What is an Analogue Repeater?
The function of an Amateur Radio Repeater is to receive an incoming RF signal from a radio operator such as hand portable, mobile or base, regenerate the audio and then retransmit in real time on a different frequency.
By allowing the repeater to amplify the signal, they allow transmissions to travel a much greater distance or into areas such as valleys, or populated areas where buildings would normally not allow line of sight transmissions.
An Amateur Radio Repeater is essentially a receiver and transmitter, with interfacing logic and more importantly some special RF filtering such as a set of cavities or duplexer. This RF filtering allows the transmitter and receiver to operate at the same time, without interfering with each other.
A repeater may operate on either a single antenna or a separate pair of transmit and receive antennas. The antennas are carefully chosen to maximise the effective range, coverage and purpose of the repeater. These antennas could be a simple dipole, beam or vertical collinear.
What is CTCSS?
CTCSS is an abbreviation for Continuous Tone-Coded Squelch System and is used to reduce the annoyance or interference when listening to other radio operators or stations on the same frequency.
A CTCSS system uses a superimposed low frequency audio tone signal with the outgoing microphone audio from the transmitter and is known as a CTCSS encoder. The receiver has a CTCSS decoder and will only allow audio to be passed through to the speaker if the decoder receives a specified CTCSS tone.
Typically CTCSS tones are standardized by the EIA/TIA and consist of a set of 38 tones ranging from 67 Hz up to 250.3 Hz. Some non-standard tones are used in some systems such as Military.
CTCSS is also referred in some countries as PL (Private Line), or even Tone Squelch, and is primarily used in commercial Private Mobile Radio to allow a number of different groups of people to use the same frequency. Each group of people or company being allocated a separate CTCSS tone.
In Amateur Radio, CTCSS is primarily used in normal Analogue Repeaters and Internet Links. This reduces the risk of interference between repeaters and links, typically under lift or high pressures, where VHF and UHF signals travel much further.
Originally repeaters used to require a 1750 Hz audio tone burst in order to open up for the first time. Over the years this fortunately has been replaced with CTCSS access so reducing interference and the annoying need for the tone burst. I am sure many of the long standing radio amateurs can still remember how to whistle a good 1750 Hz!
While Analogue Repeaters and Internet Link stations require to have a CTCSS decoder on the receiver as part of the NoV license, not all Repeaters and Internet Link stations encode CTCSS on the transmitter. This can be annoying from the radio operators perspective in that he/she will need to use open squelch. This is fine providing the radio operator is not located in between two repeaters or internet links on the same frequency.
The UK CTCSS is split up into regions and a link is provided below showing these.
What is D-STAR?
D-STAR (Digital Smart Technologies in Amateur Radio) is a digital voice and data protocol specification developed as the result of research by the Japan Amateur Radio League to investigate digital technologies for amateur radio.
D-STAR compatible radios are available on VHF/UHF and microwave amateur radio bands. In addition to the over-the-air protocol, D-STAR also provides specifications for network connectivity, enabling D-STAR radios to be connected to the Internet enabling repeaters and simplex nodes to be linked together enabling worldwide communications and provisions for routing data streams of voice or packet data via amateur radio call signs.
D-STAR supports both simultaneous digital voice and digital data enabling GPS location/short messages in addition to voice transmissions.
The first manufacturer to offer D-STAR compatible radios was Icom. As of February 1, 2013, no other amateur radio equipment manufacturer has chosen to include D-STAR technology in their radios.
What is an Internet Link Station?
An Internet Link Station can be an Amateur Radio Repeater or Simplex RF station which is connected to Voice Over IP (VoIP), systems via the internet. Examples being Echolink, , IRLP and CQiNet. The most common system in Worldwide use between radio operators and repeaters/links is using Echolink. IRLP typically is used to connect repeaters and links together but as it’s a closed system, it cannot be accessed other than via RF.
Over the years, Echolink has expanded to be the Worldwide number one VoIP system in that it allows radio amateurs to not only speak across the world using RF using VHF or UHF radio but also from a PC, tablet and even mobile phone application.
Some feel this is not amateur radio but it is in fact a modern addition to the modes of operation that we use and for some it’s a life line – for that reason we should embrace this. Examples are where in our compact communities, towns, even in nursing homes, some do not have the privilege of being allowed to put up aerials for a number of reasons. This restricts the radio amateur to maybe local VHF and UHF operation or sadly even close down operation and the hobby completely. Using Echolink from a PC or RF to a local repeater/link or IRLP on a local repeater/link, the radio amateur can speak to another station anywhere in the world.
In Eastbourne, we have a VHF Echolink Simplex Station on 145.3375 MHz CTCSS 88.5 Hz. This can be used by any local radio amateur to RF connect to another station anywhere in the world. Details of the RF link and requirements is provided below.