The TASS Coaxial Relay System

The TASS (Totally Awesome Switch System) is a general purpose RF switch for use from DC to 150 MHz. It is designed to more-or-less replace the HP 59307A coaxial switch for computer-controlled signal routing. It also has a number of uses in ham and SWL radio operation, such as switching receive antennas, filters, and transverters.

There are two boards in the system: the TASS-R relay board, which is by far the most interesting, and the TASS-SHIELD board for use with an Arduino Mega 2560 microcontroller. The TASS-SHIELD and open source software from TAPR allow up to 4 relay boards to be connected in a system.

The TASS-R board has 8 connection ports grouped into two busses. Each port connects to its bus via an individually-controlled relay. External connectors may be added for increased flexibility as shown in the "Use Cases" section below. The TASS-R is designed to be used with the TASS-SHIELD though it can be used with any controller that provides 9 digital outputs. Mechanical switches can also be used.

Block Diagram

Use Cases

Since each relay on the TASS-R is independently controlled and more than one relay may be selected at the same time, the board can be used in many different configurations:


The TASS-R is designed to be controlled by a microcontroller such as an Arduino or PIC. The test software is written for the Arduino. I'll provide more detail elsewhere, but the idea is that the relay board has an independent control line for each relay. The Arduino mates with the TASS-C shield, which connects to the TASS-R via a 10 pin ribbon cable. The user issues commands to the Arduino via USB or network connection; the shield sets the appropriate relays.

Here is the current command syntax:

For example:

Schematic and Layout


Top Placement

Bottom Placement

Layer 1

Layer 2

Layer 3

Layer 4