• After putting it off for several years, I've finally embarked upon a major revamp of this website. The site was originally created in 2009 using Apple's iWeb web publishing software. iWeb has been obsolete for several years now and no longer runs on current versions of MacOS. I've had to keep an older version of MacOS running on one of my computers in order to maintain the site. Unfortunately, iWeb keeps the site source in a proprietary file format, and over the years that file has become corrupted, making it dangerous to try to make changes to it. I'm now redoing the site page by page (there are about 65 pages in total). This will take some time, but in the end, the html format will be much cleaner, the page files will be considerably smaller, should load faster, and the site will be much easier to maintain. When complete, the pages should display more consistently across different browsers. The Home page has already been completed and uploaded. You may notice some slight changes from the previous format. Most notable, the content will now be aligned with the left side of the browser window rather than being centred as it was in the past.


  • The site has been moved to a new web hosting company. With the improved hosting service this site should soon be able to support secure https connections.


  • Minor updates to PIC Nixie and Arduino Nixie pages. Explained the reason for the 60 volt input to pin 1 of the driver IC.


  • Found and fixed yet another bug in the program code for the 16F630 and 16F1703 versions of the DDS Frequency Synthesizer that, again, affected only the AD9850. This bug prevented the AD9850 from working in sweep mode.


  • Fixed the remaining (known) bug in the program code for the 16F1703 version of the DDS Frequency Synthesizer that affected only the AD9850. For more information, please refer to the notes at the bottom of the DDS page.


  • A bug has been discovered in the program code for the DDS Frequency Synthesizer. There are actually two different bugs: One affecting both the 16F630 and 16F1703 versions (when using an AD9850), which has now been fixed, and a second one affecting only the 16F1703. For more information please refer to the notes at the bottom of the DDS page.


  • Updated the 455 kHz Signal Generator Page replacing the hard to find ceramic filter with a simple LC filter. Also made some other minor changes to the circuit component values, to give a better frequency range for the audio modulation.



  • Updated the DDS Frequency Synthesizer page with revised hardware and firmware to improve performance

  • As one of my New Year’s resolutions, I’ve decided that it’s about time that I learned how to design printed circuit boards properly. Until now, my circuit board designs have been done with basic CAD drafting software. I’ve now started to work with both KiCAD and DipTrace. As time permits, I’ll update some of my older PCB artwork, to include Gerber files that will allow boards to be fabricated by most PCB companies. I’ll also be adding new PCB designs to projects that didn’t previously have them.



  • Corrected an error in the antenna reactance formula on the Low Power AM Transmitter Antenna Matching Page. It was missing a factor of two which should have been included when the formula was changed to use antenna diameter instead of radius. Added a chart to the same page to aid in the selection of the optimum loading inductor.


  • I’ve fixed some bugs and added some new input options in the Multi-Layer Coil Calculator. Please refer to the Revision Notes on that page for details.


  • My former web host was bought out this year, and my site was recently migrated to one of the new company’s servers. There were a couple of glitches that resulted in the site being offline occasionally over the past couple of weeks. Hopefully, everything is back to normal now.

  • The email address for feedback to this site has been changed. It was formerly a Yahoo Ymail account, but following the merger of Yahoo and AOL, they’ve recently changed their terms and conditions (probably also related to the recent Facebook scandal) to include things that I cannot legally comply with. As such, their their terms and conditions are not likely legally enforceable, but I don’t intend to wait and find out. Agreeing to their terms would impose a legal liability on me for things that are beyond my control. If you’ve previously contacted me at the Ymail address, please go to the Contact Page to get the new contact info. (If you have a Ymail or AOL email account, you may wish to seek legal advice before accepting their new terms.)


  • I’ve added a new project, AD9850/51 DDS Simple Controller Interface which is a stripped down low parts count version of the project posted in the 2017-11-30 update. No keyboard, no display; just two rotary switches to set frequency.

  • As a consequence of the programming work for the above DDS project, I was able to do a lot of program simplification that applied to the original project. and have updated those webpages as well.


  • I’ve added a new project, AD9850/51 DDS Frequency Synthesizer Controller which is a simple PIC microcontroller interface to the popular AD9850 and AD9851 DDS signal generator chips. (There are already a zillion similar projects on the Web. One more couldn’t possibly hurt, could it?)

  • I’ve started to pull some of my project demo videos off of YouTube, and am now hosting them directly from my site. Eventually, I’ll have all of them transferred to my site. I don’t have any serious complaints with YouTube. It’s just that it’s becoming cumbersome to have my videos on a separate host. This change makes it much easier to manage them.

