HD: Where's my signal gone?

gunjin

Active Member
Bought myself a Bush HD freeview receiver last week for the World Cup. It worked perfectly out of the box drawing oohs and aahs from mates invited over to watch HD games.
Until this afternoon that is, when all of the HD channels suddenly stopped working. Nothing has changed at my place. No wires moved, settings changed, same aerial and it is a beautiful day so not atmospheric interference.
Argos tech support says that HD signals drop all the time but this is the first time for me. So:

Has anyone with working Freeview HD had serious signal problems too?
Is this likely to be a Mux problem or a box problem?

I want my HD football back!

Thks
 
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glesgaguyav

Active Member
Abreviations, well I first thought you'd bought the box for you toilet, funny place to invite your mates:facepalm:

Anyway, my only suggestion is to do a factory reset if there is one and rescan for channels see if that sorts it.
 

gunjin

Active Member
Might also help if you told us where you are?

8 miles from crystal palace in w london. "Very strong" signal quality according to the box whilst it was getting HD channels. All other Freeview channels working fine. Just the HD ones that have suddenly stopped working.
Edit: In fact, am now getting "poor" signal quality. Why on earth would it change from one week to the next just for the HD channels?
 
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Colin London

Well-known Member
8 miles from crystal palace in w london. "Very strong" signal quality according to the box whilst it was getting HD channels. All other Freeview channels working fine. Just the HD ones that have suddenly stopped working.
Edit: In fact, am now getting "poor" signal quality. Why on earth would it change from one week to the next just for the HD channels?

Well I live significantly further from CP than you and the signal is rock solid, as it has been since I got my HD TV.

You can probably isolate it either to a fault that has developed in your aerial system, or a change in the local environment. I used to live in Shepherds Bush and one day when I came home from a weeks holiday my reception was severely degraded with (ON Digital as it was then) unwatchable. I then noticed that a large crane had been erected on the other side of the Green whilst I had been away. Putting 2 & 2 together.......

What is the box showing for non-HD multiplexes? Are they degraded too?
 

gunjin

Active Member
What is the box showing for non-HD multiplexes? Are they degraded too?

All the other freeview channels are fine. Just the HD ones have gone from good quality to no signal or poor quality in the space of 24 hours. Completely bizarre.
 

Colin London

Well-known Member
All the other freeview channels are fine. Just the HD ones have gone from good quality to no signal or poor quality in the space of 24 hours. Completely bizarre.

It has an RF loop through doesn't it? The modulator hasn't set itself to UHF 31 by any chance? If so, change it to 68 or 69.

Have you done the factory reset as suggested yet?

If neither of these work it would seem that you have a box fault of some description that is only affecting the DVB-T2 tuning capability. :confused:
 

N.Dean

Active Member
...it is a beautiful day so not atmospheric interference...

Sometimes ( like now, for example ) high atmospheric pressure causes VHF & UHF signals to travel further than normal. You could be getting foreign interference.
 

gunjin

Active Member
It has an RF loop through doesn't it? The modulator hasn't set itself to UHF 31 by any chance? If so, change it to 68 or 69.

Have you done the factory reset as suggested yet?

If neither of these work it would seem that you have a box fault of some description that is only affecting the DVB-T2 tuning capability. :confused:

I have done a factory reset and no change.

It has RF out which i use but i cannot find how i might be able to re-assign the channel. Any ideas?
 

gunjin

Active Member
Sometimes ( like now, for example ) high atmospheric pressure causes VHF & UHF signals to travel further than normal. You could be getting foreign interference.

causing complete disruption of the HD channels only?
 

JeffD

Well-known Member
causing complete disruption of the HD channels only?
The HD channels are being broadcast at much lower power than the SD, about a 1/4 of the power if I remember correctly.

Do you know a neighbour you could go round to and to test the Bush on their aerial system, this might tell you if it's a problem with the box or your aerial system? have you checked if your aerial is still aligned as it should be, a bird landing on it could have slightly moved it if it wasn't firmly secured?
 

grahamlthompson

In memoriam
Does the box have a modulator?. I thought it merely has rf passthrough. But yes if it has or there is other kit in the aerial loop that does have (a vcr or sky box for example) then that could easily wipe out the HD-Mux if set to the same or close to the UHF channel used by the HD-mux. It would have caused problems right at the start though not just suddenly. Could well be a local interference problem, try removing any hdmi leads and see if you can watch the HD channels using a scart lead.
 

gunjin

Active Member
The HD channels are being broadcast at much lower power than the SD, about a 1/4 of the power if I remember correctly.

Do you know a neighbour you could go round to and to test the Bush on their aerial system, this might tell you if it's a problem with the box or your aerial system? have you checked if your aerial is still aligned as it should be, a bird landing on it could have slightly moved it if it wasn't firmly secured?

i have now replaced the box and still have problems although for some reason they are now not as severe. The picture still breaks up every 10 seconds or so vs lasting for 2 seconds then freezing/ disintergrating into perpetual pixel mayhem as before.

I am going to get the aerial checked out. Am on ground floor of 5 floor house so shared aerial which obviously raises the potential of someone else having done something.
 

gunjin

Active Member
Does the box have a modulator?. I thought it merely has rf passthrough. But yes if it has or there is other kit in the aerial loop that does have (a vcr or sky box for example) then that could easily wipe out the HD-Mux if set to the same or close to the UHF channel used by the HD-mux. It would have caused problems right at the start though not just suddenly. Could well be a local interference problem, try removing any hdmi leads and see if you can watch the HD channels using a scart lead.

