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.

IMG_0789

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.

IMG_0788

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

 

WA4PAW

Just got an email this morning from FCC about approved allocation of a new callsign as per my application – WA4PAW.