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Hi @SpehroPefhany, yes 220V is peak to peak, and the purpose of proposing a DAC is being able to generate multiple frequencies, even extremely low frequencies (under 1 Hz). For a clearer insight it's for a heater pilot wire for which you can find the needed waveforms at: goo.gl/CnnD1k
@Mikey Thanks for your help, I considered already all these points and spent enough time on the problem to know for sure that beside the battery nearby the problem is, the design of ground plane and its size/antenna combination
@Mikey, I already removed the battery, re-tuned the antenna the radiated power increased to -8 dBm, but still not enough (measured in Anechoic chamber at 3m from antenna and with standard EMC lab amplification)
I already tuned the antenna, the radio chip outputs 13 dBm however it only radiate around -14 dBm. There is also a coin cell battery placed under the PCB which reduces the performances further. Other PCBs with bigger ground plane can radiate 5 dBm