Modes

The operating mode can be just as important as propagation. depending on who or where you want to work.

Modulation When it comes to communications, we Hams, have a variety of modes to chose from. A mode refers to the way the signal is modulated during transmission. In order to have your transmission both transmitted and received it must be modulated electronically, not to mention both radios need to be operating in the same mode, in order for it to be a successful QSO. The following table gives some of the preferred voice used by general agreements.

LSB

160, 80, 40 meters

USB

20, 17, 15, 12, 10 meters

FM

2, 1.25 m and 70 cm. Some USB is also used.

Characteristics of each mode is unique. An example of this is the amount of bandwidth a signal uses. CW is rather narrow (less than 250 Hz), on the other hand FM is wider (15-20 kHz) The narrower bandwith the more activity on a band and more signals being transmitted. The down size, of this is poorer quality in your transmission. Now lets look at each form of modulations individually.

CW (continuous wave) is a simple unmodulated signal unlike others which use some form of modulation. By using a key to interpret and send CW, you then have Morse Code. Morse code however is not a mode, but a code, used to control the CW signal. When learned, Morse Code is the most reliable form of communication around and reliable, able to reach out even under the worst of conditions.

AM (amplitude modulation) is one of the early forms of voice transmissions. Just like CW, it has an upper and lower sideband that are modulated by varying the strength of your signal. Most shortwave broadcast stations use this method. if you ever tune in to an AM station, you can here the continuous tone the more you move the dial slightly from the center of the signal. With this mode it requires twice the bandwith of SSB, so is not widely used amongst hams (though some still use it)

SSB

SSB (single side band) is a mode where the carrier and one sideband of the AM mode has been suppressed. When using this you focus more of the signal in either the USB or LSB (upper or lower sidebands). This results in further traveling of the signal, and a clearer copy on the other end. This is a favorite amongst the HF users.

FM (frequency modulation) is the one you hear when working 2m on the club repeater, and usually where most of us hams start out. It has exceptional voice quality without fading or the noise you get with the other modes. Usually limited to 2m and 70cm, do to the bandwith required, you mat also catch it on 10m around 29Mhz.

Digital Modes

Having been around since RTTY, digital mode has exploded with the computer age. Just like a computer uses binary to send it’s signal across the internet, so does digital modes across the airwaves. In order to use digital modes, you will need a computer, hooked up to your radio using special software and cables. You send a message by typing it on the keyboard and see the reply on the screen. Some of these different modes are.....

RTTY - Radioteletype (RTTY) uses a baudot (5 bits per character) or ASCII code (7 bits per character) to communicate. RTTY is almost as reliable as CW and there are many hams who use this mode on a regular basis on the HF bands.
Packet - uses the complete ASCII character set which permits both upper- and lowercase characters in a transmission. Packet is error-free which is achieved by sending data in small packets with a check bit. If an error is detected by the receiving station it replies and requests that the packet be resent. This is repeated as needed to receive the packet correctly. When signals are good a packet rarely needs to be sent twice but under poor conditions the resending of error packets slows down the exchange of information.
Tor Modes - TOR means "teleprinting over radio." These modes include AMTOR, Pactor, G-TOR and Clover. Basically they all use some variation of the technique mentioned in packet for ensuring error-free transmission. Each use specialized algorithms for transmission resulting in improved speed and accuracy.
PSK-31 - is a relative newcomer to the digital scene and is fast becoming a primary digital mode. One reason for its appeal is that it uses the sound card in the computer to send and receive through the radio. No other special equipment is needed. PSK-31 uses very little bandwidth, less than CW and can function very well at low signal strengths. Unlike Packet and TOR it is not error-fre

FSTV/SSTV

Fast scan and slow scan television are just like it sounds. You can send your own picture or video across the airwaves. SSTV is usually used to send still photos on the HF, due to low data rate and bandwith. While SSTV offers motion pictures on UHF. Now days you can even find some radios with built in cameras and screens.

IRLP

With the invention of the internet comes IRLP (Internet Radio Linking Project). In basics you connect to a local repeater that’s hooked up to the internet. From there you enter a code on your radio, to connect to another repeater somewhere else. This could be across country or even the world. This mode eliminates propagation and gives you the same quality as a local call would.

IRLP is a Canadian invention by VE7LTD and uses Voice over IP (VoIP) to instantly interconnect one or more repeaters around the world. Now with your basic license new radio amateurs are able to use an HT to communicate worldwide.

There are many programs used for IRLP, including Echolink, IRLP, and such. Some will also allow you to use your computer to connect to the service, so if you don’t have a local tower nearby, you can still make those DX calls.


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