BBC4 Freeview Panasonic DMR-BWT735 AutoTune

MarBinz

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I tried to record a BBC4 HD program a week or so ago by setting it up from the program guide. In the Prog Check page the following day it showed that it had not been able to record it. A little annoying, its the first time a timer recording has not worked. I thought no more about it.
Switching on the unit yesterday, and it flagged the message 'new channels found, do you want to retune?' (or words to that effect).
I always do when this pops up. Needless to say, I have now lost BBC4 HD completely from the program guide. The odd thing is, that it must have been found last time it told me there was an updated channel list which was not that long ago!

I have read various things in threads on the BBC moving some channels to 'com7' or something, but included other hd channels which I think I still have - not sure... but some of those threads are from some years ago!

Any ideas on how I get BBC4 HD back? (it was annoying enough loosing BBC3, considering we pay a licence fee to get these channels!)

The tuning info is 'Oxon & Bucks'

I did check to see if there was a s/w update, as it had also been mentioned about not being able to receive more than one multiplex or something at a time on one forum. But there was no update available; present version is 1v30.

There has been no change to cabling etc since the previous autotune which I think was in the last month or so?

I do not have a favourites list set up either.

Any advice on why it disappeared after autotune last night, and how to get it back would be appreciated.
 
It seems likely that you are receiving from the Oxford transmitter. A few checks should confirm it, and it will be useful to know.
Note that BBC 4 SD is on a different multiplex, the same as BBC1, so you should be able to record that until you get the problem sorted out.

Your aerial elements should be horizontal. If vertical you will be receiving from a relay somewhere else.
If you have a look in the tuning menu and see which RF channel you receive BBC1.
If Oxford, it should be Channel 53.

Whilst you are in there, check the signal strength and report it back here.


Have a look at the details for Oxford transmitter here.
See down the left hand side of the 'Which Freeview channels does the Oxford transmitter broadcast?' box and look for multiplex Com 7 which is where BBC4 HD resides.
If you do not have BBC4HD you will have none of those other channels from Com7.

Have a look at the channels on Com 8. Do you receive any of those?
If so choose one and check its signal strength ( The signal strength will be the same for all channels on the same multiplex.)

My suspicion is that these two mutiplexes are right up the waveband on RF channels 37 (com 8) and 31 (com7) where your aerials reception response will be tailing off.

The relative signal strengths you get may or may not confirm that.
 
Hi Gavtech,

Not sure on the aerial elements, I'll have to get into the loft to check that... `¬)
BBC1 Oxford is '1' and on ch53; signal strength is a bar 0-10 and shows as about 6or7; Quality=10 bit err = 0
BBC1 HD is '101' and on ch57 and strength etc as above.
Interesting that checking the 'com7' entries, they are missing except for '71' CBS Drama, but that says its ch55 with the same strength etc as above. all other entries on com7 are missing though.
'com8' entries I have them all on ch37; strength=4 quality=5 bit err=0
It does look as though I've lost the com7 entries, I wondered if I had more than just BBC4 HD missing! They were there the other day... I know I also had ch4+1HD, as I have some past recordings from it.
It does look as if they are tailing off as we get towards ch37.
Any thoughts on why they may have dropped off my auto-tune last night? (and can they be recovered?)

Thanks,
Martin
 
I think you need to get the general signal strength up.
The strength seems only moderate in the 'sweet spot' around the BBC one mux.. and evidently has fallen below the reception threshold at the edge of the band.

It is impossible to know what your received signal strength would normally be - and why it has seemingly changed now. As your aerial is in the loft, weather effects can probably be ruled out.
Unless the aerial or something else has moved in the loft, any problems are more likely to have occurred at ground level.

Whatever cabling arrangement you have at ground level you should try the most direct route from the aerial possible with the minimum number of joints - and with a meaty flylead if one has to be used - at least to try a retune.
If in any circumstances you can achieve a successful retune - DON'T retune therafter. If channels go missing again, they will return once you sort out whatever the reception problem is.

Check as much of the aerial installation as you can. All joints should be clean and well made. Try a different flylead if the connection comes from a wallplate.
 
As this is a general Freeview reception problem, I'll move the thread to the Freeview Section where more good advice is likely to be forthcoming.
 
ok, thanks GavTech. `¬) I will have a look in the loft to see if the mice have been busy! I take the cable direct from the socket downstairs directly to the back of the machine.
What sort of strength would you expect for the 'sweet spot' all being well? (the quality indicated is green and all the way at 10, only the strength seems to be 6 to 7)
Thanks for your help!
Martin
 
Really - I don't expect anything, but ideally you want a signal that is strong enough, but not so strong it is at risk of overloading which can also cause problems.

