HF Digital Messaging - Emergency / Disaster Relief - Interoperative Communications - Ham Radio
The following information is provided as an aid in constructing, using, and understanding computer-to-radio hardware control, for use with PCALE, other ALE software, or external ALE hardware controllers. The same interfaces may be applied to most digital modes and other computer programs for interface with computer control of radios. Unlike some other types of ham radio software though, most external ALE controllers, including PCALE, only send commands to the radio via the serial port, and do not receive commands back from the radio via the serial port.
The good old standard RS-232 serial port is used by the computer ALE controller to send control signals to the radio. On older desktop computers designed in the 1980s through the 1990s, the RS-232 serial port used a DB25 (male 25 pin connector). The DB9 connector (male 9 pin connector) was found on computers designed after about 1997. Most modern computers have a USB port and don't have an RS-232 serial port, so a USB-to-Serial Adapter must be added as an external accessory plugged into the USB port. A USB-to-Serial Adapter is a commercially available device containing a small circuit built into the enclosure of a DB9 male plug, with a USB connector on the other end. It requires a software driver to be loaded and run on the computer, so the computer can recognize it as a "virtual" RS-232 serial port. The COM PORT number is often randomly assigned every time the USB to Serial Adapter is plugged into the computer, so be aware of this as a setup issue when dealing with fixed port numbers in the software. The COM PORT number may be discovered by using the Control Panel>System>Hardware>Ports or similar menu in the main control software of Windows.
4 pins of the serial port connector are used for the ALE controller interface:
TXD [Transmit Data] DB9 pin 3 - For the frequency control of the radio. Known as the CAT transmit data, this goes low and high rapidly at the serial port baud rate during the transfer of frequency information data from the computer to the radio. [Pin 6 of DB25]
RTS [Ready To Send] DB9 pin 7 - For the PTT (Push To Talk), goes high to transmit. It is also known as the Hardware PTT line in ALE jargon. [Pin 4 of DB25]
DTR [Data Terminal Ready] DB9 pin 4 - For the Speaker Mute, goes high to mute the speaker, and commonly controls a relay in the station's external speaker line. This un-mutes by closing the speaker line relay contact whenever an incoming ALE call is received, to alert the operator and provide easy monitoring of traffic on the channel. [Pin 3 of DB25]
GND [Common Ground] DB9 pin 5 - Connected to the computer's logic ground and the chassis and earth ground of a desktop computer, this is the common ground reference for the TXD, RTS, and DTR signals on the RS-232 serial bus. It is connected to pin 5 on a DB9 connector. [Pin 7 of DB25]
See DB9 Pinout
The control signal voltage on the RS-232 pins is not standard, and the design spec can vary quite a bit by manufacturer and model. Modern computers are often in the range of about +/-3V to +/-12V, depending upon how much resistive load you put on them. USB to Serial dongles generally run about +/-3V to about +/-8V, and they can source (drive) about 5 milliamperes to 10 milliamperes of current into a load. Logic LOW (0) is a negative voltage (or ground) and Logic HIGH (1) is a positive voltage. To determine the voltage level on any particular serial port, it is easy to simply measure one of the pins with a voltmeter.
An effective interface takes the nominal range of the above signals from the RS-232 serial port, and converts to the proper polarity and logic levels of the radio. Also, some interfaces provide RF isolation and/or AC-DC isolation between the computer and the transceiver. This isolation prevents noise from the computer from being conducted into the receiver audio, transmit audio, or the antenna. It also prevents transmitter power starting at the antenna from being conducted to the computer and causing RF feedback and other problems on transmit audio.
A Simple ALE Control Interface for use with PCALE or MARSALE
PCALE APPROVED
This circuit is made from a bare minimum of commonly available parts and provides about 1k ohm of RF and Ground isolation. It contains circuits for: CAT control of Icom radios, PTT, and Speaker Muting.
