Timewave DSP-59+ User manual

DSP-59+
Audio Noise Reduction Filter
Operating Manual
Manual Version 3.1S
Timewave Technology Inc.

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Table of Contents
1. Introduction to the DSP-59+ 2
2. Description of Controls and Connectors 2
3. Specification 5
4. Installation 7
5. Operation 9
6. Troubleshooting 16
7. Warranty 19
8. Electromagnetic Interference 20
9. Schematic Diagram 20
10. Appendix - Connector Requirements24
Copyright 1994, 1995 Timewave Technology Inc.
St. Paul, MN USA
[phone]
Manual Rev. 3.1, 27 June 1995

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1. Introduction to the DSP-59+
The DSP-59+ is an audio noise filter for amateur radio voice, data and CW operation.
The DSP-59+ filters and reduces noise and interference to improve radio reception.
The DSP-59+ uses digital signal processing technology to implement algorithms that
perform four basic functions: 1) Random noise reduction, 2) Adaptive multi-tone notch
filtering (Tone noise reduction), 3) Bandpass/Highpass/Lowpass filtering, and 4) RTTY
remodulation.
Random/Tone Noise Reduction
The noise reduction functions of the DSP-59+ operate by examining a characteristic of
signals and noise called correlation, and dynamically filtering out the undesired signals
and noise. The degree of correlation is relative. Random noise such as white noise or
static is uncorrelated. Speech is moderately correlated. Repetitive noise such as a
heterodyne is highly correlated. The DSP-59+ measures correlation and filters out
signals and noise that are outside its correlation thresholds. The amount of noise
reduction varies according to the correlation characteristics of the noise. Typical noise
reduction ranges from 5 dB to 20 dB for random noise and up to 50 dB for heterodynes.
Highpass/Lowpass Filters
The DSP-59+ has 15 highpass and 15 lowpass filters that are independently selectable
from front panel controls. There are many uses for the 225 combinations of highpass and
lowpass filters that the DSP-59+ offers. In a typical example of a voice mode
application, highpass and lowpass filters can improve a signal with a poor signal-to-noise
ratio. The independent highpass and lowpass filters remove the low and high audio
frequency components that do not contribute significantly to the speech intelligibility,
thus improving signal quality. Another common voice mode example is the
improvement of a SSB signal corrupted by adjacent channel interference (QRM). The
steep skirts of the highpass and lowpass filters allow the high side and low side
interference to be eliminated independently with minimal impact on the desired signal.
Although the DSP-59+ has bandpass filters for CW and the most common data modes,
the 225 selectable highpass and lowpass filter combinations also allow precise filtering
for modes such as wideshift RTTY. The DSP-59+ highpass filter adjustment range is
from 200 to 1600 Hz. and the lowpass range is from 1700 to 3400 Hz.
Bandpass Filters
The DSP-59+ has 316 bandpass filters that are used in data and CW modes. Narrow
band signals like CW and RTTY require bandpass filters with steep skirts and linear
phase response. Linear phase response maximizes the usable signaling rate for a given
bandwidth and minimizes ringing often heard on extremely sharp filters. The DSP-59+
has 195 CW filters with skirts so steep that a signal literally falls off the edge of the
passband as you tune through a CW signal. Bandwidths for these filters range from 25
Hz. to 600 Hz., and center frequencies from 400 to 1000 Hz. The narrow filters are
useful for trying to dig out extremely weak signals from the noise and QRM. The wider
filters allow easy tuning and listening to multiple CW signals simultaneously. Three

