All posts by jb38
Below are all of jb38's postings, with the most recent are at the bottom of the page.
Keith: In addition to that already said, the only aspect of what your aerial installer had done that did make me wonder is with regards to him aligning the aerial after having repositioned it, because if his signal meter was temporarily tagged onto the aerials termination point then did he consider that the readings obtained were perfectly OK or not?
If it transpired that they were, and as said in your reply that he tested the signal before and after the splitter then that's inclined to indicate that the aerial feed into the garage is OK, as least anyway at the time he checked it prior to it possibly having been rained on.
To be perfectly frank about it, the only way I see your problem possibly being solved is by another "on site" investigation being carried out whilst your reception is down, and with the signal being measured starting from the TV then back tracking with measurements being taken at all cable access points prior to the aerial itself, then finally on the aerial itself should this prove to be necessary.
The reason for the test being made on the aerial itself is due to the fact that you "might" be located in a position where the signal strength shows significant variations in level every few yards or so, and the only way of verifying if this applies or not is to move around whilst holding a test aerial (log types perfect for this) connected into a signal meter that's strung around ones neck so as to be able to observe the signal strength being indicated, this being a standard fault finding procedure.
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Lyndon Freeman: I realise that you have said you are using the Bethesda transmitter @ 1 mile / 257 degrees (V polarity) which uses mux channels 57 - 60 - 53, but though the Bethesda North transmitter @ 0.6 miles / 257 degrees (V polarity) is indicated as providing superior reception, it operating on mux Channels 28 - 25 - 22.
As far as your neighbour is concerned, what are these extra channels you refer to? as if he is managing to receive anything "extra" from the Llanddona transmitter @ 9 miles / 341 degrees (H) polarity then its purely through chance as its commercial channels are not indicated as being possible to receive at your location, the three commercial muxes being identified by being able to pick up ITV3 (10) - Pick TV (11) - Film 4 (15), and so does your neighbour receive any of those programme channels? these programme channels corresponding to mux channels 43 - 46 - 40.
The other point to note being that the PSB channels from Llanddona are single frequency with Bethesda i.e: 57 - 60 - 53 whereby making it difficult to know where you are picking the signal up from.
I will say though that your neighbours old BBC2 aerial aerial which might be a C/D type (identified by green plastic end plug on the elements horizontal support boom) would be better for Llanddona reception "if" your aerial is a group A type (red plastic end plug) which was installed for Bethesda North transmissions at the bottom end of the band, although if you reside in the end property with what looks like a flowering cherry tree in the garden then the two far end houses behind the metal gate could be blocking the signal from Llanddona, that is apart from the major block indicated on the terrain predictor at roughly 1 mile away from you.
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Keith: If you are accessing the signal strength indications via the technical set-up section then were you viewing a programme at the time you accessed this section? because if you were then the programmes mux channel should be indicated along with the strength.
As far as replacing the cable is concerned I would certainly agree with that, as on reading back what you had previously said I just noticed what I had missed before insomuch that you referred to the extra length of cable being added, suggesting that the original section of the old cable is still in use.
As far as I see it though, when an aerial installer is involved then the problem should be easily resolved, as its simply a case of him verifying that the signal level indicated on his meter when tagged onto the actual aerial is above the minimum level for satisfactory reception, then taking it from there right down to the TV's aerial point, a straightforward exercise with the minimum of complications!
I realise that your TV is not bang up to date and likewise its tuner may be slightly lacking sensitive wise to that fitted in your newer Technica, but you did also mention that the Technica was patchy as well which somewhat eliminated the possibility that the Sony had developed a problem.
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Rashid: If you have a satellite outlet in the living room and also one in the bedroom then the two outlet positions cannot share the same feed "if" your dish only has two coax cables going into its LNB, because should this apply then only one Sky box at a time can be connected into the system or they will clash with each other as satellite boxes communicate with the LNB.
If though on the other hand your dishes LNB has four coax cables connected into it then two will go to one room and the remaining two to the other.
Further advice dependant on reply.
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Rashid: Also meant to say, that what has been said is based on each room having twin outlet sockets as are necessary for Sky+ operation or indeed any satellite device that is capable of recording.
