Recent & not so recent additions & corrections

2017-08-17. Started porting optical & photographic articles from the Cameras Underwater Info website.

2016-05-13. The English translation of Paul Drude's 1902 paper "On the construction of Tesla transformers: Period of oscillation and self-inductance of the coil." Can now be downloaded from and cited accordingly: arXiv:1605.04196 .

2016-05-09. Self-resonance and self capacitance of solenoids. v 1.00
Coils terminated by a parallel impedance behave differently from coils operated with one or both ends open circuit (vertical antennas, Tesla coils, helical resonators). The troubled history of self-resonance and self-capacitance modelling is due to the unrecognised impossibility of analysing these two very different situations using the same formulae. This article demonstrates that standard helical transmission-line theory does not apply in the uniform current case, and that it also needs considerable extension if it is to be applied properly to free coils. A new semi-empirical free-coil model is based on an Ollendorff helical transmission line terminated by its own axial field and fringe field capacitances. The author's well known 2008 update of Medhurst's formula (CL-DAE) remains valid.

2016, Mar 9th: Solenoid self-resonance measurements by Alex Pettit, KK4VB.
Added information on the use of a neon bulb array to visualise fields. Some changes to the discussion in view of work on the main self-capacitance and self-resonance article.

2016, Mar 6th: Bob Weaver has a new article on the Geometric Mean Distance method for calculating inductance, including the first ever estimation of the error inherent in using it. He also introduces the use of Monte Carlo methods as solution to the mathematical intractability of many GMD determinations.

2016, Feb 14th: I have issued a new version of Notation Symbols and Abbreviations (1.09). Despite the IOP guidelines, I have not (yet?) made the decision to put all mathematical variables in italic type, but I am in the process of eliminating any difference in meaning between plain and italic symbols. All articles with version dates after Feb. 14th 2016 will reflect this change (although few are actually affected). The main issue was that in some documents I had used an italic form to represent a quantity per unit length. I had thought of creating new symbols to get around this early bad decision, but actually it is easier and less confusing simply to put length into the equation, e.g., resistance per unit length becomes R/.

2016, Feb 4th: A new version of Solenoid Inductance Calculation is available (v 0.20). There are some minor additions and a partial re-write of the introduction. Most of the changes are to the typesetting and layout of equations. The work is still unfinished.

2016, Jan 1st: A new (still unfinished) draft of Diode detectors for RF measurement is available (v 0.09).

2015, Nov 27th: A reworking of the complementary follower detector by Patrick Turner. A full discrete component op-amp circuit with long-tailed pair for NFB gives -3 dB @ 10 MHz.

2015, Nov. 16th: Updated version of Inductor resonance experiments article.

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