The strength meters on equipment are just a rough guide and they are not calibrated to any meaningful benchmark... but to avoid problems of lack of signal you might look to achieve a strength of 6 to 8 for the weakest mux.

You could also try manually tuning the missing com 7 on Channel 31.. which may permit you to monitor the signal strength for that multiplex and see if it improves with any changes you may make.
 
Gavtech has given good advice. Does the aerial only feed the one TV outlet, or is it split to feed many? (If so how?). Keep aerial leads and hdmi cables well apart. Do consider remaking any hand-made TV plugs; it's often the connections that are the cause of problems.

Location? How far from the mast at Beckley (aka Oxford) are you? (How strong is your signal likely to be?) The transmitter network is designed around the use of outside aerials at 10m above the ground. Loft aerials will be 6 to 10 dB down on one outside and higher.

How old is the aerial in loft? Oxford was a C/D analogue transmitter and most such aerials have little output at ch31 cf frequencies in the design band. Gain (curves), Again Do you get ThatsTV on lcn 7 (local tv for Oxford) as that is lowest power, -10dB, but on frequency ch 51?

Reception in lofts can be affected by things placed in loft. Or even a neighbouring loft. Relocating the aerial can sometimes help. Sometimes only a small adjustment is needed: higher/lower, crabbed left/right or fore/aft. However you need to check, having improved reception on frequency ch 31 by moving it, that reception on a different frequency has not been harmed! So check the meter for all 9 muxes from Oxford now, before moving the aerial!
 
One thing in this whole equation to take into account regarding any remedial actions taken to sort this problem, is the impending frequency changes coming to this transmitter in June 2018.

Judging by the frequencies involved it will require a change of aerial... either of a different group or of a wideband nature.
I've not looked into that - and I don't know what the recommendation is, or if it is feasible to future proof at this point.
It is just a surmise on my part.
 
I see that a group K aerial is recommended for the June 2018 changes.

At present Martin, you may have a group C/D aerial or a 'W' (Wideband) aerial.
I'm guessing it will be a C/D group aerial judging by the responses.
The new channels are all going to be located on the part of the band that you are already having problems receiving.

This may be useful for future planning.

Edit - I see the proposal is that in the 10% of homes which will require a new aerial when these changes come about ( the 700 MhZ band clearout) the aerial will be supplied and fitted free.
There's a surprise.
 
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I see that a group K aerial is recommended for the June 2018 changes.
As a K group covers 21 to 48 then it will be the post 700MHz clearance wideband. However, it is not a suitable choice for Oxford until that date. Should the OP (Martin)'s aerial needs replacing now.
Edit - I see the proposal is that in the 10% of homes which will require a new aerial when these changes come about ( the 700 MhZ band clearout) the aerial will be supplied and fitted free.
There's a surprise.
Yes especially as the the official line is DCMS has yet to decide... Digital UK | 700MHz clearance
Brandon B @ ukfree often makes erroneous statements (allegedly) ;)

It's IMHO likely there will be a repeat of the Digital Switchover Helpscheme for those deemed eligible (over 75, disabled etc.,.) and a contribution charge, again (waived for those on low income, as before).
 
@Gavtech; I will check the manual tuning as you suggest, to see how low that strength is compared to the ch37. My guess is it must be on the borderline not to be picked up be the autotune, when it was ok before; any idea what the cut-off level would be that makes the Panasonic autotune ignore it?
Nice to know I might get a free aerial in the future! `¬) - I assume there will be an 'announcement' or something so we know what is happening, rather than simply loosing reception and having to find out why! Even if as Rodders53 suggests it may not be totally free!
 
@Gavtech; I will check the manual tuning as you suggest, to see how low that strength is compared to the ch37. My guess is it must be on the borderline not to be picked up be the autotune, when it was ok before; any idea what the cut-off level would be that makes the Panasonic autotune ignore it?

I would expect anything below around 5 or 6 is likely to give you problems.
Signal strength varies all the time because of the vagaries of circumstances... so whereas you may be able to receive a stable signal at, say for example level 5, the natural variations in signal strength will at times probably drop below that level into more critical regions - The so called 'digital cliff' where reliable reception breaks down.

But as I said earlier, these are just rough guides. RF reception is extremely circumstantial and can be affected by all sorts of local conditions and potential interference sources.

Because of the constant strength variability, in cases of cusp reception like this, you can be just a likely to find that another retune will find lost multiplexes depending on receiving conditions at the time you happen to retune.

