ITV4,Film4 etc (ARQB) up the creek!

[Luke]

Ofcom report: "Reducing interference into higher channels is expected to be more challenging."
Ofcom report: “In general the higher the channel used, the more expensive and bulkier the filter will be.”

The number of homes who they are predicting may not be working even after suitable filters and aerials systems is small but if any of them have multiple PVRs the cost would be a lot higher than the report appears to take account of.

I'm pleased I haven't changed any of my aerials to suit the immediate post DSO situation. (Wideband and grouped pointing in different directions). I’m now totally lost concerning which single aerial would be best for me in the long term.

There is a large number of mitigation techniques that could be used (ref 5.12). Once the technical mitigation approach is specified it is still going to be difficult for someone to know if and how they will be effected. A lot will also depend on the location of the 4g transmitters and that is not something so easily predicted.

Each 4g transmitter will operate at a fixed frequency within the 4g frequency range. Which frequency someone’s local transmitter broadcasts at will help dictate how efficient it is at interfering with the higher DTT frequencies.
I’d hope that those in the most populated fringe DTT reception areas of transmitters that use the higher frequencies will have a bias towards 4g transmitters using a higher range as well. But I do not see that suggestion in the report.

 

[RedEarth]

This is a very interesting and informative website about TV aerials (from an aerial installer's point of view), the link is to the page about Rowridge transmitter, but explore the rest of the site too:

http://www.aerialsandtv.com/rowridgetx.html

 

[Ezra Pound]

That's not how I am reading the Ofcom report. To quote: "A DTT receiver becomes overloaded if the power of the signals at its input exceeds a certain threshold. In the presence of overload, a DTT receiver stops working altogether and reception of all DTT services is lost."
This apears to be totally different to direct interference with the signal.

Are you saying that a band A aerial will feed more 'overload' in the presents of the 4G 800MHz to the Humax than other aerials will, It seems to me that the other aerials tuned nearer to 800MHz are more likely to feed this overload to the Humax

 

[antipodean]

That sounds like the SINR issue.

Yes. But in the band A area only the guy who was sold a wideband aerial would need to do that and not his neighbour who stuck with a band A aerial?

Technically it is known as an intermodulation problem, with its own set of terms.

 

[Luke]

Are you saying that a band A aerial will feed more 'overload' in the presents of the 4G 800MHz to the Humax than other aerials will, It seems to me that the other aerials tuned nearer to 800MHz are more likely to feed this overload to the Humax

And also it seems to me that the other aerials tuned nearer to 800MHz are more likely to feed this overload to the Humax.

Within the ofcom report (http://stakeholders.ofcom.org.uk/binaries/consultations/dtt/summary/dttcondoc.pdf ) I have not found a mention of replacing wideband aerials with a grouped aerial to avoid overload.

The lack of a mention of a group aerial as a mitigation option does make me wonder why.

 

[Luke]

This is a very interesting and informative website about TV aerials (from an aerial installer's point of view), the link is to the page about Rowridge transmitter, but explore the rest of the site too:

http://www.aerialsandtv.com/rowridgetx.html

Thanks for the reminder of that site. I'd been dipping into it for the years leading up to my regions' DSOs and thought I would know what to change the aerial system to after DSO. I’ll keep an eye out for when Justin starts to introduce 4g factors into his experiments.

I only get a very small amount of pixilation and it is rare when that occurs. Strangely the sound never has the slightest glitch post DSO. I was thinking that post DSO I would be able to fit an aerial system in to a stable environment and forget about it. The introduction of also considering 4g has put a spanner in my more recent aerial plans. My next and newest plan is a bit more like my DSO plan. I am going to wait until there is a fair amount of 4g transmitters in my area before I replace my aerials. The main issue I can see with that plan is that 4g may start to interfere with both aerials' reception from my nearest (but not so local) transmitters on the same day. Also as with most homes a new 4g transmitter could be introduced at short notice.

Personally if the 4g transmitters get put in the same place as the 3g transmitters then I may be safe from overload. Not only am I between DTT transmitters and not near any but the same applies to my home and 3g. Every cloud has a silver lining.

 

[Luke]

Technically it is known as an intermodulation problem, with its own set of terms.

Thanks for that. It has enabled me to google the subject better.

 

[antipodean]

Thanks for that. It has enabled me to google the subject better.

Your'e welcome, I'll look forward to your treatise on 3rd order and 5th order intermodulation ...

 

[Black Hole]

This is interesting (I have edited it for brevity):

You could well be plagued by interference from the new fourth generation (4G) mobile radio networks when they come on stream next year. About one home in ten will be affected, and the fur is flying over who should pay to sort it out.

There seems to be little dispute that 4G mobile signals will cause interference to Freeview viewers living within 2km of a 4G base station, and installing a replacement TV antenna and filter to eliminate the interference will cost around £200.

Freeview says that "consumers should not have to pick up the bill and the mobile operators should be responsible for the full costs associated with protecting viewers' TV services".

"Freeview homes should not be subject to further inconvenience and additional cost to make way for mobile broadband. By the time 4G services roll out, over 90% of the UK will have Freeview".

The most recent word from the government came in July, when communications minister Ed Vaizey stated in a letter to OFCOM: "The Government is keen to mitigate the effects of interference, so that no television viewer loses access to television services." Help will be available to affected homes, he continued, with filters to prevent interference problems, provided free of charge be the government help scheme.

Vouchers will be provided to eligible households to pay for the installation of a filter to a rooftop aerial, if required. Where filters cannot improve reception, Mr Vaizey said assistance would be provided to switch to free-to-view satellite or to cable TV.

So far so good, but do the proposals go far enough? Not according to TV transmitter Arqiva, which stated "We remain very concerned that disruptions to secondary set users and households that depend on set-top or loft-mounted aerials have been completely ignored".

At face value that seems to confirm there is a potential problem, and reading between the lines I suggest a significant one. When C5 came along and interfered with VCR outputs, all we needed to do was retune the VCR output or eliminate the C5 frequency with an indoor filter. If eliminating 4G requires a masthead filter, it confirms the power levels involved risk the intermodulation mentioned before and the signal has to be notched out before it gets into the wiring.

At least the Everything Everywhere 4G-on-3G-frequencies announced recently should not create a problem, only when 4G proper comes along. It does rather seem the telecoms authority (ie the government) has been rather hasty selling off the bandwidth released by analogue switch-off.