NI underpowered Interleaved multiplexs

Sam the Aerialman

I've been reading through information from the DTG on proposals for the interleaved usage for Brougher and Divis. The radiation patterns look highly restrictive they've noted 30dBw for use of channel 30 from Brougher which will contain a main lobe to the east of Brougher, Arqiva won't publish gain figures but if you take a calculator and add 2.15dBi you are left with an ERP of 1100 watts.

Divis is set for 40dBw and use of channel 48, noted as the only channel left in available spectrum which will allow for an ERP of 10000 watts (10Kw). Significantly down on projected estimates of 30Kw. There is still no mention if the interleaved space will be dedicated to the DVB-T2 mini mux with 256 QAM 32K this will lead to a further tightening of radiated power.

I just hope this doesn't end up a restricted dog's dinner and Arqiva/ DTG are back to pulling rabbits out of hats. They don't seem to be sure what's actually going to happen, Digital UK have also very quiet on the subject.

reslfj

Sam the Aerialman wrote: »

Divis is set for 40dBw and use of channel 48, noted as the only channel left in available spectrum which will allow for an ERP of 10000 watts (10Kw). Significantly down on projected estimates of 30Kw. There is still no mention if the interleaved space will be dedicated to the DVB-T2 mini mux with 256 QAM 32K this will lead to a further tightening of radiated power.

The Ofcom/Qrqiva paper - I have read - is based on the pre 800 MHz clearing and is only one of many 'what if' papers Ofcom makes and sometimes publish.
The RTE/TG4 NI mux is a joint UK/ROI project and coverage projections includes ROI spill-over into NI.

Forget the (analogue) RF parameters - these cannot be compared without including the difference in proposed modulation and FEC. Digital is another world.

The DTG press release states "The DVB-T2 mode chosen for the new multiplex is QPSK rate 5/6,..."

This mode requires 12-13 dB less C/N ratio. This translates til an equivalent lower ERP requirement ( as N is about the same)

Look at* a Ricean channel for QPSK CR 5/6 (5.6dB) with 256-QAM CR=2/3 (17.8dB) or compare the figures for a Rayleigh channel (indirect reception)

You can also take a look at the Nordig.org T2 spec.

Lars

* To the figures quoted some small correction should be added - EN 302 755 - but this does not change the 12-13 dB much.

Mr. Rabbit

Anything's better than the 2.5 KW that we have at the moment from Divis.

Sam the Aerialman

Mr. Rabbit wrote: »

Anything's better than the 2.5 KW that we have at the moment from Divis.

You've missed my point - If the radiation patterns are close to those the DTG have then this new multiplex with not benefit for example North or South Down were improved RTE/ TG4 reception would be a blessing. The new antenna proposed for this service (There is some grey area over which this is the existing S1 antenna currently putting out the analogue services or a new antenna entirely) is protected 10db to the south east to protect Moel Y Parc.
Massive great big null slapped over County Down. The radiation pattern has three lobes south west, north and west all these areas stand adequately covered by Clermont Carn. 10Kw or 40dBw doesn't justify the expense, i'm hoping this is not another fannying around session were a service is promised and it ends up underpowered and of low aerial height.

reslfj

Sam the Aerialman wrote: »

If the radiation patterns are close to those the DTG have ..... (There is some grey area over which this is the existing S1 antenna currently putting out the analogue services or a new antenna entirely) is protected 10db to the south east to protect Moel Y Parc.....

What data do you have about the Divis antenna ?

A 6kW ERP for the proposed RTE/TG4 mux will have about the same coverage as the 100kW PSB muxes. (6 kW = 100kW - 12.2dB)

Lars