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optional CW center frequencies may be internally programmed for older Collins KWM-2
and S-Line equipment.
The DSP-59+ also has 12 RTTY, AMTOR, PACTOR, G-TOR and HF packet bandpass
filters centered at 2210 Hz. One of five optional center frequencies may be internally
programmed for other common operating modes such as European standards or 1600-
1800 Hz. HF packet. The selectable bandwidths of the bandpass filters provide optimum
filtering for 170 Hz. and 200 Hz. shift data signals of various baud rates.
The DSP-59+ has individual linear phase fixed bandpass filters with steep skirts for
SSTV, WEFAX and CLOVER. Since the bandwidths for these modes are fixed, the
filters are primarily QRM filters for adjacent channel signals rather than noise reduction
filters for eliminating random noise. The SSTV filter is a dual passband filter with one
passband centered around the SSTV sync pulse at 1200 Hz, and the other passband
around the varying FM picture tones from 1500-2300 Hz.. WEFAX is similar to SSTV
but has no separate sync pulse so the filter bandpass covers 1500-2300 Hz. The
CLOVER filter has a 500 Hz. bandwidth with a center frequency of 2250 Hz.
RTTY Remodulator
The DSP-59+ has a special data function for RTTY only. After passing through the
optimized RTTY bandpass filter, a precision DSP-based FSK detector in the DSP-59+
demodulates the noisy incoming RTTY tones and uses the recovered digital data to drive a
precision DSP-based AFSK generator. This remodulation process takes place entirely in
the DSP-59+. The precise clean tones from the RTTY AFSK remodulator can feed any
analog multimode controller or TU via the DSP-59+ line audio output. Many analog
RTTY demodulators have difficulty with noisy signals of varying amplitude, but virtually
all of them can adequately demodulate the precise DSP AFSK generator output. The
Tone (or Marker on some units) push-button selects either the remodulator with RTTY
filters or the RTTY filters only.
Automatic Gain Control
The DSP-59+ has switch-selectable automatic gain control to optimize the signal levels
for best filter performance and to enhance listening by minimizing audible signal level
variation.
Test Mode
The DSP-59+ has two test modes: a self-test to verify proper operation of the DSP-59+
circuitry, and a audio signal generator mode to test other equipment. The self-test mode
checks the internal digital and analog circuitry, push-button switches, LED indicators and
connectors. The self-test mode not only verifies the operation of the DSP-59+, but also
aids in verifying the proper installation of the DSP-59+. The audio signal generator
mode produces low-distortion, precision frequency sine wave test signals at the
frequency of each highpass and lowpass filter. Also, the Tone or Marker mode produces
low-distortion, precision frequency sine wave signals at the center frequency of each
bandpass filter. The test signals include single sine waves, two-tone signals for SSB
testing, and mark-space tones for modem testing. These precision tones may be used for
calibration and/or trouble shooting of other equipment the user may own.

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2. Quick Description of Controls and Connectors
(See Section 5, Operation for complete details)
Front Panel
1. Overload LED
Red LED indicates too high signal level into DSP-59+.
2. Normal
Yellow LED indicates normal signal level into DSP-59+.
3. Headphone Jack
Stereo headphone jack for 1/8” stereo plug only.
4. Bypass Switch
Press in to Bypass DSP filtering.
5. AGC switch
Press in to activate AGC.
6. HP/LP / BP
Push-button out - Highpass/Lowpass for Voice mode. HP/LP uses blue letters.
Push-button in - Bandpass for Data and CW modes. BP uses red letters.
7. Nrt / Tone Switch
Push-button in - Heterodyne elimination for Voice (HP/LP) mode. HP/LP uses blue
letters.
Push-button in - Marker Tone for CW and Data (BP) modes. Also selects RTTY
Remodulator. BP uses red letters.
8. NRr
Push-button in - random noise on for Voice (HP/LP) mode. HP/LP uses blue letters.
Push-button in - random noise on for CW (BP) mode. BP uses red letters.
9. High Pass / Center Freq Control
Selects the high pass filter in the Voice (HP/LP) mode - use blue letters.
Selects the bandpass filter center frequency for CW and Data modes - use red letters.
10. Low Pass / Bandwidth Control
Selects the low pass filter in the Voice (HP/LP) mode - use blue letters.
Selects the bandpass filter bandwidth for CW and Data modes (BP) - use red letters.
11. Gain / Power On/Off
Turns power on and off, and volume control for speaker output.
Back Panel
12. Power In
12-16 Volts D.C. Use 5.5 mm/2.1 mm matching plug. Center positive.
13. PTTI
Switch to ground to mute speaker output in Voice mode, and to electronically
bypass DSP-59+ in CW and Data modes for sidetone monitoring.
14. Audio Input
Audio input from radio speaker output.
15. Line Output
Line level output to multimode data controller. Gain control doesn’t vary this output.
16. Speaker Output
4-8 ohm speaker output.