It has RF pass through only i believe. I have replaced the box and done a fresh install with no pass-through. I have nothing else using RF. Problems remain but are not as bad.
The fact that it went from perfect to no signal in 24 hours with no changes at my end suggests it is a transmitter or aerial problem rather than local HDMI interference...
 

N.Dean

Active Member
causing complete disruption of the HD channels only?

I think that the HD channels are on their own frequency. If that frequency suffers interference from another transmitter ( abroad or in the UK ), then, yes, I think this could happen. Off the top of my head, I don't know the frequency used for Crystal Palace HD, but I seem to recall that it share with another nearby transmitter ( Sandy Heath? ).
 

grahamlthompson

In memoriam
Sometimes ( like now, for example ) high atmospheric pressure causes VHF & UHF signals to travel further than normal. You could be getting foreign interference.

Much more likely is a UK analogue or digital transmitter using the same uhf channel. To the OP try tuning the HD channel UHF channel using manual tune on both the analogue and freeview tuners in the TV.
 

gunjin

Active Member
Much more likely is a UK analogue or digital transmitter using the same uhf channel. To the OP try tuning the HD channel UHF channel using manual tune on both the analogue and freeview tuners in the TV.

I am not using the TV's freeview and have only an HDMI feed from the Bush HD Freeview tuner to the TV. I have tried to do a manual tune of the Bush box to no effect as all it allows me to do is select channel 31 and do a search for stations broadcast on it. It finds all three HD channels but does not allow any further adjustment or searching.

The problem with this route is it still leaves the question as to why it suddenly stops working after over a week of flawless HD reception unanswered?
 

gunjin

Active Member
BTW, thanks everyone for your helpful suggestions. Still not solved yet but do keep the ideas coming!

one quick question, does a shared aerial present potential ch31 disruption problems?
 

Colin London

Well-known Member
Quite possibly.

Depends on the size & complexity of the system. If it's a small system it may be a simple divide and amplify system. This may be OK if the signal coming into the system is high, but if it is marginal then the noise introduced by the amplifier may mean that the S/N (Signal to Noise) ratio becomes too small for the decoder to overcome.

Does your box give stats such as S/N ratio and error rate?

If it's a large system then it's likely to be channelised, with the incoming signals being filtered, amplified & transposed onto different channels before being piped around the building. These systems would require to be set up especially to distribute the temporary HD MUX, and this is very unlikely for the short period before DSO in 2012 in London. If you use one of these systems then it is very unlikely to allow you to watch HD until 2012 - if you do get a signal it will just be pick-up from the long runs of coax and will be very unreliable.
 

raydawson

Active Member
If this is the Bush from Argos you can check the signal strength and quality by going to the Manual tuning page and entering the channel number in the box - channel 31 in your case. After a few seconds it will tell you the signal strength. Compare it with the SD channels, although they will always give a better reading as the transmitter is on full power for them and reduced power for HD.

I have one and I'm a lot further away from CP than you are - west London in fact - and I get a good signal.

Cheers,

Ray D
 

gunjin

Active Member
If this is the Bush from Argos you can check the signal strength and quality by going to the Manual tuning page and entering the channel number in the box - channel 31 in your case. After a few seconds it will tell you the signal strength. Compare it with the SD channels, although they will always give a better reading as the transmitter is on full power for them and reduced power for HD.

I have one and I'm a lot further away from CP than you are - west London in fact - and I get a good signal.

Cheers,

Ray D

Yup, that is what i have been using to isolate the cause down to signal problems. Until Tuesday it was perfect, thereafter the signal is either "None" or "poor". It occasionally leaps to "very good" but this does not last more than a second or so. Today is overcast but i still have no HD reception so i am beginning to rule out atmospheric interference. i will soon be left with just Gremlins to blame :(

Has anyone returned one of these for a refund? since i cannot get HD, this box is useless to me but the receipt says no returns are allowed...
 

grahamlthompson

In memoriam
I am not using the TV's freeview and have only an HDMI feed from the Bush HD Freeview tuner to the TV. I have tried to do a manual tune of the Bush box to no effect as all it allows me to do is select channel 31 and do a search for stations broadcast on it. It finds all three HD channels but does not allow any further adjustment or searching.

The problem with this route is it still leaves the question as to why it suddenly stops working after over a week of flawless HD reception unanswered?

Whether you use the freeview tuner in the TV is not relevant. If the atmospheric conditions are causing multiple transmitter reception it's the signal from your aerial that's affected. Did you try looking for a signal on uhf 31 with a SD analogue and a SD digital tuner ?
 

SirPeter

Standard Member
I would bring around an aerial man to look at your wiring and your direction. One problem I have seen is boxes picking up the wrong transmitter. That can result in break up or no pictures. However it is not uniform across the range of channels. BBC1 can crack up - but the others are fine. Digital signals can look perfect on a very weak signal - but drop just a few percent points (which can be caused by the weather) then you get nothing!

(It is not like analogue where problems give ghosting.)

Your Mr Aerial will test all your equipment and wiring and you will be sure to be getting the 100 percent best system. If it hasn't been done recently it is a wise investment anyway.
 

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