Vacuum capacitors can die! Welcome to the fascinating world of «exotic» RF components! «Exotic» means «difficult to locate», because a typical electronics shop will usually not carry these high-voltage items. Below lists of suppliers are non-exhaustive, but will hopefully help you find what you need. Beware of glass vacuum capacitors that have been badly handled or that have been poorly protected during transit. The glass envelope may have cracked, destroying the vacuum. In capacitors with clear glass envelopes and copper electrodes, air ingress is indicated by slow discolouration of the copper. The voltage rating of an air-filled capacitor at atmospheric pressure (760torr or 1.01bar) is about thirteen times lower than that of an otherwise identical vacuum capacitor (at 10 torr).1 Over the years, many amateur radio magazines have been publishing articles about building transmitting magnetic loop antennas. These antennas appeal by their very compact size, sharp directivity nulls and high signal-to-noise ratio on reception.
The great flaw of these antennas is their very limited radiation impedance. Consequently, the radiating efficiency of these magnetic dipoles is extremely low. —That is, if you are not resorting to super-conducting materials!— Due to the resulting high Q-factor of these antennas, voltages and currents are extremely high. This lead to a number of very interesting ideas about home-brewing high-power RF capacitors being published in articles about magnetic loop antennas. One idea I successfully employed on VHF, consisted out of a copper fitting, lined with a 1.5mm-thick PTFE (Teflon) sheet, and inserted by a snugly fit brass bolt. 1. Knight D. Vacuum capacitors. In: From Transmitter to Antenna. This work is licensed under a Creative Commons Attribution‑NonCommercial‑ShareAlike 4.0 International License. Other licensing available on request. Unless otherwise stated, all originally authored software on this site is licensed under the GNU GPL version 3.
This page employs a server‑side script. This page includes an open-source client-side script, written in and transcoded by to make it run as secure JavaScript in the browser. Static XHTML generated from Markdown by and the make, sed and gpp commands. math markup rendered with . references are best read with . Unattended CSS typesetting with . My OpenPGP public key…Dr Alex UR4LL has quite a few Russian electronics parts and some equipment for sale. The list is updated periodically, and some items have pictures (click on links for details and/or pictures of each item); (Email UR4LL for details). It is also possible to contact Dr Alex via Skype, address: alexgavva Emtek Privacy Lock Push Pin Emtek Extended Button Tip Emtek Neos Backplate for Cabinet Knobs Emtek Art Deco Square Backplate for Cabinet Knobs Emtek Petal 1 Inch Cabinet Knob Emtek Brittany 1 Inch Cabinet Knob Emtek 3 Inch San Carlos Fixed Drawer Pull
Emtek 3 Inch Normandy Fixed Drawer Pull Emtek Brittany 1 1/4 Inch Cabinet Knob Emtek Petal 1 1/4 Inch Cabinet Knob Emtek Providence 1 Inch Cabinet Knob Emtek Waverly 1 Inch Cabinet Knob Emtek Egg 1 Inch Cabinet Knob Emtek 2 Inch Stainless Steel Bar Knob Emtek Round Backplate for Cabinet Knobs Emtek Square Backplate for Cabinet Knobs Emtek Atomic 1 Inch Knobs Emtek Cadet 1 Inch Knobs Emtek 3 Inch Wire Pull Emtek Full Lip Strike Plate - Square Corners Emtek Full Lip Strike Plate - Rounded Corners Emtek Extended Lip Strike Plate - Square Corners Emtek T Strike Plate Emtek Standard Heavy Duty Deadbolt Strike PlateSee all items in this storeHave you selected to search with title and description? If you haven't, try to use this filter and might get more results.000Cut glass doorknobs for sale at a salvage store. (Photo: Courtesy of Architectural Salvage of Greensboro)When you're trying to select doorknobs for your old house, the options—both antique and reproduction—can seem virtually endless.
But spend a few afternoons browsing online or through your local salvage store, and you'll probably notice that the same types of knobs tend to show up again and again. Like most items that have been subjected to the test of time, certain doorknob styles have risen above the rest to become definitive classics. If you're restoring a house built between the mid-18th and the mid-20th century, you can't go wrong with one of the knobs below.BrassWhile doors in the earliest American homes would have featured thumb latches instead of knobs, simple brass doorknobs began appearing in upscale homes in the 1700s. Though they never fell completely out of fashion, the popularity of brass doorknobs waned a bit in the Victorian era, when myriad other styles captured the attention of homeowners. With additional decoration (including molded and beaded rims), the style made a big comeback during the Colonial Revival. (Note: If you're worried about bright, shiny brass knobs stealing the show, look for antique versions, which generally have a more mellow patina.)
White PorcelainWhen American pottery companies began making white porcelain doorknobs based on imported European examples in the mid-1800s, the style took off and stayed in vogue through the first part of the 20th century. Porcelain knobs could be found in a variety of house styles, including Italianates, Greek Revivals, early Victorians, and bungalows. On many antique versions, you'll notice a web of hairline cracks (called "crazing") on the surface; crazing was a manufacturing side effect and is merely a patina, not damage. For the most accurate look, pair white porcelain knobs with black rim locks.Brown MineralA cousin of the white porcelain knob, brown mineral knobs are prized for their swirly, almost marble-like surface, which was created by mixing two colors of clay. They're commonly referred to as "Bennington knobs," after the Vermont potteries that helped to popularize the trend. The popularity of brown mineral knobs was relatively short-lived (roughly from the mid-1800s to the turn of the century), and they were most favored by owners of Greek Revival homes.
Cut GlassAnother perennial favorite that spans styles and centuries, cut glass knobs transitioned from high-style homes to everyday ones in the early 19th century. They came in a variety of shapes and colors, but the faceted clear glass knob is undoubtedly the most enduring form of the style, widely available today in both antique and reproduction forms. Owners of Italianate houses were especially fond of cut glass knobs; early 20th-century homeowners also relied on them to dress up their Colonial Revivals, bungalows, and Foursquares.WoodenNot quite as popular as metal, glass, and porcelain knobs, wooden versions nevertheless enjoyed their own boom in the mid-19th century. Wooden knobs were primarily plain—either smooth and round, or a squared-off shape with a series of incised lines decorating the edge—but some intricately carved examples did exist. Because they're relatively obscure, wooden knobs tend to be harder to find, particularly as reproductions—check salvage stores or eBay for antique versions, which will have a well-worn patina.