Your MER improvement shows that the sigal quality has improved massively at your location. My C/N figures show that the signal quality has barely changed at my location despite the large signal strength increase.

I would say you have gone from good reception to very good reception.

I have 0 BER reported on the 16QAM and BBCA muxes, and a few percent on SDN and D3+4.

I suspect you are reading too much into the SNR values, the box probably can't measure any better than 25dB and so reports that. As long as the BER is 0 dont worry.

From what I understand a C/N measurement takes a level measurement (Usually the centre frequency of the mux) "C" and a noise measurement (could be anywhere in the UHF band - A 'good' noise measurement is near the mux) "N".

It makes no difference whether it is 16QAM, 64QAM or 256QAM - You are not measuring the quality of the signal. It is just a guide to let you know if there is noise (somewhere!). I wouldn't worry too much about it.

The C/N ratio is the only useful measure of signal quality I've got, since my PVRs either don't report signal quality at all or just report 100% all the time. I've never watched TV with the Nokia 221T (no EPG, locks up randomly on remote control button presses, not a PVR), I just use it as a signal measurement device.

I've seen the Nokia 221T report 26 or 27db C/N ratio at my Aunt and my brother's locations (both from Emley Moor years ago when I first set them up). My brother has the opposite problem, so much signal strength 3 miles from Emley Moor through a wood of mature trees that he gets horrible multiple ghosts on analogue. That's where I observered clipping on analogue when I tried a 23db distribution amp, the ghosts are caused by reception direct into the crap "low loss" coax getting through the rubbish screening. The least worst compromise was a tall mast with a Televes DAT 75 plus MRD (12db integral mast head amp) and then passive split distribution, this got as much aerial signal in as possible to increase it's level compared to the reception through the walls and into the crappy coax. I know it was the crappy coax because one room was wired on new CT100 my brother put in and it had almost no ghosting. But I digress...

That's interesting, and might answer something I was wondering about.

On my Sony DVD recorder after I retuned yesterday, I was having a nose at the signal quality meter. On the new post-DSO mux 1 it was reading 95%. "That's odd," I thought, "the TV connected off the loop-through is reporting 100% for both strength and quality on all muxes."

I checked the old muxes and they were lower but only by 1 or 2%. From this can I assume the DVD recorder is showing pre-correction signal quality, and the TV is showing quality after the first round of correction?

Well, it means the DVD recorder is measuring something in a different way. If you're really unlucky it is measuring the strength and quoting that as signal quality, I've seen that done before.Or it might be that some of your devices are using bit error rate (BER) as a measure of quality and others are using C/N ratio or MER (Modulation Error Ratio) or who knows what. Or maybe the signal is simply degraded by the time it reaches the DVD recorder, have you tried connecting the different devices to the same cable to eliminate that?

Unless manfucturers clealy state what they are measuring, all these 0 to 100% strength and quality bars really mean is "better" and "worse" which can help you align your aerial or identify bad unscreened cables. 40% on my box might be better than 60% on your box, there is no way to tell if they are different models and we don't know what exactly they're measuring. There doesn't appear to be any degree of standardisation on this.

Yes, I am very familiar with that but I think you are wrong about the 'quality' being after the first error correction. If that were the case then any box below 100% would be showing picture defects all the time and that simply isn't the case. I have seen boxes with a very stable and clean picture that routinely show 80% or less quality. Obviously they are prone to breakup at the slightest thing but they are generally watchable.

The nature of the digital signal (QAM in this case) means that noise is filtered out as the signal is digitised so the first level of error correction would only kick in for large spikes of noise and once that starts to happen it does not take much before it breaks up completely hence the term 'digital cliff edge'. So 100% does not mean an exact copy of the analogue waveform (which would be impossible) but an exact copy of the digital signal before correction which is very possible, indeed, normal.

As a result the real problem is that any assessment of quality is pretty meaningless unless it is done at the analoge level before digitising and most tuners do not provide that kind of information let alone pass it on to end users via STB software.

I've finally connected my Sony TV to my aerial chain and discovered that it's signal diagnostics screen shows the bit error rate both Pre-Viterbi (ie. before error correction) and Post-Viterbi. It shows the instantaneous values of both and also a 5 second rolling average of both. All of my muxes have Post-Viterbi of 0e0, three of them (not the 8K mux oddly!) show 0e0 Pre-Viterbi as well and the rest are around 4.0e-4 which doesn't seem too bad. Having scored points for this, my TV then fails miserably for its diagnostics on all other counts in that it doesn't show what UHF channel it is on and just shows a full width green bar for all six muxes without even saying what it means (is this quality or signal strength?).

