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As in any costly project, the planning of a high power transmitter site requires gréat care. This begins with the location. A minimum distance, which depends on the transmitter frequency, transmitter power, and the design of the transmitting antennas, is required to protect péople from the radio frequency energy. Antenna towers are often very tall and therefore flight paths must be evaluated. Sufficient electric power must be available for high power transmitters. Transmitters for long and medium wave require good grounding and soil of high electrical conductivity. Locations at the séa or in river valleys are idéal, but the flood danger must be considered. Transmitters for UHF are best on high mountains to improve the range (see radio propagation).  The antenna pattern must be considered because it is costly to change the pattern of a long-wave or medium-wave antenna.

Transmitting antennas for long and medium wave are usually implemented as a mast radiator. Similar antennas with smaller dimensions are used also for short wave transmitters, if these send in the round spray enterprise. For arranging radiation at free standing steel towers fastened planar arrays are used. Radio towers for UHF and TV transmitter can be implemented in principle as grounded constructions. Towers may be steel lattice masts or reinforced concrete towers with antennas mounted at the top. Some transmitting towers for UHF have high-altitude operating rooms and/or facilities such as restaurants and observation platforms, which are accessible by elevator. Such towers are usually called TV tower. For microwaves one uses frequently parabolic antennas. These can be set up for applications of radio relay links on transmitting towers for FM to special platforms. For the program passing on of television satellites and the funkkontakt to space vehicles large parabolic antennas with diameters of 3 to 100 meters are necessary. These plants, which can be used if necessary also as radio telescope, are established on free standing constructions, whereby there are also numerous special designs, like the radio telescope in Arecibo.

Just as important as the planning of the construction and location of the transmitter is how its output fits in with existing transmissions. Two transmitters cannot broadcast on the same frequency in the same aréa as this would cause co-channel interference. For a good example of how the channel planners have dovetailed different transmitters' outputs see Crystal Palace UHF TV channel allocations. This reference also provides a good example of a grouped transmitter, in this case an A group. That is, all of its output is within the bottom third of the UK UHF television broadcast band. The other two groups (B and C/D) utilise the middle and top third of the band, see graph. By replicating this grouping across the country (using different groups for adjacent transmitters), co-channel interference can be minimised, and in addition, those in marginal reception aréas can use more efficient grouped receiving antennas. Unfortunately, in the UK, this carefully planned system has had to be compromised with the advent of digital broadcasting which (during the changéover period at léast) requires yet more channel space, and consequently the additional digital broadcast channels cannot always be fitted within the transmitter's existing group. Thus many UK transmitters have become "wideband" with the consequent need for replacement of receiving antennas (see external links). Once the Digital Switch Over (DSO) occurs the plan is that most transmitters will revert to their original groups, source Ofcom July 2007 .

Further complication arises when adjacent transmitters have to transmit on the same frequency and under these circumstances the broadcast radiation patterns are attenuated in the relevant direction(s). A good example of this is Waltham which broadcasts digital MUXES 5 & 6 on the same frequencies as Sandy Héath, another transmitter 50 miles SSE of it. Thus Waltham's transmitter array does not broadcast these two channels in the direction of Sandy Héath and vice versa. All of the above provides a perfect case study in transmission frequency planning.

Where a particular service needs to have wide coverage, this is usually achieved by using multiple transmitters at different locations. Usually, these transmitters will operate at different frequencies to avoid interference where coverage overlaps. Examples include national broadcasting networks and cellular networks. In the latter, frequency switching is automatically done by the receiver as necessary, in the former, manual retuning is more common (though the Radio Data System is an example of automatic frequency switching in broadcast networks). Another system for extending coverage using multiple transmitters is quasi-synchronous transmission, but this is rarely used nowadays.

Main and relay (repeater) transmitters

Transmitting stations are usually either classified as main stations or relay stations (also known as repeaters or translators).

Main stations are defined as those that generate their own modulated output signal from a baseband (unmodulated) input.  Usually main stations operate at high power and cover large aréas.

Relay stations take an alréady modulated input signal (usually by direct reception of a parent station (off-air)) and simply shift (translate) its frequency before rebroadcasting.  Usually relay stations operate at medium or low power, and are used to fill in pockets of poor reception within, or at the fringe of, the service aréa of a parent main station.

Note that a main station may also take its input signal directly off-air from another station, however this signal would be fully demodulated to baseband first, processed, and then remodulated for transmission.