UBITX TX level diagramme

Henning Weddig


in preparing my talk to be held at the "UKW-Tagung" in Weinheim Germany next Saturday about my UBITX I prepared a level diagramme with some assumptions: the maximum powe rlevel at the input of a mixer is in the range of -1 dBm (near the 1 dB compression point?)

The result is intersting: als Allison already stated the gain of the TX stage after the first mixer is 48 dB under these assumptions. My guess is that "normally" a lower level (-10 dBm) will do better in respect of IMD resulting in nearly 60 dB of gain!

Another guess for the resultant spurs observed at higher output frequencies: the bidi amp (45 MHz) is not free of harmonics, i.e. also can and will produce harmonics! If true, these harmonics could be easily removed by introducing a low pass filter between the mixer ("45 MHz port") and the mixer itself. Who can and will try this mod?

Henning Weddig


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