All posts by jb38
Below are all of jb38's postings, with the most recent are at the bottom of the page.
Stuart Tier: Just checked on Hannington as well as other stations that you could be receiving from and do not see any event taking place on the date you have mentioned.
I would be inclined to treat the message as an error.
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Antony: You will really have to try and trace where the feed to the socket comes from, as one could be for a TV and the other for an FM radio, or alternatively one of them being for the purpose of feeding a signal into another room.
If you have a loft then have a look in there just in case someone has been using an aerial amplifier but has taken it away with them again when they left leaving the coax input / output plugs not connected, but there are all sorts of theories about what it could be.
The other check you could make though is to slacken the socket from the wall just enough to see behind it just to verify that there are actually cables connecting into it.
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Nick: I would not let yourself be over influenced by looking at the gain figures claimed for aerials such as the type you have mentioned, as these figures are gathered from when the aerial is tested under strictest of conditions and in the most ideal of conditions, something which bears no resemblance to where most of them are used in the real world, as in practice and especially where difficult non line-of-site situations are involved, the general rule is the larger the aerial the sharper its acceptance angle is, the last thing thats wanted where elements of signal path warping is liable to occur, an aerial with a wider acceptance angle always performing better in these situations, and aided if necessary with an amplifier.
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Nick: Sorry, and although this may sound a bit odd, but although being a long standing engineer I dont really get involved with DAB radio or its reception, and as such am unable to advise on issues concerning it.
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Stuart Tier: Yes, no problem. The reason that I automatically mentioned Hannington is that this station is indicated as providing a slightly better level of signal over that of Rowridges powerful VP transmitter, but as aforementioned, I checked all stations seen on the predictor associated with the code provided and none gave any significance to the date you had seen.
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Nick / Dave Lindsay: Regarding the illustrations of the gain curves for the various aerials seen on ATV's site and the comments / recommendations made about their use, it should be appreciated that these are made in general terms irrespective of whether the aerial is used for analogue or digital reception, and my comment is not at variance with what's been said on the site (one of the few I have always approved of) but is simply a qualification concerning the possible snags that may crop up if using a particular type of aerial for digital reception under certain difficult conditions, namely non line-of-site and where the problem is not one caused by excessive distances.
Reception issues do not generally occur in very near to open line-of-site situations even at considerable distances, and so a high gain multi-element aerial can be of benefit there as it can be effectively focused to where the mast is located, however in circumstances such as completely non line-of-site then any signals received obviously has to have a reflective element attached to them or they could not be received in the first place, but because of being received that way they nearly always have an erratic and in many cases rapidly fluctuating element attached to them as is witnessed by the quality frequently being observed to dive up and down, and although this type of problem is mostly caused by trees it can also be caused by numerous other intermittently occurring reasons like the signal path being near to, or even crossing a main highway frequented by high sided vehicles.
Unlike the stability of analogue reception, the critical characteristics of digital reception cannot cope with this sort of thing resulting in the quality taking a dive, and so if an aerial with a narrow acceptance angle is used under these sort of conditions then any fluctuations on the signals being received will have much more of an effect that it would do in a lower gain wider acceptance angle aerial, and with this resulting in a much higher level of picture glitching being noticed.
The other problem with the use of a tight acceptance angle aerial in these type circumstances being that its alignment doesnt always hold for long, and so its case of peaking it for quality every month or so dependant on weather related issues.
Regret delay in replying, but I was held up by an unexpected snag at at a job today.
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Dave Lindsay: I have always found that vertically polarised signals are generally better all round, although I do have to admit that most of my non domestic involvement has always been with FM and AM equipments and as such the effect I referred to would not be applicable to these modes, as it only really applies to the reception of digital TV signals as anything of a digital commercial nature doesn't operate on the same hit and miss basis as domestic TV.
That said though, now that Rowridge transmits in both polarities I would love a chance to carry out some tests at various points around the area, but by it being a bit distant to me will just need to be content and wait to see what kind of complaints are being made from the area and with the type aerials being used by the complainants.
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Dave G: Yes, you would have to use one of these video sender units as sold by Argos and such likes, the sender being connected into the Sky boxes scart socket and the receiver likewise connected into the new TVs scart socket, the plus point of these devices being that the quality of picture is superior plus you have stereo sound, and as you do not have any cables between both you can position the remote TV anywhere there is a power socket.
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Nick: Regarding the booster you are referring to what gain do you see it rated as having? and as regards to their use, the only reason they are recommended to be installed as near to the aerial as possible is because it limits the chances of any electrical based interference being amplified if picked up in the cable before it enters to the booster, as obviously the amplifier would boost the interference as well as the signal.
Of course the other reason is, that if the signal is at a higher level before passing down the coax then the ratio of the signal to any possible interference will be greater thereby limiting its effect.
On the other point regarding what you are intending doing with the booster, its not advisable to have it in a plastic casing as that doesn't offer any screening, as even these relatively low cost high gain (13db+ boosters that you can get nowadays made by Vision and others are all contained within a metal casing, and these little devices are excellent.
Also, I don't want to put a damper on your variable voltage idea, but dependant on circuitry used you would most likely find that the variation in gain would be virtually negligible between these voltages as it would have to come down to about 3 volts or so before much of an effect would be noticed.
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Wednesday 25 April 2012 6:03PM
michael: It sounds as though you are trying to store more channels that the boxes memory is capable of storing, so carry out a factory reset on the box (sometimes called default setting) or if you don't see that option offered then take the aerial out and auto-tune without it, as that will blank the channels out, then when completed reconnect the aerial and carry out a further auto-tune to store the channels again.