Mixing LT Spice and MMANA-GAL, what a clever idea 👍! I like to build my own transmitters, antenna tuners and antennas too. Thanks to your explanation : I am now able to simulate the whole thing 😁, and with free tools ! 73, F1SOC
👍 Another thing worth being mindful of when measuring antennas is common mode current, when the external side of the coax cable work as part of the antenna. Making baluns that will reduce this current is another fascinating topic for future videos.
I made me an antenna cable with plenty of ferrite clip absorbers for measuring purposes. Looks funny like a pearl chain and is quite heavy but quite effective up to 100 MHz.
The modelling of antennas like MMANA-gal does is fascinating - putting bits of electrically unconnected conductors of certain lengths at certain distances from the driven conductors affects things in profound ways (which is how Yagi-Uda "TV antennas") work, they're just a dipole in the middle with a bunch of unconnected metal rods on either side)!
5:10 A half-wave dipole has a theoretical impedance of 73 + 42.5j. In practice, the dipole is shortened until the imaginary reactance goes to zero, at which point the radiation resistance will be below 73 ohm.
Indeed you are right... the ideal, infinitely thin, dipole impedance at L/2 is ~73+42.5j; you can get it to resonate at a slightly smaller length, where the impedance will be ~70R+0j
i am a materials scientist, and was wondering the state of antenna research now. do you have any insights on the materials aspect? Do you need a more conductive material? A material with variable impedance or capacitance? hehe thanks
Just curious. I've tried to replicate the LTspice model, but R1 is always generated in the netlist before "subckt" block (independent of the block positioning) and the program can not find the definition. Is there an extra requirement in settings or something else to implement such a frequency dependant model?
The same happens in my case as well, the resistor is first; however, its not a "resistor" but rather a subcircuit - the resistor component is set to be of "X" type - Ctrl+Right click on the component and set the prefix to "x". Let me know if it works out.
