Loss of HD

[eshjim]

Hi,
This is my first post here and hoping someone can point me in the right direction. I have owned my box now for about 6 months without problems. Less than a week ago, the HD channels started pixellating a little. This gradually increased until now they are not showing at all. I confirmed with digitaluk that I am tuned to the correct transmitter - Pontop Pike in Durham (HD channel 63). Upon manual retune, the HD channels all show 0% signal strength and quality. All SD channels are fine. Digitaluk state there are no current issues at Pontop Pike and that the problem must be receiver-related. The box is linked to the TV by HDMI and as I say, the HD has been flawless until now. Hoping someone may have some suggestions.

Jim

 

[MartinLiddle]

Upon manual retune, the HD channels all show 0% signal strength and quality. All SD channels are fine. Digitaluk state there are no current issues at Pontop Pike and that the problem must be receiver-related.

Have you checked the aerial cabling for any signs of water getting in or other damage?

 

[Sam Widges]

Martin's right - Channel 63 is to the top of the band and, if you haven't got a wideband antenna and good quality cabling, it will be one of the first to suffer in the event of problems.

Other things to check for are a tree that's growing up between you and the transmitter or a wireless USB dongle near the Hummy as that can interfere with specific channels. The first needs a chainsaw to cure but the second is simpler to fix by using a USB extension lead to move the dongle away from the box and other cabling.

 

[eshjim]

Thanks Martin & Sam. There is no apparent aerial damage. Pontop Pike is a good few miles from me, but there are certainly no nearby trees that have sprung up. I understand that Pontop Pike's SD and HD transmissions are both at the same strength, but my SD quality is unchanged. I have, however, had a brainwave! I'm sure my Samsung TV has inbuilt Freeview and of course is HD-ready, so if I plug my aerial directly into the TV and tune it in, if the HD channels are captured, the box is faulty. I will let you know when I have had time to try that.

 

[ChrisDaniels]

That method will only work if the tv is capable of receiving Freeview HD otherwise they won't show at all.

 

[raydon]

Thanks Martin & Sam. There is no apparent aerial damage. Pontop Pike is a good few miles from me, but there are certainly no nearby trees that have sprung up. I understand that Pontop Pike's SD and HD transmissions are both at the same strength, but my SD quality is unchanged. I have, however, had a brainwave! I'm sure my Samsung TV has inbuilt Freeview and of course is HD-ready, so if I plug my aerial directly into the TV and tune it in, if the HD channels are captured, the box is faulty. I will let you know when I have had time to try that.

Pontop Pike HD transmissions are only at 10% full strength till DSO in 2012 so you'll need a really good aerial before then. And HD ready doesn't mean it has an HD tuner. Some Sammy's do but you'd need to check to be certain.

 

[eshjim]

Of course, you're right, and I don't think it has an HD tuner. What I don't understand, though, is why HD reception was perfectly possible up until a few days ago. That means I must have a suitable aerial - signal strength and quality showed the same for both HD and SD. In the absence of any tweaks that may be possible to the box itself, I think I will just put up with SD until 2012. If it doesn't work then the Hummy must have packed up after just 6 months so I will be looking around for an alternative.

 

[Black Hole]

That is the down-side to digital signals. With analogue reception, if the signal degrades a little due to weather or whatever, the picture just gets a bit noisier. With digital, the picture is perfect until the bits are no longer above the noise margin, and then it falls off a cliff. If you were on the edge before, you only needed a very small change in propogation conditions to get practically nothing now.

I've got a problem with ITV4.

 

[Kev_w]

I had the same problem. HD channels deteriated over a couple of weeks then disapeared. I had a mains signal booster handy and plugged it in and all is well. Plugging in the signal booster also gained me itv4 which I didn't even know existed! My HD is broadcast from winter hill (manchester) so doubt there is a direct link - funny that they degraded around the same time though...

 

[gomezz]

With digital, the picture is perfect until the bits are no longer above the noise margin, and then it falls off a cliff

There is a narrow ledge just below the cliff-edge where the error correction system will try manfully to keep serving up a half-watchable picture. But it is very narrow.

 

[eshjim]

Just thought I would update you on this. After above posts, just gave up and watched in SD. Today gave it another go - at first, still nothing on HD, then noticed that the HD channels were all set to Transmission Type DVB-T. Changed this to DVB-T2 and they're all back - signal strength 24%, quality 100%! Should the HD channels always be set to DVB-T2? If so, I cannot understand how they got changed, as my HD reception was originally spot on and I certainly did not change the settings. Anyway, wonder how long it lasts this time!!

 

[Black Hole]

DVB-T2 is correct for UK Freeview HD.

 

[Owen Smith]

Just thought I would update you on this. After above posts, just gave up and watched in SD. Today gave it another go - at first, still nothing on HD, then noticed that the HD channels were all set to Transmission Type DVB-T. Changed this to DVB-T2 and they're all back - signal strength 24%, quality 100%! Should the HD channels always be set to DVB-T2? If so, I cannot understand how they got changed, as my HD reception was originally spot on and I certainly did not change the settings. Anyway, wonder how long it lasts this time!!

Signal strength 24% is very low (and would benefit from a mast head amp), so I wouldn't be surprised if you lose HD again. Signal quality 100% seems to be meaningless on the HDR Fox T2, I've never seen anyone quote a figure other than 100%. I think it means post-Viterbi ie. after error correction, which is pointless. Once the errors become uncorrectable the picture will rapidly become unwatchable, so as soon as the quality drops below 100% you'll know about it anyway as you have blocks all over the screen. The quality measurement should be pre-viterbi so that it means something ie. you can tell how good or bad the signal really is even when you have a perfect picture (due to error correction).