Experimenting with FT8CN and the (tr)uSDX

I think it was over at the forum at DL2MAN’s (tr)uSDX site that I read a post about FT8CN, an Android app (written by BG7YOZ) for the FT8 digital mode, which recently acquired the ability to do CAT control and audio over the USB connection of the (tr)uSDX.

I have thought about operating digital modes for many years, picked up all sorts of hardware for it at various hamfests, loaded the software of the day on various shack computers … and never gotten as far as the final step of actually operating digital, for one reason or another. As far as digital in portable operation, well, I find my field gear bag quite heavy enough without adding any more stuff! The idea of being able to do digital operating with only the addition of a USB cable was … interesting, and I decided to give it a try! Finding N0BOY’s page over at GitHub and downloading version 0.91 took very little time, as did installing it on my phone. Now all I need is a cable …

Several phone calls later, I had learned that the necessary cable, (USB-C to micro-USB) was not available locally. All right, Amazon it is. A week later, due to some misrouting and delay with my shipment, there it was, in my hand.

That evening after dinner it was off to the Radio Room upstairs to give it all a try. A short BNC cable connected the (tr)uSDX to the QRPguys SWR / power meter, (set to dummy load and power meter), plug in both ends of the new cable and … everything went well. FT8CN came right up, instantly recognizing that it was connected to a (tr)uSDX; once I granted it permissions and selected a port it took control of it, and within just a minute I had it sending a CQ!

I wanted to take a picture of it all lighted up and running, but also needed my phone to take the picture! Oh well, this shows the basics, anyway.

There was just one problem; the power meter showed nothing. Zero point zero.

Hmmmm. I let it run for a while; the phone showed a program that seemed to be running okay, alternating between CQing and listening. The radio switched between transmit and receive modes under CAT control, both on the display and by making relay-clicking sounds as might be expected. The power meter seemed to be getting something, it would go from blank display to showing all zeroes when the radio started to transmit; one time it actually showed 0.10 for a moment. What’s going on here?

I shut down FT8CN, leaving the phone supplying power over USB, and pressed the PTT button; speaking into the internal mic caused the meter to show output, about 500 mW as would be normal for the radio on 5 volt USB power, so everything was okay there. Several more tries gave about the same result.

Since then I have read everything I could find online (not very much) about operating this hardware / software combo and tried again with the same setup and same result. I turned up every audio volume setting to 100%. I downloaded and installed version 0.91 patch 1. I tried other bands; 20, 30, and 40 meters gave the same results: an occasional flicker of output at the beginning of a transmit cycle, at best; mostly 0.00.

As I type this, another thought occurs to me: maybe it is only sending a single CQ {callsign} {grid square} per cycle? That might plausibly explain the occasional flicker, when the brief output coincides perfectly with the ADC’s internal sampling cycle. Maybe? How can I test for that?

Okay, tried typing in a longer CQ message to see if that would cause a longer transmission; FT8CN appears to truncate the CQ message to 13(?) characters.

Oh well, back to plan A; taking everything out to a park where I can set up a resonant antenna (probably the Buddipole / 17′ whip combo, which is a flat 1.5:1 across 20 m.) and giving it a try on the air instead of into a dummy load. I will probably take the whole heap of stuff I carried last weekend, so if FT8 fails I can still get an activation in. Maybe tomorrow? We’ll see.

Thanks for visiting driftlessqrp! Check back soon for an update!





One response to “Experimenting with FT8CN and the (tr)uSDX”

  1. Chuck Eglhaut K3CWE Avatar
    Chuck Eglhaut K3CWE

    OK I been seeing a similar problem with my set up. On several different setups.
    I am receiving and decoding but when it switches to Tx I shows just a burst of out let with little power.
    I using an older,Nextbook tablet but it seems to be receiving the signal and decoding. I have on on occasion made a contact and it log in the FT8cn log.
    I need a cable also but I waiting till I upgrade the Nextbook.
    Have you got the set up to work and how it work for POTA?

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