In view of this it can be seen why even high power HF radio broadcast stations may only be audible for a few miles from the transmitting site via the ground wave.
42.
Longwave, in particular, had good long-distance transmission characteristics due to their limited interaction with the ground, and thereby provided excellent great circle route ground wave propagation that pointed directly to the transmitter.
43.
Longwave in particular had good long-distance transmission characteristics due to their limited interaction with the ground, and thereby provided excellent great circle route ground wave propagation that pointed directly to the transmitter.
44.
A skip zone is an annular region between the farthest points at which the ground wave can be received and the nearest point at which the refracted sky waves can be received.
45.
As the frequency gets lower the attenuation with distance decreases, so very low frequency ( VLF ) and extremely low frequency ( ELF ) ground waves can be used to communicate worldwide.
46.
Even with the expanded network, some areas were not adequately covered and for this reason up to 1700 voluntary interceptors ( radio amateurs ) were recruited to detect illicit transmissions by ground wave.
47.
When using medium to high frequency radio telecommunication, there are radio waves which travel both parallel to the ground, and towards the ionosphere, referred to as a ground wave and sky wave, respectively.
48.
At frequencies between 3 and 30 MHz, a large portion of the energy from a horizontally polarized antenna reflects off the ground, with almost total reflection at the grazing angles important for ground wave propagation.
49.
Ditmeyer of the railway administration says that 40 old Air Force ground wave emergency stations, previously used for early warning in case of a Soviet attack, are being converted to bases to receive data from satellites.
50.
Turning analog ground wave broadcasting into a digital format costs a tremendous amount of money _ as much as 500 billion yen ( $ 4.5 billion ) per one commercial broadcasting group, according to one estimate.
