Help with Freeview, aerials?
Friday, 1 June 2012
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Robert7:23 AM
JB38 I'm not sure if your comments were aimed at my question about what Arqiva were doing to the Crystal Place transmitter or not but let me clarify. The transmitter has, at the very top the aerials which were used to transmit the 4 channel analogue TV service below are the array of digital pods, These are aerials which transmit the Freeview digital TV signals. These were taken off the mast (not all at once as Freeview did not go off the air). The array was then rebuilt. In the Victorian age, a lot of devices were described as electric despite NOT using electrical power. Digital has the same fait in marketing speak today. My Electro Magnetic Transmission Theory dates back to 1981 but am reasonably confident that a UHF modulated wave for analogue TV would look very different to a UHF modulated wave for digital TV even if both wave are analogue is nature. Optimised for the reception of UHF modulated waves used for digital TV would be a better description. Although I dont know enough to be sure such optimisation is possible. DigitalUK say any outdoor TV aerial over 30 years old probably will need to be replaced for Freeview but it is hidden in the section about communal aerial systems used in flats. In my quest to get my digitally perfect reception (Interference and nose within the ability of error correction to correct ) post 4th April (BBC) and18th April (all the rest) I bought a new indoor aerial (made no difference). It was HD compatible and 3x Noise Filter which I cannot check on the accuracy of those statements. However I can shot holes in Amplifies terrestrial HD TV signals and active triple noise reduction filters because to amplify you need active electronic components like transistors (unlike passive electronic components like capacitors and resistors) and active devices need electrical power to work. As this aerial does not have batteries or plug into the mains it cannot have active components inside. Trading standards might have a go on this one. Im having a go at Total tripe I fail to see where cows stomachs come into this.
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Stephen P10:21 AM
<< Optimised for the reception of UHF modulated waves used for digital TV would be a better description. Although I dont know enough to be sure such optimisation is possible >>
Can't see how it could be.
Incidentally your indoor HD Ae might be powered by the TV up the coax. But more likely they use amp for gain.
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Robert: Just noting in passing you wrote
"The transmitter has, at the very top the aerials which were used to transmit the 4 channel analogue TV service below are the array of digital pods,"
Your tense is incorrect. The top of the mast WAS used for digital services, but this part of the transmitter was upgraded about a year ago for DSO and then was used for the analogue four until DSO happened. Since DSO the new equipment at the top of the mast is used for digital output.
The "pods" as you call them - the usual name is "panels" are no longer in use. On some site they are being retained in case the main stuff fails, on others the equipment is being stripped.
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Saturday, 2 June 2012
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Robert1:51 PM
Braintist & Stephen P.
Thanks very much for comments and it's a good case in point of trusting the web for information. The Radio & Televison Interfence Service will not touch this one with a barge pole as it is an indoor aerial. Since the 4th of April I have been clutching at straws trying to cure an intermitent reception problem. The signal quality and strength monitor is too much of a blunt tool, I've had quality of 1 (Red) and perfect picture & Sound and unwatchable TV on 10 Green both times the reading was constant. The 29th looks like a red herring coupled with what you have said above about the transmitter configuration, I've still got an intermitent probelm that can degrade into unwatchable TV. Logan's Run on CH4 HD had 2 small glitches until the last segment when the action climax became unwatchable, 2 hrs into the flim! I upgraded in October 2011 and the system ran for well over 700 hours of perfect glitch free video until 4th April. It has got thought some very long records glitch free since but it is still too unstable and unreliable. I stopped moving the aerial about two weeks ago and had concluded it was a transmitter problem. After a decade of perfect reception I might have to move to cable. I have not found anyone yet around here who has not thought Freeview reception had degraded since DSO. I have a degree in Physical Electronic and in 1981 knew the theory of how Yagi aerials worked, the cleaning up of digital signal down fiber optics cables and Electro Magnetic wave transmission theory. Unlike 405/625 changeover, I thought Freeview was all about using the same UHF aerial configurations but diggin deep into the DigitalUK website paints a much darker picture.
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Robert: As a non-professional like yourself, I wonder if 6dB attenuation is way too low for your location. Have you tried a higher level such as 24dB?
Perhaps the aerial cable is picking up more signal, particularly if it is not low loss and if it is the thin flimsy stuff you get on set-top aerials.
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Mazbar3:13 PM
Robert a simple question why carn't you have an outdoor aerial instead of an indoor aerial. Your problems proberly have nothing to do with too much signal as the signal has to travel through your walls befor it gets to the aerial if it is amplified all it will do is increase the signal strenght but not the signal quality. Indoor aerials are poor and they can work in sime bedrooms ie upstairs downstairs they have more things for the signal to get through. people on this site seem quiet happy to tell people to get antenuators but in most cases they arn't needed an un amplified aerial giving signal over 75dbuv will give perfect pictuers but an aerial with 35dbuv and a 30db amp = 65 dbuv and break up of signal. so robert if you can have an outside aerial fitted for yourself if you are scared of hights and want the job done right.
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jb385:27 PM
Mazbar: There is a factor concerning Roberts location which I feel that you might not be aware of, that of him residing in an apartment block that appears to situated at only just over a hundred yards or so from the mast, the type of area where high levels of RF mush can generally be found that can cause problems in some receivers.
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jb385:42 PM
Robert: You may have already mentioned this within the depth of your postings, but what kind of reception do you get when using nothing more than a piece of wire of about 12" or so in the aerial socket?
Another interesting test would by to know what kind of reception you would get if using one of these older fashioned loop aerials that were always supplied with small analogue TV's, the loop on these aerials usually terminated straight into a coax plug.
Finally, does the room where your TV is located face directly towards the mast?
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Mazbar5:54 PM
Didnt know there could be other problems is the apartment made of lots of steel or is the insulation in the walls foil or foil backed plasterboard if so the signal will allways be poor. One other factor if you are very close to the transmitter the signal will just go straight over head and no type of aerial will pick it up .
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Stephen P6:23 PM
To put jb38's comment in context, in Herne Hill - 2-3 miles away - I get GOOD reception with just a fly lead, and usable with nothing at all - as we did for analogue.
Rob have you tried nothing?
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