SIMPLE ALE INTERFACE - PARTS LIST
J1 DB9 CONNECTOR FEMALE
J2 MINI STEREO PLUG
J3 MINI STEREO PLUG
K1 RELAY SPDT, WITH 12VDC COIL
Q1 2N2222 or PN2222 or Similar NPN Transistor
Q2 2N2222 or PN2222 or Similar NPN Transistor
Q3 2N2222 or PN2222 or Similar NPN Transistor
R1 1K RESISTOR, 1/4 Watt or 1/2 Watt
R2 10K RESISTOR, 1/4 Watt or 1/8 Watt
R3 10K RESISTOR, 1/4 Watt or 1/8 Watt
R4 10K RESISTOR, 1/4 Watt or 1/8 Watt
SP1 SPEAKER
SW1 SPST TOGGLE SWITCH
MISC WIRE
MISC CABLE
MISC ENCLOSURE
MISC PERFORATED PC BOARD
Simple Icom C-IV Adapter for use with PCALE
This simple RS-232 to C-IV adapter can be built inside the shell of a DB-9 connector. It requires no power, and it works with all Icom radios for use with PCALE. Remember, it is only a one-way C-IV, you will be able to send CAT data from the computer to the transceiver, but the transceiver will not be able to send data back to the computer.
Balanced Audio Computer Interface With Hardware PTT
For transceivers requiring balanced, differential, and/or DC isolated audio.
The audio section of this interface may also be used for broadcast quality 600 ohm impedance audio connections between a computer and any audio source or input.
Balanced Audio Interface schematic
Isolated ALE Interface: Audio, CAT, Hardware PTT, Speaker Mute
PCALE APPROVEDThe following interface circuit provides RF, DC, and AC isolation between the signals of computer and the radio, and between the grounds of the computer and the radio. It is recommended for use with PCALE and other ALE controllers. The interface has all features needed for ALE, including:
1. Audio transformer isolation
2. Opto isolation of the computer control signals
3. Speaker muting (operator alerting / channel monitoring when called by other stations
4. Transmit inhibit switch to prevent undesired computer processes from transmitting
5. CAT control of Icom radios.
Click on the schematic to zoom:
Parts for the Isolated ALE Interface
Like the previously described Simple ALE Interface, this Isolated ALE Interface is made from common parts, while keeping total parts count to a bare minimum. New parts for this circuit may be acquired at some local electronic parts stores (where they still exist) or via online electronic parts stores such as Digikey or Jameco. Homebrewers are encouraged to recycle parts from old equipment... many of these parts may be found in the junkbox, or scavenged from old consumer computer peripherals, telephones, radios, or telephone answering machines. Links to download the datasheets / and spec sheets PDF files for the optocouplers, relays, and transformers are in the Parts List.
For part substitution, most of the parts and part values are not critical, and a lot of leeway for the homebrewer is provided in the design. For example, almost any of the common 6-pin opto coupler ICs may be substituted in the circuit. The transformers may be substituted with almost any small audio transformer, various impedances (100 ohms, up to 50k ohms or so) and even a speaker transformer from an old transistor radio... but 1:1 transformers with impedances of about 600 ohms or 10k ohms will probably work best (such as a telephone modem transformer). The relay may be almost any low power 12VDC coil relay that has Double Throw. The power to run the relay is taken from the transceiver's switched 13.8VDC output, normally found on the transceiver's rear panel accessory connector, or it may be taken from the main 13.8VDC supply (through a 1 amp fuse). Alternatively, a relay with a different coil voltage may be substituted with an appropriate DC supply to match the coil voltage of the relay... or an appropriate value and power of resistor may be inserted in series with the relay coil to substitute a low voltage coil, such as 5V coil, running on a 12V supply.
