report No. K-175 (1964/43) R.C. Vercoe H.T. Madoc-Jones J.H. Causebrook J.A. Carter (W. Proctor Wilson)

3 This Report i. the property of the British Broadcasting Corporation and ma1 Dot be reproduced in any form without the written permission ot the Corporation.

4 July 1964 Technological Report No. K-175 (1964/43) THE SERVICE AREAS OF THE WENVOE TELEVISION (BAND I) AND V.U.F. SOUND TRANSMITTERS SUBJECT This report gives the results of a re-survey of the television (Band I) transmission and a survey of the v.h.f. sound transmission. The re-survey of the television transmission is more detailed than the original survey carried out in SUMMARIZED DESCRIPTION OF TRANSMITTERS Band Channel Frequencies Site Height (above mean sea level) Aerial Height (above ground level) Transmitter Power Aerial E.R.P. Polarization H.R.P. Vision: Sound: Television I Mc/s Mc/s 420 ft (128 m) 735 ft (224 m) 50 kw (one 50 kw unit) Two tiers of four dipoles 98 kw Vertical Onnidirectional V.H.F. Sound II Light: Third: Home (West): Home (Welsh): 420 ft (128 m) 647 ft (197 m) Mc/s 96-8 Mc/s Mc/s 94-3 Mc/s 20 kw (2 x 10 kw) Eight tiers of four slots 113 kw Horizontal Onnidirectional 2. SURVEY RESULTS Maps T.592 and F.186 show the field strength contours for the television and v.h.f. sound transmissions respectively.

5 2 Worwork~ ~ 40 + Map. T WENVOE Band I Channel 5 (66 75 Mc/s) (Measured) 0 SITE HEIGHT: 420 ft (128 m) a. m. s.l. AERIAL: TWO TIERS OF FOUR AERIAL HEIGHT: 735 ft (224 m) a.g.l. DIPOLES (PHASE NOTES: E.R.P. : 98 kw ROTATION) POLARIZATION : Vertical H.R.P. : OMNIDIRECTIONAL 1. The contours represent the field strength in decibels (db) relative to 1 uv/m at 30 ft (9 0 1m) above ground exceeded at 50% of receiving sites in a given locality. The value exceeded at 90% of receiving sites may be as much as 10 db below the value indicated by the contours, particularly in hilly and built-up areas. 2. x--x~ Limit of service area free from perceptible co-channel interference from all U.K. co-channel transmitters for 90% of the time based on a protection ratio of 45 db with a reduction of 10 db for cross polarization and 10 db for frequency offsets, allowance being made for receiving aerial directivity.

6 3 Map F WENVOE Band 11 (Measured) (Light Mc/s; Third 96 8 Mc/s; Home (Welsh) Mc/s; Home (West) Mc/s) SITE HEIGHT: 420 ft (128 m) a.m.s.l. AERIAL: EIGHT TIERS OF FOUR AERIAL HEIGHT: 647 ft (197 m) a.g.l. SLOTS (SPLIT AERIAL E.R.P. : 113 kw SYSTEM) POLARIZATION: Hori zontal H.R.P. : OMN I DI RECTI ON AL NOTE: The contours represent the field strength in decibels (db) relative to 1 ~V/m at 30 ft (9 1 m) above ground exceeded at 50% of receiving sites in a given locality. The value exceeded at 90% of receiving sites may be as much as 10 db below the value indicated by the contours, particularly in hilly and built-up areas.

7 4 In the interests of economy of effort only the field strength values exceeded at 50% of the locations in towns have been extracted from the charts, but the 10% and 90% values for any particular town(s} can be made available on request at short" notice. The 50% location values are given in the Appendix (Table 1 Wales; Table 2 England). 3. COMMENTS ON SERVICES The Wenvoe Band I television service is almost entirely free from United Kingdom co-channel interference. It is also largely free from interference radiated by Continental stations propagated via the troposphere, and, because it radiates on the highest Band I channel (f = Mc/s), interference from distant Continental transmitters propagated by the Sporadic E layer is rarely troublesome. The effective limit of the service area, therefore, corresponds to a field strength of about 40 db(~v/m}. The map T.592 shows that, while a very good television service is provided on both sides of the Bristol Channel, the mountainous terrain severely restricts the service in Wales. Nevertheless, the highly populated South Wales area IS, on the whole, provided with a good television service. The v.h.f. sound service (map F.186) is also, on the whole, very good, but because the nominal limit of the service corresponds to a field strength of 48 db(~v/m} the overall service area is substantially less than for the Band I television service.

