Tuesday, January 7, 2020

Ultimate digital portable station concept progress

PE4BAS digital portable concept
If you want to know about my previous efforts and concepts I would like to redirect you to my 2018 posts:

The ultimate portable digital unit (1)
The ultimate portable digital unit (2)

The heart of the unit is a concept I thought of and actually is very simple. It is a bluetooth connection for CAT control, Audio in/out and GPS for time and location keeping. This is something that doesn't exist commercially as far as I know and I had to develop something myself.

I managed to get the GPS over bluetooth first with the help of a BT GPS module and BKTtimesync. After I did some experiments via a USB port and a Ublox7 GPS USB stick which didn't work at all. I also realized I could not simply split one USB port into multiple ones without problems even not with a USB hub, it would involve many cables which I wanted to avoid.

Bluetooth headset outside/inside
Second was the bluetooth audio connection. I bought a nice device with internal battery which could receive and transmit. However it didn't work because it could only receive or only transmit, you had to switch it with a external switch. I had to search for a full duplex unit to avoid switching. I bought a few 2 euro bluetooth in-ear headsets, the gold ones were the cheapest. Of course I tested them first before I dismantled them for the experiment. I really had no connection problems at all with these devices, they are real plug and play. However, they are only working in W10. In W7 I got it to receive audio but couldn't get any audio output for transmission. In W10 there was no problem at all. I mounted the BT module on a printboard and soldered in/outputs to connectors for the audiocables from my homemade digital modem, after some failures I finally managed to get it right with the third headset. To be shure I wouldn't get too much signal I mounted potmeters in both audio lines. I fitted the whole print in the same box as my GPS using the same (tablet)battery.

Third was the implementation of bluetooth CAT control. I bought one of those cheap ones from China. They cost about 10 euro including postage. First tests with connection via a Android app called pocketrxtx on a tablet are successful. But unfortunately connection on any computer with Windows failed. When I finally could get it paired, ham radio de luxe (or any other software) couldn't find the COM port connected to the bluetooth device although it was clearly there. I found a solution redirecting the port with serial splitter software, it worked, however this software isn't free and free versions (like for example VPSE) did not work. I didn't want to spend more money on software I spend on the whole device. Imagine it took me over a year to experiment, I couldn't find a good solution for this. And without CAT control the unit would not be ready. After a few tips I decided to try com0com again which is open source software and free. The problem with this software is that it is very basic and I couldn't get it to do what I wanted to. The hub4com package would solve my problems, but you almost guessed it.....it did simply not see the bluetooth assigned COM port. However, the strange thing is that ham radio de luxe does find the port now and I can finally connect to the radio via BT. Don't ask me why and how but com0com seems to install something so ham radio de luxe is able to find every COM port now.

Test of the prototype concept setup
I decided to test the device  working on a dummyload with 1W this afternoon. My base station was configured as FT8 robot answering automatic CQ calls on 10m for the experiment. Here some video footage of the experiment:

Now, this is working but far from ideal. The best option would be one box with BT CAT/BT audio and BT GPS in it, voltage supplied from the radio like the BT CAT is now. That would be a technical challenge but not impossible. However, time is a issue as usual. I'm already glad it is finally working now after such a long time. Things would be so easy if this box was commercially available. Since the new Icom IC-705 has bluetooth I suspect you can CAT control and connect audio via BT like I do. But I'm not shure and time will tell. Would it be commercially interesting to fabricate such a BT device?

Total cost of the bluetooth devices: BT GPS bought in 2017 15 euro, BT in ear headphone (full duplex) 2 euro, BT CAT control unit 10 euro. 27 euro in total, the box and battery were given to me and free. Of course you need some device to connect the audio to your radio, I simply made it myself. It is capable to trigger transmit via VOX but if CAT control is available PTT via CAT is a better option.

There is another approach to wireless connect your portable station. OH8STN for example does use a Raspberry-Pi minicomputer with linux OS connected to his radio. Another computer, phone or tablet can connect the Raspberry-Pi over WiFi for wireless remote. I don't know what the costs are for such a setup but I think the bluetooth solution is cheaper. Both systems are difficult to configure without knowledge of computers and operating systems.


  1. Replies
    1. Don't think so John. If you count what the Raspberry costs including a soundcard, box to fit it in and a GPS. I think you pay at least twice the amount of money I spend now. But in the end everything has pro and cons. 73, Bas


Thanks for your comment. Bedankt voor je reactie. 73, Bas