Isolated ALE Interface - Parts List
C1 1000PF CERAMIC, 50VDC
C2 10UF 16VDC
C3 1000PF CERAMIC, 50VDC
C4 10UF 16VDC
C5 10UF 16VDC
D1 1N4004 OR SIMILAR DIODE
J1 MINI STEREO PLUG MALE, 3.5MM
J2 MINI STEREO PLUG MALE, 3.5MM
J3 MINI STEREO PLUG MALE, 3.5MM
J4 DB9 CONNECTOR FEMALE CABLE CONNECTOR, WITH SHELL
J5 MINI STEREO PLUG MALE, 3.5MM
K1 RELAY SPDT 12VDC COIL (TAKAMISAWA SY-12-K, OMROM G5V-1-12VDC, OR SIMILAR)
R1 1K RESISTOR 1/8W
R2 1K RESISTOR 1/8W
R3 10K POTENTIOMETER 1/8W, PCB MOUNT, TRIMMER
R4 4.7K RESISTOR 1/8W
R5 4.7K RESISTOR 1/8W
R6 10K POTENTIOMETER 1/8W, PCB MOUNT, TRIMMER
R7 4.7K RESISTOR 1/8W
R8 1K RESISTOR 1/8W
R9 1K RESISTOR 1/8W
R10 1K RESISTOR 1/8W
SP1 SPEAKER 4 TO 16 OHMS, 4WATTS, WITH ENCLOSURE
SW1 SPST SWITCH ON/OFF, TOGGLE
T1 AUDIO TRANSFORMER 1:1 (TAMURA TTC-5023, TRIAD TY-141P, OR SIMILAR)
T2 AUDIO TRANSFORMER 1:1 (TAMURA TTC-5023, TRIAD TY-141P, OR SIMILAR)
U1 OPTOCOUPLER 4N25, H11A1, OR SIMILAR
U2 OPTOCOUPLER 4N25, H11A1, OR SIMILAR
U3 OPTOCOUPLER 4N25, H11A1, OR SIMILAR
W1 COAXIAL CABLE RG-174
W2 COAXIAL CABLE RG-174
W3 COAXIAL CABLE RG-174
W4 COAXIAL CABLE RG-174
MISC WIRES
MISC CABLES
MISC TRANSCEIVER REAR PANEL ACCESSORY CONNECTORS
A Single Transistor PTT Interface Circuit
The following interface circuit is a very simple circuit only for PTT keying of the transmitter to transmit. No bells, no whistles. Bare minimum. It is useful not only for ALE (without automatic CAT scanning) but it can be used for almost any digital mode or computer control of a Push-To-Talk of most modern transceivers. It does not provide RF or ground isolation, but has protection and RFI filtering to prevent any RF feedback from keeping the transmitter keyed or causing it to be keyed due to high RF fields. The circuit may be also applied to other pins of the RS-232 to provide logic level conversion from the +/- voltage of the RS-232 via open collector output, to the input of radios or other types of control systems that require a corresponding logic signal to ground. The collector output may also be used to drive a morse CW keying input. Or, it may drive a relay, by connecting one side of the relay coil to a grounded power supply, and the other side of the relay coil to the open collector of this circuit.
Click on the schematic to zoom:
Note: R2 and D1 (protection circuit), and C1 (RF filter) may be deleted if not required.
DB9 Connector RS-232 Pinout
Audio Test Signals for Interface Frequency Response
Sweep Test Files
The following files are Audio Sweeps for testing transmitter audio, IF, and RF chain.
The signal consists of a single sine wave tone, swept from low to high frequency over a duration of 10 seconds, while maintaining exactly the same constant amplitude throughout the sweep.
How To Use an Audio Sweep Test File:
- Transmit the signal into a dummy load at full transmitter power setting.
- Turn down the soundcard output until no ALC is displayed on the transmitter meter. The actual power output should be in the range of about 6 to 10 watts.
- Measure the transmit power output with a power meter, oscilloscope, or RF spectrum analyzer.
- For a flat response, the observed power output should not vary throughout the duration of the sweep.
700Hz to 2600Hz Sweep Audio Signal
(ALE modem signal bandwidth)
Download
300Hz to 3300Hz Sweep Audio Signal
(full 3kHz channel bandwidth)
Download
300Hz to 3100Hz Sweep Audio Signal
(full bandwidth specified by ALE standard)
with blip markers at 750Hz, 1625Hz and 2500Hz
Download
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