white4
Newbie level 6
Hi,
I have acquired a small helix antenna for 433Mhz. According to its datasheet, it is matched to 50Ohms with a very good VSWR 1:2. Of course, it has been tested on a PCB with an specific groundplane and matching networks to achieve this VSWR, but there was not information about that.
I have connect the small helix to my VNA and it it's not matched, it has a high capacitance as expected. A vertical groundplane - a piece of 5x5cm methacrylate - is placed under the helix but it doesn't improve, neither get worse. However, if the groundplane is placed parallel and close the antenna it is matched, even if I surround the helix with dielectric it works too. How is it possible? Does dielectric get an inductive effect? Antenna is connected directly to VNA, with out matching network.
Thanks
I have acquired a small helix antenna for 433Mhz. According to its datasheet, it is matched to 50Ohms with a very good VSWR 1:2. Of course, it has been tested on a PCB with an specific groundplane and matching networks to achieve this VSWR, but there was not information about that.
I have connect the small helix to my VNA and it it's not matched, it has a high capacitance as expected. A vertical groundplane - a piece of 5x5cm methacrylate - is placed under the helix but it doesn't improve, neither get worse. However, if the groundplane is placed parallel and close the antenna it is matched, even if I surround the helix with dielectric it works too. How is it possible? Does dielectric get an inductive effect? Antenna is connected directly to VNA, with out matching network.
Thanks