Linux and MicroHAM USB3

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1 Project Scope

Recently I purchased a microHAM USB 3 interface which is supposed to work with our Kenwood TS-870S. It is supposed to be used from our RaspberryPi3 club station computer.

Since we do not use Windows but Linux all the way, and since there is no really good documentation how to get it up and running, here is my collected experience.

2 Implementation

The advantage of the microHAM USB 3 ist that it does not require an additional sound card and it is thus perfectly suited for operation with the Raspberry Pi.

In order to access all the devices on it, you first need to make sure to load the according USB sound support.

lsusb will show you what the kernel can see on the USB bus.

Before connecting:


After connecting:


Please note that libusb can only see what the devices report about themselves. And there is no link to userspace capabilities yet. In order to provide specific capabilities, you still need to ensure the loading of according kernekl drivers. In case they are loaded automatically, that's fine. If not, you need to help a little.

In my case the sound driver was not loaded automatically, so I had to write a little udev rule: I created the file .... which contains:


3 Notes about the microHAM USB 3

There are two different cables that can be used for the connection to the Kenwood TS-870S:

  • DB15 T9
  • DB37 T9

In our case we used the DB15 T9 type.

I assigned the according jumper setting that is given on the little sticker that comes with the box.

Note that the interface provides the following capabilities:

  • TxD
  • RxD
  • RTS
  • DTR
  • Audio In
  • Audio Out

It is clear that data goes over the RxD and TxD, you can see little LEDs flashing if connectivity between the computer and the transceiver is working fine.

Note that PTT (only RX/TX switching) is done on the line RTS.

Note also that CW keying is done on the line DTR.

Audio works perfectly right away. There are two knobs to conrol sensitivity.

4 Notes about the Kenwood TS-870S

Check in minicom first which serial port speeds you can select. Maybe you cannot select 57600, so you need another serial speed. For most devices, you can select the speed of the transceiver's serial port. For the Kenwood TS-870S there are the menu 55, 56 and 56:

  • Menu number 54, TRNSFER, Data transfer function enable, should be 'on'
  • Menu number 55, DIRECT, Method of receiving transferred data, should be 'on'
  • Menu number 56, COM.RATE, Communication parameters for COM connector, should agree with the speed of your serial port in the computer. I picked '96 1' for 9600 Bit/s and 8N1.

5 Notes about FLDIGI

Relating to FLDIGI 3.23.20 there is a little restriction with CW: Keying is only provided through Audio Out, and NOT via the DTR line. There are programs that can key the DTR line, but FLDIGI cannot as of now. FLDIGI can switch the DTR line, but it simply does not attach it to the CW keying. I hope there will be a patch soon, but I cannot tell.