All posts by Michael Perry
Below are all of Michael Perry's postings, with the most recent are at the bottom of the page.
Dawn Pascoe
Under no circumstances should a TV aerial be fitted in a tree! The tree moves in the wind but the aerial needs to stay carefully aimed at the transmitter, at Redruth in your case. Finding a location for the aerial that is free from the interruptions of the view to Redruth by trees and wind turbines is the key and your aerial contractor should look for such a position.
4G is not yet available in your area, but when it is you may, only may, get some interference and @800 will supply one free filter to fit in the aerial lead. Redruth transmits on channels: 41, 44, 47, 48, 51 and 52. All are some way under the channels used for 4G. The O2 mast may or may not be used for 4G services, it is not expected until at least 2014 according to O2's coverage checker.
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Bryce
You need the azimuth, elevation and skew angles which depend on your location. You do not aim your dish at 28.2 East!
For Milton Keynes Station, I calculate them as: Azimuth from TRUE north = 145 degrees (or 35 degrees eastwards from TRUE South), Elevation = 24.4 degrees up - but allow for the offset angle of your dish as are most these days, Skew = 20.9 degrees clockwise when viewed from in front of the dish. Note that the azimuth and elevation depend on not only where the satellite orbital position is (28.2 East for Astra) but also on the latitude and longitude of the receiving dish site. All because the Earth is roughly a sphere and we are not on the Equator.
The elevation offset has to be calculated for your dish and they vary. If yours is, say a 5 degrees offset (that is the angle between the flat surface formed by the edges of the dish and the centre of the LNB 'inlet' horn [usually has a plastic cover over it]) then you take the elevation and subract the offset angle (as the dish actually looks more upwards and it appears because of the LNB being mounted so that it is below the dish centreline). So in my example the flat surface formed between the edges of the dish would need to be set with an elevation of 15.9 degrees upwards.
Once you have the azimuth and elevation set approximately, you then need to rotate the LNB body by 21 degrees clockwise from the vertical when looking at the front face of the dish.
There is a useful 'calculator' at Satellite Look Angle Calculator - Elevation Azimuth Skew that uses the selected satellite and a map you can adjust for location.
Note that my calculations are approximate and only for Milton Keynes Station, so you should slightly adjust azimuth, elevation and skew for the best signal strength and quality - but only by very small amounts and allowing the signal to settle. Sky boxes can display the signal strength and quality and I will assume others do as well.
Hope that helps?.
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Peter Winfield:
A TV that can connect to the internet would have to be equipped with an Ethernet connector on the back, or have a WiFi capability, and be linked through your broadband connection. Few, if any, 'set top boxes' have the ability to use the internet either.
The Alba STB300HD has an Ethernet connection - but it's not equipped to connect to the internet! (It seems to be for use in the factory to load the firmware program.)
Your need a modern 'smart' TV for internet connection, but the features are quite limited and it's nothing like using a computer on the internet. TVs sold in the last year or so may be equipped, but not all.
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simon lindley:
You could well be suffering from the transmission problems due to the high pressure pattern around the country. Many Freeview viewers are being affected byt this and reporting their problems on this wevsite on various pages.
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Tina
Yes, just disconnect the Sky SD box and connect the FreeSat box in its place. The coaxial cable from the LNB on your dish should have a screw on connector that will fit onto the Dish input of the Freesat box. There is no need to adjust the dish position, assuming your we getting good results on Sky.
Hope that helps?
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JLM,Ely:
Personally I would be very surprised if any TV set provided a DC voltage at the aerial input socket. The normal connection via a coaxial cable to the aerial would be compromised by having a voltage present. The aerial system presents a DC short circuit but a 75 Ohm impedance circuit to RF signals in the wanted design frequency range (around 450 MHz to 800 MHz). [DC continuity is a standard test for intermittently poor signals as it would be likely to show any cable breakages if they are present when tested.]
Any DC power required to operate an aerial amplifier would normally be provided by a power supply unit designed to add the required DC voltage, typically 5 Volts, using an input socket with the DC voltage present and an output socket that has no DC voltage (that output socket connecting into the TV RF input). Normally, the aerial amplifier would be fitted close to the aerial (so it only amplifies wanted signals from the aerial and not the 'noise' picked up on the coaxial cable) and is between the aerial itself and the power supply - so as close as possible to the aerial. That allows the supply to be in a convenient place for an electrical supply connection that is indoors and away from wet weather, etc. The masthead amplifier is weather sealed so should not allow water ingress if the connections are made properly.
Any terrestrial receiver would, therefore, be very unlikely to have this supposed 5 Volts present at the aerial input socket. (Satellite receivers do have voltages present at the input connections from the LNB on the dish, somewhere between 12 and 18 volts. That is set by the receiver so it can select horizontally or vertically polarised signals are received by the LNB. Freesat receivers also provide these voltages to operate the LNB on the dish.)
Thinking in 'first principles' terms, a 5 volt DC supply connecting into a 0 Ohms at DC circuit will potentially have infinite current flowing in the circuit! That would rupture any fuse! Formula I=V/R, so I=5/0, hence I=infinity!
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Laura
It is a well known phenomenon that during certain weather conditions, as we have had for the last few weeks, that RF transmissions travel greater distances than normal due to temperature inversions, sporadic-e, etc. In analogue TV days, it showed up as flickering interference on screen and odd noises. With digital, the interfering signals conflict with the wanted signal and prevent decoding - hence the No Signal message. Digital TV is LESS tolerant of such problems than analogue.
Saying you don't believe it doesn't change the fact that it is true and very well documented.
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Personally I still prefer FM - but with a 'proper' ratio detector and not a regenerative detector. Ratio detectors are rarely used in integrated circuit designs as the regenerative detector is included on chip. Discrete component designs often use a ratio detector and they do not suffer from the whistles, warbles and hissing common with regenerative types.
Regenerative detectors are easier and cheaper to incorporate in the chip design but are not so good where the signal is weaker or variable.
In my experience, DAB is not good in cars due to the varying signal reception, DAB+ would be better but BBC transmit DAB and have no plans for DAB+. DRM signals are not transmitted in the UK yet.
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Tuesday 17 September 2013 7:38PM
Mrs Julia Quinn
The lady at your aerial people doesn't know anything about how the system works! It makes no difference how many people are using the services from any transmitter, the signal strength is not affected by the numbers using it! The signal is radiated all round the aerial of all main transmitters like Crystal Palace and almost everyone in the London area who are not in a valley or shielded by a large building will get a signal. It is often the case that people on the top of a hill, like Box Hill, Reigate Hill or Tandridge Hill will get quite good signal strength - and that could be too strong rather than too weak. (My work area included Warlingham before I moved north.)
Are you sure you have a booster? Many homes these days use a distribution box that sends several signals to different places around the home. Some have a boosting effect and some do not. The box would look something like the one shown at
8 x Aerial Distribution Amplifier : Aerial Amplifiers & Distribution : Maplin Electronics
if it is a distribution unit, but more like the one at
1-Way Aerial Amplifier : Aerial Amplifiers & Distribution : Maplin Electronics
if it is only a booster indoors (outdoor ones are protected from the weather by more complex casings). These images are for illustration and each maker has different designs.