All posts by jb38
Below are all of jb38's postings, with the most recent are at the bottom of the page.
Tony: I think your suggestion of trying a test with the aerial facing Sandy is a good idea, although I would be most interested to know what the difference in levels are when the aerial is actually facing the Sandy transmitters, as on quite a number of aerials the difference is not quite so great as might be expected, therefore maybe you could carry out a quick signal check on a few mux channels immediately before proceeding with the task of swinging the aerial around, and then a similar test on the same muxes when completed, and which as far as accuracy is concerned should really be made not more than an hour or so from the previous test.
As far as aerials are concerned, I wouldn't be over influenced by what's seen on these aerial gain curve charts, and the reason I say this is, that although these charts are indeed handy for reference purposes it should always be kept in mind that what's seen indicated is the result of that obtained when the aerial is tested under perfect conditions over an area about the size of two football fields, and with the signal source being located at the other end of the field and usually from a single element radiator fed by a highly stable variable sweep oscillator that gives a constant output level over the entire band, not exactly similar to what happens in reality where the signals received are from six different distant transmitters and which in many cases are usually in non line-of-sight locations, meaning signals are frequently received at differing levels.
Its really up to yourself what you do and the aerial you mentioned would probably be OK, but with digital reception I would always look along the lines of using a Log 40 or similar in conjunction with a 15db (min) amplifier, as in many situations this can generally provide a more consistent level of signal that's less prone to glitching over what's obtained from larger and highly directional larger pieces of metalwork.
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Sam: Well with regards to my comments about the box, although I fully appreciate that the box in question may well have been working OK until September, however its when a signal received by the box is somewhat less than perfect that the circuitry deficiencies that nearly all of these lower price range devices suffer from will show up.
The booster / splitter you have is an OK brand, but though its not exactly unknown for these to fail and so you should test that its operating OK by selecting BBC1 (or ITV1) on one of your receiving devices, entering the signal strength check screen and noting the indication seen, then switch off the power supply to the SLX booster / splitter and if its working OK then you should notice a reduction in strength.
Should it be OK then the next thing you could try "if" you know which output from the booster goes where, because if you do then take the coax plug out of the booster port that's used to feed the signal to the device you are using as a signal strength monitor, then reconnect the plug again into the "full" port on the booster, re-checking the signal strength on the monitor TV to observe any changes.
The other point is concerning your location, "if" you are a resident of Church Lane then the majority of aerials seen there appear to be facing towards Sutton Coldfield? and with only a very few facing Waltham, this begging the question of, have you made any local enquiries about reception from households where the aerial is seen to face Waltham? the direction of Waltham if standing directly in front of, and looking at the Dog & Partridge Pub, being to the right and straight down Church Walk towards the East.
That said though, you have to keep in mind that work is still taking place at the Waltham transmitter and with warnings of weak signals etc, and so its not the best of times to be diagnosing potential problems in situations like this albeit the booster check that I mentioned is still valid.
By the way the aerials referred to were seen using Google earth, and its appreciated that this situation might have changed by now as Google E does not have bang up to date images.
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Tony: Thanks for the update on the results of your test, and which on studying same rather indicates that atmospherics plays quite a part in your reception from both Sandy and Sudbury.
Regarding your present aerial, if its a Group B then as you will probably realise its not really the best for reception from either station, as Sandy's muxes span channels 21-52 and with Sudbury's from 41-60, and of course a Group B aerial is listed as covering 35-53, however within the ranges covered by these groups its always best to knock off a few channels from each end the range as tapering effects towards the extremities of coverage nearly always applies no matter what might be maintained, this of course making the span somewhat tighter.
My reason for having a reservation about the aerial you suggested, or indeed any other so called high gain types, is simply because of digital reception being much more critical regarding alignment, this being where the highly directional characteristics of high gain types can be a positive disadvantage as far as low quality glitching is concerned.
The reason for this is that in "any" aerial (excepting a Log periodic) there is only one active element, the one situated immediately in front of the reflector, and with the multitude of directors seen located in front of the active element being for purposes of "focussing" the signal onto the active element, now this is all very well in situations where near to line-of-sight might apply and with the minimum of reflected elements being part of the signal received, but in situations such as yours where signals are subject to fading indicates that these reflective elements are part of the signal being received and with this somewhat upsetting the operating principal of the aerial, because the focussing elements then become restrictors by partially blocking any signals received from a slightly different angle, this being why picture glitching is always more prevalent where high gain aerials have been used for digital reception.
