Question Lost SD & HD reception Sandy Heath transmitter

mrNobby

Novice Member
Lost SD & HD reception Sandy Heath transmitter

Hi

Since around Monday 3rd July have lost muxes 21 32 34. Strangely these are the ones that carry all HD channels from Sandy Heath but the SD channels on 32 and 34 are missing too - no signal at all.

Checked for planned works and only reduced signal since 10th July is reported. All other muxes are fine. Have checked aerial signal with meter and it is at max. Also tested with set top aerial on several TVs and recorders and get the same results.

Any ideas??
 

Rodders53

Distinguished Member
Sandy is fully duplicated transmitter kit at the bottom, two line feeds in, main and reserve transmit antennas. Should have two electricity mains in feeds too (though they did join to one a good distance from site at one time in the past) and have backup auto start generators.

Thus, extremely likely to be off on any mux (particularly the BBC ones). Even during maintenance it will remain on at almost the same power and coverage. (Reserve antenna being lower on mast doesn't go quite as far, so if used may account for the 'reduced power's planned work.)

Not at home atm or could check to 100% confirm it is ok.

21 is BBC B DVB-T2 mux inc ITV,C4, C5 HD channels
32 is COM 7 also a -T2 mux mostly HD but some SD chsnnels
34 is COM 8 again a -T2 mux
This suggests an issue with the DVB-T2 bit of the tuning side on your kit?

Some receivers (Humax HDR-FOX-T2 for example) require the mode (DVB-T / DVB-T2) to be selected when manual tuning otherwise it doesn't recognise the signal. Might this be the problem?
 

mrNobby

Novice Member
@A1944 Unfortunately too late, only realised this was a silly thing to do after reading other threads on here.

@Rodders53 I have been struggling with this for about a week now. My setups all exhibit the same symptoms:

Panasonic DVB-T TV
MythTV on Gentoo DVB-T2 PC
MythTV on Gentoo DVB-T PC (This one hasn't been retuned)

So are you saying that the DVB-T tuners cannot pick up SD channels on the DVB-T2 muxes? If so would that point at the DVB-T2 tuner being the problem?
 

TJT1

Distinguished Member
What, all three receivers break on T2 simultaneously? I'm not that much of a believer in coincidences like that.
You have lost 2 SD and 3 HD mpxs on three different T/T2 tuners. (Not left with many then) and all three were working 'till Monday last? Surely there must be something wrong with your aerial setup then. Got an amp that perhaps isn't working?

If you manually tune a Humax HDR T2, you have to do two passes, one on T and the other on T2. Auto tune 'just works' and gets T & T2 in 'one hit'.
 

mrNobby

Novice Member
Only one of the MythTV boxes is capable of DVB-T2 and it can tune for everything in one go. It and the TV are on the main aerial and the other MythTV box is on a set top aerial. I even bought a 800GHz filter as a new mast went up nearby about a week before this happened.
 

grahamlthompson

In memoriam
@A1944 Unfortunately too late, only realised this was a silly thing to do after reading other threads on here.

@Rodders53 I have been struggling with this for about a week now. My setups all exhibit the same symptoms:

Panasonic DVB-T TV
MythTV on Gentoo DVB-T2 PC
MythTV on Gentoo DVB-T PC (This one hasn't been retuned)

So are you saying that the DVB-T tuners cannot pick up SD channels on the DVB-T2 muxes? If so would that point at the DVB-T2 tuner being the problem?

The modulation mode applies to the mux. To tune a DVB-T2 mux requires a DVB-T2 tuner. The fact that it may contain SD and HD channels is not relevant in any way to tuning the mux and the channels it has. In the not too distant future all Freeview-mux will be DVB-T2.

Surely everything points to a issue with your aerial. Water in the coax and corroded connections due to waterproofing failure would be a good place to start.

Quality is what you should be looking at not signal strength.
 

Rodders53

Distinguished Member
Location may be relevant? Whereabouts are you receiving Sandy from? Set top aerial reception would suggest fairly strong signal, but that one is -T not -T2.

Model of panny TV?.. DVB-T suggests old SD only tuner set (albeit a HD ready display)? or is it -T2?

How is aerial split to the two receivers (TV and Myth)? Try aerial direct to one at a time and a manual tune of the affected mixes? COM 7/8 are only -6dB c.f. 21 which is sometimes at an aerial gain curve droop spot, but would suggest aerial system very borderline if that is the issue. Water in the aerial connection box and or downlead may be an issue... Binoculars or telephoto lens might help spot any such damage? Remake all/any suspect TV plugs and sockets.

Does the aerial point through trees that have grown up and are in full leaf now? Is there any scaffolding or other building works that are now obscuring plain line of sight to the transmitter?

4G affects ch 59 & 60 unless amplifiers get swamped and overload. AT800 leaflet affected locations and supply filters for free. Most unlikely to be issue imo.
 

mrNobby

Novice Member
Many thanks for your suggestions. I'm slightly embarrassed to report that it's nothing to do with the signal (It's a loft aerial so everything is dry). Once I realised that the SD channels in the DVB-T2 muxes could only be tuned by DVB-T2 equipment (it now makes sense when I think about it), I knew the fault must be with the DVB-T2 tuner in the MythTV box.

Turned out to be some corruption in the backend database so MythTV thought it had access to 8 tuners when in fact there are only 2. Somehow that stopped the DVB-T2 channels being tuned. Once I found which one it should have been set to everything was fine. I now have to work out how to delete the 6 bad ones...

Thanks once again for all your responses and ideas.
 

TJT1

Distinguished Member
Good end result though.
 

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