R

Rain fade

Rain fade refers primarily to the absorption of a microwave radio frequency (RF) signal by atmospheric rain, snow or ice, and losses which are especially prevalent at frequencies above 11 GHz. It also refers to the degradation of a signal caused by the electromagnetic interference of the leading edge of a storm front.

View Source: https://en.wikipedia.org/wiki/Rain_fade

RF

A rate of oscillation in the range of around 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals. RF usually refers to electrical rather than mechanical oscillations; however, mechanical RF systems do exist. Although radio frequency is a rate of oscillation, the term "radio frequency" or its abbreviation "RF" are also used as a synonym for radio – i.e., to describe the use of wireless communication, as opposed to communication via electric wires.

View Source: http://en.wikipedia.org/wiki/Radio_frequency

RFID

Radio-frequency identification (RFID) is the wireless use of electromagnetic fields to transfer data, for the purposes of automatically identifying and tracking tags attached to objects. The tags contain electronically stored information. Some tags are powered by electromagnetic induction from magnetic fields produced near the reader. Some types collect energy from the interrogating radio waves and act as a passive transponder. Other types have a local power source such as a battery and may operate at hundreds of meters from the reader. Unlike a barcode, the tag does not necessarily need to be within line of sight of the reader and may be embedded in the tracked object.

View Source: https://en.wikipedia.org/wiki/Radio-frequency_identification

RHCP

Right Hand Circular Polarization - Circular polarization is commonly used in satellite communications where the orientation of the satellite and the receiver cannot be linearly aligned. The circular polarization of an electromagnetic wave is a polarization in which the electric field of the passing wave does not change strength but only changes direction in a rotary manner.

View Source: http://en.wikipedia.org/wiki/Circular_polarization

RS232

In telecommunications, RS-232 is a standard for serial communication transmission of data. It formally defines the signals connecting between a DTE (data terminal equipment) such as a computer terminal, and a DCE (data circuit-terminating equipment, originally defined as data communication equipment), such as a modem. The RS-232 standard is commonly used in computer serial ports. The standard defines the electrical characteristics and timing of signals, the meaning of signals, and the physical size and pinout of connectors. The current version of the standard is TIA-232-F Interface Between Data Terminal Equipment and Data Circuit-Terminating Equipment Employing Serial Binary Data Interchange, issued in 1997.

View Source: http://en.wikipedia.org/wiki/RS-232

RS485

TIA-485-A, also known as ANSI/TIA/EIA-485, TIA/EIA-485, EIA-485 or RS-485, is a standard defining the electrical characteristics of drivers and receivers for use in balanced digital multipoint systems.

View Source: https://en.wikipedia.org/wiki/RS-485

RSSI

In telecommunications, received signal strength indicator (RSSI) is a measurement of the power present in a received radio signal. RSSI is usually invisible to a user of a receiving device. However, because signal strength can vary greatly and impact functionality in wireless networking, IEEE 802.11 devices often make the measure available to users. RSSI is often done in the intermediate frequency (IF) stage before the IF amplifier. In zero-IF systems, it is done in the baseband signal chain, before the baseband amplifier. RSSI output is often a DC analog level. It can also be sampled by an internal ADC and the resulting codes available directly or via peripheral or internal processor bus.

View Source: https://en.wikipedia.org/wiki/Received_signal_strength_indication

RUDICS

The Iridium Router-Based Unrestricted Digital Internetworking Connectivity Solutions (RUDICS) is an enhanced data service that allows customers who have requirements for large data transfers the ability to transfer data via reliable, affordable, multi-protocol Mobile Originated (MO) and Mobile Terminated (MT) circuit switched data connectivity across the Iridium satellite network.

View Source: https://www.iridium.com/products/RUDICS.aspx