Revised via spacing Tests of PCB antenna performance revealed a sharp drop in received power at 2440 MHz, roughly the middle of the antenna's frequency range. This drop can be seen in the red (ant-120A0) and blue (ant-120B2) curve of [1]. The test setup consisted of an atusb board with discrete balun and an antenna with only a single ground plane as the sender, and a set of antennas (see directory ../ants/) connected to an USRP2+XCVR2450 as the receiver. The receiving antennas had two ground planes, connected with vias spaced roughly 5 mm apart. (See ECN0004.) According to figure 1 of [2], the vias connecting the ground planes at the edge of the antenna should be spaced at around 50 mil, four times closer than 5 mm. After adding more vias to one of the receiving antennas, sensitivity improved drastically, as shown in the purple (ant-120C0) curve of [1]. The same improvement could be observed in a set of ten antennas that all had shown the drop before the addition of more vias. The remaining drop of about 10 dB in the middle of the spectrum is probably caused by the sending antenna. A commercially produced 2.54 GHz antenna at the receiver showed a similar drop when used with the same sender. [1] http://downloads.qi-hardware.com/people/werner/wpan/three-ants.png [2] http://www.ember.com/pdf/120-5052-000_Designing_with_a_PCB_Antenna.pdf Conclusion: place vias at the edge of the ground plane facing the antenna with a spacing no larger than 50 mil.