Custom Products for the Digital Radio Amateur Enthusiast

What is it - and why do I need it?
The DRA-MIX-MUX is used in instances where you want to connect different applications using separate radio interfaces - simultaneously, to one radio. The board uses a high-performance op-amp to provide isolation and prevent loading issues. This board allows DRA's or older packet modems / TNC's to be connected to one radio. Supports 1200 and 9600 baud operation, and high-speed (HS) SoundModem or licensed VARA FM Wide. Up to three interfaces can be connected simultaneously to one radio. Two sound card ports (SC-1, and SC-2) and RADIO port accommodates the connection of Mini-DIN-6 cable(s) directly. The third modem connects to holes that allow wiring to a different jack (not suopplied). Custom build options are available - like letting the connectoes off. LED's indicate the presence of power and the assertion of PTT from any modem or sound card. Uses a high-performance / low-noise TL074 op-amp and requires a source of clean power (12 VDC at less than 100mA - provided externally).

REV2 boards adds a relay for keying the radio PTT.
Some ICOM radios require this, as simple diode logic "OR" gating doesn't work on all radios.

No case or enclosure is currently available.

The board is inspired by Walter Kaelin KB6BT and is a result of his original work.

Description of its operation:
This board allows two (or three) applications using two (or three) separate sound cards or modems to be connected to a single radio - simultaneously. Configuration headers and jumpers allow selection of baud rates (audio types) for matching the correct audio for the application. Works best with radios that have a dedicated Mini-DIN-6 data port but can be used with any type of radio with the right cables. The board could be built without installing the Mini-DIN-6 connectors and wired to/with different connectors. There's even additional "holes" to allow wiring up a third modem or attaching yet a different radio connector. Alternate connectors are not provided. Email below for more information and options.

Easily movable on-board jumper "shorts" allow this board to be configured for "1200" or "9600" baud audio for Sound Card inputs 1 and 2 and the radio - no soldering required.

Detailed technical description:
This board produces a PTT logic signal (ground) when any sound card or the optional third (modem) connection is producing a PTT signal. Transmit audio from all three sources is mixed together and buffered for isolation, and routed to the radio. This audio is not switched or gated - it's simply mixed together. Receive audio from the radio is split into three sources which are individually buffered for isolation and routed to the sound cards or modems. These active stages eliminate interaction of audio levels that can change when simple resistive (only) mixing and splitting practices are employed. Either "1200" or "9600" (narrow or wide) audio can be selected from configuration headers for each sound card port. It's possible to select 1200 for one and 9600 for the other - but this might not be a functional configuration depending on the exact equipment being utilized.

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DRA-MIX-MUX Unassembled Kit

DRA-MIX-MUX Assembled & Tested

Add DRAC-12 Radio Cable(s)

DRA-MIX-MUX Documentation and Construction:
DRA-MIX-MUX Construction Article.

Support Documentation - jumper settings, schematic, parts list, installation and set-up instructions for the DRA-MIX-MUX.

DRAC-12 - 6-foot Mini-DIN-6 Radio Cable  can be added optionally to connect data capble radios to the DRA-MIX-MUX.

Email Kevin Custer for ordering information, ordering by check, and/or support of this exciting product.

Product of Masters Communications, all rights reserved.
Specifications may change without notice.
Images are property of Kevin Custer - W3KKC
Inspired by Walter Kaelin - KB6BT
Board layout by Kevin Custer - W3KKC
HTML October 26, 2021, W3KKC All Rights Reserved!