Loss of HD

E

eshjim

New Member
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 :confused:
 
eshjim said:
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.
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Have you checked the aerial cabling for any signs of water getting in or other damage?
 
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.
 
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.
 
eshjim said:
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.
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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.
 
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.
 
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.
 
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...
 
Black Hole said:
With digital, the picture is perfect until the bits are no longer above the noise margin, and then it falls off a cliff
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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.
 
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!!
 
eshjim said:
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!!
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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).
 
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