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3. Specifications
AUDIO INPUT
Impedance 2 K ohms or 22 ohms, jumper selectable
AUDIO OUTPUT
Speaker output power 1.6 watts into 8 ohms at 13.8 VDC
2.5 watts into 4 ohms at 13.8 VDC
Line output -6 dB, referenced to input level, into 10K ohms. Not controlled by gain control
Distortion less than 1% at rated output
NOISE REDUCTION FILTERS Frequency range Attenuation Type Delay
Random Noise Reduction entire freq. range of Up to 20 dB, varies with Adaptive 5 msec max
selected bandpass filter noise characteristics.
Noise reduction aggressiveness
jumper programmable.
Tone Noise Reduction entire freq. range of Up to 50 dB, varies with Adaptive 5 msec max
(multiple automatic notch) selected bandpass filter noise characteristics
Note: The random noise reduction and bandpass filters can operate simultaneously.
The random noise reduction, tone notch and highpass/lowpass filters can operate simultaneously.
CW FILTERS CW filters Bandwidth = 25 Hz to 600 Hz, 60 dB at 50 Hz FIR Linear 30 msec max
15 steps. outside the passband phase
Center freq. = 400 to 1000 Hz.,
50 Hz. steps,
Optional Collins Bandwidth = 25 Hz to 600 Hz, 55 dB at 75 Hz FIR Linear 18 msec max
KWM-2 center freq. = 1350, 1500 or 1750 Hz. outside the passband phase
& S-Line filters
CW Marker Tone Sine wave at center freq. of selected CW filter.
Sine wave distortion less than 1%.
DATA FILTERS
RTTY, Bandwidth = 100 Hz to 600 Hz, 40 dB at 60 Hz FIR Linear 18 msec max
AMTOR, 12 steps. outside the passband phase
PACTOR, Center freq. = 2210 Hz. plus option
G-TOR, of 1700(default), 1360, 1300, 1530 or
& HF Packet 2125 Hz.
SSTV 1100-1300 Hz & 1500-2300 Hz. 50 dB at 75 Hz Composite 18 msec max
outside the passband FIR
Linear phase
WEFAX 1500-2300 Hz. 55 dB at 75 Hz FIR 18 msec max
outside the passband Linear phase
CLOVER 2000-2500 Hz. 55 dB at 75 Hz FIR Linear 18 msec max
outside the passband phase
Note: RTTY, AMTOR and PACTOR (100-350 Hz.) filters have a notch at the center frequency.
FSK Marker Tone Sine waves at mark-space freq. of selected data filter (170 or 200 Hz. shift).
Sine wave distortion less than 1%.

