Custom Products for the Digital Radio Amateur Enthusiast

Background - AllStar Link COS and CTCSS logic inputs, and how they work under Windows®.

You may encounter a situation where the transmit audio level changes on its own. This will happen if the COS and/or CTCSS logic pins are getting logic from the radio. Many radios output a COS from the accessory or DATA jack. If not disabled or disconnected, the COS logic will make the transmitter audio go to zero, taking a step down (or more) every time the radio squelches or unsquelches, eventually resulting in no transmit audio.

Overview - Remember - the DRA-Series sound card interfaces are an evolution of our RA-Series AllStar Link radio adapters, and they can still function in that capacity. RA-Series interfaces can be used with digital data programs under Windows® even though they weren't originally designed to.

The Problem - The hardware COS and CTCSS logic inputs on a RA or DRA (used for AllStar Link) are not needed for VARA, SoundModem, Winlink or other digital modes. In fact, if something is connected to the COS and CTCSS inputs when the RA or DRA is operating under Windows®, bad things can (will) happen. One BIG issue is unintended transmitter audio level change. Most radios with a Mini-DIN-6 "DATA" connection have the COS logic connected (by default) through the 6 conductor (PS/2 type) cable. Some of you have replaced a Kantronics KPC TNC with a DRA. Some of you want to use RA's for digital beacuse you're familiar with them. Depending on who (or how) the interface cable is made Squelch / COS Logic may be connected. This connection causes an unintended / unwanted transmit audio level change every time the receiver squelches or unsquelches (depending on the radio).

AllStar Link client software (running under Linux) use the VOL-UP and VOL-DOWN inputs on the C-Media chip to convey the presence of the COS and CTCSS logic status, like most repeater controllers do. These inputs are remapped in the ASL software to accommodate and process these functions. VOL-UP and VOL-DOWN are connected to tactile switches when the CM119A is used in its native application as a USB headset sound card adapter. For Windows® programs, however, these inputs indeed change the speaker volume level. In digital applications, speaker level is transmitter audio level.

For our RA Series, there are no COS/CTCSS disable jumpers and disabling requires these inputs to be physically disconnected from the DB9 radio connector.

On our DRA-Series interfaces - these functions can be disabled by removing the appropriate "JU" jumpers at the defined locations. As such, even if these pins are tied back to the radio somehow, it won't matter; their existence won't affect the operation of the DRA for usage under Windows, as long as the jumpers are removed.

Please refer to the jumper settings for your particular radio adapter. You can identify the correct jumpers by going to the "DOCS" (support documentation) page and selecting the link for connectors and jumpers - or use the quick reference below. Each radio adapter has its own set of documentation, and the jumper assignments are different between boards.

Quick Reference:
DRA-30 - COS = JU1 - CTCSS = JU2
DRA-34 - COS = JU1 - CTCSS = JU2
DRA-36 - COS = JU1 - CTCSS = JU2
DRA-45 - COS = JU3 - CTCSS = JU4
DRA-50 - COS = JU3 - CTCSS = JU4
DRA-54 - COS = JU1 - CTCSS = JU3
DRA-65 - COS = JU3 - CTCSS = JU4
DRA-70 - COS = JU3 - CTCSS = JU4
DRA-80 - COS = JU3 - There is no CTCSS input on this DRA.
DRA-100 - COS = JU3 - CTCSS = JU2
DRA-SR - COS = JU3 - There is no CTCSS input on this DRA.

Again - these jumpers should be removed (or side-stepped - hung from one pin) to disable these functions running under Windows®.

These jumpers are installed to enable AllStar Link functionality in Linux.

Email Kevin Custer for additional support.