
Originally Posted by
kojax

Originally Posted by
William McCormick

Originally Posted by
PritishKamat
William, you are missing the whole point here!
This guy Tolkis or whatever, is attempting to appease the scientific world, in order to wake them up. And I can understand that. The new scientists are destroying knowledge, and the next generation.
He got you to attack your own math as a form of proof though. Ha-ha. You just called your own math a joke as a form of proof. Ha-ha.
At ten thousand cycles a second two planes traveling at 1500 miles an hour respectfully, away from each other, will cause almost six inches of wave length difference, at 10,000 hertz, if one broadcasts to the other.
Yet both planes are going to receive a perfect broadcast. Set to a certain frequency/wave length.
It is because the transmission is still the same speed and almost instantaneous. From both planes.
I am though the first to admit that radios do not even use wavelength but rather frequency. However it is funny to watch you guys beat each others heads in.
If he states that the new scientists are just science fiction freaks, and that ambient radiation is what I say it is. I would think he is on the level.
Sincerely,
William McCormick
Alright. I do have to comment on this. Airplane analog radios are not affected enough by the motion for it to matter. Digital radios probably do have to adjust, but it's not all that difficult.
Of course there's a slight redshift effect, but most radios are robust enough in their operation that they don't need an absolutely, perfectly, exact signal. In fact, very few radio transmitters can even consistently emit a signal at the exact right frequency to begin with.
Well, first off, WM's transmission frequency is off by a factor of ten for the wavelength difference he gives. It takes a frequency of 100,000 hz to produce that diffeence at the given relative speeds.
Secondly, when compared to the entire wavelengh(3 km), the change is very small. The equivalent frequency difference is only about 4.75 hz.
Thirdly, radio receivers are not designed to just receive at the single frequency it is tuned to, but to a range of frequencies on either side of the carrier frequency. This is because when you modulate the carrier so that it carries information, you create sum and difference frequencies called sidebands. Your receiver has to be able to receive these side bands as well, so it is designed to recieve signals across a given bandwidth. For instance, if the signal is carrying audio, the bandwith must extend to about 20,000 hz above and below the base carrier frequency.
A 4.75 hz difference in a 100,000 hz carrier wave is just not going to cause any noticeable difference in reception.
Once again, WM speaks of which he knows not.
As a side note, there is a way that radio receivers can take advantage of the creation of sidebands. One of weaknesses of early radio designs was
due to the fact that the radio signal received had to be graetly amplified before it could be demodulated and the audio signal extracted. This required passing it through a series of RF amplifiers.
The problem was that you couldn't make RF amplifying circuits that had a flat frequency response over the whole tunable range of the radio. Thus you designed the amplifiers for the best response at the miidle of the dial and accepted fall off at the ends of the dial.
To get around this, they changed the way you tuned the radio to select a given frequency. The old way was to use a tunable band-pass filter. Only the radio frequency band tuned for was allowed to pass though to the RF amps.
The new way used a local oscillator and a "mixer". What happened was that you tuned the oscillator to a frequency a given number of hz above the desired station. (For AM radios this was about 450Khz.)
The oscillator signal and the radio signal were both fed to a mixer, which produced upper and lower sidebands. The lower sideband would be the difference between the radio signal and the local oscillator. This means the sideband for the desired signal would be always be at a fixed intermediate frequency (again for AM, 450 Khz). The mixed signal was fed through as fixed band pass filter which centered around this intermediate frequency and thus selected only the frequency of the lower sideband for the desired station. All the rest of the amplifiers were designed to have the best frequency response at this intermediate frequency. (And thus were called IF amplifiers. )
For example, if you wanted to receive a station at 620 khz, the oscillator would be tuned to 1.07 Mhz which created a sideband for the signal at 620 Khz at 450 Khz.
This tuning process is called Superheterodyning. Those of you old enough, might remember when the word "Superheterodyne" was printed on radios as a selling point. (Not that most consumers new what it meant, only that it implied that the radio was better in some way.)