Bluetooth PSK31/WSJT/Digital interface for Yaesu FT817 (and a tablet/PC)

I used a bluetooth CAT control with my Yaesu FT817 for quite awhile ($14 on ebay) and was generally happy with it. There is a small lag but one can get used to it. The advantage is no wires between a laptop and transceiver. Also, I could use my HP Stream tablet with it (Win 8) this way.

Given this success, I entertained an idea of making a digital (soundcard) interface wireless too. As the connection would be simplex and mono (1 channel), a regular bluetooth phone headset seemed up to the job.

I happened to have one laying around without much use so the first step was to prove the concept which was very easy. Once paired with the laptop / tablet, the headset became available as a soundcard in HRD DM780 settings. I tried sending some RTTY to it and it worked. I guess now I understand what Alexander Graham Bell felt like when his first phone worked (hi hi).

However, receiving (listening) from the headset did not work. After some googling, I found a hint – set bluetooth headset soundcard as a Default device in the Control Panel -> Sound -> Recording Devices settings. That helped right away so the next step was wiring the headset to the transceiver.

After disassembling the headset, I removed existing battery, speaker and mic and soldered new thin wires to the connecting pads.

Headset with wires


For TX (audio out) – I added a 1:25 resistive divider to decrease the output voltage off the speaker wires and to match the voltage requirements of Yaesu; and soldered the speakers wires to it. For RX (audio in), I needed to match Yaesu output to the headset mic. After some experimentation, a combination of two SMD capacitors to both pins and a small resistor in series to avoid overloading and to provide DC isolation finally worked.

Finally, I added a new bigger OEM Li-Ion battery (insulated with black tape) and a USB charger PCB with a switch to improve on portable operation time of the headset.

Li-Ion battery with a charger PCB

The headset, battery, charger, and the existing CAT BT control PCB all managed to fit into a small plastic enclosure. Some hot glue helped to secure them in place.

The boards sit on top of the battery / charger; to isolate the layer I cut a small sheet off a thick polyethylene water jug.


The enclosure is secured with two small strips of a velcro tape. The battery can be charged via a USB connector; the switch turns on/off the bluetooth headset.


The PTT is controlled by the software via the CAT control. Now to chase DX with WSJT QRP mode!



QSL cards received and answered

Fresh QSL cards in the mail today – all received direct and to be confirmed direct via Canada Post mail tomorrow morning:

QSL_i2rib qsl_kd0cdm qsl_k4bll

What’s really puzzling me is that most of the QSL cards I receive recently were for digital modes. Before, most of my QSL cards came from my CW correspondents. Generally speaking, I would generally expect a modern digital mode like JT65/JT9 to be confirmed via LOTW…  Still, it’s a thrill discovering a familiar size envelope in the mailbox: it’s like a box of chocolates -you never know what you’re gonna get.

One week on JT65 on 40m


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Unattended (somewhat) JT9 / JT65 on 40m and JT-Alert

Once I had my digital interface in place, I used my new FT817ND with great success for ragchewing using PSK31, several contest-style contacts with W1AW on RTTY, and then some WSPR propagation tests, before I stumbled upon the WSJT-X app by K1JT following some questions from a ham on a local amateur radio club forum.

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Wired (and wireless) interface for digital modes for Yaesu FT-817ND

I had bought a sound card interface kit ( some time ago which I planned to use with soundcard-based digital modes such as PSK31 and RTTY.

Recently, I finally found time to build it and wire it to my new Yaesu FT817ND radio. Overall, it was an easy and pleasurable build – took me less than an hour. The design is very well thought and easily expandable.

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