microHAM USB Interface III


Out of stock

USB Interface III from microHAM is a low cost, high performance USB interface that provides high quality build-in sound card for digital modes, with optically isolated transceiver CAT control, CW and PTT.

Contact us if you need a radio specific cable!

158.49 $

  • EUR: 145.00 €
  • SEK: 1 701 kr

Out of stock

USB Interface III provides a solution to the lack of available Serial (COM) ports on laptop and newer desktop computers for controlling your radio.

The USB interface III includes full optical isolation of all control signals (radio control, CW,  PTT and Squelch) and built-in USB sound card with front panel level controls for transmit via your transceiver’s Accessory audio input and the constant level (pre-volume control) audio output.

microHAM USB Interfaces have built-in hardware support for your radio – you no longer need additional level converters like CT-62, IF-232, FIF-232, CT-17.   USB Interface III includes support for CW keying (DTR) and PTT (RTS) as well as a detector/driver for pseudo-FSK and QSK CW on the soundcard’s right audio channel for use with FLDIGI on any platform.

USB Interface III uses same cable as DXP, USB Interface II or DIGI KEYER II.

eHAM.net Reviews



   • Just one USB port for audio and Control  
   • Complete “Computer <-> Radio” electrical isolation
– bidirectional transformer isolation between sound card and radio
ALL digital signals: Radio Control, CW, PTT, FSK, and Squelch,
optically isolated from USB port
   • Standard Sound Device – no custom drivers: 
The USB Sound Device is an industry standard device recognized by
Windows XP and Vista (all versions), Macintosh OS 10 and LINUX. There are no custom device drivers to install and no compatibility problems with your applications. Windows 98SE is not supported.
   • Ultra low noise: 
– The sound circuits are designed with special attention to low noise
– Receive noise floor is better than -90 dBm (typical) in 600 Ohms.
– 87 dB (typical) dynamic range rivals that of professional products.
– Special circuit design maintains full dynamic range and low noise floor
with all radios – both high level and low level outputs.
   • Independent transmit and receive clock  
– Transmit clock: 32000, 44100, 48000 Hz
– Receive clock: 8000, 11025, 16000, 22050, 32000, 44100, 48000 Hz
– sampling rates are native: no up/down conversion or “rounding” errors
   • Right channel audio detector and FSK/CW driver   
– FSK output for FDIGI “pseudo-FSK” mode
– Provides a “hard keyed” CW output for software that generates
only audio (sidetone) CW
   • Support for all radio control standards (CI-V, FIF-232, IF-232, RS-232)
– fully supports Icom, Kenwood, Ten Tec, Yaesu and other radios
– no separate level converter required
– based on FTDI chip
   • Squelch input for signaling to computer
– two inputs, one is active low, second is active high
– ideal for Echolink and remote interfacing applications
   • No external power adapter for most transceivers
– Computer part is powered from USB
– Radio interface is powered from transceiver or transceiver power supply
   • Strong immunity to RFI
– integrated chokes and filters for best RFI immunity
– advanced shielding and circuit design for RFI product suppression
   • Quick change connectors
– Radio – DB15
   • LEDs for easy visual feedback of CAT, CW, PTT, SQL
   • Metal/Aluminum case, powder coated and silk screened
   • Free software upgrades via the Internet
Weight 0.34 kg
Dimensions 16.6 × 13.4 × 4.2 cm

DXP Specifications


  • USB 2.0 Full speed, isolated
  • CDC – serial ports
  • UAC1 asynchronous/synchronous downstream, max. 24-bit/48kHz
  • asynchronous upstream, 24-bit/48kHz


Power consumption:

  • USB – less than 250mA


Radio Port:

  • RxD, TxD – max. 115200 Baud
  • Levels: FIF-232, IF-232, CI-V, RS-232



  • open collector, max 30V/400mA



  • optoMOS, max. 300VAC/VDC @ 0.1A


Foot Switch/PTTIN:

  • active when closed to ground, max load: 1 mA at 3.3V


Audio Line Output:

  • 600 Ohm, max. 1.5Vp-p
  • AC coupled


Audio Line In:

  • 10K Ohm, max 3Vp-p
  • dual channel (Stereo)
  • Dynamic Range: min. 95dBA, typ. 105dBA
  • THD: 0.0012%
  • IMD+Noise: 0.006%
  • AC coupled



  • W 150mm x D 105mm x H 30mm



  • 0.35 kg

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