On a log periodic aerial all elements are active, and with this being why they have a much more even response across the entire band, plus they are not near so critical as far as slight fluctuations in the angle that the signal is being received on, the inevitable slight lack of gain that these aerials have being more than adequately compensated for by using them in conjunction of a booster.
By the way Panasonic Viera's have top tuners, this being why you can manage to view a picture when the quality is so low.
If you manage to have a look at your mast head amp I would be interested to know what gain rating is seen printed on its internal label.
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Tony: I realise that my reply might already be a bit lengthy, but as you have a Viera I would like you to try a test by going into the tuning menu / manual tune and entering Ch44 but do not press search, as the strength / quality that the channel is being received at will be indicated, then whilst still on that screen pull the aerial plug out of the set and connect a single piece of insulated wire (about 3 feet or so bared at one end) into the aerial socket and see if anything is indicated strength wise.
You could also try changing the channel to 27 and similarly checking the strength bar.
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P. Kieran Ward: Thanks for the update, and pleased to hear that you were successful on this occasion and are now able to receive Alba as its one I view myself on occasions, at least when the Ceol Country series is on.
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Gary: Yes, keep us posted, as this device really has to be verified as being OK (or not) before looking elsewhere for a possible reason for your problem.
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Tony: Thanks for the update re: test requested, as I just really wanted to completely eliminate from my mind the "very" remote possibility (at your distance from the TX anyway) of your signal actually being slightly too strong, as the symptoms experienced when in this sort of situation can in many cases be similar to yours, high strength accompanied with very low quality.
On the other hand though, should you have managed to obtain a picture of sorts with a wire then the situation described could well have been applicable.
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Tony: Well, speaking as person (albeit a long standing RF engineering one) who gets involved in troubleshooting missions when wearing my domestic hat, so to speak, I always use logs in conjunction with amplification, because although areas do exist where signals are so poor that virtually nothing will help, this of course being where Freesat comes into its own!, however in other problematic DTT reception situations that do not come into the aforementioned category I have always had a high percentage of success with the Log Periodic / amplifier combinations rather than anything else, and as such use nothing else nowadays.
Of course I fully admit that its not just always a case of an aerial change over, as in some situations repositioning of the aerial is required, and this could be to either side of its present position but NOT necessarily meaning upwards, as the "higher the better" only really applies in cases where a transmitter aerial is involved, unless of course its seen that there is an obvious obstruction to an aerials signal path located nearby (50/100 feet) and increasing the aerial height would clear it.
Link for aerial supplier.
A.T.V (Aerials And Television) TV Aerial, DAB Aerial, FM Aerial.
/onlineaerials.html#Log40
Just purely for reference purposes, this is an example of an excellent SLX brand variable booster, and although I do realise that you already have a mast head amplifier it depends on what its gain is rated at, as should it be under 15db or so then I would not consider that as being sufficient for your requirements.
0-20db Variable booster. Argos item number: 534 / 4235 (£11.99)
Buy Plug-In 1 Way TV Aerial Signal Booster at Argos.co.uk - Your Online Shop for TV aerial boosters.
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heather: Its unfortunate that you are only using Sky as you do not have an alternative signal source to use as a comparison to the Sky box, as your problem could be caused by either the TV or the HD box as I very much doubt if it would be the HDMI lead at fault, although anythings possible!
What I suggest is that you carry out a test by only switching one device off at a time and NOT both, in other words switch the Sky box off for a few minutes (5 ideal) before switching it on again, because if its the TV at fault then as soon as the Sky box comes back on the picture defect will be seen without having to wait.
You then carry out a second test, but this time leaving the Sky box running and switch the TV off, because if when you switch the TV back on again the picture appears as normal until its been running for a while, then the TV is the problem.
Another simple test that you could try "before" trying the above is to remove the HDMI coupling with the Sky box and temporarily use a normal scart lead between both, that is if your TV has a scart socket, as some of the latest TV's dont.
By the way switch the Sky box off before disconnecting the HDMI lead, because although these type of connectors have a safeguard built into them its best not to take chances.
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Sunday 18 November 2012 8:40AM
P. Kieran Ward: Just for information purposes, I checked the info given on the BBC site and it corresponds to a satellite signal test made whilst BBC Alba was being received on two of my own Freesat devices, and if you select DTV manual tuning - Satellite (DVB-S) on 28.2 and enter the details as seen on the site and with "free to air" being the search option I cant see any reason for Alba not being amongst the list of programme channels that will (or should) appear. Details / 10.80275 (might come up as 10.803) DVB-S Symbol: 22.000 FEC: 5/6 Your TV does not allow Transport stream and SID to be entered and so not mentioned.