8 5 APPENDIX TABLE 1 WALES (db(,uv/m) ) (db(fl'v Im) ) Television V.H.F. Television V.H.F. (Band 1) Sound (Band 1) Sound Abergavenny Haverfordwest 39 Abercarn Hay-on-Wye 36 Abercynon Hirwaun Aberdare Aberti11ery Kidwelly Amman ford Laugharne Bargoed Llandi Barry 100 >100 Llandovery 27 <31 Beaufort Llanelly B1aina Llangadock Brecon Bridgend Maesteg Bri ton Ferry. 45 Manorbier Brynamman Merthyr Tydfi Brynmawr Monmouth Builth Wells 33 Mountain Ash Burry Port Mumbles B.v1ch Nantyg Caerleon Narberth Caerphilly Neath Cardiff Newbridge Carmarthen Newport Chepstow New Tredegar Cilfynydd C1ydach (near Swansea) Pembroke 41 Cowbridge Pentre Crickhowell Pontardawe Cross Hands Pontardu1ais Cross Keys Pontllanfrai th Cwmbran Pont1ottyn Cwmbran Newtown Pontyberem Pontypoo Pontypool Road Ebbw Vale Pontypridd , G1yn-Neath Porthcaw Port Talbot 55 48

9 6 (db(,uv/m)) (db(,uv/m)) Television V.H.F. Television V.H.F. (Band I) Sound (Band I) Sound Raglan Treharris Rhymney Treherbert Risca Treorky Tyntetown 64 St. Clears Saundersfoot Usk Sennybridge Swansea Whitland Williamstown 74 Tenby Tonypandy 69 Ystalyfera Tonyrefail Ystradgynlais Tredegar Ystrad Rhondda 68 63

10 7 TABLE 2 ENGLAND (db(flv/m) ) (db(flv/ m) ) Television V.H.F. Television V.H.F. (Band I) Sound (Band I) Sound Axbridge Dunster Axminster Dursley Bampton Evesham Barnstaple Exeter Bath Exford Beaminster Bideford Fairford Bishops Lydeard Fremington Blandford Forum Frome Br aunt on < Bridport Glastonbury Bristol Gloucester Broadway Great Malvern Bridgwater Gillingham Burnham on Sea Great Torrington 37 Calne Hatherleigh 29 Cannington Hereford Castle Cary Highbridge Chard Highworth Cheddar Holsworthy Cheltenham Honiton Cherhill Chippenham Ilfracombe Chipping Campden Ilminster Chipping Sodbury Instow 30 Cinderford Cirencester Keynsham Clevedon Coleford Langport Combe Martin Lechlade Crediton Ledbury Crewkerne Lyme Regis Cull ompt on Lynton Devizes Malmesbury Dorchester Mal vern Link Dulverton Malvern Wells 35 40,

11 8 (db(pv/m) ) (db(/.n Im) ) Television V.H.F. Television V.H.F. (Band I) Sound (Band 1) Sound Marlborough South Zeal Melksham Stonehouse Mere Stow on the Wold Midsomer Norton Stratton Milverton Stratton St.. Margaret Minehead Street Mitcheldean Stroud Swindon Nailsworth Newent Taunton Nether Stowey Tetbury Northam Tewkesbury Northleach Tiverton North Petherton Trowbridge Norton Fitzwarren Upton on Severn Okehampton Ottery St. Mary Wareham Warminster Painswick Watchet Peasedown St. John Wellington Pershore Wells Pewsey Westbury Pinhoe Weston-super-Mare Porlock Westward Ho Weymouth Radstock Wickwar Ross-on-Wye Williton Wincanton Salisbury Wiveliscombe Seaton Wool Shaftesbury Wootton Bassett Shepton Mallet Wotton-under-Edge Sherborne Worcester Sidmouth 31 <36 Wrought on Somerton South Molton Yeovil MB Printed by BBC Research Department, Kingswood Warren, Tadworth, Surrey