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Neil: What you have reported are the classic symptoms experiencing by viewers in areas who do not have line-of-sight reception (or anywhere near to) with the transmitter, and any signal that they do receive being purely through diffraction which is signal bending, this unfortunately resulting in reception which relies on this type of condition always being vulnerable to changes in weather plus being affected by other climatic based reasons, all of having the effect of altering the angle that the signal is bending.
I carried out a few tests using an RG14 6LR post code as a substitute for your own (partially unknown) one and came up with the following results.
Hannington : 7 miles @ 149 degrees obstructed from just over 1 mile away.
Crystal Palace : 54 miles @ 87 degrees multiple major obstructions from just under 30 miles out.
Oxford : 28 miles @ 13 degrees major obstructions from 11miles out.
I realise that you may not be in an RG14 6 postal code area, but at least it gives you an idea of the reasons for reception being iffy in your area, and the very fact of you having said that the aerials in your street are seen to be pointing in all sorts of directions is always an indication of an area being problematic for reception.
Needless to say, and as you will probably have already been aware of, nothing can really be done to improve things when reception is being made under these conditions.
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Derek Matravers : A quick check on the terrain indicator reveals that the line-of-sight between the Wenvoe transmitter and your location is obstructed from just under 4 miles away, this (dependant on conditions) usually always resulting in erratic reception of one or more of the six mux channels used by the station at certain times of the year due to the fact that the signal is only reaching you in the first place by diffraction (bending), this frequently being responsible for receiving the muxes at slightly different strengths to each other as variables will always exist between the muxes even before they are subjected to bending.
Of course the trees as mentioned by Dave Lindsay making matters even worse.
Terrain between ( m a.g.l.) and (antenna m a.g.l.) - Optimising UK DTT Freeview and Radio aerial location
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Neil: Although I fully appreciate that your reception has prior to recent times been OK but that's the misleading thing about digital reception, insomuch that provided a signal is not suffering from rapid fluctuations in quality the picture will appear exactly the same from being received at a high strength right down to just before the lower cut off threshold, and so its possible that your signal could have been dropping in level over a period of time but is only now being noticed because its encroaching on your receivers lower cut off point.
If your aerial had been in the loft then I would have been inclined to suggest that you try moving the aerial a few feet to the left or right of it present position, as in non line-of-sight situations where a signal is being received via an element of diffraction this type of action can sometimes bring results by re-capturing the signal, because in areas such as yours if a person moved along a rooftop from one end to the other carrying a test aerial coupled into a signal meter, its not uncommon to observe the signal rise and fall in a ripple fashion from one end of roof to the other, not of course that it really helps an aerial installer to know this when a really good spot does not correspond to a chimney breast, although this being where gutter mounting is usually OK.
Another thing about reception under these circumstances being that picture glitching etc is always worse if a high gain aerial is used, because a high gain aerial is only that because the elements towards the front of the aerial called directors focuses the signal onto the aerials active element positioned immediately in front of the reflector, but when a signal is being received via diffraction the angle its being received at is not constant and can vary slightly to either side of the centre line that the aerial has been aligned on thereby defocusing the aerial, and so what's a director element one minute turns into an obstruction the next by partially blocking the signal path to the active element.
It would be interesting though to know the result if you cared to make a local enquiry regarding reception from some other household whose aerial is facing the same direction as your own.
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Sunday 30 June 2013 4:33PM
Keith: With regards to the May 29th event, I feel that your problem having apparently started around then is purely coincidental, as the only change that was made at Oxford was to the SDN transmitters (ITV3 etc) operating frequency which moved from Ch62 down to Ch50, nothing else having been altered.
With regards to aerial having been moved, I fully agree with this action if indeed the previous position resulted in the aerial facing into a large tree, as trees can have a serious effect on RF signals and especially so if located at close range, and so this possible reason for your problem had to be eliminated from the equation.
The only point I am not clear about is by you having mentioned the cable from the location of the old aerial into the garage, insomuch when the installer moved the position of the aerial did he not run a new cable from the aerial down to the splitter? or was the old cable of sufficient length whereby it was just diverted? because judging by what you have said with regards to your neighbours reception being OK then the pre-splitter feed from the aerial down to the garage must come under suspicion, such as water having seeped into it at the aerials termination point