All posts by Robert
Below are all of Robert's postings, with the most recent are at the bottom of the page.I bougth a new 'HD' indoor aerial and run it though a 6dB attenuator. But got no improvement over the original indoor UHF aerial which served me well for years. My last changed was Oct 2011 when I went HD and have recorded over 700 hours of perfect freeview up until 10th April when a BBC4 program demonstrated error bursts of 20-30 pixels every few seconds. Unwatchable TV the sound cuts out on half words and you get a digital kiss every so often. I have been monitoring at the quality and power indicators on the muxes and channels and this was a first clue that Arqiva were adjusting the transmitter (some days before). The pods going up and down attached to a guide wire and a man in a cage was a bit of a clue. My Freeview is 'digitally perfect' at the moment the problem is intermittant and linked to rain at Crystal Palace. I also bought a UHF signal finder and was looking for an alternative signal but no luck. The pattern of errors suggest it is co-channel interfence and the corruption to the data is so massive that the built in error correction is totally overwhelmed yet the quality signal can stay in the green. I have enough spare equipment to confirm my belief it is the transmitter at fault. I did a local survey and no one who uses broadcast Freeview had not noticed a decline in reception quality.
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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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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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Does anyone else consider that Crystal Place now has an insidious intermittent transmitter problem for people very local to the transmitter? Their Freeview reception can go totally to pot when the transmitter mast gets wet. And this is a new phenomenon post 4th April BBC and 18th April the rest. How much does anyone, world wide know about the behaviour of the multiplexers run at higher power. What changes were made to the configuration? How well is the science understood? How much field testing was done? I have had the very sensible suggestion of using attenuation which I have experimented with. But I also have noted a steady drop off signal powered as measured by my hard disc recorder, over the weeks since 4th April 2012. A few days latter after purchasing new aerials and attenuators, I thought the signal power measurement did not work, because it was always 10, even with 18dB of attenuation. It was only when I tried an unterminated VCR RF lead that I got a reading of 6. A few weeks later when I froze my configuration and stopped trying to find a new sweet spot for my new indoor aerial, as I had come to the inescapable conclusion the fault was outside of my equipment, I ran for a while with 12 dB but have reduced to 6 and then 0 in response to the measured power levels and continuing problems. Seven people or 100% of the people I talked too who use broadcast Freeview; in my block have noticed a decline in reception quality. 5 have the same insidious fault where TV can become unwatchable since DSO. Lots of indoor aerials and two independent communal aerial systems now longer are reliable for Freeview. After over 50 years of successful broadcast from Crystal Palace, TV is no longer a wireless device in this area. How can you watch a film error free for 2 hrs and the reception become totally unwatchable just at the climax of the film? Our communal aerials would be condemned in an eye blink because of their age according to DigitalUK. UK TV is not designed to be received by anything but an outdoor aerial here lots of people use a bit of wire, coat hanger or nothing, It gobsmaked the engineer who was doing the pre tune for channel 5 that all these TVs worked and on my post DSO survey I found a lady who uses Freeview and still has no aerial. The advantage of digital transmission is that with error correction, noise and interference can be filtered, Schmitt trigger circuits can clean up a digitally modulated analogue signal before it is converted back into in digital data all this help to make the medium far more tolerant and resilient but there are limits. Whatever is going wrong is far s beyond the scope of the signal processing and error correction circuits to cope with. Professional investigation is required. Any comments?
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JB38: You make some very interesting observations. All my poratble TV's use a straight radio type aerial so a loop aerial is not to hand. My main TV is in the living room which has large windows from which I can see the trasnmitter mast at the top of the hill. I have had a decade of perfect Freeview reception and made he last change to the coniguration of my AV equipemnt in Oct 2011. Everthing worked and was 'rock solid' until April 4th. I will follow your suggestions when I have some 'I/O' time or 'downtime' with he system as I watch TV in timeslip with the HDR set to record everything I might want to watch days ahead. I've manage to get though 2 of the 3 Lord of the Rings films on CH4 HD without error. My professional background is trouble shooting Mini computer errors especially disc drives. Although I later switched to Oracle databases. Your help is appreciated.
