Timewave DSP-599zx, Operating Manual

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DSP-599zx Audio Noise Reduction Filter
March 6, 1997 A-3
Appendix B
Glossary
AFSK (Audio Frequency Shift Keying)
A common RTTY mode most often used for VHF and
UHF communications. The signal is generated by
switching between two audio tones fed into the micro-
phone input of a FM transmitter.
AMTOR
Amateur Teleprinting Over Radio is an error correct-
ing digital mode. Date is sent in three character blocks
then waits for a response of ACK or NAK to indicate
successful or unsuccessful transmission.
Bandpass Filter
A filter that allows only a given range of frequencies
to pass through. All frequencies outside the range are
either eliminated or significantly reduced in volume.
Center Frequency
The nominal frequency at which the RTTY data signal
is transmitted. The signal is actually a rapid switching
between two frequencies (Mark and Space) centered
on the nominal frequency. Nothing is actually trans-
mitted on the center frequency. The normal range is
1200 to 2500 Hz. The North American standard is
2210 Hz.
CLOVER
A digital communications mode that utilizes a four-
tone modulations system and digital signal processing
to pass data on the HF bands. It has a relatively narrow
signal bandwidth of 500 Hz. Because CLOVER sta-
tions share information concerning signal conditions
and power output levels, it has the ability to automati-
cally adjusts power output to maintain stable commu-
nications. It is however, extremely sensitive to
frequency shift. It cannot tolerate frequency drift of
more than 15 Hz while linked.
DCD (Data Carrier Detect)
A “squelch “ circuit for data. This is done by sampling
data transmissions to verify that it is valid data in the
mode selected. When found, the circuit opens the cir-
cuit to allow data to flow through.
FSK (Frequency Shift Keying)
A common RTTY mode most often used for HF com-
munications. The signal is generated by switching a
HF carrier between two separate frequencies.
G-TOR
A data mode that use several compression, checking or
correction techniques besides automatic repeat re-
quests. Faster than either AMTOR or PacTOR.
Heterodyne
The combining of two different frequencies to produce
beats whose frequency is either the difference or the
sum of the two frequencies.
Highpass Filter
A filter that permits frequencies above a certain cutoff
frequency to pass and eliminates or significantly re-
duces signals below the filter frequency.
Lowpass Filter
A filter that permits frequencies below a certain cutoff
frequency to pass and eliminates or significantly re-
duces signals above the filter frequency.
Mark-Space Frequency
The two frequencies at which RTTY data is actually
sent. The common frequency shifts between Mark and
Space are 170 Hz and 200 Hz.
PacTOR
A packet-like digital mode combining aspects of pack-
et and AMTOR and also has AX.25 compatibility. Un-
like standard packet radio, PacTOR does not allow
frequency sharing. PacTOR is faster than AMTOR
and uses the complete ASCII character set and can eas-
ily handle binary data transfers.
RTTY
The original data communications mode and is well
suited for “roundtable” QSOs with several stations. It
does not support frequency sharing or error correction.
RTTY was originally designed for use with mechani-
cal teleprinters, predating personal computers.
SSTV
Slow-Scan TV is a narrow bandwidth image mode
popular on the HF bands that transmits pictures at 8, 16
or 32 seconds per frame.
WeFAX
Weather facsimile image format. There are two modes
HF and satellite. The DSP-599zx currently supports
only HF mode Detailed information on satellite mode
can be found in The Weather Satellite Handbook pub-
lished by the ARRL