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Thread: radio gaga

  1. #1 radio gaga 
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    A dipole radio antenna radiates uniformly in all directions as Megabrain states in the current topic about free energy and Tesla coil. I agree. But I wondered how this changes when the electrical system is at one side connected to earth (as is common in distributional networks that are used by radiostations).

    It is a well known fact that radiosignals tend to follow the shape of the earth and I think this maybe is an effect caused by that the radiotransmitter functions relatively to earth. Or said in a different way, the earthed pole and thus the earth functions as one pole of the radiotransmitting system hence the other pole's signal is deformed around it which would not be the case without the earth connection of the electrical system.

    Wtih lower frecquencies this effect is most obvious maybe because the higher frecquencies get more resistance in watter????


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    Radio waves do not "follow the shape of the earth" - what happens in fact is that they bounce off the ionosphere (this works better at lower frequencies). If radio waves did 'bend' then you would simply not need to put your tv transmitter on the top of a ruddy great mast! :wink: VHF & UHF stations are generally 'line of sight' since it is rare for them to be reflected back down. The sun and it's spot activity plays a great part in all this.


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    http://en.wikipedia.org/wiki/Longwave

    Here it states (or better someone states) that what you say is right for higher frecquencies being "more energetic" but not for the lower frecquencies, they follow the curve of the earth being "heavier" and not - or hardly - reach the ionosphere.

    Think of it as follows : if I have a battery with two wires and I tap them to each other there will be a primitive kind of a radiosignal (a receiver nearby will react on it).

    But now I connect one pole to a earth electrode reaching deep in the ground and I tap the other pole to this electrode there will be a signal too but the connection to this electrode will change the shape (or better the fieldlines?) of the signal in a relativistic way I think.
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    hehe... Without the atmosphere we have, longwaves would definitely not follow the earth's curvature, therefore to say "It is a well known fact that radio signals tend to follow the shape of the earth" is [in my opinion] a misunderstanding of radio wave propagation (albeit an easy one for most people to make).
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    Aint that a contradiction; "without the atmosphere they don't", means they do..and how do you explain this then. I thought the regular explanation is that the earths mass bends timespace and the radiowaves follow a straight line so for us they follow a curved route. But that does not explain at all why the higher frecquency signals would follow a different route.
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  7. #6  
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    low frequancy radio waves are most diffracting meaning they bend round objects therefore staying to the earth rather than travelling in a straight lines off it. Higher frequancy radio waves diffract less and so do not follow the curvature of the Earth they can although be transmitted around the earth as they hit the ionisphere around the earth and having to little energy to push through it are repeled back down towards the other side of the world. So high wavelength do not follow the curvature of the earth they are reflected around it. Similar to the way microwaves are reflected off sateliettes arounf the earth they can defenitely no the describes as following the curve of the earth by doing so so neither should radio waves
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    That's how I understood as well but theory explaining it and practice are two things. I was thinking of kind of an explanation and thought that because the electricity of a phase of the electricity network is mostly relative to earth (because of earthing for making earth detection switches work) this relativity could still exist within the electricity the transmitter is working on, like lines going backward. Then the curving could be a result of this relativity instead of a general "curving around masses". Because under water (the earth elektrode reaches in to the groundwater that runs endless - in the sense of going all round the earth - to the seas) low frecquencys reach further this could also explain that this tendency is stronger if the frecquency is lower.
    Also higher frecquency could do the same but taking a higher path they reach the ionosphere where the lower frecquency's don't.

    Now offcourse I know the earthed parth of a three phase electricity system has almost no tension to earth but it changes the tension of every phase at itself relative to earth nevertheless which is proven when we measure potential difference between a phase and earth. With an electricity system that has not been connected continuously to earth such a potential difference will not be measured.
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    The waves appear to 'follow' the earth only because they are restricted by it and the ionosphere, these two simply act as a kind of waveguide. A bit like driving down a tunnel the walls guide you generally, whatever course the tunnel takes so will your vehicle follow the same approximate course.
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  10. #9  
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    I dont think it's just that it appears to happen around masses. so for instance a tesla coil only works if connected to earth giving a specific relativity to earth of course.
    There the signals are made visible because of ionisation and eventually the sparks curl back to earth because of the relativity caused by the earth electrode.
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  11. #10  
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    Now that's not put right I no, yhe ionisation is more like an electric chanel inside the signal
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  12. #11  
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    Has it ever been proven that a "radiowave" would follow the earths shape with ecquipment (the electricity network normally used for radio, tv etc) that was not attached to an earthing electrode. If so I would be very supprised.
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  13. #12  
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    Radio waves propagate via a variety of means depending on the frequency.

    It is big subject. You need to study ground wave propagation, line-of- sight, troposheric, inosopheric. There are modes which are less common and get used only by amateurs such as meteor scatter, auroral reflection, sporadic E, long distance tropospheric and moonbounce.

    A vertical dipole will radiate horizontally in all directions but in the vertical plane the radiation falls off gradually with increasing angles to zero at directly up (and down for that matter).

    Aerial systems only use the ground because it would be difficult to contruct and elevated vertical dipole at low frequencies...too big. The 'earth' in this case plays no actual part in the radiation. It is just that both sides of the feeder cable need to be terminated. Higher frequency aerials sometimes use a 'false' earth called a 'ground plane'. It means a coax cable can be run up a pole without interfering with the lower leg of a vertical dipole.

    Horizontal dipoles do not perform well at low frequencies because reflections from the ground make them radiate mainly straight up which is generally of no use. In terms of wavelength they are too close to the ground....
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