Using TIARA technology with a modified USB sound fob [BETA]

Thanks to the hard work of Steven Henke, W9SH and Jim Dixon, WB6NIL, TIARA technology can now be used with USB sound fobs which have a CM108 interface chip. The sound fob will require some modifications to bring out PTT, block DC on the audio outputs, and attenuate the receive audio to match the microphone levels.

You might ask, why would I want to use the Quad Radio PCI card when it costs more? -or- Why should I use the Quad Radio PCI card when the modified USB sound fob is much less expensive?

The differences between the two interfaces boil down to reliability and the level of support offered. Obviously, we at QRV Communications LLC believe that the Quad Radio PCI card is the reliable interface. The modified USB sound fob is a brand new interface, and it has not proven itself in the field like the Quad Radio PCI card. The modified USB sound fob also does not scale very well in systems where multiple radios need to be interfaced to one machine running Asterisk, or when the system has limited computing power. For the Quad Radio PCI Card, we offer 1 hour of commercial software installation support via Email, and SSH and phone if necessary to help get your system up and running quickly. No support is offered by QRV Communications LLC for the modified USB sound fob or DMK Engineering URI. Support for modified USB fob issues is limited to asking the community questions on the mailing list. You may or may not get the answer you are looking for. In short, if you are a tinkerer or Amateur Radio Operator with more time on your hands than money, the the modified USB sound fob is probably the avenue to persue.

There is a firm which is offering to build complete commercial turnkey solutions (PC, radio, Asterisk) around the modified USB sound fob called Xelatec. They are offering complete turnkey solutions for commercial applications as well as a broad level of support in all aspects of VOIP and Push-To-Talk two way radio.

TIARA Technology Dedicated Linux distributions compatible with the modified USB Sound fob

A version of Limey Linux (which is a Compact flash based distribution) is now available which provides initial support the modified USB sound fob. This is currently in the testing phase, as we have found that most of the VIA Mini-ITX boards are not powerful enough to support the demands of the DSP code for the USB channel driver. Version 1.0.4 of Limey Linux has been released to support the Intel/Jetway D201GLY2 motherboard is more capable of handling these DSP tasks.

Xelatec has released an installer which installs a modified version of Centos, Asterisk and App_rpt with support for modified USB sound fobs as well as the Quad Radio PCI card and ARIB interfaces. Everything is taken care of

by install scripts, so users with little or no Linux system integration skills can get up and running quickly. This is a hard disk based distribution.

Technical Details

There is an Asterisk channel driver called chan_usbradio.c. This channel driver when used with the Asterisk application app_rpt.c version 0.73 or later and the modified USB hardware allows app_rpt to be used with very inexpensive hardware. Unfortunately, Asterisk 1.4 does not yet include the chan_usbradio.c channel driver which means that you'll need to get if from our repository, and follow the instruction link below to install and compile it. Please also note that chan_usbradio.c requires all of the files in the xpmr directory to compile properly. You will also need to make sure that libusb, libusb-devel, libasound (aka lib-alsa), and libasound-devel are installed on your system before you compile chan_usbradio.c

The latest version of app_rpt.c, chan_usbradio.c, and the xpmr directory can be downloaded from here

A tarball of starter configuration files can be downloaded from here. There are 4 directories underneath the main

directory inside this tarball. There is one directory for each of the hardware platforms supported. Use only the files

in the usbradio directory.

chan_usbradio.c and the xpmr library source files contains all of the interface code to interface app_rpt to a CM108 based USB sound fob. In addition these files contain DSP code to do CTCSS encoding and decoding, squelch, pre-emphasis and soft limiting, de-emphasis, and audio level adjustments. Basically, you only need to make 3 or 4 connections to your radio:

Discriminator audio, de-emphasized audio, or speaker audio.

Transmit audio (direct to modulator, or microphone)

You can opt not to use the DSP-based squelch and, and bring a COR line in if that is what you want to do. However if you don't use discriminator audio, you will not be able to use the DSP-based CTCSS decoder.

Audio level adjustments, and CTCSS are done with commands from the Asterisk CLI. More details about these commands are available in the software setup howto below.

A typical unmodified USB sound card fob looks like this:

The USB sound fob above was purchased from geeks.com for $7.95.

After the modification has been performed, you end up with something like this:

The USB sound fob modification instructions are located here.

A asterisk/app_rpt/chan_usbradio software setup howto can be found here

Regarding the cable used in the modification instructions:

I am making available 1ft. pieces of the 28 awg 6 conductor cable with 2 conductors inside a spiral wrapped shield and a solid drain wire for $5.00US including shipping. This is high quality PUR cable used for industrial process control applications and it is perfect for use with a modified USB fob. Payment is via Paypal only, and the item will be shipped to your Paypal confirmed address via USPS first class mail. This is only available to US customers. Please send me an email (see below) for more details. Here is a picture of the cable:

The black and white wires are wrapped inside of a spiral shield, the red, green, orange and brown wires are unshielded.

USB sound FOB to Radio Interface Schematics

TMG707 frequency agile remote base

Email address for questions or inquiries: