Channels not found - 64 QAM MUXes

[Simon]

Have tried to manually tune the two channels which changed on the Mendip transmitter on the 11th but the Humax says no channels found and signal quality is low. My Panasonic TV which is fed from the aerial output of the Humax has retuned all channels with a 70% signal strength. Is the Humax tuner not very sensitive or is it something to do with the fact that the modulation of these two channels is 64QAM whereas the other SD channels on Mendip are 16QAM? Also a Samsung TV in the house receives all the channels after the retune so signal strength must be acceptable.

I believe that if I do an automatic retune it will lose my recording schedules, am I correct?

 

[Simon]

Have tried to manually tune the two channels which changed on the Mendip transmitter on the 11th but the Humax says no channels found and signal quality is low. My Panasonic TV which is fed from the aerial output of the Humax has retuned all channels with a 70% signal strength. Is the Humax tuner not very sensitive or is it something to do with the fact that the modulation of these two channels is 64QAM whereas the other SD channels on Mendip are 16QAM? Also a Samsung TV in the house receives all the channels after the retune so signal strength must be acceptable.

I believe that if I do an automatic retune it will lose my recording schedules, am I correct?

Just to update, I also tried clearing the programme list and both automatic and manual tunes but still no luck. I guess that if its down to the tuner in the Humax needing a stronger signal that my other TVs then there isn't much that can be done... but annoying nonetheless.

 

[bixieupnorth]

yr right about the recording schedules going, high up many peoples wishlists in next firmware update i think??

dont know what to suggest about the missing channels tho, if you've already done auto and manual tunes, you could try pulling the aerial out, rescanning then replacing and doing it again, not sure why but seems to solve many problems??

 

[Simon]

I will try the scan with no aerial then rescan routine. But if its due to lack of sensitivity of the Humax will this help? What I don't understand is why the signal sterbgth/qhality is so much worse than the other TVs. Is the tuner of the Humax so much worse... which would surprise me considering how good in so many ways the PVR is.

 

[bixieupnorth]

always found humax tuners to be excellent, not sure why yr having this problem but not with yr other gadgets, is the aerial straight into the hummy?

 

[Simon]

Aerial is fed around house through a distribution amp. One feed goes into the Humax and then into the Panasonic TV which is receiving all channels despite being second in the chain, so I know the signal getting to the Humax "should" be adequate. Also the Humax was fine until they messed with the channels on Mendip transmitter.

 

[parish]

I think there is something screwy on Mendip since the 11th Jan mux changes.

When I re-tuned my Sony TV and Hummy, the TV re-tuned correctly, but the Hummy found loads of duplicate channels (BBC1-4 and a few others) which it put in the 800 range. This has never happened before (and the TV didn't do it) and Mendip is the only transmitter I can "see".

Using the channel list in this Arqiva document - http://www.arqiva.com/corporate/pre...-29 - Re-tune required for Mendip viewers.pdf - I tried manually scanning the 6 channels listed, but two of them (can't remember which two, but I'm sure ch58 - BBC B - was one) had no programme channels; all the HD channels were missing and quite a few more.

Mendip tuning information
After 2 pm on 11 January the UHF channel numbers for manual tuning of the six digital TV multiplexes will be:
BBC A (PSB1) ch61 SDN (COM4) ch62
D3&4 (PSB2) ch54 Arqiva A (COM5) ch56
BBC B (PSB3) ch58 Arqiva B (COM6) ch67 (was ch59)

 

[Simon]

I tried bixieipnorth's sugestion of a re-tune with no aerial to clear and then tuning again, but again the scannels were missing.

Whilst I agree with parish that arqiva may possibly have done something is it odd that non Humax equipment is not affected. As these channels are now transmitting on low power I go back to assuming the Humax does not have a tuner which copes with these lower signals. Can they improve this in a firmware update?

 

[Simon]

Another observation:

Channel 56 is lower signal strength than the missing Channels (62 and 67) but has high quality. Now this is 16QAM modulation whereas C62 and C67 are 64QAM modulation. I don't understand the technicalities but is it that the Humax tuner is bad at demodulating 64QAM signals?

 

[MartinLiddle]

Channel 56 is lower signal strength than the missing Channels (62 and 67) but has high quality. Now this is 16QAM modulation whereas C62 and C67 are 64QAM modulation. I don't understand the technicalities but is it that the Humax tuner is bad at demodulating 64QAM signals?

Not that anybody has previously reported. I suggest ringing up Humax and discussing the problem with them emphasising what you have done so far; it might be a transmitter problem and Humax probably have enough influence to get it investigated.

 

[parish]

One odd thing I noticed when I re-tuned that I hadn't noticed before is that the Hummy scanned all the channels twice. It got to ch69 then started again at 21 and went all the way through to 69.

When I tried re-tuning a second time I paid more attention and it founf more channels on the second pass. These, presumably, were the duplicates that it put in the 800 range.

Anyone else notice this?

 

[Simon]

I have an email to Humax earlier and await their reply.

But... if the signal is received OK by two other tuners in TVs then it is unlikely to be a transmitter problem. It is not true that no-one has reported it, it sounds to me that parishes problem is the same, and someone on another forum had the same issue. I would suggest it is only affecting those of us in outlying areas with Humax equipment... not exactly a larege group, but still an annoyance nevertheless.