It is also worth checking the relative position of the HDMI cables before a retune, as Rodders mentioned, and / or trying with other HDMI cables, as these can markedly affect incoming incoming UHF.
 
@Rodders53; The aerial originally went through a splitter in the loft to the upstairs bedroom, but reception was so bad that I completely disconnected it when I moved in: there will be one connection I guess in the cable where I removed the splitter which was next to the aerial in the loft. The cable then comes down inside the wall to a standard socket into the living room, which is then chained through various equipment, BUT it goes into the Panasonic blu-ray recorder (the Freeview tuner being discussed) first. It is using a decent short cable to do that. I can try replacing it though.

The aerial is probably old, it was here when I moved in, which is over 10 years ago, BUT nothing has changed in the connection path since being able to get the BBC4HD on this tuner, (I may have just been lucky to get it on the previous re-tune?). There is nothing else in the loft. There is nothing in the way between me and the horizon, i.e. the house looks out to fields with no buildings opposite me.
I am in Ambrosden, just outside Bicester - not sure how far away that makes the transmitter?

I do have a reel of aerial cable somewhere, I will have to check and see how long it is, as I've probably got some new connectors to make up a new cable to go direct from the antenna to the Panasonic to see if that makes a difference - provided there is enough length left on the reel!

I guess there is not much that can go wrong with the aerial itself, its more likely to be cable / connectors? I guess there is not much point getting a new one, if it then needs replacing again next year...

If I get the chance, I will see if I can do some of those basic things suggested this weekend `¬)
Thanks for all the help so far guys!

I would try and confirm the aerial by connecting to the Panasonic Plasma, but that's Freesat so receives BBC4HD in any case! Not sure if it has a Freeview tuner as well, I suspect not without looking! `¬)
 
@Gavtech; I'll check also the relative cable positions in the back, as there are quite a few between various recorders, etc and the TV. Most of the cables inc. the HDMI go up to the tv through a metal tube at the back of the stand, and I think the aerial cable does not, as it goes straight to the wall; I will check all positions though, as well as maybe moving the Panasonic to the rhs of the bottom shelf which means the aerial lead will go over a shorter distance to the socket at the wall. (Presently there is other equipment on the rhs, with the Panasonic on the lhs, so any advantage is worth trying!)
 
@Rodders53; P.S. no, I do not have 'ThatsTV' lcn7, I have ITV2 SD on 6 and then next is BBC4SD on 9.
 
@Rodders53; P.S. no, I do not have 'ThatsTV' lcn7, I have ITV2 SD on 6 and then next is BBC4SD on 9.
Reception prediction for a local school: (click change address to get more accurate for your own home): says 10km from Beckley. Coverage Checker - Detailed View
Local TV is on frequency ch29 not 51 :facepalm:(why do I ever trust ukfreetv?:mad:), and only 4kW erp not 10kW.
Wolfbane predicts clear line of sight fields of: 74dBuV/m for PSBs (100kW erp), 71dBuV for main COMs (50kW), and therefore about 66dBuV for COM7/8 and around 60dBuV for the local.

To put those numbers into context, at my home I get 69dBuV predicted (for all 6 mains and 66dBuV for 7/8). A bit of 'wet string' works - my bedroom TV is working on a home made dipole (a bit like this one DIY Over-The-Air HDTV Antenna ). My main aerial is in the loft of a ground floor room (don't ask - it's a hangover from the previous owner's installation) which feeds back up into the main loft and then back down to the lounge.

NB The recommended levels for DTT signals terminated into TVs is between 45 and 65 dBuV. Too much can be as bad as too little.

So I'm convinced you have a group C/D aerial and/or a really really poor cable / connection issue. Heating and cooling of cables and joints can eventually mean they become loose/poor, in extremes this can cause an unseen wire break {happened to me with a telephone extension wire that was in the sun}.

Check the loft wires... and don't forget to include the connection to the aerial itself. Also remove the backplate of the lounge socket and check that, too. IF any wires go outside try to examine them via a camera zoom lens or binoculars for any evidence of damage. Bent/kinked or crushed coax cables should be replaced.

If you do end up needing to replace the aerial a wideband log periodic will be future proof enough. A filter to stop any mobile phone frequencies can easily be added later (and likely to be supplied 'free' if it is needed) {free as in paid for by the mobile companies} especially in loft installs. ATV`s Choice Of Aerials for digital TV is worth reading.
 
I wonder if MarBinz has any 'non soldered' Belling Lees using the 'kink the centre wire' method as a (unreliable) connection?
 
