Timewave DSP-9+, Operating Manual

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10
Default mark-space frequencies vary among modem and radio manufacturers, and
common mark-space frequencies also vary in different parts of the world. Some modems
have default HF Packet mark-space frequencies different from their RTTY, AMTOR, and
PACTOR mark-space frequencies. The DSP-9+ mark-space frequencies factory settings
are 2125-2295 Hz. for all 4 data modes. The mark-space frequencies of the modem, receiver
and DSP-9+ must match. Some modems and radios have programmable mark-space
frequencies. If your modem or radio defaults to mark-space frequencies other than 2125-
2295 Hz., you must change the modem or radio mark-space frequencies to match the DSP-
9+ or change the DSP-9+ mark-space frequencies to match the modem and radio mark-
space frequencies.
Note that some receivers do not have specific provisions to use their narrow (200 - 600 Hz
wide) filters for data. Operate these radios in their SSB voice filter bandwidth. Other
receivers may have fixed or variable mark-space frequencies - check your operating
instructions carefully!
The Kantronics KAM+ usually has the HF Packet mark-space pair set to 1600-1800 Hz.
See the KAM+ manual for the procedure to change the KAM+ mark-space setting via
software.
See the Back Panel Jumper Function Table on page 12 for DSP-9+ filters and settings.
Jumpers 7 and 8 set the mark-space frequencies.
RTTY Remodulator
To select the RTTY remodulator, first press in the RTTY push-button to select the RTTY filter.
Then, press the RTTY push-button rapidly twice (“double-click”) to enable the remodulator.
Leave the button pressed in after you have selected the remodulator. To switch the remodulator
off release the RTTY push-button for one second or more. The remodulator mode is easily
recognized by a lack of any receiver background noise - only the pure audio RTTY tones are
audible when the remodulator is on and a RTTY signal is present. The DSP-9+ mutes the audio
output when no FSK RTTY signals are detected.
Data AGC
The AGC (automatic gain control) can add up to 18 dB extra gain for weak signals, and can
control the variation in levels of stronger signals. Depress the “AGC” push-button to turn on
the AGC. Use the AGC whenever it enhances the readability of a signal. Sometimes, the AGC
appears to increase the noise level because of the additional gain of the AGC. This is normal
when signals are weak, and may enhance readability in spite of the higher audible noise.
Data Bypass Mode
Depressing the Bypass push-button places the DSP-9+ into a bypass mode. In the Data mode,
the bypass mode routes the signal through an allpass DSP filter which has precisely the same
delay as the normal narrow band filter. When switching from data mode to bypass mode, this
prevents a time discontinuity which can cause an AMTOR or PACTOR link to lose
synchronization. The bypass mode has precedence over the Data mode. When the DSP-9+ is in
bypass, the settings of the gain control and the parameter select push buttons do not affect the
signal.