 

[parish]

On Mendip we needed 3 re-tunes:

1. When analogue was turned off
2. When BBC One HD came on air
3. When the COM6 mux moved from ch59 to 67

My understanding is that after the first two at least one mux (possibly more than one) would be transmitting at reduced power to prevent interference with transmitters in adjacent areas which were still transmitting analogue. For me, the mux that includes ITV3 has always had a much lower signal strength than the others.

This final re-tune was, IIRC, to move everything to its final channel location when these adjacent transmitters had analogue turned off. This would also mean that all the muxes on Mendip could now be run at full power, but this doesn't seem to be the case as ITV3 still has a low signal strength.

 

[Simon]

... and we have more to come!

on 28 September:

Mux A/SDN will move from Ch 62 to Ch 48
Mux D/Arq B will move from Ch 67 to Ch 52
Mux C/Arq A will remain on Ch 56 but modulation will change from 16QAM to 64QAM - I hope this doesn't mean I lose these on the Humax!!

I believe that power should increase slightly on this date and then again to its final full power in 2012 but without any further channel changes. As you say we were led to believe it was a much simpler process, I guess they didn't want to admit at the start it would be caussing so many problems!!

 

[Simon]

One odd thing I noticed when I re-tuned that I hadn't noticed before is that the Hummy scanned all the channels twice. It got to ch69 then started again at 21 and went all the way through to 69.

When I tried re-tuning a second time I paid more attention and it founf more channels on the second pass. These, presumably, were the duplicates that it put in the 800 range.

Anyone else notice this?

I think you will find the first pass is SD channels (DVB-T) and the second pass is HD channels (DVB-T2), so only channels on the second pass should be the four HD channels.

 

[parish]

Thanks for that useful info Simon - I thought it was all over, guess not!!

Although I'm sure it found more than 4 on the second pass - guess that as well as the 4 HD channels it re-found some of the SD ones which it put in the 800 range?

 

[Simon]

It is now, its four!!!

I understand that anything that's put in the 800 range is from a neighbouring transmitter. I don't have that problem as I'm the other side of the region in the downs. So although "its four" on the HD Mux it is conceivable that you could pick up another four from the neighbouring transmitter. Channels for Mendip are 54, 56, 58, 61, 62 and 67 so I would think you will find the TV channels in the 800 range are other channels (if I haven't confused you by the use of channels in two contexts!).

 

[Simon]

Not that anybody has previously reported. I suggest ringing up Humax and discussing the problem with them emphasising what you have done so far; it might be a transmitter problem and Humax probably have enough influence to get it investigated.

Humax's response when I called them (no reply to my email) was that I can't expect to receive a signal in my location! The other TVs without a problem must have a more sensitive tuner or signal booster according to them, but as there's no problem with the Humax tuner there is nothing they can do. I explained all I have discussed on here but was basically told that its purely down to signal strength... thanks a lot!

 

[parish]

I understand that anything that's put in the 800 range is from a neighbouring transmitter.

So do I, but AFAIK I can't pick up anything from another transmitter - I'm in BA14 8 postcode.

My TV doesn't have duplicates in the 800 range, my 9200 didn't, and my HDR-FoxT2 didn't use to.

Humax's response when I called them (no reply to my email) was that I can't expect to receive a signal in my location! The other TVs without a problem must have a more sensitive tuner or signal booster according to them, but as there's no problem with the Humax tuner there is nothing they can do. I explained all I have discussed on here but was basically told that its purely down to signal strength... thanks a lot!

Hmm, how do they determine that? If it's from your postcode then take it with a pinch of salt.

When I moved into my previous house (in 1995), the DTT postcode checker said I couldn't get Freeview - and would never be able to. Based on this I got Sky (never again!!!). A few years later I found out that loads of people in the village had Freeview (although it needed a high-gain 18-element ariel to get a decent signal). Investigating, I discovered that all the houses in the village had postcodes where the second part was 9Nx but mine - and all houses built after - had 9Qx. Seems that they'd used all the 9N ones so went to 9Q. Unfortunately, 9Q "belonged" to a nearby town so the postcode checkers thought the geographic centre of the 9Q postcodes was 3 miles away, on the other side of a hill which blocked signals from Mendip!!!

 

[Simon]

Hmm, how do they determine that? If it's from your postcode then take it with a pinch of salt.

When I moved into my previous house (in 1995), the DTT postcode checker said I couldn't get Freeview - and would never be able to. Based on this I got Sky (never again!!!). A few years later I found out that loads of people in the village had Freeview (although it needed a high-gain 18-element ariel to get a decent signal). Investigating, I discovered that all the houses in the village had postcodes where the second part was 9Nx but mine - and all houses built after - had 9Qx. Seems that they'd used all the 9N ones so went to 9Q. Unfortunately, 9Q "belonged" to a nearby town so the postcode checkers thought the geographic centre of the 9Q postcodes was 3 miles away, on the other side of a hill which blocked signals from Mendip!!!

Yes, you are right it was the postcode checker so I pointed out that was just a "prediction" and said that if knew the terrain here even the house next door could be a few feet difference in elevation and line of sight. He just repeated that it was not a faulty box so I suggested that although not faulty it could be a design issue, particularly with the tuner's ability to cope with 64QAM modulated signals? I then highlighted how if we wanted to be pedantic about the signals that I receive then DTT suggest I shouldn't get as good a signal on C56 as C67, but in fact it is fine. This comment did not go down well and I ended up with one very stroppy customer service guy!!!