All posts by jb38
Below are all of jb38's postings, with the most recent are at the bottom of the page.
MikeW: This type of problem can only really be caused by interference being picked up either via the aerial or alternatively from the mains supply, and this not necessarily being from within your own property.
A good way to test for the latter is if you have a small portable radio of the slightly older variety that has long and medium wavebands (particularly LW) is to switch the radio on and tune it away from radio 4 where no stations exist, then with the volume turned up slightly position the radio close to any mains socket or a cable coming from, then when you see the problem on the TV move the radio about as close to the socket as possible and listen if you can hear noises corresponding to the problems with the picture, if you do then its a mains borne problem.
Should though it prove as not being, then although its something that lots do not like doing, but you really have to know if anyone else locally (a neighbour) is suffering from similar problems, as the cause of this annoyance may well be totally outwith your control.
Although I am acquaint with your village by having passed through it on a number of occasions recently I cant remember if your electrical supply is via overhead cables or not? as should it be then these cables are great for picking up impulse interference along the way.
Anyway, if at all possible try the radio test, and by the way this device is also excellent for sniffing out interference from all sorts of domestic appliances such as the types you have mentioned plus sewing machines / food mixers / electric bread knives / hair driers / vacuum cleaners and a multitude of other gadgets that use "brush" type motors.
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MikeW: Of course all that's been mentioned is not really taking into account that the fault "might" be originating from within the TV itself, but you can soon prove this (or not) by temporarily trying another set in the same position, or of course just asking a neighbour if they are having problems.
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MikeW: Thanks for that update / explanation. The problem with reception in the whole of the Bourne to stretching past Morton areas is that signals received from either Waltham (@18mls / 272degrees) or Belmont (@ 39mls / 11 degrees) has to come over a forest at some point along the way, and as such vulnerable to suffering from elements of seasonal variation cause by vegetation (trees) as well as other naturally occurring reasons of an atmospheric nature, and with reception from Waltham being particularly affected by the somewhat closer location (and slight elevation) of the Bourne Woods range.
As far as having noticed a slight difference in the timing of these glitches when using the Philips TV is concerned, I would simply put this down to the fact that no two TV's / boxes have the same sensitivity of tuners, the one with the higher sensitivity always being more resistant to glitches in the signal, although this up to a point is only because as the signal (strength / quality) is running at a higher level it has further to drop before approaching the receivers cut off threshold and causing picture / audio problems.
However that said, you should try a test by observing the signal "quality" (not so much strength) over a few minutes or so to see if it dives up and down, as I suspect that it might be (unless too fast to be observed!) and also have a look outside during the test to see if any tree branches are blowing around, as if they are this can affect reception even if not directly in line between the aerial and the signal source.
With regards to the person across the street not experiencing any problem, this could be because they are positioned to be able to receive a slightly better signal than you are, and this possibly coupled to using a device with a more sensitive tuner such as found in Panasonic ranges. (plus some others of course)
But though, the test for possible interference using the LW/MW radio referred to is important (if only MW tune to 530khz end) as that will instantly reveal any impulse interference in the mains supply and is something which has to be eliminated as a possible reason for your problem, although if none is detected then about the only thing you can try is moving your aerial to a different position in the loft, this meaning in the horizontal plane and preferably done while being able to observe the signals quality changes, as this is more important than the strength and which is almost guaranteed to reveal sizeable variations during any experiments made.
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Richard Jones: Not really, except to record them either onto DVD's using a cheap DVD recorder, or much better onto one of the these DVD recorders with a built hard drive, as you can then store everything at the one time, the only bind with doing this being that it has to be done in real time, and that can be for a very extended period of time depending on exactly the size of the content stored in the Sky boxes hard disc.
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Keith Wright: There is absolutely nothing anyone can do to stop high pressure signal inversion problems from happening at certain times of the year, this being the reason for your own present difficulties.
Analogue reception has always suffered from this effect as well but is far in a way more tolerant to interference, and especially if from another station on the same frequency and will still in many cases display a picture of sorts, unlike Freeview that operates on a reception threshold system whereby if the signal drops to under a predetermined level it cuts out, and with the same happening if the receiver happens to pick up another distant transmitter using the same frequency, this instantly causing data corruption resulting once again in the reception cutting out.