OK; (feel free to call me an idiot! `¬)
Problem solved!
I'll relate everything I did, just because... but the solution was straight forward in the end... (Note to self - never assume anything!)
Went into the loft, (really itchy now from the insulation!), cable connection to antenna all ok. I replaced the connector between the aerial and the cable where I had removed the splitter (it was actually marked as an 'antiference' thing, so why it caused me issues years ago, no idea...), pity the main cable was about nine inches too short to connect directly. Yes, neither connector had the centre lead soldered into the connectors, but I left that for the time being.

No real change to the signals etc. I did check all levels prior to starting for all nine muxes (in coverage checker link from Rodders53 above (thank you!);-

ch60 SigStrength=6or7 SigQuality=10
ch59 SigStrength=6or7 SigQuality=10
ch57 SigStrength=6or7 SigQuality=10
ch55 SigStrength=6or7 SigQuality=10
ch53 SigStrength=6or7 SigQuality=10
ch50 SigStrength=6or7 SigQuality=10
ch37 SigStrength=3 SigQuality=4or5
ch31 SigStrength=3 SigQuality=0
ch29 SigStrength=0 SigQuality=0

I then decided to move the Panasonic recorder to the rhs of the shelf so the antenna cable did not stretch across other cables. As soon as I pulled the kit out on the shelf, I could see that the aerial chain was not how I had assumed... (like I said, call me an idiot for not checking this first!).
On the bottom shelf, RHS I have an old vhs video which has an old Grundig freeview tuner on top of it... The Grundig had the first shout from the aeriel, and then it chained to the Panasonic HD freeview, before then going to an older Panasonic recorder (std freeview).

I connected the antenna directly into the Panasonic HD Freeview and checked the levels which are now as below... I think the Grundig has finally given up the ghost, as I do recall that it does not pass the aerial signal through properly if its not plugged into the mains - I only went as far as seeing if it would switch on, which it wouldn't, so in effect only a limited signal seems to have been getting through; time to drop kick into the bin, as I'm never likely to record sd to vhs again in any case `¬) - this is probably why I previously had the channels (even chained the way it was), but then lost them when the Grungedig died?

Levels with the offending item removed are now;-

ch60 SigStrength=10 SigQuality=10
ch59 SigStrength=10 SigQuality=10
ch57 SigStrength=10 SigQuality=10
ch55 SigStrength=10 SigQuality=10
ch53 SigStrength=10 SigQuality=10
ch50 SigStrength=10 SigQuality=10
ch37 SigStrength=10 SigQuality=9
ch31 SigStrength=9 SigQuality=10
ch29 SigStrength=5 SigQuality=10

Doing an autotune has given all my channels back; I had felt there were several missing, as I had nothing on ch31 or 29. I also seem to have some on ch42, 44, 45, 47, although not sure what they are; all I know is I now have a mass of the channels that I had not realised I was missing!

Thanks for all the help, links and suggestions, it is greatly appreciated! `¬)

P.S. @Rodders53; love the wet string design I will have to play with something like that for upstairs! `¬)
 
Good of you to admit everything and pleased to hear that you are sorted.
I also seem to have some on ch42, 44, 45, 47,
Sounds like it could be Hannington, but it's quite a distance from you.

love the wet string design
I have found that in really strong areas it only needs to be damp.
 
Excellent news! The numbers are about what I might expect for the 4kW cf 100kW erps. You should be able to split that signal with a passive splitter to feed another TV as well. A 2-way splitter will provide -4dB to each outlet cf the input signal (-3dB being half the signal to each port - a theoretical figure not achievable in practice). If a simple passive splitter loses too much signal, a powered splitter (aka a distribution amplifier) should be used. The gain to each port should be low (as its to make up for cable losses to the outlets mainly).

ALL devices with RF loop-through have powered amplifiers inside to make up for the signal loss they impose by splitting the signal into their tuner(s) and also to the output (older ones also add in an analogue modulator in). So they 'boost' the signal level slightly. With no mains power these should pass very little signal... So you were receiving mainly via the interconnecting cables!! Some have a 'power saving in standby' option that has to be disabled to allow them to pass the signal.

The 'wet string' aerial design was shown to me by a colleague in the 90s... it was used to get off air reception from Crystal Palace (clearly visible) at the, then brand new, BBC White City building in West London.

Edit: Hannington (63km distant) is predicted as being receivable (albeit not fully reliably, due to co-channel interference). It is more or less on the same bearing as Oxford so on the aerial's peak gain. The local ITV and BBC One news programmes would be different to Oxford (and the ads on some other channels). You may find the unit has stored some of those in the 800s? (Although PVRs can sometimes get upset with reception from two transmitters and misbehave recording wise as a result.)
 
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