The following are measurements of my U3 on four band, namely 160m, 80m, 30m and 10m. The spectrum analyser is Advantest R3361C. The U3 was powered by a laptop USB port. The U3 is using 5V PA supply and with no additional BS170 PA transistors. The Low Pass Filters were built simply by following the instructions, without any attempt to measure and adjust any component, e.g. inductances by spreading turns, etc. The spectrum analyser input was set to 40dB attenuation.

The U3S kit will produce different, but mostly similar results. In particular the response curves of the LPF's will be the same as on this page, of course.

  160m 80m 30m 10m
Frequency used 1.900MHz 3.500MHz 10.140MHz 28.130MHz
Power (dBm) 22.35dBm 22.47dBm 21.75dBm 21.17dBm
Power (mW) 172mW 177mW 150mW 131mW
2'nd harmonic -42dB -44dB -55dB -42dB
3'rd harmonic -65dB -68dB -46dB -41dB
4'th harmonic -70dB -64dB -45dB -52dB
5'th harmonic -68dB -61dB -47dB -51dB
6'th harmonic       -58dB
7'th harmonic       -62dB


The Spectrum analyser screen photos are shown below. Please CLICK the images for larger versions. The LPF responses were plotted using the spectrum analyser tracker generator, with the LPF enclosed in a die-cast aluminium box. Note that the LPF response plots use 5dB/vertical division.



30m (sorry no LPF filter response, I forgot to do it).


600m spectrum, by David G0LRD showing 2nd and 3rd harmonics at about -50dBc. Oh woe is me, David's spectrum analyser is obviously so much nicer and new than mine, hi hi.