Shortened dipole. How does it work?

Recently I was asked about the shortened dipole. In a nutshell: the question was pretty simple - is this possible to create a small yet effective antenna for 80 meters band. Below is a result of my thoughts on this topic as well as some number of diagrams, which, as everybody knows, worse one thousand words.

Let's start from basics: the antenna is a wire conducting the RF current. As far as we are talking not about the conducting of the DC, the basic understanding of the RF transmission is a must, although this is out of the scope of this article.

Chebyshev BPF. PCB design #2.

After some short discussion (or rather asking questions) the design of the PCB has been changed. Now all coils are placed onto the line, capacitors are located symmetrically in respect to coils. The second view of the PCB is following.

Open, Short, Load... OSL calibration.

If you have some kind of VNA you have to be sure your measurements are correct. And this is true: the non-calibrated tool always returns incorrect data regardless of how nice and correctly do they look. To avoid such an inaccuracy of measurements you have to calibrate your device first. There is a well-known procedure named OSL calibration. The OSL calibration is being made against the cable used to measure some device. This is required to subtract the cable from the results of measurements. This is why you have to store results of calibration to separate files (if your device allows you to do this) and then use the corresponding file accordingly.

New measurement device on my desk - OSA103mini

Some time ago I have bought a small but reliable device named OSA103mini. This one is a contemporary all-in-one device allowing you:

• watch the form of signals up to 200 MHz in real time or up to 10 GHz in stroboscopic mode.
• generate signals up to 50 MHz (with the unevenness of the amplitude-frequency characteristic less than 0.5 dB).
• measure frequency (8 digits)
• analyze the specter (using FFT, up to 1 GHz)
• VNA
• LC meter
• SDR transceiver