Voice (AF)

The frequency of the wave changes but the amplitude stays the same. Over modulation causes a
distorted signal and interference to other frequencies.

Other forms of modulation

Speech can also be carried by Single Side Band (SSB)

Data can be carried by Continuous Wave (CW or Morse code) and by using a modem called a TNC (terminal node controller)+
As with a microphone the gain must be adjusted so that no interference is caused to other frequencies and
the signal is not distorted.
Carrier wave

= modulated signal.

The Radio Frequency (RF) amplifier

The signal is made bigger so it will travel further.
The antenna (Aerial)

The antenna sends the signal as a radio wave at the speed of light.

The correct length of antennal MUST be connected to the transmitter or you will damage your radio. This is
called matching the antenna.

How do I know if my antenna is correctly matched?

Frequency Modulation (FM)

Find a clear frequency and send a short transmission. Look at your
Standing Wave Ratio (SWR) meter. It should read less than 2:1 if your
antenna is correctly matched. If it is any higher then you have a problem
with your antenna or feeder, NOT with your radio.

The SWR meter measures the ratio of power transmitted by the antenna
and power reflected back to the antenna.

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