  • My Nixie Frequency Counter project became unexpectedly obsolete not long after I built it, when a critical part—the Allegro A6818—suddenly went out of production. Now, a newly discovered part, the Maxim Max6922, appears to be an exact clone of the A6818, requiring no circuit changes or circuit board changes. I’ve updated the page to include this information.

  • I’ve fixed a glitch in the Multi-Layer Inductance Calculator. In the output section, the coil outer diameter was incorrect because the radial depth was inadvertently doubled. It didn’t affect the calculated inductance value, but may have caused some consternation for anyone relying on the overall diameter value.

  • I’ve added a link to the PIC source code file for the 6U5/6E5 Solid State Substitute Project.


  • Due to some problems with the .ods format spreadsheets on my Downloads page reported by Excel users, I’ve created .xls versions of the files and posted them there.


  • Added a new construction project as a companion to the switch mode B+ power supply. It is a Current Sensing Switch that monitors the current drawn from a radio’s filament supply ‘A’ Battery, and turns on the ‘B’ supply boost converter when it senses that the filaments have been switched on.

  • Added a page explaining my low tech method of soldering surface mount parts.




  • I’ve rebuilt the entire site and it is currently live. If you’re reading this, then you’re looking at the new site. Yes, it looks almost exactly the same as the old one, but the HTML is much cleaner, and I’m hoping that this will fix some minor glitches on the Calculator Pages, as well as some other items. If you experience any problems please Contact Me. Otherwise, this will become permanent.

  • I’ve added a note on the 6U5/6E5 Solid State Substitute Page listing current sources of the circular LED display.


  • Added a new project: Magic Eye Tube Solid State Replacement. It’s a microcontroller based LED display that replaces 6U5 or 6E5 magic eye tubes in antique radios.

  • After getting some feedback about how hard it is to find my various online inductance calculators, I’ve added a direct link from the home page.


  • Added new Online Inductance Calculator (Multi-Layer Coils). This is an omnibus calculator that, in addition to circular multi-layer coils, can calculate inductance of multi-layer polygonal coils (triangles, squares, hexagons, etc.), circular and polygonal flat spirals, as well as large diameter short loops (circular or polygonal, flat or box style) typically used for loop antennas. In essence: nearly any air core coil that you can wind.





  • I’ve been experimenting with some of the graphics features that are available with the HTML5 specification, which most of the current web browser versions support (even Internet Explorer, surprisingly). This opens up many new opportunities for web site features. The web version of my Bandspread Calculator produces the same numbers that the downloadable Tracking Calculator application does (see downloads page), but until now, didn’t produce any graphics. As an experiment, I tried to see if I could use the new HTML5 graphics to create the tuning dial graphic on the web calculator page. After much programming, debugging, crashing, and nearly destroying the entire website, the new version seems to be working. However, for those who have problems with the new version, the original bandspread calculator page is still available here, temporarily at least.


  • Added a new project: Tube Audio Amplifier. It’s a low power stereo tube audio amplifier (one tube per channel) to drive my computer speakers.

  • Corrected an error in the formula for the area of a polygon in Part 1b of Numerical Methods for Inductance Calculation. The original formula had been incorrectly transcribed when the page was created, but subsequent derivations and calculations are correct. I've also corrected a few other minor typos on these inductance calculation pages, as I do from time to time, but unless the errors are serious ones, I don’t bother pointing out the corrections.

  • And finally: A not so new page. It’s been here on the site for a few months, but there has been no way to navigate to it directly. It’s an analysis of Negative Resistance Devices using load lines. I don’t like to post pages that aren’t substantially complete, and this one still has much to be done. But since I posted a link to it from another site, and the search engines have found it, it’s only sensible to mention it here. Though, at the moment, the only link to it is the one highlighted above. It will eventually be listed on one of the index pages.


  • Made some revisions to the 6CQ8 AM transmitter project write-up and added some video clips showing real time trapezoidal scope traces.





  • Corrected Inductance formula (34) in Part 3b of Numerical Methods for Inductance Calculation. While its derivation in the accompanying spreadsheet was correct, I had made a serious error in transcribing it onto the webpage, accidentally inverting two of the terms. My thanks to David Knight for pointing out this error as well as a slightly lesser offence, where I had incorrectly stated in Part 1a of Numerical Methods for Inductance Calculation that the date of Nagaoka's work was 1911, when the correct year was 1909.

  • Also, in Part 3b, I've now added formulae (35), an SI version of the inductance formula, and formula (36) the equivalent empirical formula for Nagaoka's coefficient.


