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UK Broadcast Transmission |
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THE TRANSMISSION GALLERY
| Photos by Dan Glover | Page last updated: 2016-10-12 |
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| Located in the London Borough of Lewisham and just off Honor Oak Road, this site is known to Ofcom simply as "Lewisham" for the CR station and less ambiguously as "Honor Oak Park" for the small-scale DAB trial. Reprezent entered service in March 2011 and the DAB trial in October 2015 using a Single Frequency Network with a second site at Highgate. The multiplex carried eight programmes as of October 2016 - a mixture of CR (including Reprezent), "specialist" London commercial stations and others previously carried only via Internet streams. The site is at a local high point and very close to that once used by the Met Police for their 99 MHz (and later 152 MHz) radio system - there is a clear view towards central and south east London. Results of the DAB Trial (see Ofcom report linked below) however seem to be slightly below expectations: "The coverage of one of the two SFN trials was broadly as predicted by computer modelling. However, the distance between the two trial transmitters was relatively large, and reception around the mid-point between the transmitters was more ‘marginal’ than expected: this area happened to fall into a densely built-up city centre, which is also likely to have contributed to the issue." |
| Unusually the block doesn't seem to have been named separately but is simply "1 - 49 Greystead Road" - this is possibly one of the original signs from when the development was new |
| As sometimes happens this first "quick snap" whilst trying to find a suitable location turned out to have everything (just) visible. The CR station appears to use the vertical dipole on the left and the DAB trial is the long colinear on the right - with the SHF dish and GPS antenna also forming part of the installation. At the bottom left is part of what seems to be a Band I dipole - more details below. |
| The broadcast (and other) antennas are on the 9-storey block at the end of Greystead Road. |
| In this view the DAB antenna is on the left of the mobile phone panels and the Band II dipole on the right - and there's a hint of the site's "take off" towards central London - The Shard is just visible on the extreme right |
| Further round (looking approximately north). The Band II dipole is on the pole to the left of the "domestic" installation. The DAB antenna is rather "long" - the Ofcom report on the DAB trial says "6 dBd colinear aerials were delivered to the London trial...This aerial type was also helpful in ameliorating (to some degree) blocking caused by a business radio system with many mobile stations, and ‘reverse ACI’ from other DAB networks which lay down much higher field strengths (due to the greater number, and higher power levels, of the transmitters in those networks.)". The London sites are shown by Ofcom as 200 W ERP - the others in the trial are 100 W (or less) and were provided with a 3 dBd antenna. |
| The London DAB Trial uses a Single Frequency Network with a second site at Highgate. The GPS antenna is needed for timing and the SHF dish is understood to provide a direct link between the sites. The dipole is possibly just for monitoring purposes. |
| From a different position - the Band II antenna has a "home made" appearance. The effect of the support pole will create a null (the TV antenna, naturally, faces Crystal Palace). Ofcom parameters show the station with 100 W ERP horizontal and 80 W vertical, maximum ERP just west of south (bearing 209). Looking at the detailed parameters serves to add further mystery and confusion - there is stated to be a 25 dB reduction on bearings 120/300 in the horizontal plane. Was there once a horizontal dipole where there is now an empty clamp? In the vertical plane the detailed parameters suggest there should be a cardioid pattern with the null around north east. Maybe it's the perspective, but the current arrangement doesn't seem to fit in with the parameters... |
| ...this is from the north side of the building - it certainly looks like the "shadow" from the support pole is now on the southern side. Curious. |
| One final piece of the jigsaw is this Band I dipole, facing north west. Reprezent seems to have studios near Brixton station. |
| An indication of the site's potential coverage towards central London... |
| ...and towards the City. Alexandra Palace is just visible to the right of The Shard. |
Ofcom: Small-scale DAB trials: final report
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