Andrew77

Sitecom xn 300 wml3600 Adding two external antennas

With disk axial ratio is not good (13 dB) This last design without disk axial ratio is around 3-4 dB

12,5 dB helix antenna for 432 mhz 13 turns, 223 mm diameter 4 degree pitch 645 mm Long 50x50 cm ground plane Helix_433_NB_3.cst

Also this, RTL8187, 1,5W (declared), 8dBi antenna

impressive!

some tests Waveguide port, transient analysis (950 K mesh)

Right!

For waveguide port CST explains here: "Very low reflections can be achieved when the waveguide mode patterns in the port match perfectly with the mode patterns from the waveguides inside the structure. CST MICROWAVE STUDIO® uses a 2D eigenmode solver to calculate the waveguide port modes. This procedure can provide very low levels of reflection below -100dB in some cases" for Discrete port: "Discrete ports are mainly used to simulate lumped element sources inside the calculation domain. These ports are a good approximation for the source in the feeding point of antennas when calculating farfields. In some cases, these ports may also be used to terminate coaxial cables or microstrip lines. However, due to the transmission between transmission lines of different geometric dimensions, reflections may occur that are much larger than those for the termination with waveguide ports. For lower frequencies (compared to the dimension of the discrete port), these reflections may be sufficiently small, such that these kinds of ports may also be used successfully for the S-parameter calculations of multipin connectors" To my opinion I prefer waveguide port where it is possible use it, But I don't understand your picture: are you using a 150 ohm port because you expect that antenna shows around 150 ohm at feed point? Impedance is lower when first turn is close to ground..

thanks, Yes, impedance matching is not performed here due to much higher meshing needed (for the stub close to the feed...) My goal is to design and realize a 432 MHz Helix the shortest possible with the highest gain so to couple 4 of them for my Ham communication Now I'm designing a narrow band Helix for the same frequency with a little higher gain (more coils: 11) same length ... I'm not very sure about integral equation solver because I've always used Transient Analysis but in this case antenna is big. I've noticed that increase "Steps per wavelength" doesn't change much the gain (about +/- 0,2 dB) could you confirm that? thanks Andrea

Can this disk be applied to longer helical antennas (2 wavelength) and @ lower frequency? (EG 430 MHz)?? thanks