DRA-54 Header / Jumper Assignments:

JU1 - Remove this short "shunt" to disable AllStar Link COS   (Remove for Digital)
JU2 - Normally in the "A" position.
JU3 - Remove this short "shunt" to disable AllStar Link CTCSS (Remove for Digital)
JU4 - Left or Right transmitter audio source to RJ45 radio connector.
JU5 - Install this jumper to disable PTT LED falsing protection.

H1  - Install short over the center two pins of this 4-pin header.
H2  - Install short over the center two pins of this 4-pin header.

H1 and H2 are white 4-pin headers directly beside the LM-386 amplifiers. By default, 
a jumper short or "shunt" is installed onto the center two pins of the header. See 
the "H1 and H2 header pin assignments" document for details.

R12 (the larger blue pot) controls the receiver audio level.

By default, we recommend NOT installing the short on JU1, JU3 and JU5 for VARA FM or 
other digital mode usage.

Detailed explanation of these headers and jumpers:


JU1 and JU3  - AllStar Link COS and CTCSS logic inputs:
The hardware COS and CTCSS inputs (used for AllStar Link) are not needed for 
VARA FM or other digital modes. In fact, if something is connected to the COS 
and CTCSS (Windows Volume UP and DOWN pins) bad things can happen with digital 
programs.  In addition, DCD (XDC) and/or other logic or control lines might be 
connected in existing installations using the KPC-3 or similar TNC. These functions
affect pins 4 and 5 on the RJ45. These RJ45 pins can be disabled by the absence of 
the  "JU" jumpers at locations JU1 and JU3.  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-54 for digital use.  Jumpers can be installed into locations 
JU1 and JU3 to restore the AllStar Link functionality.
Default is both are removed or side-stepped.

Plus, these hardware inputs may be implemented sometime in software  - permitting 
DCD or some other digital feature, so I don't want to limit the hardware from using
them in the future. 

JU2 - Audio amplifier powering.
Position A = Amplifiers powered from USB 5VDC. Suitable for many radio applications
where  the maximum required P-P voltage doesn't exceed 5 volts. 
Position B = Amplifiers powered from external source 6 to 15 VDC. Some radios 
require more than 5 volts P-P of audio. Many radios have a source of 10 to 15 volts
readily available. The voltage source must be well filtered but regulation isn't 
necessary as long as enough current is available for the load. Driving speakers 
will require a power source capable of several hundred mA, depending on speaker 
impedance and desired listening level. Default is position A.

JU3 - See JU1

JU4 - LEFT or RIGHT TX Audio Output:
JU4 selects between Left or Right transmit audio channels. A = Right, B = Left.
Default is A - Right.

JU5 False PTT LED illumination protection:
Jumper JU5 is removed to enable this illumination protection.  The jumper can be 
placed if this option should it create a problem for a particular installation. 
The jumper simply shorts out the diode.

Why is it necessary?
Partial (or full) illumination of the PTT LED can happen if the radio adapter is
connected to a radio that has a PTT switching voltage (bias) of less than 5 volts.
This is the case with many portable radios.  This situation causes the red PTT LED 
to partially illuminate. This illumination can also happen with just about any radio 
when the radio's power is turned off, falsely making it look like the radio is 
transmitting. Placing JU5 disables the BAT43 diode protection.
Default is removed.

By default, we recommend NOT installing the shorting bar on JU1, JU3 and JU5 for 
VARA FM or other digital mode usage.