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External Audio DSP Filter Module for SSB&CW

CW & SSB Audio DSP Filter

SKU: H160530 Categories: , Tag:
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Product Description

Amateur Audio DSP Filter Module, an external DSP module for SSB, and CW

ITEM No.: H160530


Tired of the noises when doing the HF SSB or CW with your homemade or commercial QRP rigs? Tired of the pileup interferences when answering a call in CW contest? Get yourself a Funtronics FADS-02 external audio filter module. The QSOs will get much more straight-forward with this tiny external audio DSP module. The FADS-02 is an audio digital filter which is designed to eliminate and filter out the unwanted noises and interferences in a SSB or CW QSO by using the software algorithms called DSP. Unlike the single filter unit in the analog filters, the DSP filter work in a different way by a DSP chip powered by the software algorithms which makes it more flexible, and the most important thing is the DSP filter integrates many filter units that have different bandwidths and different central frequencies based on an sampled audio spectrum.

Each FADS-02 module has 52 sets of CW filters onboard with the center frequency in a 50Hz step and 1 set of SSB filter with 100Hz in step from 200Hz to 900Hz and 200Hz in step from 1100Hz to 2700Hz. In addition, each DSP module offers an 8-level adjustable NR (Noise Reduction) function, it is up to you to enable or disable it by just pressing the button on the front panel. Either the filtering or the NR function could be enabled, but they can not be used for both at one time. You can disable them all. This is quite useful as you can monitor the differences with and without a DSP effect. All of the main operations are through the 2 buttons on the front panel by a single tapping, long pressing, and dual tapping. There is a third button on the up center edge of the module, and it’s for recording the audio signal and entry of the menu system. The DSP module offers an audio signal recording feature that enables you to record a CW or SSB QSO from your transceiver without a DSP effect up to 512 seconds in a total of 11 channels, and the 11 channels share the total 512 seconds of voice memory on the module. You are able to replay the recorded original audios, or open the NR and filter function while replaying them.

In order to make all of the settings visible, the FADS-02 has a 1.3″ OLED display onboard. With the help of this OLED, the CW or SSB filter settings could be very straight-forward. Moreover, the whole audio spectrum is also visually displayed at the bottom of the screen. By the way, this little screen features with a high contrast in display, and it does make the unit be operated easily even in the sunshine.

This tiny DSP module has been designed for the ease of use, and this could be reflected from the use of the AA-size battery as the power supply, which is easy to access in daily life. The average current draw for this module is only 150mA, and it could last up to 10 hours for the use of 2 cells AA-size batteries.

With the tiny size, powerful DSP effects, this FADS-02 DSP filter module should be a useful accessory for ham radio QRP lovers, CW enthusiasts.

Note: Due to the air shipment restrictions, no batteries are included in the package, you need to prepare the them by yourself. 2 AA-Size batteries  are used in this module.


  • Tiny in size, only 2.5″x1.3″, could be integrated into an existing active speaker
  • 52 sets of CW filters, and central frequency adjustable
  • Flexible SSB filter, lower cut down to 200Hz in 100Hz step, and higher cut up to 2700Hz in 200Hz step
  • Low power consumption, only 150mA current drawing
  • AA size battery as the power supply, easy to access
  • Oled display, makes every setting visible
  • Audio Recording features, up to 512 secs in 11 channels


  • Supply voltage: DC 3V by 2 AA-size batteries
  • Typical current: 150 mA @ 3V DC
  • Filter type: Audio DSP in Multi-tap FIR < CW 256 taps, SSB 2×128 taps>
  • Module size: 5mm x 33 mm (approx 2.5 x 1.3 inches)
  • Oled display: 1.3″, with 128×64 dots
  • Weight: 29g without Batteries < 0.0639341 pounds>
  • Ultimate rejection: ≥ -55dB
  • Passband ripple: < 0.1 dB
  • Input impedance: 40K Ohms
  • Output impedance: 32 Ohms
  • Output type: Single-ended
  • Maximum AF input Voltage: 5.0V pk-pk
  • Minimum AF input Voltage: 0.3uV pk-pk
  • Maximum AF output Voltage: 3.3V pk-pk
  • Processing delay: ≤ 10 mS


Theory of Operation:

The DSPIC33FJ64GP202 is the DSP core of the module, it is a 40 MIPS chip from the Microchip with up to 64K flash memory and 8K RAM. It transforms the sampled audio signal from Time Domain to Frequency Domain by implementing the FFT (Fast Fourier Transform) algorithms, then it takes the DSP filter and NR reduction algorithms to eliminate the unwanted frequencies and reduce the noise with reduction calculations. Meanwhile, the DSPIC33FJ64GP202 also works as the MCU for controlling the buttons and the OLED display. All of the operations to the unit are via the 3 buttons, including filter settings, NR operation, ON/OFF DSP, recording and menu operations. The PCM1803 is a single-ended, 24bit AD converter with up to 96KHz sampling rate from TI. It is commonly used in many HIFI areas. It converts the analog audio signals to 24bit digital formats in a fast sampling rate and transfers the data to the DSP core for DSP processing. The AIC23 is a codec device for transforming the DSP processed audio data to analog voltage, which is what we called DAC, digital to analog converter. The converted analog voltage is then processed and amplified in an analog way to the OUT port of the DSP module. Regards with the power supply, the TPS61030 is a high efficiency DC-DC booster from TI, it boosts the voltage from the AA batteries to 3.3V and 5V in order to power up the whole power line of the unit.


Additional Information

Weight 0.35 kg
Dimensions 150 x 90 x 110 mm


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