Schematics for the CTR2 project are provided to help you understand how the system works and for troubleshooting purposes. The hardware for this project is not open source (i.e. CAD and Gerber files will not be published). Schematics for the RJ45 Switch, Radio Antenna Switch Controller, and Antenna Switch Controller will be published here after the article on them in the November/December 2021 issue of QEX is published.


CTR2 hardware was designed using Kicad. One of the plugins available for Kicad generates an interactive bill-of-material. In addition to providing a list of components to build the board this plugin provides graphical parts placement. Just open the file in any web browser. Selecting a part on the list highlights the location of that part on the board (C13 is selected above). You can also track component sourcing and placement on this form.

The Excel CTR2_BOM_xx-xx-xx.xls file provides a list of all the components you’ll need to purchase in order to complete each sub-system. Links are provided for individual components from Mouser. Boards and enclosures can be ordered from my order form. You can use the included links to get manufacturer and part # information if you want to order from another supplier such as Digikey.

The interactive BOM is great when assembling the boards that I supply with just the SMT components factory installed on them.


Here’s a few photos of the boards to give you an idea of what’s involved in building this project.

This is not a beginners project! You should have good soldering skills and be comfortable soldering .1″ pin headers and compact connectors (such as the RJ45 jacks) to a PCB… there are a lot of them!.


The photo below shows the completed and tested HMI board that I supply before the development boards the builder supplies are installed.

HMI Boards with development boards

This photo shows the HMI board with the Teensy and ESP8266-01 development boards installed.

Completed HMI board


The next photo is the new Auxiliary board. The Auxiliary board can be ordered with one of two options. This board comes completely assembled and tested.

Option #1 includes a Radio I/O circuit on the board to allow the HMI to interface to a single radio. This option comes with all of the components installed except the RJ45 (J3) jack.

Option #2 of the Auxiliary board comes with just the RJ45 jack (J3) and the 10-pin ribbon connector (J4) installed. This adapts the 10-pin Radio I/O ribbon connector from the HMI to an RJ45 jack so you can plug the HMI into a manual RJ45 switch using CAT5 cable. Use this option if you want to control two or more radios using a manual RJ45 switch.

NOTE: These options are mutually exclusive, i.e. only one can be used at a time. You can order Option 1 of the Auxiliary board to control a single radio. When you are ready to add more radios to your system just open JP5 through JP10 to deactivate the Radio I/O circuit and install the RJ45 jack to provide an RJ45 interface to a manual RJ45 switch so you can control two or more radios.

A third option is to eliminate the Auxiliary board and the manual RJ45 switch altogether and build the CTR2 RJ45 Switch to automatically switch Radio I/O signals instead. The CTR2 RJ45 Switch along with two antenna switch controllers will be presented in an article scheduled to be published in the Nov/Dec 2021 issue of QEX.

3D rendering of the Auxiliary board


This photo shows the Display adapter mounted in the display enclosure. It converts the RS-232 data signal from the HMI‘s Rmt Display port to 3.3 volt levels to drive the display. It also provides an interconnection for the rotary encoder.

This board comes completely assembled and tested. The kit includes the mounting hardware and four Dupont female jumpers to connect to the builder supplied encoder. You can order either an encoder with detents or the encoder with no detents for smooth rotation. I prefer the encoder with detents because it’s too easy to bump the smooth encoder and change frequency when you don’t intend to.

Display adapter


The next photo is the completed Radio I/O board mounted in the PacTec CN-XRL enclosure. The RJ45 jack on the left connects to a port on a RJ45 switch (either a manual RJ45 switch or the CTR2-RJ45 Switch) using CAT5 cable. The pluggable terminal strip on the right is used to connect to the radio. The DIP switch is used to configure the CAT port’s electrical interface.

The board is supplied with only the SMT devices installed. The builder must purchase the through-hole components to complete the board. The required components are listed in the CTR2_BOM_xx-xx-xx.xls file.

WARING! The RJ45/CAT5 wiring used on the Radio I/O interface is not Ethernet. These ports should NEVER be plugged into an Ethernet hub, switch, or router. It is highly recommended that you label each Radio I/O cable so as to not confuse them with other CAT5 cables in your station.

Completed Radio I/O module

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