Poor man's microwave
From The RadioReference Wiki
"Poor man's microwave" is a colloquialism which refers to RF linking by means of dedicated transmitter and receiver strips as a cost-effective solution versus implementing a microwave or leased telephone line. These systems are licensed as FXO fixed operational stations and are secondary to voice communication which uses the frequency or the full frequency pair, if the frequency being used is paired with another. Despite the colloquial name, actual microwave frequencies are not used. This type of system is an equivalent of a DS0 channel.
Poor man's microwave systems are typically used to connect to and from remote locations where other transport facilities are not present. UHF is typically used and frequencies are coordinated so that they do not interfere with other operations under normal circumstances. Frequencies on the input side of a UHF pair are commonly used. Although the frequencies are avoided by coordinators, when no other choice is possible, a primary user may be placed on the same frequency pair. At that point, the FXO operations must not interfere with the primary user, and, in some cases, must cease regardless of function or need. Therefore, using poor man's microwave linking presents with some risk, particularly in areas where UHF frequencies are in demand.
Poor man's microwave systems are frequently used to backhaul voting receivers. As such, they are subject to limitations by the FCC. For example, continuous transmission of a voting status tone is prohibited unless the FXO operation is licensed and placed into operation with a transmitter of no greater than 0.12 Watts (120 milliWatts per 90.217(d)). There is lo limitation to ERP, however a directional antenna must be used. With a typical 9.0 dBd Yagi antenna, the effective radiated power of a 0.12 W output transmitter may be just under 1.0 W, presuming negligible transmission line loss. The characteristics of the signal, defined by calculated ERP, antenna polarization, azimuth of the main power lobe, as well as the horizontal beamwidth (the arc from half power point to half power point) must be specified on the license. Many antenna manufacturers provide this data on both specification sheets, as well as three-dimensional plots of signal radiation that can be imported into professional propagation modeling programs. Care should be taken to not use vertical beamwidth, which is typically a much smaller arc, in place of horizontal beamwidth.
90.217(a) also allows for a wider occupied bandwidth than 11K2 ("narrowband"), however this will subject the operation to greater interference potential both to and from other licensees.
Analog stations which link back a voting status tone continuously should be licensed for both F3D and F3E emissions, with the first 4 number/letter combination indicating occupied bandwidth. For example, 11K2F3D and 11K2F3E both.