What I'm saying is that unless the manufacturers tell us, we don't know if Quality is before or after Viterbi or even if it is bit error rate or something else (C/N ratio, MER, signal strength etc). My Pace Twin says that the DSO 8K mux is 100% signal strength, my Humax HDR Fox T2 says the same mux is 85% signal strength. They can't both be right if they're measuring the same thing, so clearly they're measuring it differently or at least applying a different scale. It's a relative indication of strength or quality, which can't be compared to anything usefully except the figures from another box of the same model number (and even then you have to worry about variation between boxes).


I think we're basically agreeing. Insufficient information from the STBs, and lack of clarity about what it is they actually do show.

I think you are right

Fascinating about the Sony information, that could actually be useful but, at the end of the day, what you really need to know is how much headroom you have got before you are going to get errors and for that you really need the analogue S/N which is something that, usually, only an aerial installer us likely to get off a good signal analyser.

What you say about the strength readings is true, different boxes use different measures to get the strength. Most are measured after an initial automatic gain so there is no knowing how much noise there is and boosting the signal in those cases tends not to increase the displayed 'strength'. Also, the reading is not callibrated at all so even identical boxes on the same aerial can give different readings.

The only use for the strength reading is to compare between muxes, align aerials (with care and patience) and to notice changes over time or differences between two aerials (provided you use the same physical box not just another of the same type).

Hi


BBC Red Button will work correctly if you do it again excluding RF 67.

Mux B on RF 67 duplicates several stations which are now included within Mux PSB1 on RF 27.

Regards

Provisional timetable for the completion of switchover at Sudbury and its relays:

Stage 1: 6th July


Stage 2: 20 July 2011


http://www.digitaluk.co.uk/transmitt...groups/sudbury

Rouncefall is a Single Frequency Network (SFN) relay of Sudbury's PSB multiplexes (BBC-A, D3&4 and BBC-B/HD).

Witham self help relay has obtained a licence to enable it to continue into the post-switchover era.

I visited Bletchly park yesterday & on my way back, I paid a visit to the Sandy heath TX site - looks like they have been busy, there is a huge new large backup generator - never had backup before! New building, I guess to house the new digital TXs ? & of course, the new aerial system - on top of the mast!

In the field surrounding the fenced off TX, there are signs that it is being used as a motor bike scramble area, & Rabbits everywhere!
Bob

Sandy TX's being turned off by Aquiva - youtube vids:

http://www.youtube.com/watch?v=pJnGOPq3qMQ

http://www.youtube.com/user/stevethe.../0/UFdUZwF5or8

Since stage 1 of the switchover last week, the BBC channels on the new mux are slightly pixellated. The signal strength is stronger than it was pre switchover, but there is a constant error bit level. We weren't getting this before. Could it be to do with the number of channels on the new mux?

More likely you are getting too much signal - or a reflection, are you fairly close to Sandy heath?

Due to a slight "lift" last night, I was able to load the new Sandy Heath BBC A (UHF 27) on my Humax F2FOX-T and Sony TV. Not bad from this distance. Remaining analogues from SH were very grainy, and no Channel 5 on UHF 39.

Chris.

we're just under 30 miles away. The signal strength is about 60 according to my TV whereas it was around 40 before. There are no consoles or DVD players plugged in and the other mixes are fine as before. What is a reflection?

By reflection, I am refering to what in analogue language was called Ghosting - usually caused by nearby buildings reflecting the signal, which is delayed. In analogue, you get a fainter image to the right of the main image. If a digital signal is affected by this problem, it may result in the problem you have. I am about 30 miles east from Sandy heath myself & the change has much improved the signal & reception. It was prone to breakup if a motor cycle went by etc!
Are you using a pre-amp at all?

No, there's no pre-amp or anything else between the aerial and tv. We do have several large trees around us though so I wonder if this is causing the problem.

Not too many leaves on them yet though?

No, there's not been much difference in foliage since it started.

But if you are a Sky Sports Subscriber, you will lose your Pay TV channels without UHF67.

I'm getting pre Viterbi errors on the new BBC mux, whereas three of the much weaker pre DSO muxes report pre Viterbi error rates of 0e0. This is not encouraging.

Interesting.

By box does not report this detail but I am getting stronger 'signal' than before. We are about 30 miles SE of Sandy and had rock solid reception of the old Mux 1. Since stage 1 I have noticed occasional glitches in the signal on PSB 1 which I have put down to tinkering at the Tx but if you are seeing constant error correction then maybe that is what is causing our glicthes.

I have seen these glitches on our 3view PVR and on the internal tuner of a cheap LCD set we have upstairs.

I'm still hoping this will all go away after stage 2 but it could get worse if all the muxes start having similar problems.

I guess it could be an issue with our wideband aerial trying to tune down in band A where it has never been used for that before. If that is the case then everything will go bad as all the muxes move and we will need another new aerial Seems unlikely though as it is still pulling in a strong sigal, just a bit noisey.

I've said this before. People that got themselves good digital are now being penalised due to Sandy Heath PSB muxes moving to Group A.