Hi all, 

My ubitx is assembled since two days and I am starting playing with it. 

I've flashed the board with Kd8cec fw and with the standalone WSPR beacon mode I'm able to have at least 20 reports in less than 5 minutes, sometimes very far (up to 10000km).

So I guess the transmit is OK. 

I've tried also to connect my radio to my computer with 2 Jacks (BTW on the transmit cable plugged to mic you need to isolate the ring otherwise the PTT will be triggered : I've used a very small piece of tape around the tip to make the job done). 

Anyway with this setup I receive quite well other stations but when I transmit I've difficulties to be heard by two stations in 30 minutes. 

So I guess transmit levels are not OK but everything has been set to 100 % (both windows audio out, TX pwr in wsjtx and set to 40dbm 10w).

Do you have any idea of what is going on? 

Thank you. 
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73's
Adrien F4IJA
https://www.qrz.com/db/F4IJA

Hi Adrien,

One possibility is the computer time.  Must be very precise.  If you do not already have a time setting program, there are several available.  I happen to be using Dimension4 from:
http://www.thinkman.com/dimension4/download.htm

Is there a way to monitor your signal with another receiver?  Distortion or ground loops to the mic input could be an issue. ???   I like to use transformer isolation between the sound card and the rig.  Eliminates any potential ground loop issues.  Also isolated the PTT line (using RS-232 output) with an opto-coupler.

Here is what I did to interface my Elecraft K2, my 20 Meter Homebrew rig, and the uBITX.:

73, Woody

Hi woody. 

Thank you for the schematics. I'll try first to check time but it seems to be OK. After that I could try something like your circuit. 
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73's
Adrien F4IJA
https://www.qrz.com/db/F4IJA