View Single Post
  #6  
Old 01-20-2008, 08:31 PM
Seldom Seen's Avatar
Seldom Seen Seldom Seen is offline
Rising Sun Member
 
Join Date: Aug 2005
Location: Highlands Ranch
Posts: 524
Default T6

Notes on the T6 section - Communication Modes and Methods


Phone – voice transmissions by radio

- includes AM, SSB, and FM

Modulation – a way of altering a radio wave so that it can carry information

- involves mixing a radio wave (the “carrier”) with a voice or other signal

Amplitude Modulation (AM) – modulation method where the carrier’s “height” changes when it’s mixed with your voice

Single sideband – when an AM signal is created, there are three parts: the carrier, the upper sideband (USB) and lower

sideband (LSB)

- voices sent using AM sound very natural but are very wide on the band

- by removing one of the sidebands, we can make the signal narrower (about 2 to 3 kHz wide)

- used for worldwide communications on HF

- used for long-distance and weak signal contacts on VHF and UHF

- LSB is used below 14 MHZ

- USB is used on 14 MHz and above, including VHF and UHF

Gateway – ham radio connected to the internet

FM – frequency modulation

- used with repeaters on two meters a lot; very clear and natural sounding

- very large bandwidth (about 5 to 15 kHz wide)

CW – Morse code signals

- narrowest bandwidth of all

- only send at speeds at which you can comfortably receive

- repeaters often use CW to identify

Fast-scan TV – extremely wide bandwidth (about 6 MHz)

- often used on 70 cm since it is a wide band

Echolink – uses the internet to send voice transmissions (Voice over internet protocol, VoIP)

- any ham can use this

- it is possible to hear DX on 2 meter repeaters this way

- active nodes using VoIP can be found in a repeater directory or on the internet

IRLP – internet radio linking project; also uses VoIP

- use the keypad on the radio to send the ILRP node numbers to select a node

Packet radio- digital (computer-to-computer) communications

APRS – automatic position reporting system (for sending GPS info over ham radio)

-requires a GPS receiver

NTSC – national television system committee

- a standard fast-scan color TV signal

Technicians can use point-to-point digital message forwarding on 1.25 meters (219-220 MHz)

PSK – phase-shift keying

- modulation method involving varying the phase of a signal

PSK31 – low-speed PSK that works well in noisy conditions

Q-signals: abbreviations used on ham radio

QRM – Q-signal for “interference”

QSY – Q-signal for “changing frequency”
Reply With Quote