I've been enjoying my KX3 for some time, especially when mobile in the RV and camping.  While I've operated mainly SSB and CW, my attempt at RTTY and PSK for the 13 Colonies event during July 2014 didn't go so well.  I was portable at a campground in SC, setup comfortably on a picnic table with my portable dipole erected on a Jackite pole.  I made some contacts, but I suspect my problems were a result of directly connecting the KX3 to my MacBook Pro.  While I know the KX3 lacks the audio in/out isolation of the K3, I thought I'd try it anyway.  Fail!

In preparation for the event this year, and to make sure I have a fully functional portable station, I began the search for an audio interface.  I ready many reviews (and posts on the Elecraft reflector) concerning audio interfaces and rig control.  Ultimately, I placed an order via G3LIV's web site for a Isoterm Traveller USB interface.  Johnny was extremely responsive via e-mail and carefully ensured I was receiving what I needed to be successful.  A++ for customer support!

The interface arrived in just a couple of days and I was able to quickly get setup and make contacts.  Johnny includes a CD with the required drives (which can easily be found on the Internet) and some popular utilities.  Once I installed the USB driver, I verified in the KX3 menu that MIC BIAS = OFF and MIC BTN = PTT.  After that, I connected the cables and with a little twisting of the audio controls on the interface to get the proper audio levels (KX3 manual page 18), I was operational.

There's plenty of info on Johnny's web site about the technical details.  Here are the top things that sold me:

  • Is not a sound card.  It's simply isolation, level control, and keying
  • USB Powered
  • Small package (not much larger than a deck of cards)
  • Full input and output isolation
  • True keyed TX instead of VOX
  • Audio controls on the front of the interface box
  • Removable cables for easier transport and use with other radios

Front view when connected and receiving.  There's a red LED that switches on when in TX.


Rear view with connections.  One really nice thing is that the interface can be used with many different radios by simply swapping cables.  Which use standard plugs, so homebrewing cables is a snap in the future.


I'm using an iMic audio interface so my fiddling with the MacBook sound output for other things doesn't effect my setup.  Plus, the iMic packs down very well into my travel bag and can also be used with my iPad.  The input and output plugs are marked so that you get them into the correct ports.  The rig side connections are easily distinguishable due to the mic port plug having all 4 conductors.

To test the interface and to make sure I had a solid solution, I worked two contests with this setup (plus my KXPA100) and it worked flawlessly.  I'm extremely happy with this setup and would highly recommend it to anyone looking for an audio interface to use with their Elecraft KX3 or other rig.