A USB Interface for the DX Doubler – The Last DXDUSB Prototypes

I have been working on a USB-only interface for the Top Ten Devices DX Doubler for some time. I recently completed the 3rd generation prototype. This is still a prototype – it uses a very small Arduino board with attached wires, but it is shoved into a nice small Ethernet drop-box enclosue.

This version has been in testing for several months. I have tested one, and a friend, K7SV, has also been testing one. He is a much more active and accomplished SO2R operator than I, so his feedback has been very helpful and much appreciated – thanks Lar.

At this point, I feel this is a viable design and it seems to be reliable. The only issue known is that I have to recycle the 5 volt power on mine after a week or two of inactivity in my shack. Not sure why, and I know Lar has not had this problem. I am wondering if my PC is shutting-down the port.Recycling the power once always resolves the issue.

There a a couple photos of the latest prototype below.



This version uses a tethered DB25 connector that attaches to the DX Doubler box. The USB connector you see is for 5v power ONLY – this seemed like an easy way to power the device, but I am still experimenting with other power options. I need a version that uses 12vdc for my shack. I also plan to make the final unit capable of working with supplies of up to 15vdc, so it can be used in nearly any station, Home or Mobile. Notice the attached snap-on ferrite. I put these on nearly all of the peripheral devices in my shack, and especially in my Mobile. I have not had any indication that this is needed to combat RFI, so it is only a precaution. My antennas are too close to my rig, so I do not want to push my luck.

The RJ45 port seen in the lower photo is for connection a USB to Serial interface. This is the actual port that is used for communication between the DX Doubler and the PC. There is a standard USB–>Serial cable that is made for connecting to Cisco routers. I have opted to use this cable, which is available at Amazon for under $ 14. It uses the popular (though somewhat expensive) FTDI chip, which is known to be compatible with the N1MM+ software I use. With this cable connected, I can utilize all of the DX Doubler functions, including computer-generated PTT and CW keying. This design has been setup for use with N1MM+ Logger software. It should be compatible with other software that can use the DX Doubler but I have not yet found any testers to configure and verify this. I am in the early stage of trying the DXDUSB with WRITELOG software, another popular contesting application.

I have now turned my attention to designing a printed circuit board version, that will be enclosed in a small chassis, and could possibly be embedded inside the DX Doubler chassis as well. more on this later. I have received a couple inquiries about providing this as a product. That is my plan if there is enough interest. Sorry, but I am not yet ready to ship these in any quantity. I may be able to send a couple out for testing, but delivery time would be at least 2-3 weeks. Any additional feedback or questions would be welcomed.





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