Television is a method of reproducing fixed or moving visual images by the use of electronic signals. There are numerous kinds of TV systems and different standards have been adopted around the world. Moreover, TV standards are in a state of flux since there is a worldwide push to adopt a new high-definition television (HDTV) standard.
The rated power of a TV visual signal is the effective isotropic radiated peak envelope, EIRP, and is usually called simply the effective radiated power, ERP. The EIRP is the power that would be required to be fed into an isotropic antenna to get the same field strength as that obtained from an antenna that is actually used as measured in the in the direction of its maximum radiation.
The actual equation is
PERP= P PEP Ga GL
Ppep=peak envelope power out of the transmitter
Ga= power gain of the antenna
GL=total gain of the transmission line system from transmitter output to the antenna
For a VHF TV station operating on channel 5, a typical value is ERP of 100Kw, which is the maximum power licensed by the FCC for channels 2 to 6. For a UHF station operating on channel 20, a typical value is ERP of 500Kw.
Color television pictures are synthesized by combining red, green, and blue light in the proper proportion to produce the desired color. This is done by using a color CRT that has three types of phosphors-one type that emits red light, one that emits green, and a third type that emits blue light when they are struck by electrons.
The National Television System Committee (NTSC) compatible color TV system was developed and adopted in the United States for U.S. transmissions in 1954.
U.S. Television Channel Frequency Assignments
The U.S. channel frequency assignment is as follows:
Channels 2 to 13 (VHF) 54MHz to 216 MHz
Channels 14 to 83 (UHF) 470 MHz to 890MHZ
TV Marti is one of the most powerful weapons against Castro. Castro has had a complete embargo of information over the Cuban people. As they say, a picture is worth a thousand words. To inform the Cuban people, daily, via TV signals, of the true world, what is happening, how is life in the United States, in the rest of the world, is something Castro cannot afford and what he fears most.
To interfere TV Marti, Castro uses AM radio signals, like the signals transmitted in the United States by your local AM stations. In Miami, signals like WQBA, WAQI, etc. Why? Because TV video signals are transmitted using AM radio signals, at a higher frequency and bandwidth.
Instead of voice or music, the signal used to interfere TV Marti is called a "tone" that can be compared to a whistle or the sound that we hear on the radio when they simulate an emergency situation as a test. However, the Cuban government uses a sequence of tones distributed over the bandwidth of the TV Marti signal
The maximum power allowed in the United States by the FCC to radio stations is 50,000 Watts. And even so, very few stations get so high because it costs money to do so. This is, by the way, also an international regulation, to avoid interference of stations.
The radio signals that Castro uses to interfere TV Marti have a power of 500,000 Watts. This is ten times more powerful. Castro has 5 stations dedicated to interfere TV Marti. Three of them "donated" by the former Soviet Union, and 2 purchased in Japan.
Five antennas are used. They are located at: Hotel Habana Libre, Hotel Triton, Guanabo, Alamar, and Mirador de Lawton. Why in these places? Because the signal transmitted by TV balloon is a narrow beam signal concentrated in those neighborhoods. Whenever the TV Marti signal has been deviated just a few degrees from that area, the signal has been seen without interference in Matanzas, or Pinar del Rio, depending on the directional deviation.
TV Marti is presently transmitted in VHF, that is, in the range of frequencies occupied by channels 2 to 13., as indicated in the Table above. TV Marti transmits in Channel 13, that is, in the 210 to 216 MHz band UHF are the channels from 14 up, as indicated also in the Table above. Castro also has in place some special equipment to interfere UHF signals. Castro purchased these equipments in the late 80s, anticipating the change of frequency spectrum of TV Marti to UHF. The equipment has not been properly kept, and they are not in working conditions.
Castro needs, in order to have an efficient interference signal for the entire country, one station per approximately 50,000 inhabitant neighborhoods or geographical regions. That is, to interfere TV Marti, if transmitted to the entire Island, Castro needs approximately 350 stations and 1,750 antennas. This is not feasible, technologically, neither financially. However, TV Marti has been, and still is, transmitting only to a certain area of La Habana.
Each of these stations uses, because of the high power, a consumption of 1.7 barrels of oil per each hour of functioning. This is not feasible either for Castro if TV Marti were transmitted to the entire Island.
What is needed to transmit TV Marti in order to be seen in the whole Cuba properly?
For channel 13, 210 to 216 MHz, the frequency band behaves as any other VHF propagation waves, which travel beyond the horizon, taking into account or assuming 5,278 miles/8494 Kms, which is 4/3 times the actual earth radius to correct for atmospheric refraction.
In practice, it has been experienced that the high frequency channels, upper levels, 7 to 13, will not be absorbed or totally attenuated by the water, but it will be reflected mainly when using directional propagation antennas.
An antenna about a height of 1000 to 1500 feet range will reach Cuba territory with no fading or with very small one. The code of Federal Regulations ( 47, parts 70 to 79) specifies parameters for distance separation between FM and TV coverage contours.
However, the effective radiation power, which is limited by ERP and height above the average terrain (HAAT), is an important parameter to not interfere with other stations. For example, 98.3 MHZ located on the channel 4, which belongs to NBC/RCA, when modified from class A to class C, or 100Kw ERP, required to change frequencies for FMs located in Arcadia and Immokalee, with distances from channel 4 tower which are respectively 252 Kms and 127 Kms.These data indicate the reach of a signal over terrain.
The antenna height above the average terrain is an important parameter to determine the directivity of the signal to the desired zone (Cuba) so as the number of elements that comprise the antenna in order to orient the signal properly.
Consequently, the VHF and the UHF bands are practically with a radiation beyond the curvature of the earth. Also, the ionosphere plays an important role on the reach of the signal by the line of sight mainly.
In both cases of VHF and UHF they are increased by approximately 15% beyond the optical line, which also helps the signal to reach beyond the horizon. The elevation of the antenna and the inclined angle of the elements are factors to direct and reach the desired point of reception (Cuba).
For VHF, we have
Distance, d, in miles = 1.41 (H)1/2
Where H = combined receiver and transmitter antenna height, feet
Sky waves apply to VHF and UHF
For UHF, we have
Depression angle of radio horizon and distance to radio are:
A, angle = 0.0153 (H)1/2
D, miles = 92.1518 A
Other costs: wire installation, engineering design, etc,.
Transmission medium: Video,Vestigial sideband, VSB; audio FM, video AM.
Change of frequency spectrum from VHF to UHF, or keep channel 13,VHF
If this is implemented, TV Marti will be seen in all Cuba without a trace of interference.
TOTAL COST: Not over $2 million dollars.
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