Digital TV Technical Discussion


#596

Can confirm that it’s still broadcasting; receiving it fine right now as we speak.


#597

Maybe they are trying different DVB-T2 versions?

There was a change made in 2012 (from version 1.2.1 to 1.3.1) to make decoders more power effective, but a lot of manufacturers of STBs and Tvs still use old tuners as a cost cutting measure.

https://www.dvb.org/news/dvb-t2-v131-plug-fest


#598

It’s probably a signal strength issue, since I am well outside the Sydney TV licence area.


#599

What antenna do you use?

You’re facing south off the hill at Charlestown?


#600

Just a pair of rabbit ears.

It also helps that I am 6 floors above ground level in an apartment and with a pair of binoculars, I can see the Wyrrabalong TX site (Forresters Beach) which is 53 kms away. So that gives you an idea how good my LOS is in that direction.

I am 105 km from the Artarmon TX site.


#601

It’s a wonderful result then to receive this test broadcast.

You are in a most wonderful location. Sydney quality TV in a wonderful quality of life area, the Hunter.


#602

It’s not perfect reception.

Channels will pixelate momentarily here and there most days, but still very watchable.
Channel Ten will go missing altogether occasionally, but not for long.
When ducting occurs, the signals can get unstable and drift in and out below the digital cliff.

But yeah, that I can get Central Coast reception too, I can’t complain.
Even though the above imperfections apply here as well, except for the TEN issue.

But that’s a nice trade off to have for when the local channels go missing totally for up to several days at a time during strong ducting.


#603

I am also getting 402 coming up from time to time, it is down at present. However my Sony Tv cannot decode the picture when it is transmitting.
Does anyone know the specs of test 402 v 401.

Also if DVB-tv2 is adopted will they still need 5 tv frequencies like with the current DVB-tv? NZ uses DVB-tv2 and uses 6 channels but that includes SKY pay tv encrypted services. It is being discussed in the long distance tv thread If channels can be freeed up with DVB-tv2 Wollongong and Newcastle tv could be restacked onto different frequencies to eliminate interference during ducting events.


#604

No, it seems like DVB-T2 will only need 1 or 2 frequencies to accommodate all 5 networks.

I think the plan by the ACMA when this is fully rolled out and the current DVB-T format is switched is to sell even more UHF spectrum to the telcos.


#605

I bet if a restack of the UHF band takes place for DVB-tv2 they will probably again allocate Newcastle and Wollongong on the same frequency.

Ideally a future restack would mean all DVB-tv2 broadcasts would be on UHF in Australia, and open up the band 3 VHF for expanded Dab+ broadcasts Australia wide.


#606

I think the main metro wide transmissions will stay on VHF, as there would be a number of households who never bothered with a UHF antenna just to get SBS on analogue.


#607

That still would achieve the objective of restacking the UHF band, removing co-channeling, and allowing the expansion of dab+ radio in Australia. Provided they don’t sell off so much of the spectrum that we have the same situation as now.


#608

Agreed. Aside from anyone who got a new antenna after the analogue switchoff, the majority of households with VHF-only antennas in metropolitan markets are probably older viewers that are really important to the TV networks.

Metro-wide TV will probably be on the higher range (10, 11, 12) of the VHF band in the DVB-T2 era, leaving 6/7/8 for the future expansion of DAB+ in the regional markets surrounding metropolitan areas? If so, I think that could work OK since regional DAB+ will probably just consist of an ABC/SBS multiplex and a single multiplex (rather than the two in the East Coast capital cities) for commercial/region-wide community stations.


#609

All new antennas installed in Brisbane over the last couple of years are VHF only.


#610

You wouldn’t restack in a way that doesn’t maximise the sale value.

5 blocks of 3 channels of DVB-T2 results in a slight capacity increase, which you would split as 6-8, 10-12, 28-30, 31-33, 34-36.

That could also be split as two channels of DVB-T2 and a legacy service In MPEG-2 DVB-T2, for a slight drop in capacity but a smoother transition.

That would mean being able to auction off the entire 600MHz band. I don’t think you could justify a transition for anything less.

The commercial networks will obviously just dangle 4k and want the government to give them a free extra channel and not restack. But they will eventually lose that battle when a Government does the sums on a spectrum auction.


#611

Good analysis @Moe. The government has already done the sums and eagerly awaits this. Will be some years away.


#612

I cannot see how there would be enough spectrum to accomodate the current metro and regional broadcasters in areas such as Sydney and Brisbane without massive cochannel interference?


#613

The same way you do currently. There’s 5 blocks of channels, just you would use the efficiencies gained with DVB-T2 to have 5x3 instead of 5x6.


#614

why push off C31 then? If they can squeeze that in somewhere


#615

May as well go all in on outlining a transition -

Phase 1 -
Commence a full DVB-T2 service on the current unassigned channel - with each of the networks getting to use 1/5th of the data rate (~7.5Mbps) on that multiplex.

This would likely be sufficient capacity to provide two 1080p services, or one and some SD services.

Phase 2 -
ABC and SBS shift to a single combined DVB-T multiplex - likely by removing HD services from DVB-T, and a secondary DVB-T2 service launches on the channel freed up.

The networks would then get 1/5th of the total multiplex space - with one network split between two. This would result in ~15.5Mbps per broadcaster.

Phase 3 -
Switch off three of the remaining four DVB-T multiplexes. Restack the services to be in the 3 channel blocks. Profit.

Each broadcaster would have 4.5Mbps for an MPEG-2 main channel simulcast, or optionally decide that enough viewers have switched and utilise it for additional HEVC services.

Phase 4 -
Switch the DVB-T service to DVB-T2. This restores each broadcaster to their original 23Mbps that they had with a full DVB-T multiplex, and potentially allow 4k services.


Difficulties with this would be mostly around the markets with the two sets of commercial channels, as there is only one unassigned channel in those areas.