- Category: Ham Spot Presents
- Published on Friday, 17 February 2012 12:00
- Written by David L Norris, KG9AE
In this video we examine a variety of specialty capacitors as well as some common components. I smash open a high voltage capacitor to see what's inside. I show you a vintage resistor-capacitor tester. Another look at how I store all of these devices. And at the end is a tidbit for Ham Radio operators who have need for high power medium-wave/short-wave antenna matching.
There are an endless variety of capacitors available on the market as well as many you can salvage from old equipment.
Be careful about where you purchase capacitors, as well. There are plenty of counterfeit devices on the market today, unfortunately. Newark.com and Digikey.com are excellent, reliable and inexpensive sources for components.
I usually buy new electrolytics just to be safe. Electrolytics deteriorate with age. Some are very poor quality to begin with.
However many types of capacitors are ripe for salvage. Air dielectric, high voltage, high capacity and many specialty capacitors are worth the trouble of salvaging. Some types of capacitor simply are no longer manufactured and suitable replacements do not exist. In those cases you are forced to purchase work-alike circuits from antique vendors such as Antique Electronics Supply that are often disguised to look like the original part. Not always ideal especially if you can find a working original replacement part.
Air dielectric capacitors can be purchased directly from MFJ Enterprises, as well. These will be the type more suitable to building radios and antenna matching circuits. Other commercial sources for these components have largely gone extinct.
Your best bet is to grab an assorted parts bag from someone or somewhere. Honestly, you don't need all of these values. Which values you'll need are entirely dependent of the types of devices you build. When in doubt, remember you can (almost) always combine smaller values effectively. Tolerances on capacitors are pretty loose unless you're dealing directly with RF and usually you can adjust the other nearby components a little to make up for not having an exact value. These tables may also help you select the correct type of capacitor for the function it will be performing.