The DX Doubler (DXD) is a Single Operator Two Radio (SO2R) control box. You plug your headphones, mike, keyer, and footswitch into the DXD, connect the DXD to your radios with easily made cables (or optional cables available from Top Ten), and you are ready to operate! The photo at left shows the layout of the front control panel, which is arranged in an easy to understand and intuitive way. Headphone audio controls are on the left side, while the transmitter selection controls are on the right. Red and green LEDs are located on the left and right sides of the DXD, and follow the popular FT-1000MP convention for visual indication of which of the two radios is being heard in the 'phones, and which is the selected transmitter.

Click here to download an Adobe PDF of the Instruction Manual.

DXD Features

The following is a summary of key DXD features:

• One box, permanently installed.  No reconfiguration required for everyday vs. contest use.
• 2 x 9 x 5 inch (HWD) enclosure.
• Independant auto/manual controls for receive audio and transmit.
• Compatible with N1MM, CT, NA, TR, WriteLog, and WinTEST for automatic operation.
• Audio MIX control on front panel.
• Green LEDs for Rx1 and Rx2 and red LEDs for Tx1 and Tx2, like the FT1000MP.
• Supports main and sub audio for each radio.
• Relay driver outputs for Tx1 and Tx2 for special set ups.
• CMOS logic with lots of RF bypassing. No microprocessors.
• Mike and mike return are isolated from ground.
• Band decoder output from LPT port connection.
• PTT mode that can run with or with out computer control.
• Responds to the Rx1, Rx2 or Stereo commands from NA.
• Draws only 30 mA. Can be powered from the radio's aux power jack.

Installation of the DXD is straightforward.  Your mike and headphones plug into the front panel, allowing for quick and easy changeout during the contest period if desired.  Keyer and footswitch plug into jacks on the rear panel.  A single cable from the rear of the DXD to each radio carries mike, audio, PTT, and CW key lines.  A standard 25-wire straight through computer cable connects the DXD to the computer's LPT port.  Once the DXD is installed, you never have to touch the cabling again.

Digital Voice Keyer and CW Memory Keyer Issues

The DXD accepts one mike audio line.  If you use a digital voice keyer, this will need to be configured externally.  However, this is not difficult.  For example, with the K1EA DVP, which is typical of computer-installed voice keyers, the microphone plugs into the DVP, and the DVP's audio output is either the memorized speech or the mike audio, depending upon computer keyboard commands.  The cable supplied with the DVP may be used with an adapter (easily homebrewed or available from Top Ten), or new cables can be easily made to interface the mike to the DVP and the DVP's output to the DXDoubler.  Other digital voice keyers can be integrated into the station configuration in the same, easy manner.

CT, NA, TR, and WriteLog have standardized on a given pin on the computer's LPT port for the CW keying signal.  The 25-wire cable from the LPT port brings the keying signal into the DXD.  The external CW keyer is plugged into the rear of the DXD, the two keying signals are combined, and a single CW keying signal is sent to the selected transceiver.

NA and TR users can plug their CW paddle into a jack on the rear of the DXD, and use NA's or TR's built-in manual keyer, thus eliminating the need for an external keyer.

Manual and Automatic Mode

Many of the popular contest logging programs, such as N1MM, CT, NA, TR, and WriteLog, have SO2R features.  These features typically include keyboard selection of which transceiver is active, reflected by a control line on the LPT port.  NA also provides keyboard selection of headphone audio source, again via pins on the LPT port.  The DXD accepts these control signals.

The DXD has separately selected and independent Manual vs Automatic Control for both headphone audio and transmitter selection.  Headphone audio can be in Manual while Transmitter Selection can in Automatic.  This provides enormous flexibility to the operator.
 

Headphone Audio Control

The DXD handles up to four audio streams, Main and Sub VFOs, from both radios, if the radios provide it.

In Manual, the operator can select either Radio 1, Both, or Radio 2 as the audio source.

In Automatic, two options are available:

1. PTT - Used for agressive search and pounce operation
2. Auto - Audio is from the computer selected transceiver

In either Manual, PTT, or Automatic mode, an audio Mix control is provided to blend a little bit of the left and right headphone audio signals together.  A front panel toggle switch enables/disables the audio mix feature.

Transmitter Selection Control

In Manual, the operator can select either Radio 1 or Radio 2.

In Automatic, the operator selects the desired transceiver by using the appropriate computer keyboard commands or keystrokes.

LEDs are provided on the DXD front panel to inform the operator at a glance which transceiver will be the one to transmit, and which transceiver is the one being heard in the headphones.  The LEDs are arranged on the left and right sides of the front panel, with a red and green LED on each side.  The green LEDs indicate the headphone audio source.  Note that if "Both" is selected manually, or if the NA "Stereo" command is issued, both green LEDs will be illuminated.  However, only one red LED can be on, since it is not possible to transmit with both radios simultaneously.  In the example shown, Radio 1 is the selected transmitter, while the left headphone is connected to Radio 1 and the right headphone is connected to Radio 2.

This highly intuitive visual feedback scheme is identical to that employed by the very popular Yaesu FT-1000MP/Mark V as regards to which VFO is active for transmit and headphone audio.

Interconnecting Cables

Details for making all the various cables required for a complete installation are provided in the DXD manual.  Additionally, Top Ten can provide the following optional cables:

• DXD to Yaesu transceiver (typically FT-1000D/MP/Mark V/2000/9000)
• DXD to Kenwood transceiver (typically TS-930/940/950)
• DXD to Elecraft K3 transceiver (NEW!)
• DXD to non-specified radio (DXD plug applied, radio plugs for mike, Rx audio, and CW keying provided in kit form)
• Adapter cable to allow DVP cable to be used without modification

The cable required to connect the DXD to your computer's LPT (printer port) is a standard DB25M-DB25M, full 25-wire cable. This cable is very cost effectively acquired at your local computer store.

DX Doubler - Two Radio Controller....................$225 + s/h

Cable, DXD to Kenwood, Yaesu, or Elecraft K3, 6 feet long......$ 35 + s/h

Cable, DXD to generic radio (kit), 6 feet long ......$ 20 + s/h

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