A Capable Shack Computer!

Like almost every other radio ham, I use a computer for log keeping, digital modes and other tasks.

For the majority of computing processes in the shack I employ the use of a home built Windows PC.

The computer hardware was originally based around an ECS GF8100vm-m5 motherboard with 4GB RAM and a 500GB hard drive.

This machine started showing a problem with one of the SATA channels. At very infrequent random periods data would get corrupted – not good.

Therefore, I replaced the motherboard before I lost any crucial data. An Asus M5A78L-M was installed as the replacement for the ECS motherboard.

After replacing the motherboard, I also installed a new larger hard drive and decided that due to the amount of use the machine had seen a new PSU would be in order.

A few more upgrades later, the system now comprises of:

  • Asus M5A 78L-M motherboard
  • 8 core AMD Processor
  • Corsair CX-550, 550W PSU
  • 32GB RAM
  • Crucial 120 GB SSD (drive C)
  • WD 2TB hard drive (drives D, and E)
  • Seagate 2TB hard drive (drives F, and G)
  • Samsung DVD-RW drive (drive Z)
  • Nvidia Gigabyte GTX-1650 graphics card – 3x HDMI version
  • Generic Serial Port Card
  • 2 x HP 24FW widescreen LCD monitors
  • Logitech wireless keyboard and multi-function mouse
  • Windows 10 Professional

Shack Computer InternalsOriginally installed on this machine was Windows 7 professional. I took advantage of Microsoft’s free upgrade offer to get a fully licenced version of Windows 10 Pro.

Admittedly, I didn’t really like the initial version of Windows 10 and went back to Windows 7 for a brief period.


My introduction to radio related software was MixW for digimodes and logging. Due to it’s ease of use, configuration and the extremely flexible macro capability of the software and very low use of computer resources it’s ideal for use with older hardware, although now lacking a lot of more modern features.

Currently running under Windows 10 Pro is Ham Radio Deluxe (HRD), and a host of other radio related applications. HRD has grown in popularity, the original version was written by a radio amateur who distributed it for free, it’s now a paid-for commercial product.

The main programs in the suite are computer radio control (CAT), logbook & digital modes software (DM780). The HRD logbook has the ability to use a MySQL database which is a lot faster than the MS Access database.

It also allows the log to keep a wide variety of information compared to the MixW log, which is one of the reasons I switched from MixW to HRD.

The only feature that I miss from MixW is the ability to easily print QSL cards on a custom layout. It has to be said that HRD is catching up a bit and printing out QSL labels is starting to get easier, however, the system employed still doesn’t fulfil my needs.

To overcome this, I have written my own QSL printing program which takes the information I need from the MySQL database to print on my QSL cards. At some point in the future I may develop the program further and release it to enable other HRD users to print their own cards directly from their logs.

Computer (CAT) Control

CAT (Computer Aided Transceiver) control of the radio consists of a cable connected to either a USB port or COM port on the host computer and to a dedicated port on the radio.

Most modern radios now feature a USB port to support CAT control and soundcard interfacing using a single cable.

The computer and radio communicate with each other and the software displays the radio status on screen and sends commands to the radio allowing the operator to change the frequency, alternate between transmit and receive, access the radio memories etc.

Both my Yaesu and Kenwood radios are using serial port connections, while my Icom uses a USB adapter for CAT communication with the computer.

Serial COM Ports

All my radios allow the use of an external keyer, which is an electronic device for generating CW (Morse code). In my case I use the computer as a keyer.

HRD is configured to use one of the serial ports in the PC (hardware, not USB adapter) DTR signal for CW keying. Through a simple opto isolation circuit, I am able to use a single COM port for all the radios without any interaction between them.

Radio audio interface

To connect the computer audio to the transceiver and vice-versa, I currently use a Signalink manufactured by Tigertronics which also incorporates a built in soundcard and connects to the computer by USB. The signaLink also provides control circuitry to switch the radio’s between receive and transmit.

Homebrew Computer to Radio Isolating InterfaceIn the past I used to use a home made isolation interface, download a copy of this schematic here.

This interface ensures that there is no physical electrical connection between the PC and transceiver to eliminate ground loops and minimise RFI problems.
It consists of two 1:1 audio isolation transformers for the audio and an opto-isolator for receive/transmit switching.