All posts by jb38
Below are all of jb38's postings, with the most recent are at the bottom of the page.
Stephen P / Nigel: The aspect of the signal that I would be concerned about is the fact of it fluctuating by about 20% or so as well as it dropping to zero on occasions, as this type of problem is usually always associated with trees as well as in many cases the actual signal received being partly achieved through reflection, and in these type of circumstances using a Unix 52W is liable to be detrimental to reception rather than assist it, this being mainly caused by its relatively narrow pick up acceptance angle of only +/- 15% or so and creating the situation whereby the 52W's output level will drop with even the slightest deviation in the angle that a signal is received from, whereas on an aerial with a wider beam width this would hardly be noticed, or at least very much less!
To help this situation it would be much better to use an aerial such as a DM log or similar through an amplifier, but though (and dastardly as it may seem) if about half the directors on the 52W were removed then that would widen the aerials beam width, then the aerial could be fed into an amplifier of about 10 - 15db or so and with its output being fed into the 8 way distribution amp.
Getting back to the 8 way splitter, the only way that you could properly judge the difference between it being in and out of circuit is to note the level seen on the TV's signal check screen with it in circuit, then pop up to the loft and by-pass the splitter by connecting its aerial input plug straight into the coax that's used to feed the TV being used for checking purposes.
This said taking it that the splitter is self powered.
This is a link for the type of aerial being referred to.
Online TV FM DAB Aerial sales
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Jen Pettitt: The answer to the first part of your question is YES! although its not actually Freesat by Sky's "free to view", but though the answer is NO! to the second part as Sky permanently retains access to the recording side of the box, and that also includes the playback of anything previously recorded.
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Dave Lindsay: Just spotted your query as I was spinning down the list, and yes I basically agree that the problem could possibly be due to a large differential in power levels between the muxes on adjacent channels as its something that can really test a tuner to the limit, some types getting desensitized or even swamped very easily, and to be quite honest about it I sometimes wonder if the powers that be who are involved in deciding on the ERP power to be used by multiplex transmitters sited on adjacent channels actually take a minute to consider the possible effects that the creation of this type of situation could have on the receiving side of the equation, as two radically different power levels on adjacent channel frequencies is something that I have never witnessed being done anywhere else except on TV multiplex transmitters.
That having been said, it would be interesting to know the result if a box of a different manufacture was used, like for example a Humax.
Regarding the variable attenuator, although I have serious doubts about the effectiveness of these devices as in some cases the variable aspect can act more like an on and off switch, and so the first chance I get I intend to take one apart and have a look at just how crude the circuitry is (if you can call it that!), still it would be interesting to know the outcome of that test should it be done.
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Alan Thompson: That M&S TDR100 is a TVonics model DTR-FP1600 and which very limited information is known about except that it dates back to 2008, but when you purchased the box did you carry out a complete reset on it to return it to its original default settings?
I would also have requested that you carry out a test by manually tuning in a BBC channel and checking the result, then trying the same test on ITV as I would like to know if you can get these two, but though I am unable to provide the mux channel numbers involved without knowledge of your location, i.e: a post code or one from nearby.
By the way I do have the manual for the box, and when this problem happens can you hear the hard drive running if you place your ear near to the top of the casing?
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rob: As you are not that terribly far away from the transmitter I would be inclined to try a test using a set top aerial or a piece of wire about 12" long pushed into the inner part of the aerial socket, and if a picture of sorts is obtained then a simple loft aerial could be fitted as that should be suffice for satisfactory reception.
And with regards to the communal aerial, it might be prudent to ask any neighbours that you might be friendly with if they are also experiencing any of the problems you are having.
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Nigel: Just in addition to my main posting, even although I very much doubt that this would apply, but so that I can completely exclude a niggling thing I have in my mind regarding the possibility of circumstances applying that might (albeit remotely) be the cause of your reception difficulties, I would like that if you have access to a set top aerial could you plug that into the TV and see if anything is picked up, or if you do have access to this type of aerial just try a short piece of wire of about 12" or so connected into the TV's inner part of the aerial socket, giving an update on results.
The only reason I am asking this is, that with you being located at only 27 miles away from the 200Kw transmitter you should (in theory anyway) be getting reasonably good reception without any form of amplification unless some other factor is applying, like as referred to in my main posting.
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Stephen P: If you are referring to Nigel these are the two indications I get, and the reason for my extra comment is because that a large section of the signal path between the transmitter and Nigel's location is over water, and a signal passing over water can in many cases appear stronger because of the skipping effect than if over the same distance on land, this having the effect as though the person receiving the signal is closer than they are in reality.
That said though, and as mentioned in my additional posting, I very much doubt if the signal is too strong, as although this can totally upset the accuracy of indications given on a TV or boxes check screen it cant on the Labgear checker that Nigel used.
UK digital TV reception predictor
Postcode Checker - Trade View
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Mike O'Pray: Well, certain areas of Northampton are (and have always been) known for iffy reception and the fact of others having made similar complaints to yourself has to be taken into consideration, although when a person has previously received a signal which magically disappears when its transmitter changes frequency and moves to high power then some other factor applies.
Now you have mentioned the fact of the other aerial facing a different direction and being diplexed onto your Eastern facing aerial used for Sandy then this could be the other factor that's causing the problem, that is "if" the other aerial is picking up a really strong reflection of Ch51 from a distance away, as diplexers don't kill a signal they just reduce it as well as having the effect of slightly reducing the signal that's actually required to under what it would be if the diplexer wasn't in circuit, and so to cut a long story short I suggest that the diplexer is by-passed so that your signal is purely from the aerial facing Sandy without another being tagged on to it.
Is the diplexer installed on the aerials supporting pole?
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Mike O'Pray: Also meant to add, that although the diplexing of two aerials facing different stations was maybe OK back in the analogue days its not necessarily the case now, and in your own situation is totally useless and is even detrimental to your reception.
The reason being, that Waltham's analogue transmissions covered a channel span of from Ch54 - 64 but with Ch35 (Ch5) being added later, and in the case of Sandy it spanned Ch21 - 31 with Ch39 having been added for Ch5, so excluding the blip that Ch5 caused you can see that diplexing both stations was perfectly OK.
However the reason that the diplexer on your aerial is of no use nowadays is because that Freeview from Waltham spans Ch29 - 61 and from Sandy its Ch21 - 52, and you cannot diplex these two without reducing the strength of channels that you require as the majority of the channels are intertwined.
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Wednesday 16 May 2012 7:35AM
Lisa: Yes, its one of these type of situations whereby all a viewer can really do is to make sure that there is nothing amiss with their receiving equipment / installation as the problem is basically out with their control, as when a signal source changes from 20Kw up to 170Kw any problems with lost channels is usually caused by the tuner in their TV / boxes being overloaded, this resulting in either no reception on that particular channel or in more extreme cases no reception of anything, the "set top aerial" test always proving if this condition is applying or not.
Of course area's not too far away from you must be iffy for reception or the 40watts Dallington Park relay (@ 2 miles) wouldn't have been necessary, although I would find it very interesting to know what type of reception your neighbours are having on these channels if they are also receiving from Sandy, as Waltham is indicated as a possibility for reception in your area albeit that its SDN (ITV3 etc) dips into a variable reception status early September.