• Power is different in AC, and is expressed as Peak Envelope Power, measured as an output power to the antenna
    • The average power at the point where we have the peak power (think of an AC signal, calculating the average power at the point where the wave is the strongest)
  • Bandwidths exist for all signals, and the centre of the band is the frequency we refer to
    • CW/Morse: 500Hz of bandwidth
    • Data/RTTY: 1kHz of bandwidth, 250-500Hz of separation
    • SSB: 2-3 kHz
    • FM: 3kHz, +/- 5kHz of deviation allowed (i.e. 10kHz deviation total)
    • No FM allowed below 28MHz frequencies
  • If you give to much gain to your signal (called overpowering), you will likely go beyond your expected bandwidth due to noise in the equipment you’re using
    • This is called splattering in AM/SSB, and “over-deviating” in FM
    • Leads to signal distortion, and affects nearby receivers
    • This can be caused by too much speech processing, too much gain, or mic too close
  • SSB: basically AM, but the carrier and one of the AM bandwidth lobes is suppressed, leading to more power and better bandwidth efficiency
    • Modulation is done by a balanced modulator, and then there is a filter to take out the other lobe
  • Most ham radios have an ALC (automatic level control) meters that cap the input to prevent overdriving the amplifier, and display how loud your signal is
    • If you’re overpowering, use a lower gain on your mic, or put it further from your face
  • FM > AM/SSB in terms of SNR, because if there’s multiple signals within a band, the frequency discriminator picks up on the strongest one → since amplitude does not change for FM, the strongest signal is always able to get picked up
  • Data has between SSB and CW in terms of bandwidth
    • Accepted data protocols are RTTY, AX.25, and AMTOR
    • Exceptions: on higher frequencies (>150 MHz), more bandwidth is allowed
  • If a data system says “connected”, it means an acknowledge packet has been received
  • 1 = mark, 0 = space
  • A terminal node controller is used to connect a computer and transceiver
  • Anyone can monitor data transmissions, but people monitoring cannot send acknowledge messages
  • Data repeaters and networks
    • There are specialized repeaters called digipeaters, which include protocols with marks/flags to indicate whether a signal should be repeated if a digipeater receives it
    • Networks of digipeaters create long distance transmission with fault tolerance