CAT Icom

This simple and low cost interface circuit is designed for use with any ICOM amateur radio equipment with CIV interface. All parts are soldered directly to pins of DB9 female connector, no PCB is needed. The circuit is powered directly from COM port, no external power supply is necessary. Voltage level generated on COM data input are not true RS-232 level, but most commonly used RS232 level converters in computers can recognize incoming data correctly. I have tested this circuit with a lot of desktop PCs and some notebooks succesfuly, except one PCMCIA COM interface. But solution was a simple change of COM1/COM2 connection of TNC and this interface :-)... For using with HF transceivers is recommended to add an RF choke betwen output of transistor and cable to rig and an blocking capacitor to ground. Diodes are ordinary small Si type, i.e. 1N4148.

I have succesfuly tested this interface for programming of popular transceiver IC-Q7E too. There is necessary simple change of connection of output cable: 3.5mm stereo jack must be used instead of mono jack for CIV interface, the live wire must be connected to second ring in connector, not to tip. Here you can find software for IC-Q7E programming .

Important note: Because this interface is powered from Com port, it depends by software. Some programs give 0 V level to DTR (pin 4). In this case you can try to use RTS (pin 7) or both these pins with Si diodes or if there are still problems simply use external power supply (small battery...).

FUENTE: http://www.qsl.net/ok2wo/iface.htm

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.

FUENTE: http://hflink.com/interface/#simple

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: