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CW Bypass Mode
Depressing the Bypass push-button places the DSP-59+ into a bypass mode. In this mode, a
relay connects the audio input jack of the DSP-59+ directly to the speaker and headphone output
jacks. The relay also connects the audio input jack of the DSP-59+ to the line output jack via a 6
dB attenuator. The Bypass mode has precedence over the CW modes. When the DSP-59+ is in
bypass, the settings of the gain control and the parameter select push buttons do not affect the
signal. Turning off or removing power from the DSP-59+ automatically de-energizes the relay
and forces the DSP-59+ into the bypass mode.
5.3 Data Bandpass
RTTY, AMTOR, PACTOR, G-TOR, HF Packet, WEFAX, SSTV, CLOVER.
In the data bandpass mode, the DSP-59+ tailors the audio input using one of 76 bandpass filters.
The filters include a standard 2210 Hz. center frequency data bandpass filter set for RTTY,
AMTOR, PACTOR, G-TOR and HF Packet, an optional data bandpass filter set for other center
frequencies (preset by four internal jumpers), and 3 fixed bandpass filters for SSTV, WEFAX
and CLOVER. The DSP-59+ also provides marker tones at the mark-space frequencies of the
selected bandpass filter for data frequencies.
To activate the data bandpass filter mode, depress the red BP push-button. Turn the Center
Freq control to the desired frequency indicated by the red numbers around the Center Freq
control. Turn the Bandwidth control to the desired bandwidth indicated by the red numbers
around the Bandwidth control. One bandpass filter is always active in BP mode.
The random noise reduction mode was not designed to aid data signals, but DSP-59+ users have
found it helpful under some conditions. Generally, do not use the NRr mode with the BP mode
for data. If noise conditions are severe, and you have tried all other filter combinations, then try
the NRr and BP mode simultaneously. To activate random noise reduction, depress the push-
button marked "NRr".
Data Operating Hint - FSK Primer
RTTY, AMTOR, PACTOR, G-TOR and HF Packet all use Frequency Shift Keying (FSK).
FSK is also called AFSK Audio Frequency Shift Keying when frequency shifted audio tones are
used to modulate a transmitter. There are three important parameters used to describe an FSK or
AFSK signal - the frequency shift, the center frequency, and the keying or baud rate. The
combination of frequency shift and baud rate determine the spectrum of the FSK signal. The
goal of a filter is to reject everything in the spectrum except the desired signal while minimizing
the degradation of the desired signal.
Frequency shift
The frequency shift is specified in one of two ways. The most common specification in amateur
radio is total shift or the difference between the low (Mark) and high (Space) tones. In the
technical literature, the shift from a center frequency is more commonly specified. For example,
a 170 Hz. shift RTTY signal is the same as a +/- 85 Hz. shift. Note the frequency shift remains
the same whether it is shifting an RF signal or an audio frequency signal. Fortunately, in
amateur radio, there are only two common frequency shifts - 170 Hz. and 200 Hz. 170 Hz. is
the standard RTTY frequency, while 200 Hz. is the standard for AMTOR, PACTOR and G-
