simplex: 
  5 miles
  earth's curvature
  equations??

duplex:
  repeater -- altitude & power
  repeater critical items:
    output frequency
    offset
    tone
    tone squelch

Problems to be aware of when using a repeater:
  front end overload of near by radios
  pause half a second before speaking

Repeater controlls:
  touch tone '5' gives time on UCF repeater
  touch tone '6' gives current meeting news (announced hourly on meeting day)

Repeater programmable features:
  slots for 30 programmable voice messages from fixed vocabulary
  40 programmable macros (5, 6 programmed now)
  slots for 60 scheduled "events"
  8 digital inputs (trigger events)
  8 digital outputs 
  digital voice recorder -- bulid??
  
Repeater messages:
  The repeater will transmit its ID:
    on the half hour and hour
    immediately after the first transmission after more than 10 minutes
    once every 10 minutes in which the repeater has been used
  Use the 10 minute ID as a reminder that you too need to ID.

  The ID will usually be given as voice; if someone transmits during
  this ID, the repeater will stop and continue the ID as CW (morse
  code) allowing you to talk through the ID.

  Periodically, especially after short transmissions, the repeater
  will say "Please identify."  This is just a reminder that you should ID.
  The repeater isn't smart enough to know if you've already done it.