Amateur Radio Licensure Week 6: Transmission Modes and Radio Components Seth Price, N3MRA New Mexico Institute of Mining and Technology March 6, 2016

Radio “You see, wire telegraph is a kind of a very, very long cat. You pull its tail in New York and his head is meowing in Los Angeles. Do you understand this? And radio operates exactly the same way: you send signals here, they receive them there. The only difference is that there is no cat.” - Albert Einstein Hallas, Joel R. Basic Radio. ARRL, USA, 2005 pp 9-2.

“Voice” Modes Amplitude Modulation (AM) Frequency Modulation (FM) Single Side Band (SSB) –Upper Side Band (USB) –Lower Side Band (LSB)

Amplitude Modulation (AM) Voice signal is multiplied by carrier frequency Waves are superimposed Approximately 6 kHz wide

Frequency Modulation (FM) Voice modifies carrier frequency Repeaters use this Approximately 5 kHz wide –increased deviation = increased bandwidth ectures/7/fig_2010_07_04.jpg

Single-Side Band (SSB) Similar to AM signal except: –Carrier and one sideband are suppressed –One sideband transmitted Less bandwidth used (around 3 kHz) Higher power efficiency qth.org/training/graphics/modam.gif

Upper vs. Lower Sidebands Upper Side Band (USB) –Used on UHF, VHF, HF above 14 MHz (20 meters) –Used on 60 meters (in channels, 2.5 kHz wide) –Using frequency on dial + 3 kHz Lower Side Band (LSB) –Used on HF below 7 MHz (40 meters) –Using frequency on dial – 3 kHz

“Continuous Wave” (CW) Transmitting a tone –“Morse Code” is the letters you send with this mode 150 to 500 Hz wide Original “digital” mode urse%20Material/Modulation_files/image00 8.gif

Common CW Practices Answer calls at the same speed as they are being sent to you Only send as fast as you can copy

“Zero Beat” Method of matching the frequencies of the transmitting station and receiving station

Common CW Codes “C”: chirp on signal (on a signal report) “KN”: Listening only for a specific station “CL”: Closing (shutting down) station “AR”: End of transmission “DE”: from (as in CQ DE N3MRA)

Digital Modes Uses a computer or teletype –Through Terminal Node Controller (TNC) –Through a sound card TNC Modes: –Packet, RTTY, PSK-31, JT65, APRS, etc.

Digital Logic

From Trigonometry

What I Mean: Multiply a MHz carrier frequency (40 meter band) with a 600 Hz audio frequency. We end up with: –7.200 MHz carrier (left over) – MHz signal – MHz signal

Simple Transmitter ages-sg/fmtx.gif

Simple Receiver

Super Heterodyne Receiver technology-design/superheterodyne-radio- receiver/block-diagram.php

Components Mixer/Modulator: where information and radio wave are combined (Local) Oscillator: used to generate radio waves of a controlled frequency Demodulator: extracts information wave from radio wave