I ran some FT8 tests with my uBITX as soon as it was assembled.??
Output power levels were 11W at 3.5 and 7 MHz, and about 4W at 10 and 14 MHz.? According to PSK Reporter, my signal was decoded all over North America, with strong SNRs reported by receivers with good propagation paths from Oregon.? I made at least one contact on each band before opening the rig back up to experiment with RV1 and the PA power supply. Note that my antenna is a fan dipole in the attic, with an embarrassingly long feedline (repurposed RG-59) and a manual tuner at the rig in my home office.? So feedline losses are awfully high.
I am running WSJT-X on a 7 inch tablet purpose-built?around a Raspberry Pi and a cheap USB soundcard dongle.? The soundcard interface is based on a design by W2DEN (which is in turn based on a design by KK7UQ).? You can see the tablet, and my uBITX, in the gallery at uBITX.net.
I'm using?KD8CEC¡¯s firmware. So I should be able to use CAT control for PTT.? But there seems to be a bug in my WSJT-X release that is interfering with CAT functionality. (Either that or I fouled something up when compiling it on the Raspi.)? So for WSJT-X I use an external PTT relay driven by a USB-Serial converter.? CAT control for Fldigi works fine.
In summary, the uBITX is a great rig for FT8, even at out-of-the-box power levels.? That said. I am now splitting off the PA power so I can drive the finals with 24 VDC.? That will help make up for the inefficient antennas that I use while portable. Early testing indicates that with a 24 VDC supply for the PA I can get 20 watts on 3.5-14 MHz, 11 watts at 18 MHz, and 7 watts at 21-28 MHz.? Total current draw was 0.7 to 2.2 amps, measured while transmitting with a 25 VDC supply.? Note that those power levels were reached after also performing the "power leveling" mods suggested by?K9HZ and?WB2VXW.
Mark (AE7TO)
