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Voice and data emissions FM phone, SSB and RTTY: what they are and why SSB is more efficient than AM.
What you will be able to do Define FM phone, SSB and RTTY Explain why SSB is more efficient than AM What are the common ways to send voice and data?
Three emission types matter for the Foundation exam.
FM phone
FM phone is a frequency -modulated voice transmissionfrequency is varied by
the audio.
SSB
SSB is single-sideband suppressed-carrier voice transmission .
Why SSB is more efficient than AM
SSB suppresses the carrier and one sideband, saving power and bandwidth .
AM sends a carrier and two sidebands; SSB sends only one sideband AM: carrier and two sidebands SSB: one sideband only carrier and other sideband suppressed frequency AM sends a carrier and two sidebands; SSB sends only one sideband
Which is the efficient one?
SSB is more efficient than AM because it removes the carrier and one sideband. It does not make
the signal louder; it stops wasting power on parts that carry no extra information.
RTTY
RTTY is narrow-band direct-printing telegraphy (radioteletype), a digital mode .
Names in the tutorial
The PDF calls these emissions "SSB ", "FM" and "RTTY ". The formal ITU designators for SSB and FM voice are J3E and F3E
(decoded in Unit 3). For the exam, use the names the tutorial uses.
You now know
FM phone is voice that varies the carrier frequency .SSB is single-sideband suppressed-carrier voice, more efficient than AM because it suppresses the carrier and one sideband, saving power and bandwidth.RTTY is narrow-band direct-printing telegraphy, a digital mode.
Source: RSK Foundation tutorial, KARE 07 §3
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