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VOICE FILTERS
Highpass Corner freq. = 200 to 1600 Hz., 60 dB at 180 hz. FIR Linear 18 msec max
100 Hz. steps. outside the passband phase for any
combination of
highpass & lowpass
Lowpass Corner Freq. = 1700 to 3400 Hz., 60 dB. at 180 Hz. FIR Linear
AGC Voice mode 36 dB
CW and Data Modes 18 dB
SIGNAL PROCESSING
A-D/D-A Converter 16 bit linear, sigma-delta conversion
Signal Processor 16 bit, 77ns Analog Devices ADSP-2105
TEST MODE
Self-test Self-test for circuitry, switches, and PTT input. User initiated from front panel.
Test tones Single or two-tone. Sine wave at the center freq. of each highpass and lowpass filter.
Sine wave distortion less than 1%.
DIMENSIONS
Size 7.6 in. wide x 8.5 in. deep x 1.9 in. high (193 mm wide x 216 mm deep x 48 mm high)
Weight 2.0 lb. (0.9 Kg.)
POWER 12-16 VDC @ 1A
Note: RTTY, AMTOR, PACTOR, G-TOR and HF Packet data filter bandwidths are
specified at -3 dB points to comply with traditional data filter specification methods. All
other filter bandwidths are specified to comply with conventional DSP FIR filter
parametric descriptions.

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4. Installation
To install a DSP-59+ in a station, the operator must provide power to the DSP-59+ and make
audio input and output connections to the DSP-59+. A typical DSP-59+ installation is shown
below in Figure 3.1.
Receiver/Transceiver
Speaker Output
Station Power Supply
13.8 Vdc 12-16 Vdc
Audio
Input
DSP-59+ Speaker
Speaker
Output
Multimode
Line
Output Controller
PTT InputPTT Output
Figure 3.1
Power Supply
The DSP-59+ requires a power source of 12 to 16 Volts dc. at 1.0 Amperes. The center pin of
the power connector is POSITIVE (+), the DSP-59+ chassis is negative. The correct power
plug size is 5.5 mm o.d. and 2.1 mm i.d.
Acceptable power sources include:
•13.8 volt dc. transceiver power supply (recommended power source for the DSP-59+
because it is better regulated than most plug-in wall outlet supplies). Note that some
transceivers with internal power supplies have accessory power jacks with insufficient
current output to drive the DSP-59+. Do not use these internal supplies!
•Radio Shack 273-1653 12 V.d.c. @ 1 Ampere plug-in wall supply. Use green tip with center +.
(Switching power supplies are generally noisy and not recommended, unless they are
specifically designed to drive amateur radio equipment.)
Connecting Cables
Shielded coaxial cables with RCA phono connectors should be used to minimize the possibility
of RF interference to the DSP-59+. Timewave recommends coaxial video cables with metal
adapters to match the connectors on transceivers and speakers. The center pin on the DSP-59+
audio input connector must not be connected to the transceiver speaker ground. Check
the connections carefully - this is one of the most common problems in DSP-59+
installations!

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Audio Input
The audio input of the DSP-59+ is an RCA phono connector on the rear panel of the DSP-59+.
Matching the output level of the radio to the input level of the DSP-59+ is necessary to take
maximum advantage of the wide dynamic range of the DSP-59+. The best way to make these
levels match is to use an adjustable audio output of the radio (typically the speaker output) as the
input to the DSP-59+. After connecting the DSP-59+ to the radio, follow this simple procedure
to match the audio levels. First, tune the radio to a strong signal after setting the radio output
level gain control to a convenient midrange position. Then, adjust the output level control on the
radio so the Overload red indicator LED on the front panel of the DSP-59+ rarely flashes and
the Normal yellow indicator LED always flashes with the normal audio input levels. Proper
adjustment ensures optimum signal-to-noise ratio and minimum distortion. Adjust the radio
output level only to maintain the proper input level to the DSP-59+. Use only the Gain control
on the DSP-59+ to control the listening volume.
The factory default input impedance of the DSP-59+ is 22 ohms. This impedance is appropriate
for most radios when driven by the speaker output of the radio. The DSP-59+ can be configured
for a high input impedance by removing a shorting jumper (position 1). This jumper is accessed
by removing the back bezel and the back panel of the DSP-59+.
Audio Output
The DSP-59+ has three audio outputs:
1) On the lower left hand corner of the DSP-59+ front panel is a 3.5 mm headphone jack
connected for stereo headphones. Use of mono headphones requires a monaural-to-stereo
adapter. Direct connection of mono headphones will short the DSP-59+ audio power amplifier
and may damage the DSP-59+. The DSP-59+ speaker output is muted when a headphone plug
is inserted. Headphone sensitivity may vary substantially among different types. If your
headphones seem too sensitive, a useful accessory is an adjustable inline attenuator (Radio Shack
P/N 42-2459).
2) The Speaker Output RCA phono jack on the rear panel of the DSP-59+ provides adequate
output to drive a 4 or 8 ohm speaker. The front panel gain control adjusts the audio level from
this output. The maximum output power is approximately 2.5 watts into a 4 ohm speaker, or 1.6
watts into an 8 ohm speaker.
3) The Line Output RCA phono jack on the rear panel of the DSP-59+ provides adequate output
power to drive a 600 ohm or greater load. The front panel gain control does not adjust the
audio level from this output. The output level is 6 dB below the audio input level to the DSP-
59+ when driving a 10 kohm or greater load. When the DSP-59+ power is switched off, the
Line Output is attenuated 6 dB (this keeps the TNC level constant whether the DSP-59+ is on or
off.) in level if it is driven from a low impedance source such as a receiver speaker output.
PTTI Input
The Push-To-Talk Input electronically bypasses the DSP-59+ in the CW and data modes, and
mutes the DSP-59+ in the voice mode. Use the PTTI bypass in the CW mode to hear a fixed
frequency sidetone which may be different from the frequency of the selected CW bandpass
filter.

