I have spoken in several recent articles about antennas that exhibit a simple series resonance with constant or near constant R near resonance.
Sometimes the impedance transformation used may hide that simplicity. Continue reading Simple resonators might not appear as such initially
Readers of (How) does this balun work? have asked about the meaning of the terms Current Balun and Voltage Balun. The following is a cut and paste from my old site.
Definition: Current Balun, Voltage Balun
The terms Current Balun and Voltage Balun are often used. This article explains the key characteristics that determine which best describes a particular balun. The approach taken is to charaterise a balun because of how it behaves externally rather than the internal implementation. Continue reading Definition: Current Balun, Voltage Balun
This article explores a generic VSWR curve for simple series resonant matched antennas. Continue reading VSWR curve of a simple series resonant antenna
This article discusses the concept of circuit Q, its application for antennas and assessment of antenna Q. Continue reading Antennas and Q
A correspondent sent me a pic of a commercial balun asking “How does this balun work”. He explained that it is a “combination 1:4 balun followed by a current choke”.
My first thought was that this is likely to have been a creation of Jerry Sevick… but let’s try and analyse it. Continue reading (How) does this balun work?
The ‘net abounds with articles describing easy to build low cost small transmitting loops (STL).
This article describes measurement of a STL for 4MHz using RG213 coaxial cable for the main loop and its tuning capacitance, and a smaller plain wire loop for transformation to 50Ω. Continue reading A QRP small transmitting loop evaluation
There are many calculators for design of small transmitting loops (STL). This article compares one quite old DOS one and a mature popular modern spreadsheet. Continue reading Small transmitting loop calculators – a comparison
The ARRL Antenna Book 21 (Straw 2007) gives equations and advice for design of small transmitting loops.
Many Hams have used these formulas and method for their designs, and some have even produced design tools (online calculators and spreadsheets) implementing these formulas.
This article reviews these formulas and advice. Continue reading ARRL Antenna Book 21 on small transmitting loops
Off centre fed (OCF) dipoles are very popular with Hams on HF.
Many claims are made for variations of the theme, but the essential common feature is that the offset feed point provides a feed point impedance that is not too unsuited to 50Ω coaxial feed line at the fundamental resonance of the dipole and half wave harmonics. Continue reading OCF dipoles
This article documents a series of tests of BLHeli v11.2 damping.
The test configuration is 4S Lipo, HK 9261000003 ESC, HK 4822-690kv motor with 1045SF prop in a static bench test. Note that the ESC uses FET driver chips that deliver quite fast switching. Continue reading BLHeli v11.2 damping evaluation