All posts by Michael Perry
Below are all of Michael Perry's postings, with the most recent are at the bottom of the page.
SteveK:
Firstly you have too much signal as 99% will cause overload of the tuner as the received signal level varies as it does all the time. That could be causing your system to be uncertain whether it is receiving 1080p or 1080i services.
I am not aware that there is any 'switching' happening as it does not change on my system fed from Mendip.
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Naseem Shafi:
Aerial system problems are well known by technical people to affect different frequncies differently and at different times. That is what's appears toi be happening with your system affecting the ARQB services.
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Chris SE:
I am very well qualified as I spent 50 years working in the TV inductry in technical roles, as a Senior Technical Trainer for a large TV rental company before moving to similar roles in other related companies. I also have a Masters Degree in Electronics and Physics. So I am very well qualified to make the comments I do based on both technical knowledge and understanding as well as relevant experience.
Further, you miss the point that we do not know what equipment is being used by the person reporting a problem. So we need a general approach unless a specific question is asked. Further, due to the varying attenuation by the atmosphere we do not know how much their signal varies, as it does on every receiver, so we need to give guidance in such a way as to avoiud the overload conditions whilst still meeting the minimum requirement levels needed by tuners.
I know of instances where a 90% signal strength gives intermittent problems. My younger brother, also an electronics engineer with higher degrees, was suffering from just such a problem and when we checked the strength it was in the 90% range and varying. So a 3dB attenuator was fitted, reducing the signal levels to 84% on most multiplexes and that cured the intermittent sound problem. A family friend was having problems with apparent loss of some channels. All the usual checks were made of the aerial system and the only feature visible was the strength being 96% on the worst affected mux. A 6dB attenuator solved that with a signal strength now showing as 86%.
You asked why I and others so often quote the 60%-85% range, they are examples of why. You assumed I didn't know what I was talking about so I have now corrected your understanding.
QED.
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Chris:
I am glad we seem to be making progress. You surmise that a side lobe of the very high gain aerial is receiving unwanted signals is quite likely. However, just turning off the amplifier tunrns it into a high loss attenuator wioth much reduced signal feed. It would be better to take it out of circuit, even if only temporarily, and coupling the two coaxial cable ends together with a coaxial coupler, very inexpensive, so the signal is fed through in full. Worth a try?
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Rob:
The last engineering work carried out at the Sudbury transmitter was on 1st August 2018, no other work has been done since.
It is worth checking your aerial system to ensure that all the cabling is in good condition and that all joints are in good order. If there are coaxial plugs/sockets then unplug those and refit them to clear any possible corrosion/oxidation from the contact surfaces.
If you have access to another Freeview TV then use that to check that your aerial system is working correctly.
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Jeff Allen:
No recent work is listed fro Rowridge. Could it be that your aerial has moved in the recent very strong winds? It needs to be pointing at 220 degrees and be a wideband type. Also check all your aerial cables are in good condition and that any joints are also in good condition. If there are coaxial plugs/sockets present then unplug those and refit to clear any possible corrosion/oxidation from the contact surfaces.
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Coach:
There are no known issues with the Sandy Heath transmitter. We really need a full post code so that we can examine the reception conditions at your location. However, you can start by checking that your aerial system is in good order, check all the cables are undamaged and unplug all coaxial plugs/sockets and then refit them (that is to remove any corrosion/oxidation from the contact surfaces, which is well know to be a potential cause of loss of one multiplex).
I am presuming that you have a wideband aerial fitted.
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Roger Leggett:
It would be better to ask the broadcaster directly as this website is entirely independent of all broadcasters.
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Steve K:
You can use an attenuator to reduce an overly strong signal to an acceptable level. The ideal in most cases is a strength of between 60% and 85%, that will have no effect on the 'bit error' as the system uses robust error correction algorithms that run automatically. Bit errors only really come into play when the signal is weak or distorted by interference.
You could use a variable attenuator, such as https://www.amazon.co.uk/…8L6, or else fixed tyoes that are available with 3dB, 6dB and 12dB strengths but you would have to try different one starting with the lowest (3dB) one. If you do fit any of those, always add an extra flylead into the aerial socket of the TV so that the weight of the attenuator does not 'hang' on the socket as they are not designed to support their weight.
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Wednesday 17 October 2018 10:28AM
Colin Sharp:
Yes it could have been. The aerial would have fed the VHS recorder directly and the output of that fed to a distribution splitter, which may have provided some amplification to bring all the signals to the same level, and thence to each of the sockets. Note that an active splitter is not the same as a signal amplifier. in splitting the signal feeds there is always some loss involved and an active splitter provides enough amoplification to recover the signal levels at each output to roughtly the same as it would have been without the signals being split. On the other hand, an aerial amplifier is mounted as close to the aerial as possible and amplifies an already weak signal. If the signal is not weak, then no amplifier is needed. In your case it seems that you need an active splitter and not an amoplifier. Please check whether the device you are calling an 'amoplifier' is either an amplifier or an active splitter - looking up the product name/part number will help.
It would help if you provided a full post code so that we contributors can look at the predicted reception conditions at your location and hence determine whether you need any amplifier at all.