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Use the PTTI bypass in the voice mode to prevent unwanted transmit audio from the transceiver
from causing audible interference. Many transceivers do not mute their audio outputs
completely during transmit. The 36 dB extra gain from the DSP-59+ with the AGC on makes
the incompletely muted transmit audio audible and may even cause oscillation by acoustic
feedback from the speaker to the microphone.
A contact closure operates the PTTI circuit. No external power is required. The return (shield)
side of the PTTI jack is connected to the DSP-59+ circuit and chassis ground.
Some linear amplifiers have 115 volt supplies for their transmit-receive relays. If a transceiver
PTT line is used to drive both the DSP-59+ and an linear amplifier, an isolation relay
and/or isolation diode may be required to prevent damage to the DSP-59+ (and any other
solid state equipment connected to the PTT line).
5. Operation
Introduction
Three knobs and five push-button switches on the front panel control the DSP-59+. Eight
internal jumpers located on the circuit board near the back panel preset options for some of the
front panel controls. One knob controls power and sets the speaker and headphone audio output
level of the DSP-59+. The other two knobs select the filter and test generator frequencies of the
DSP-59+, and control random noise reduction aggressiveness. The push-buttons select the
operating modes of the DSP-59+. Note that depressing a push-button always selects the mode
indicated below the push-button. Also note that if the Bypass push-button is depressed, other
controls will have no effect on the operation of the DSP-59+.
Power Switch/Gain Adjust Control
The gain knob on the front panel of the DSP-59+ is the power switch/gain adjust control. Rotate
the gain control clockwise to turn on the DSP-59+ and increase the volume. Rotate the gain
control counter-clockwise to turn off the DSP-59+ and decrease the volume. Turning off or
removing power from the DSP-59+ automatically de-energizes a bypass relay and forces the
DSP-59+ into the bypass mode.
5.1 Voice and Wideband Data - Highpass/Lowpass
In HP/LP mode, the DSP-59+ conditions the audio response of the DSP-59+ using a
combination of highpass filters and lowpass filters, adaptively reduces random noise, and
adaptively eliminates multi-tone noise (heterodynes). These three functions can operate
simultaneously or independently as outlined below.
To activate the highpass/lowpass filter mode, place the red HP/LP push-button in the out
position. Turn the High Pass control to the desired frequency indicated by the blue numbers
around the High Pass control. Turn the Low Pass control to the desired frequency indicated by
the blue numbers around the Low Pass control. These two settings customize the frequency
response of the DSP-59+.