Timewave DSP-8100c Noise Filter

Download the PDF Datasheet

  • Random Noise Reduction
  • Automatic and Manual Notch Heterodyne Elimination
  • Variable Voice, Lowpass and Highpass filters from 100 Hz - 5,000 Hz
  • Optimized mode specific Data filters
  • Wideband filter for AM and FM (VHF & UHF)
  • Continuous filter tuning up to 5,000 Hz using optical encoders
  • RTTY Modem
  • Built In Test Equipment - Generator, Millivoltmeter, & Tone Decoder
  • Hyper-speed DSP Processor with 80 KB Ram
  • LCD display for Visible Memory™ and Calibrated Filters™
  • Balanced line input and output
  • Built in 115/220 Volt AC power supply

Timewave's Digital Signal Processing (DSP) technology provides superior performance in reducing noise, eliminating tones and interfering signals.

The Timewave DSP-8100c is the latest generation DSP filter designed for demanding commercial/military installations. The LCD display, push buttons, and Visible Memory show the exact settings of the filter. The optical encoders allows continuous tuning of the filters.

The DSP-8100c is available in three configurations:
- Stand alone
- Single 19 inch rack mount
- Dual 19 inch rack mount

Noise Reduction

The noise reduction functions of the DSP-8100c operate by examining a characteristic of signals and noise called correlation and dynamically filtering out the undesired noise. The degree of correlation is relative. Random noise such as white noise or static is uncorrelated. Speech is moderately correlated. Heterodynes and pure tones are highly correlated. The DSP-8100c measures correlation and automatically filters out noise that is outside its correlation thresholds. The amount of noise reduction varies according to the correlation characteristics of the noise.

Data Filters

Narrow band signals like RTTY require 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 other types of extremely sharp filters. The filter skirts are so steep that signals literally fall off the edge of the passband as you tune through them. Bandwidths range from 10 Hz to 600 Hz, and center frequencies from 200 Hz to 2150 Hz. Narrow filters are useful for trying to dig extremely weak signals out of the noise and interfering signals.

The Data filters support RTTY, WeFAX and SITOR. In addition to regular filtering, the DSP-8100c offers two other RTTY functions. The RTTY Remodulator mode detects and regenerates the mark and space tones going to your radio modem, giving it the benefits of a DSP front-end. The RTTY Modem mode provides a complete RTTY Terminal Unit when used in conjunction with a PC and appropriate software.

Built In Test Equipment

An added benefit of the powerful DSP processor and LCD display in the DSP-8100c is a Test Instrument Mode. This mode is designed to provide the audio test instruments necessary for normal maintenance and setup of audio circuits in radio equipment installations. A low distortion Sine wave Generator and an Audio Millivoltmeter cover the frequency range from 20 Hz to 10 kHZ. The millivoltmeter measures true rms and peak as low as 1 mv. The sine wave generator is calibrated in the same units. The sine wave generator and audio millivoltmeter operate simultaneously for gain and frequency response measurements.

Another feature enhanced by the millivoltmeter is the CTCSS or "PL" tone encoder/decoder with the tone frequency autodetect. Millivoltmeter measurements allow relative frequency deviation measurements of a received signal's CTCSS tone. A CTCSS squelch output can switch a tape recorder or other device. A Two-Tone audio generator is provided for SSB linearity testing.


The DSP-8100c is available in three configurations:
- Stand alone
- Single 19 inch rack mount
- Dual 19 inch rack mount

The DSP-8100c has a built in 115/220 Vac 50/60 Hz power supply.

ALL Timewave DSP Filter models SIMULTANEOUSLY Reduce Noise, Kill Heterodynes and interfering signals!

Timewave DSP-8100c Specifications

Audio Input

Audio Output

Impedance 600 ohms transformer balanced Line Output
Full Scale Line output
600 ohms transformer balanced
-15 dBV to +6 dBV, front panel programmable within setup
Signal range for full output -16 dBV to +6.0 dBV, front panel programmable Monitor Output Power 1.0 watt into 8 ohms
Monitor jack 1/4" two circuit jack < 1 ohm or 100 ohms, selectable

Automatic Gain Control (AGC)

Voice 36 dB
Data Modes 18 dB

Noise Reduction Filters

Function Frequency range Attenuation Type Delay
Random Noise Reduction Entire freq. range of selected bandpass filter Up to 20 dB, varies with noise characteristics. Adaptive 5 ms max
Variable Noise Reduction Noise reduction aggressiveness front panel adjustable
Heterodyne Eliminator (Multiple Automatic Notch) Entire freq. range of selected bandpass filter Up to 50 dB, varies with noise characteristics Adaptive 5 ms max
Heterodyne Eliminator (Manual Notch) Entire freq. range of selected bandpass filter Up to 50 dB, varies with noise characteristics Adaptive Manual

Voice Filters

Function Frequency range Attenuation Type Delay
Highpass Corner freq. = 100 to 1000 Hz., 10 Hz. steps. 60 dB at 180 Hz. outside the passband FIR Linear phase 24 ms max combination highpass and lowpass filters
Lowpass Corner freq. = 1000 to 5000 Hz. 10 Hz. steps 60 dB at 180 Hz. outside the passband FIR Linear phase

Data Filters

Function Frequency range Attenuation Type Delay
RTTY, SITOR Bandwidth = 60 Hz. to 100 Hz.
Selectable Center frequency
Frequency shift - 170, 200, 425 and 850 Hz, selectable
40 dB at 60 Hz. outside the passband FIR Linear phase 37 ms max
WeFAX 1500-2300 Hz. 55 dB at 75 Hz. outside the passband FIR Linear phase 37 ms max
FSK Marker Tones 1) Sync-Nul character (Diddle) of selected data filter at selected baud rate
2) RY string (RTTY only) Alternating sine waves at mark-space frequency of selected filter

RTTY Modem

Shifts 170, 200, 425, 850 Hz
Data Rates 45, 50, 57, 75 Baud
Input Audio from receiver
Output Open collector FSK and variable level AFSK
Transmit Data Polarity Normal or Reverse
I/O Receive data, Transmit data, PTT (RS-232 compatible)

Signal Processing

A-D/D-A Converter 16 bit linear, sigma-delta conversion, dual channel
Signal Processor 16 bit, 27 ns Analog Devices ADSP-2181 with 80 KB of memory

Test Instrument

Audio Generator Single Sine wave adjustable 20 Hz to 10 kHz
Two-tone fixed 700 Hz and 1900 Hz.
Audio Millivoltmeter True RMS from 1 mV to 2000 mV, 20 Hz - 10 kHz
CTCSS Encoder/Decoder Decodes and displays CTCSS "PL" tones from 67.0 Hz to 254.1 Hz
CTCSS Squelch Open collector output pulls low when selected CTCSS tone is present.


Six Memories All configuration setups can be stored and recalled (except volume control setting)


2x16 alphanumeric characters, dot matrix, yellow-green backlit LCD

Dimensions (Stand Alone Configuration)

Size 7.6 in. wide x 11.25 in. deep x 1.9 in. high (193 mm wide x 285 mm deep x 48 mm high)
Weight 4.01 lb. (1.82 Kg.)


115/220 VAC 25 watts max., Fuse 0.5 A, 5 mm x 20 mm

Note: RTTY and SITOR 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.

Download DSP-8100 data sheet (.pdf format)

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