Neues, Interessantes, Skurriles
For my antenna modeling code pymininec (which is a Python re-implementation of the original Mininec Basic-code) I was researching why the resonant frequency computed by Mininec is always a little too high (so the real resonant frequency is slightly lower than simulated and to get the correct higher resonance frequency, wires need to be cut a little shorter than simulated by Mininec ). This means…
This is an example of using the API of pymininec together with the API of plot-antenna . So we're computing an antenna with pymininec and then we display the antenna pattern, voltage standing wave ratio (VSWR), and antenna geometry using plot-antenna . There is already a small API description for plot-antenna , for pymininec we use the main() function in mininec/mininec.py – which contains calls…
This is a write-up that really should go into the documentation of PGAPack but I was unable to include plotly graphics into a github README.rst file, even using the proxy-site raw.githack.com (which is a page that serves html and javascript files with the correct content type so that it can be displayed in a web browser – github choses to serve these files with content-type text/plain). Github…
This is an update on a previous post [Sch25] about a new implementation of non-dominated sorting for PGAPack . Non-dominated sorting is a central component of most multi-objective optimization implementations. In the recent post I did not mention how many generations my test ran. The number of generations in the last and in the following tests was 200. In the last test the code was compiled…
Some of you know that I'm maintaining PGApack , a genetic algorithm package and a corresponding Python wrapper, PGApy . PGApack implements multi-objective optimization using NSGA-II [DPAM02] and NSGA-III [DJ14] , [JD14] . Multi-objective optimization means that we have more than one objective (or fitness-) function. Since typically these functions can contradict each other – when a candidate…
In 2021 I set up a dynamic DNS server using the popular ISC bind DNS server and documented my configuration in a blog article [ 1 ] . Recently (around the second half of the year 2024) the DNS updates stopped working. In my configurations I was using the public key method for signing DNS updates also known as SIG(0). This was long supported in bind and is still documented to work – in the latest…
[Update 2024-08-20: Correction of formula for L and equivalent radius] [Update 2024-09-19: Correction of citation of article by Stearns, Supplement to Antenna Book [ 5 ] ] For my antenna modeling code pymininec (which is a re-implementation of the original Mininec code in Basic) I was researching how to model insulated wires. I had asked Roy Lewallen, W7EL, the author of EZNEC what he is using in…
[Update 2025-12-04: Fix links in bibliography] I'm the author of an antenna plotting program called plot-antenna . It is written in python and has graphics backends for both, matplotlib and plotly . As of this writing the version available on pypi does not yet support different frequency resolution for pattern and impedance plots. The matplotlib backend is better when generating graphics for use…
In my last post [ 1 ] I was wondering why my implementation of skin effect load in pymininec did not match the results we get from NEC-2 . Turns out I was wrong in assuming that the skin effect load is purely resistive, it has a large reactive component. Note: This article contains a lot of math. You may want to skip to the end and check how the new implementation in pymininec behaves compared to…
I've recently implemented skin effect loading of wires in pymininec , my re-implementation of the Mininec antenna modeling code. The original Mininec code did not have this feature. To attempt verification of my implementation I chose to follow an ancient publication by R. P. Haviland, W4MB [ 1 ] where he, among other things, investigates effect of wire resistance on feed point impedance. He has…