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ITV4,Film4 etc (ARQB) up the creek!

Hey people, sorry i havent been able to get back on here sooner. I have an update: The idea of switching the humax to the room with the bravia was a sensible one - it works no problem at all. Signal strength is 70% and quality at 100%. This confirms that the hummy isn't mad and i take back everything i said about it! It would appear then that its somethig to do with the aerial.

I'm hypothesising that either there is some sort of signal deterioration from the main aerial socket (with the bravia) to the bedroom or that different aerials feed the seperate sockets within the flat. When i look out the window i see a conventional mounted tv aerial and a satellite dish. Not sure which i get signal from or indeed if its both, but either way i am now able to watch and record Le Tour as intended thanks to your suggestions.

I doff my hat to the lot of you. Ta muchly.
 
I've experienced exactly the same thing, near Cambridge. I only noticed it when I came to watch the Tour so it could always have been like that!

Sounds like I should re-tune or something.
 
if it's anything like my flat, there'll be a little box somewhere containing a splitter and a couple of aerial feeds. It allows you to choose which aerial goes to where . Chances are you are feeding the humax the satellite cable which will probably be ok for the main transmitters
 
I have exactly the same problem with ITV4 and Film4. Other devices even on the same aerial wire have no problem. It seems to be just the Humax that cannot get these channels. Very annoying. Any ideas gratefully recieved (please note that most the the above thread went over my head!)
 
Hi Question is did you split the aerial ?

I extended aerial to bedroom and those 2 channels are the weakest on rowridge (I'm on IOW) horizontal, if I have TV in bedroom and humax on these break up on one of the devices.

My choices (well to do list is as follows)

1) get a decent group A log periodic aerial with proper mounts
2) mount it in the correct place, my current aerial points up at an angle as it's in the wrong place and it's a bacofoil type b&q special
3) mount it vertical :-) to get the full power across all muxes

4) hope 4g doesn't break it all!
 
damianiw said:
My choices (well to do list is as follows)

1) get a decent group A log periodic aerial with proper mounts
Click to expand...

Where would you source a "group A log periodic"?

damianiw said:
4) hope 4g doesn't break it all!
Click to expand...
If a group A aerial is OK where you live then 4g will not be an issue for you. Group A frequencies are at the other end of the UK TV range of frequencies.
 
Apologies I'm getting mixed up

You're correct log is a log and others are grouped :-)

Nice to hear if we're group A mux that 4g shouldn't interfere
 
damianiw said:
Apologies I'm getting mixed up - You're correct log is a log and others are grouped :)
Click to expand...

It is possible to purchase a grouped log period aerial, but as it doesn’t have any higher gain than the normal wideband log periodic there is no point. The purpose of a grouped aerial is higher gain over a smaller band of frequencies, a wideband aerial is quite inefficient at band A
BTW
The 4G frequencies fall into band C/D CH48-68 so your Band A CH21-37 won't be affected
 
Luke said:
If a group A aerial is OK where you live then 4g will not be an issue for you. Group A frequencies are at the other end of the UK TV range of frequencies.
Click to expand...
I do wish I had not posted this. I have now skim read sections of the Ofcom report 'Coexistance of new services in the 800 MHz band with digital terrestrial television'.
http://stakeholders.ofcom.org.uk/binaries/consultations/dtt/summary/dttcondoc.pdf

SINR (Signal Interference to Noise Ratio) degradation is the issue I was aware of.
There is also a another reason that 4g may cause DTT problems. This second issue is receiver signal overload.

Overload refers to receiver signal overload and results in a loss of all channels. Overload is more likely to happen in poor reception areas when using an amplifier and/or where the aerial is very near a 4g transmitter or not so near a few of them that together they cause overload. Some receivers will be more susceptible than others.

Does this mean that if someone receiving group A transmissions through a wideband aerial could lose all reception while their neighbour's TV with a group A aerial is OK?
 
Depending on the exact design of the receiver input stages, for example if there is a wide-band amplifier ahead of the superhet mixer stage, large off-channel signals could certainly drive the signal path into a non-linear region and thus cause degradation and signal loss (bear with me, I'm bluffing I know something about this stuff).

It shouldn't be too difficult to put a notch filter in the line though, as long as there is no mast-head amp ahead of it.
 
Black Hole said:
Depending on the exact design of the receiver input stages, for example if there is a wide-band amplifier ahead of the superhet mixer stage, large off-channel signals could certainly drive the signal path into a non-linear region and thus cause degradation and signal loss
Click to expand...
That sounds like the SINR issue.

Black Hole said:
It shouldn't be too difficult to put a notch filter in the line though, as long as there is no mast-head amp ahead of it.
Click to expand...
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?
 
Well, I don't know. I'm not sure a Band A aerial would reject out-of-band signals suffiently, especially off-axis.
 
Band A is as far away from the 4G 800MHz as you can get, If a band A aerial is affected then everyone in the country will be affected to an equal or greater extent.

Group A CH21 to CH37
Group B CH35 to CH53
Group C/D CH48 to CH68 Note DTT = 48 to 60 after DSO
Group K CH21 to CH48
Group E CH35 to CH68 Note DTT = 35 to 60 after DSO
Wideband CH21 to CH68 Note DTT = 21 to 60 after DSO

4G = 791MHz to 862MHz or CH61 to Ch69
 
I'm playing devil's advocate with a modicum of relevant knowledge, and the regulators ought to be more skeptical too in my opinion. OK, so there's 300MHz separation between Group A and 4G - but the systems downstream of the aerial are designed to accept everything from A to D (and sometimes more when international markets dictate). If you are close to a mobile mast there may be sufficient induced field to drive the input into clipping, especially as the consumer electronics probably has not been designed for that scenario.

When Channel 5 started up and interfered with people's VCR modulator outputs, they came around with free notch filters - though frankly it would have to be a damn good filter to tell the difference between channels 60 and 61.
 
I'm not sure how much cash was raised by Ofcom in selling Channels 61 to 69, But according to the document above they have estimated the cost of supplying and fitting filtering at £53 Million with a total cost of a £100 Million

DTT-Filtering.jpg DTT-Filtering2.jpg
 
Ezra Pound said:
Band A is as far away from the 4G 800MHz as you can get, If a band A aerial is affected then everyone in the country will be affected to an equal or greater extent.
Click to expand...
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.
 
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