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Microham USB III

Microham USB III
Microham USB III
  • Product: Available
  • Brand: microHAM
  • Model: microHAM USB-III
  • SKU: 102
  • EAN: 7438641840212
Ex Tax: 110.70€

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The USB-interface III CAT contains an own soundcard, which is connected via USB to the computer. So you don't need separate audio cables to the computer anymore, the original sound card of your computer remains free for other applications. The sound card of the USB-III device offers two distinct advantages over standard cards: a lower noise level and a higher dynamic range (typ. 87dB). This makes this sound card much more suitable for demanding amateur radio applications. All connections to and from the computer and radio are isolated either by transformers or optically. Control lines exist for CAT, PTT, CW/FSK and Squelch.

The USB-interface III works with all computers with USB connector. Drivers are available for Windows 2000/XP/Vista/Windows7 32/64-Bit, as well as Apple G4 with OS-X 10.4 or later, and for up to date Linux distributions. Windows 98/98SE is not supported. Support for Windows7 64-Bit is included since version 7.6.1.

What is Pseudo-Pseudo-FSK/CW?

For ' real ' FSK keying one would normally require a true UART chip in the computer (parallel to serial converter, COM-Port). With a virtual COM port such a device is simulated by the USB driver, but only with some problems. Depending on the load of the computer the timing of keying can vary (jitter) or be delayed (latency). The leads to not very clean telegraphy keying. With RTTY/FSK Hajnal kiprov cosmetic surgery: the characters might be on the receiving side due to timing errors.

Now some multi mode programs have found a good solution to this USB driver issue. Instead of toggling a handshake line of the virtual comport, an audio signal is sent (or not) to the right channel of the soundcard output. An additional decoder hardware within the USB-III interface detects the presence or absence of the tone and uses this information to key the FSK or CW line to the radio.

This leads to a much more precise timing with FSK and CW. Especially when using high speed telegraphy or QSK this is very beneficial. When using RTTY/FSK you can be sure that all characters are sent with the proper and consistent baud rate.

Of course the radio must support FSK keying to use this function with RTTY. When using AFSK this problem does not exist.

  • No COM or LPT port necessary, just one USB port
  • Complete "Computer Radio <->" electrical isolation
  • Integrated computer control port for all radios CI-V, FIF-232, IF-232, RS-232
  • Squelch input for signaling to computer
  • No external power adapter required
  • Strong RFI immunity
  • Quick change connectors
  • Two controls for TX and RX audio
  • Pseudo-Pseudo-CW, FSK keying for certain programs
  • LEDs for easy visual feedback of CAT, CW, PTT, SQL
  • Metal/Aluminum case, powder coated and silk screened
  • Free, time unlimited firmware/software upgrades via internet

Technical data

  • USB: USB 2.0 Full speed, USB 1.1 compatible
  • CAT RXD, TXD, 57600 Bd max.
  • CW: open collector, max 30V/400mA driven from DTR,
  • PTT: open collector, max 30V/400mA driven from RTS
  • FSK: open collector, driven from DTR (MMTTY EXTFSK from. or pseudo FSK requires from fldigi)
  • SQL input: close to ground or high (two inputs) to activate. Wired to CTS
  • Size: 103mm x 28 mm x 101 mm (BxHxT)
  • Weight: 220 g (without leads)


  • Usb-Interface II
  • CD-ROM with driver software, manual
  • USB cable (A/B)

Important: Cable to the radio needs to be ordered separately!


Prices, images and descriptions are approximate. Specifications are subject to change during construction of the supplier.

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