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I did repair a friend's Thompson DHD4000 is was not booting up and giving no video o/p. Once cracked open, I heard a tell tail click click from the hard drive. Power supply! so I powered the disc from another supply and the thing burst back into life. According to the internet weak PSUs are a known problem and i found a capacitor kit for the PSU which I then fitted. But it took months to do the final physical repair. I also have my own Thompson DHD4000 and Lite-on LVW-5045 which are both sick and need repair waitting for me.
So what's the problem?
and can you fix 'my' transmitter for me?
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There were 3 big films on Saturday on HD the Mux. I got about 2 hrs into Lord of the Ring, just after Brian Blessed did some shouting in the advert break and it started raining in Crystal Palace. Un watchable TV.
It's been raining and dull so I have nothing but dammaged video since.
I found my Fringe electronics PRO TV & Sat Signal Finder. The aerial into the HDR is 62 dBuV, Aerial into TV 74 dBuV and the 12" Wire 71 dBuV at TV aerial socket. They say 59-78 dBuV is OK.
HDR is more sensitive and susceptible that the TV but produces a much better picture across the board. The TV indicates the RF is producing bad video. Ive only just discovered were the signal condition monitor is on the TV menus so I can measure a bit rate error. Other times Ive seen signal Quality Red (1) and perfect vision and sound. When TV & HDR shared aerial, perfect Video on TV and HDR unable to find the Mux.
Dave Lindsay: Attenuation was an early theory and I have posted about reducing attenuation. Measuring the actual signal at 0dB attenuation show it to be at lower end of optimal.
Mazbar: I do have access to an outdoor aerial via a communal aerial system (74 dBuV). The problem is that ever since the days of three channel TV, I have always got a better picture by using an indoor aerial. Analogue Cable TV offered no advantage, despite claims. I have checked since but I still think the indoor aerial is superior although not as neat. I know that in my block and the next block the communal aerial systems have exactly the same problem. Both were considered working before but not after DSO. Set up for HD (Oct 2011) was no problem at all and has been rock solid until DSO1.
JB38: Did the wire test yesterday while it was raining. In the TV it gave a very similar picture and measured 80 compared 73 on a wedge type indoor aerial, the one I was using on the HDR (shared) since Oct. The lowest reading was 63 for BBC1 and 90 for ITV1.
Swapping to the HDR The wire gave a predominantly yellow signal quality against a Green quality for the aerial, the Picture was bordering on unwatchable for the aerial but being give a steady full marks (10) for quality for that channel. The Skys clear so I cannot check at the Mux level. I have fired an email asking for an advanced user guide to explain what this diagnostic is supposed to indicate as I not getting consistent results. Other times the quality signal bounces around all over the place all.
Both the TV and HDR crash out with no signal if nothing is plugged in.
Thanks for all your help. Suggestion always welcome.
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What power did Multiplex BBCA on C23 start with on 4th April. 20 or 200 MW?
Does anyone, outside Arqiva know the detailed configuration changes to the broadcase antenna and if not being able to find BBCA on C23 was a resonable problem to have on an indoor aerial or not.
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NICK ADSL UK : Thanks for your posting. I might explain a bit of a reluctance to engage I have felt from certain quarters. There is far far more to a problem of this type than the just technical issues. I was clueless to the scale of DSO and the technical risks taken. Im very glad Im not involved with any of the discussions and events that led up to DSO; however as an ex- European Technical Support engineer would love a bash at being part of the solution.
For a decade Freeview sometime took 30 minutes to set up and find a sweet spot for the indoor aerial, then it that was it, stable as a rock until I bought the next bit of AV kit and wanted to move stuff around.
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Wednesday 30 May 2012 10:31AM
London
Was any engineering work logged against the Crystal Palace transmitter on 29th May 2012. Ariva Spend the day removing and rebuilding the Digital Pods from the top down. I will continue to watch with interest. Since 4th April 2012 my pervously 'Digitally perfect' Freeview reception stopped. It can become unwatchable when it rains (In Crystal Palace) with 20-30 error pixels splatters and the sound chopping half words. Boosting from 20MW to 200MW did not work.