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Here, 'v' is called the phase speed (magnitude of the phase velocity) of the wave and 'f' is the wave's frequency<ref>https://en.wikipedia.org/wiki/Wavelength</ref>. In the context of radio, 'v' is the speed of light, or 3×10<sup>8</sup> m/s (specifically 299,792,458 m/s). For instance, if the desired emergency broadcast station was at 1650kHz, the full wavelength would be 181.69m, and so a 1/4 wave of 45.42 meter (149 feet) or 1/2 wave antenna of 90.84 meter (298 feet) could be built. | Here, 'v' is called the phase speed (magnitude of the phase velocity) of the wave and 'f' is the wave's frequency<ref>https://en.wikipedia.org/wiki/Wavelength</ref>. In the context of radio, 'v' is the speed of light, or 3×10<sup>8</sup> m/s (specifically 299,792,458 m/s). For instance, if the desired emergency broadcast station was at 1650kHz, the full wavelength would be 181.69m, and so a 1/4 wave of 45.42 meter (149 feet) or 1/2 wave antenna of 90.84 meter (298 feet) could be built. | ||
=== Receivers and tuners === | === Receivers, transceivers and tuners === | ||
( | To work with specialist and custom antennae a receiver will be needed. Unless the antenna is built with precision to listen to a particular signal, a tuner will be needed. If broadcast is also desired, a transmitter will be required. In radio terminology, a device that both transmits (TX) and receives (RX) is a 'transceiver. [[File:Transceiver.png|thumb|A modern HF transceiver with a spectrum analyzer and DSP capabilities]]. | ||
Dedicated all-in-one transceivers can vary greatly in price and features, and depending on the region the operator is in, are bound to local broadcasting laws. Typically a HAM (Hobby and Amateur Radio) license is required to operate them. | |||
==== Software Defined Radio ==== | |||
In recent years, Software Defined Radio (SDR) has emerged as a practical and accessible alternative to dedicated hardware radio transceivers and receivers. Software Defined Radio implements a software interface to tunable radio hardware, such that reception and broadcasts can be done and processed entirely in software. This gives great flexibility to the operator, even so far as allowing for them to build their own tuners, signal de-modulators and broadcasting stations. | |||
Software Defined Radio is a large topic, and will not be covered in depth here. Should the reader be interested in exploring building transceivers in an SDR context, both the BladeRF and HackRF are interesting hardware options to look at. A comprehensive list of SDRs can be found here<ref>https://en.wikipedia.org/wiki/List_of_software-defined_radios</ref>. SDRs are typically interfaced with GNUradio or another software radio programming environment<ref>https://en.wikipedia.org/wiki/GNU_Radio</ref>. Every feature and facet of a modern dedicated hardware transceiver can be implemented in software on a laptop or workstation. | |||
An inexpensive option for those wishing to build a quality receiver for their long-range antenna project is RTL-SDR. | |||
[[File:Rtl-sdr.jpg|thumb|Four RTL-SDR devices, two of them with the popular SMA style brass connectors, used to interface with antenna. Note the writing on pink tape on one citing that device's particular parts-per-million clock offset, referenced by the operator when preparing the device for use.]] | |||
== Citations == | == Citations == | ||
<references /> | <references /> | ||