  • The Website has moved! But, obviously you've found it!
    This site was previously located on my ISP's free webhosting service, which has been shut down.
    The fact that you are reading this means that you've reached the new site. It's quite likely that you were redirected from the old site. If so, please update your bookmarks, because the redirect from the old server is temporary. The new URL, as you've no doubt discovered, is as follows:
    However, I'm encountering a few glitches here and there as I get things set up. Hopefully, they will be sorted out in the next few days.


  • This Website will be relocating to a new host!
    I just received notice from my ISP that they will discontinue their web hosting service as of April 30, 2012. So, I will be relocating to a new host prior to that time. The URL for this site will change to
    http://electronbunker.ca (corrected URL 2012-03-23)
    This URL is now active, and will redirect to my current host until the site is moved to its future home. So, please update your bookmarks now, as I don't know whether my current web host will be able to redirect to the new site after April 30, 2012.


  • I made some further changes to the Solenoid (Round Coil) Inductance Calculator and Rectangular Coil Calculator so that they now allow the entry of AWG conductor sizes larger than 0. Previously, it was necessary to enter the larger sizes in millimeters only. The underlying structure of these calculators has now been made sufficiently general, that future calculators will be much easier to add. I expect to create a calculator for polygonal loops in the near future.


  • I was so inspired by the results of the Rectangular Coil Calculator (see last two updates), that I decided to redo the original Solenoid (Round Coil) Inductance Calculator. It now has a slightly cleaner interface, and makes it easier to calculate close wound coils. I'm always paranoid about making changes to these things. Typical of any computer programming, one small change can have far reaching consequences. Though it doesn't look too much different on the surface, the structure of the underlying program has more significant changes. Ironically, unit conversion seems to be a bigger problem than actual inductance calculation. I ran many tests, and everything seems fine. However, I would appreciate hearing from anyone who experiences problems.


  • Made further refinements to: Rectangular Coil Calculator, which should make it more convenient to use, and more accurate for single turn loops.






  • Nearly a year after I announced an imminent update to Part 2c of Numerical Methods for Inductance Calculation, I've finally had time to expand on the discussion, which now extends into Part 2d. The reason for the long delay is that, what I thought would be a rather simple adjustment to the helical inductance formula, turned out to be a compete re-derivation in order to avoid approximations in Snow's formula which made it inappropriate for use with coils of large pitch.

  • Made some additional security changes to the site in order to deal with renegade websites hot-linking to images on this site. Unfortunately, if you are accessing this site through a proxy server, this may cause images not to load.


  • Fixed a compatibility problem with newer versions of Internet Explorer which affected operation of the Inductance Calculator.

  • Changed some page formatting to prevent text from getting clipped, which could happen if the user's browser default font size was set higher than normal.


  • Another minor update to the FM Crystal Set page.

  • Some technical changes to provide better compatibility with some language translators.



  • Made a few security changes to the site, over the past couple of months, which may have inadvertently interfered with Google Translator's ability to display images from the site. My apologies if this affected you. It should now be fixed. (This does not apply to the Microsoft/Bing translator or the Yahoo/Babelfish translator, neither of which have ever worked with this site, and still don't work. I'm not blaming the translators; it's more likely the fault of my web design software, which produces web pages which are rather unfriendly to the translators.)






  • Expanded the discussion of tapped coil bandspreading in Bandspreading Part 3. There is now a summary showing the derived formulae so that the reader can skip the full derivation. The worked example now contains additional detail.


In doing this latest update, which includes changes to both the bandspread discussion and the numerical methods discussion, I thought it worth mentioning that I haven't adopted the most logical system for equation numbering. In both Bandspreading and Numerical Methods, the equation numbers start at one, and go up from there. So, there is duplication in the numbers. So far, fortunately, I haven't had to refer from one section to an equation in another section. At some point in the future, I see that I will have to renumber everything so that each equation no matter where it is on the site will have a unique number. Doing this revision will be fraught with danger, as I will make countless mistakes and it will take forever to clean up the mess. I don't look forward to it, and that is why I haven't done it yet.





  • Added an On-Line Bandspread Calculator;

  • Added some photos to the Nixie Digital Dial page showing the final assembly, and posted the assembly language source code for the PIC controller. Sometime in the future, I will be posting the circuit board layouts and the program hex file. However, they still need some cleanup work before they are ready to be unleashed on the unwary public. If you are desperate and want an advance look, please contact me via my Contact Page.


  • Added Part 4 of the Bandspreading discussion

  • Added a tuning characteristic “dial scale” for the example calculation on the Bandspreading Part 2 page.


  • Added this updates page;

  • Added Part 2 and Part 3 of the Bandspreading discussion;

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This page last updated: March 15, 2022