& not so recent
additions & corrections
. The camerasunderwater info collection has now been transferred to this website. See the Photography and Optics
For those who notice such things, it will be apparent that I
have decided at last to bring my HTML writing methods into the 17th
Century. I started writing this website in around 2000, using a piece of software called 'Adobe Pagemill.'
Pagemill produced terrible HTML (what the **** is a
'naturalsizeflag' ?), but it had some very clever features that were
not replicated by later programs. Particularly, it had a link
checker and manager that allowed files to be relocated; i.e., a file
could be moved to a new folder and all the pages linking to it would be
updated accordingly. That allowed the maintenance of a
logical data hierarchy, which is a serious bonus in a site with as many
files as this one.
Pagemill was never updated to keep
abreast of new HTML standards because Adobe first replaced it with a
horror called 'GoLive', which wanted to suck the victim's website into
a databse, and then acquired a piece of
software called 'Dreamweaver'. Giving GoLive a miss for obvious
reasons; I tried editing my website
using Dreamweaver, but quickly discovered that the dream was a
nightmare. I had produced my page layouts by using tables.
Dreamweaver however insisted that all data in every table
cell needed to be contained within a paragraph, so would insert
<p> at the beginning of each entry and
</p> at the end. This was not required by the 4.01 rules,
but any attempt to delete these spurious tags would result in
them being reinserted when the file was saved. So,
opening a file in Dreamweaver and then saving it had the effect of
utterly destroying the layout.
At the time of meines kampfes mit
Dreamweaver, there was talk of new browsers that were not going to
support old HTML standards. The idea, in the minds of the
individuals promoting this approach was, presumably, that people would
be able to come back from the dead to re-edit their work. I
started to panic, and tried out various other editors, but there seemed
to be none capable of editing pre-existing pages without wrecking
them. All insisted that the user had to do it their way, and
the orthodoxy seemed to be that no web page actually needed to have any
significant content; so it was obviously necessary to force vast
amounts of blank space.
So eventually, I gave up and carried on
Pagemill, while slowly converting pages into pdfs and dreading the point at which browsers would cease to
parse my HTML. That problem, of course, never happened;
firstly because all of the people who had died since the beginning of
the Internet proved to be disinclined to
update their markup,
but mainly because the idea of excluding legacy code is idiotic.
To do such a thing would be software project suicide, because it
results in a browser that can't browse. Deprecated coding methods are not
secret, and so it's obvious that a browser
just has to render what it gets. The rather wonderful Internet Archive Wayback Machine
for example, somewhat depends on that facility.
But there comes a point at which even I
have to admit that a piece of software is too old. Indeed,
Pagemill now has to be run under Wine, or in an XP Virtualbox.
So I started looking around and reading software reviews, and
discovered that the horrors of the early 21st
Century have mostly gone away. Checking for broken links, for
example, can be accomplished by means of an online link checking
service (e.g., brokenlinkcheck.com
and, better than Pagemill, these services check both internal and
external links. Furthermore, there are now HTML editors that
don't wantonly destroy pages they didn't create.
One such editor is Nvu
free WYSIWYG for Windows, Mac and Linux. It gets good reviews
(with some reservations - see, eg., sitewizard
but the real $64k question that reviewers fail to address is: "What
happens when you open and save a 20 year old page?"
In the case of Nvu, the software corrects any glaring errors and
declares the code, somewhat optimistically, to be HTML 4.01
Transitional (i.e., in this case, very loose).
Also, having performed this automatic
conversion, it does not assume that the page needs to be saved unless
the user also makes a change.
By making a minimal non-rendering
change in (say) the page header, it is possible to save the file and
see what the conversion has done; and the glorious and unprecedented
result is that the page looks exactly the same as it did before (in
Chrome and IE at least). Now, suddenly, I find that it is
possible to update old pages without re-writing them from scratch.
It's a wonder that other development teams had not thought of
this. Moreover, should you go into source mode and delete
changes made by the software, they actually stay deleted
(provided that the code remains internally consistent).
So, with thanks to the Nvu team, the
pages in this site can now be updated as and when they need editing;
and the source will then be seen to declare (in the sense
of 'Lies, Damned lies, and statements of conformity') that it is HTML
. Started porting optical &
from the Cameras
Underwater Info website
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
arXiv.org and cited accordingly: arXiv:1605.04196
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.
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.
: 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
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
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/
: A new version of Solenoid Inductance
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
: A new (still unfinished) draft
detectors for RF measurement
is available (v 0.09).
2015, Nov 27th
reworking of the complementary follower detector
Patrick Turner. A full discrete component op-amp circuit with
long-tailed pair for NFB gives -3 dB @ 10 MHz.
: Updated version of Inductor