All posts by KMJ, Derby
Below are all of KMJ, Derby's postings, with the most recent are at the bottom of the page.
pirat3uk: The signal on C41 is most likely to be Mux D3+4 from the Great Yarmouth relay. This is a Freeview light transmitter (the three PSB muxes only) and is on a bearing of 347 degrees from your location. The signal is transmitted at 400 Watts and uses vertical polarisation.
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pirat3uk: The signal could be deflected by the roof or reflected by a nearby hill, building or a water tank. It is not unusual for the polarisation to be skewed in this event. The only other transmitter in Norfolk using C41 is Little Walsingham, which at 11W really has no chance of reaching your location.
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Mrs. Smith: Could you give some details as to what area you are in? This information is used to work out whether there are any known reception issues or whether it is a case of single frequency interference affecting your receiver.
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pirat3uk: Many receivers, after finding and storing the channels on C41 would overlook C59 as the content is identical to the channels already stored. Others will examine both C41 and C59 and select the stronger of the two signals. A third option, which clearly does not apply in this case, is selecting the last frequency found and rejecting identical content found earlier in the scan.
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pirat3uk: I should have added that the solution is to clear the channel list, then do a manual tune on each of the Tacolneston frequencies to restore reception of the correct transmitter.
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pirat3uk: Hi, there are actually three relay stations in the area. The Gorleston-on-Sea transmitter that you mention is only 2W and uses C26/23/29. Great Yarmouth is on C47/41/44 and Lowestoft is on C58-/60-/56 both at 400W. The absence of C59 is most likely caused by either single frequency interference (an RF modulator of a VCR, Sky box or other equipment set on/near to C59) or the aerial is positioned in a null for the C59 signal from Tacolneston. Aerial positioning, especially in a loft tends to be a bit of a compromise between the positions of strongest signal for each mux.
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John Bolton: Digital UK show the current power to be 20kW on each mux at Hannington. After switchover the PSB muxes will radiate at 50kW, the COM muxes in their final state will radiate at 25kW. This would appear to be from 18th April 2012. Prior to this date there is mention of power restrictions and two power up events for the COM muxes after DSO2.
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Terence: The Digital UK postcode checker predicts for your location variable reception from Crystal Palace for the HD mux. This is because you are within range of signals from Sandy Heath, which also uses C31. Although the interfering signal is at a much lower level than that from CP it has emerged that digital signals are affected more adversely by other digital signals than was at first thought. The reason why the problem only occurred recently could be down to leaves on trees screening you from the unwanted Sandy Heath signal until late November. This will of course no longer be an issue after 18th April 2012 when the HD mux switches to high power working at Crystal Palace.
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Colin: If I could add to what Dave said above, 18th April 2012 is the date when Stockland Hill COM muxes increase power and Crystal Palace begins high power working on the same frequencies. The Vertically polarised option is being transmitted at Rowridge from this date to help deal with interference problems anticipated in overlap areas and at times when the inversion effect allows signals to travel beyond their normal service areas.
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Friday 13 January 2012 1:55PM
Mike: A wideband aerial at first sight does not look any different to a "grouped" aerial. The actual difference would be in the length and spacing of the rods, which affects the frequencies at which the aerial performs correctly. The original yagi design has dimensions which are based on the wavelength of the frequency that it is supposed to receive. A "grouped" aerial is a compromise worked out to cover a small range of frequencies by tweaking the length and spacing of the rods. For example Group "A" covers C21 to C37. A "wideband" aerial is a bigger compromise, designed to cover, in the case of domestic TV reception, the frequencies of C21 to C68. The downside of covering all the available frequencies is a general reduction in the gain for the particular size of aerial. The reference to an aerial not normally fitted in new installations is a type commonly called a "contract" aerial. This is a yagi fitted with a single plate reflector, as in the basic example at the top of the page. The type of yagi which would be fitted is the one shown in the second set of illustrations, the reflector being in two sections. Variations to the yagi design are the tri-boom and X-beam types also depicted in the second set of illustrations. The group of the aerial is often indicated by a coloured plastic stopper inserted at the end of the boom. Red=A, yellow=B, green=C/D, brown=E, grey=K and black=W (wideband). The group is otherwise shown by a sticker, or letter stamped on the aerial.