Echolink interface unit

The Echolink interface unit described in this article is based on the VA3TO board and is assembled in a small diecast aluminium box with jacks for the speech paths.

The radio connector is a 5 pin DIN connnector with the 'standard' TNC-2 pinout, so a standard TNC-2 adapter cable can be used for the radio. An internal trim-pot is provided for trimming the transmit audio level down to suit transceiver mic input levels.

The computer connectors are DE9 serial and two 3.5mm phono jacks.

The unit is powered from 13.8V DC power jack.

You might anticipate the need for substantial earth bonding conductors between the power supply, Echolink interface unit, and computer to avoid hum and noise injection, particularly on the audio to air.

Figure 1 is a view from the underside of the box (with the lid removed).

Figure 1: Echolink interface unit based on the VA3TO board.

PIC config word

The hex file that I obtained for the PIC did not contain the config word set-up.

The config word is addressable in the special test memory of the PIC16F84. If you wish to include the config word settings in such a hex file, so that supporting programmers automatically program the config word, insert the following line immediately before the last line of the hex file.

:0602D0005921592108002C