The only way a person can ever escape from this problem is by using Freesat, as the frequencies used by satellite are well above the ranges used by terrestrial transmitters and likewise are about 99.9% of the time invincible to this problem, 100% not mentioned as an unusually heavy thundery downpour can affect reception for a few minutes or so once in the proverbial blue moon, although using a larger dish (zone 2) can somewhat minimise this problem.
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Jonathon: If you already have a few in-line attenuators lying around then you have obviously nothing to lose, although I am very doubtful if you will achieve anything, this being because as you have already sussed out that by the time you have reduced the excessively high level of signal received from the main muxes you are likely to have killed of any signal that was there from the two very low powered commercials.
Still, its worth a try, and so the method I suggest you use for a test is to place the -20dB (variable?) in line with whatever you are receiving on and carry out a signal strength check on say BBC1, noting the indications seen, and if the level is under 95% and the -20db be of the variable type, then bring the signal up to 95%.
The next step is to go into the manual tuning section and enter Ch54 and see if anything is indicated, you should not require a scan to see this as if a signal is there its level should show as soon as you enter the channel number into the box, and if it does show then slowly "reduce" the level of attenuation until the signal level indicated starts to fall off again due to the tuner becoming re-saturated as the signal is increased, then back it off a fraction from that position and try a scan on that channel.
Of course you have to remember that even if a signal is seen indicated and you carry out a scan that this action might still result in a blank screen, as even although the actual level might be high enough to show on a scale its not necessarily the case that its high enough to break through the reception threshold of your receivers tuner, and this cannot be compensated for by amplifying this signal due to it being a vicious circle situation, amplify the low signal and the main muxes are increased as well.
Should by any remote chance this work then try scanning Ch50.
By the way, if when you insert the 20dB in-line attenuator the signal is still too high, then place another in line with it.
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Dale: Well you are correct, but only in a "partial" sense, insomuch that its not now Ch50 but Ch63 and with the power doubling to 2.2Kw, likewise Ch54 has also doubled to 3kw, but I very much doubt that this relatively mild increase in power will in real terms make that much difference to the majority of people who are suffering from the massive differential in power problem between the main muxes and the commercials, albeit that you might not be depending on your location.
In other words, I was only replying to Johnathon with reference to the original posting he referred to.
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Kent Smith: If the booster is not actually mounted on the aerial itself but on the support mast then there is no need to switch the boosters power off, as there isnt any voltage on the connections to the aerial.
That said though, "if" working on your aerial involves high level roof working then purely for your own safety you should switch all power off just in case there is any mains leakage through the power unit that could give a slight tingle if you touch something else whilst holding the aerial.
Although I might have given this qualification, mains leakage through mast head power supplies is an extremely unlikely thing to happen as I have never experienced one that doesnt use a double wound transformer.
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chris sparks: Nothing really took place during this first stage of switchover that involved the HD service hence you not having noticed any changes, but its almost a foregone conclusion that you will have good HD reception come April 18th, and with the signal received being at a similar level to that of BBC1 that's already operating on high power.
By the way the HD mux will also have changed its operating channel on the 18th from the present of Ch31 down to Ch30.
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Monday 2 April 2012 9:03PM
Paul Jones: Just to clarify a couple of points, are you saying the old LCD set in your second living room is connected to the main TV using an HDMI cable? as should you be doing this then why didn't you just link the TV into the system using the Sky boxes RF modulated output? switching the 2nd TV over to its analogue setting for viewing Sky, or did you use a long HDMI lead purely for a better quality picture?
The other point concerns your problem of losing BBC when the Sky box is switched on in the other room, as you are using the Kilvey Hill transmitter have you made sure that the Sky boxes RF modulator channel is set to operate up in the 60's, (e.g: 62 - 68) changing this accessed by pressing "Services" then in an evenly spaced fashion "4-0-1-select" and in fourth down position you will see RF output, if necessary change it and save the results.
Maybe you could update on these points before proceeding to anything else.