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All posts by jb38

Below are all of jb38's postings, with the most recent are at the bottom of the page.

J
C21 (474.0MHz) after switchover
Sunday 1 April 2012 4:48PM

todd: If you are located on the top of Gonerby Road hill or even on the down side of it provided its the side leading to the Downtown store, then you should have no problems whatsoever receiving Belmont, if though you are on the South side of the hill leading towards Grantham then you could experience problems in some areas around there, albeit Waltham is OK.

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Joseph K: I was only really referring to you being surrounded by a series of local relays to give an indication that the whole of your area is that of being problematic for reception, and if you attempted to "manually" tune in Emleys BBC & ITV mux channels I gave you and nothing was indicated then that could be classed as bad news, considering the power of the transmitters involved. That said though, when you mentioned that when you first switched on the TV that the strength was indicated at 91% but the quality was zero is something that would normally have given rise to suspicion of the reverse of a weak signal applying, as absolute zero quality accompanied by high strength is something that's usually seen when a tuner is overloaded by an excessively high level of signal, but if you have tried a manual tune on the channels given "with the set top aerial installed" then overloading cannot occur and so some other factor is in existence, and which to be quite honest about it is something that only an on-site investigation is liable to resolve. I realise that post codes do not necessarily always indicate an exact location, but should "Gatehaus" be the building in question is this relatively new? as if its been there well before last September then the communal aerial system distribution amplifiers may not have been re-adjusted to compensate for the massively increased output from the Emley Moor transmitters, this causing all sorts of instability problems associated with overloading. Just purely for information purposes the local relays I referred to are / Idle: 3mls Keighley: 9mls Oxenhope: 9mls Halifax: 7mls Beecroft Hill: 4mls Bradford West: 2mls

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james: On the subject of reception from Northern Ireland, its not until October 24th when Divis switches to high powered operation that you might have a chance of receiving from there as it is shown on the predictor as possible, Divis being located at 64 miles / 229 degrees from you.

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james: I also meant to say that commercial muxes from Divis ArqA Ch48 and ArqB Ch34 are presently indicated as being possible to receive in Girvan, but with them only being on 2Kw and 1.6Kw respectively I think there is a bit wishful thinking involved with the predictions given, but though both these muxes increase to 50Kw in October and so the situation will be totally different then.

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Harry: No problem! although if the middle pin is not touching the outer casing then just slide a wire onto it, then push the end of this wire into the female socket end of the cable that would have been used to plug into the socket, binding the outers of each other together.

Anyway you are the one on site, so only you know what's possible and what's not depending on how badly its damaged.

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Brian Duffy: Provided the analogue TV that you are feeding the Sky boxes RF output into doesn't receive anything else via its aerial socket then it doesn't really matter what channel you use for the RF, but most Sky box modulators give a slightly better output up in the 60's range, and in your case I would choose something from Ch64 upwards and see how you get on.

That said though, some Sky+ boxes modulators do give a weaker output and so you really have to do as you have already done, that is experiment until you get the best grain free picture by trying channels at each end of the scale. (21 - 68)

By the way the only way of getting over the grainy picture seen from some of these modulators is by using a mild booster amp on its output.

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optimist: As far as your mast head amplifier is concerned, if you cut off its power supply then its not the case that the signal will pass through unamplified but will actually be attenuated to less than it would be straight from the aerial, something which could possibly work to your advantage after April 18th provided that the signal received is strong enough.

My reason for saying that is that you would appear to be located in a less than ideal area for reception, as even after CP's switch to high power the predictions seen aren't exactly brilliant, and I also notice that Sandy which is 10 miles closer than CP doesn't provide good reception across all six muxes at the same time on any occasion, Sudbury having a permanent "variable" reception status across all muxes.

Its really one of these cases of wait and see, as CP might not have quite the effect
that its increase in power would suggest.

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amanda friedland: The TV in the front room should not have been affected unless at times you use it to view something other than Sky, the latter being connected into the TV via a scart or HDMI lead.

But the problem as described would suggest that the coax lead from the aerial in the roof or wherever has not been re-connected into the Sky boxes normal aerial socket, nor has the coax lead that feeds the TV's in other rooms (incl lounge) have been re-connected into the Sky boxes RF output socket again, this being either RF1 or RF2, the latter used if you use a magic eye control in any of the rooms.

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amanda friedland: Just as an afterthought to what I mentioned, this was based on the assumption that you actually view Sky in the other rooms via the Sky boxes RF output as well as normal Freeview, as if you do not and its only Freeview you use then the lead from the normal aerial has not been re-connected into the coax link to the other rooms, or into a splitter that feeds same.

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Joseph K: Yes, please give an update on what transpires, as I am also rather intrigued about your apparent vanishing signal.

As far as nothing being received during a rescan with a set top aerial is concerned, I am beginning to think that there is a great possibility that this situation might have been exactly the same if that test had done prior to the signal vanishing, and caused by the building when during construction being insulated with modern hi-tech heat reflective material between its walls, and with this leaving the only source of reception being through the communal aerial system, something which I strongly suspect as having developed a fault and a possible reason for why the signal was there one day and not the next.

Its just a line of thought, as although dealing with the peculiarities of RF signal paths etc is known as a black art, in cases like this there is usually some logical explanation, and which as aforementioned is generally only found out during an on-site visit.

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