I've build the original QRP-labs U3S from stock. Means the supplied crystal on the PLL-based synthesiser-board.

This configuration is basically working up to 20m with a lot amount of drift, but you will get many decodes on wsprnet.org. On 6m you can also get spots - once a day :-/

My WSPR data collector is now running some days and I started with some basic data analysis.

The power on the bands 60m to 20m is about 100mW!

I've read the PA bias study from Hans and tried to tweak the PA of my U3S for optimum harmonics suppression etc. The spectrum is measured using an SIGLENT SSA3021X analyzer. The power is measured using a 40dB tap and a cheap 20w Dummyload from Diamond: ATT The tap is based on the work of OZ2CPU.

Inspired from some work found on the Internet and the full functionality of my U3S I've build an automatic spot collector. The spot collector pulls every 5 minutes my spots from WSPRnet.org and puts it into a MYSQL database for later analysis. See the schematic for this setup Wspr V3

Here you can find the last spots for DL2SBA on each band within the last day and the all time farest spots.

My new U3S is online :-)

U3S 2

  Live data from my WSPR feed

Measurement of the signal quality of QRP-Labs U3s with low-pass filters.Transmitter output is fed into a homemade 40dB power pad. The spectrum is measured using an SIGLENT SSA3021X analyzer.
The bias voltage was about 2.6VDC and the PA voltage was abt. 7VDC.

Here some analysis of my recorded spots data with my spot data collector. As of today there are 45.000 spots recorded in my database.

Test setup


I made some measurements using my miniVNApro with a simple test fixture fittig the QRP labs lowpass filters.

2014 CW (Morse Telegraphy) was added to the German Nationwide Inventory of Intangible Cultural Heritage.