Electronics World articles Popular Electronics articles QST articles Radio & TV News articles Radio-Craft articles Radio-Electronics articles Short Wave Craft articles Wireless World articles Google Search of RF Cafe website Sitemap Electronics Equations Mathematics Equations Equations physics Manufacturers & distributors LinkedIn Crosswords Engineering Humor Kirt's Cogitations RF Engineering Quizzes Notable Quotes Calculators Education Engineering Magazine Articles Engineering software RF Cafe Archives Magazine Sponsor RF Cafe Sponsor Links Saturday Evening Post NEETS EW Radar Handbook Microwave Museum About RF Cafe Aegis Power Systems Alliance Test Equipment Centric RF Empower RF ISOTEC Reactel RF Connector Technology San Francisco Circuits Anritsu Amplifier Solutions Anatech Electronics Axiom Test Equipment Conduct RF Copper Mountain Technologies Exodus Advanced Communications Innovative Power Products KR Filters LadyBug Technologies Rigol TotalTemp Technologies Werbel Microwave Windfreak Technologies Wireless Telecom Group Withwave RF Cafe Software Resources Vintage Magazines RF Cafe Software WhoIs entry for RF Cafe.com Thank you for visiting RF Cafe!
PCB Directory (Manufacturers)

everythingRF RF & Microwave Parts Database (h1)

Temwell Filters

Please Support RF Cafe by purchasing my  ridiculously low-priced products, all of which I created.

RF Cascade Workbook for Excel

RF & Electronics Symbols for Visio

RF & Electronics Symbols for Office

RF & Electronics Stencils for Visio

RF Workbench

T-Shirts, Mugs, Cups, Ball Caps, Mouse Pads

These Are Available for Free

Espresso Engineering Workbook™

Smith Chart™ for Excel

Innovative Power Products Resistors Terminations

Notes on the Getter
February 1958 Radio-Electronics

February 1958 Radio-Electronics

February 1958 Radio-Electronics Cover - RF Cafe[Table of Contents]

Wax nostalgic about and learn from the history of early electronics. See articles from Radio-Electronics, published 1930-1988. All copyrights hereby acknowledged.

If you happen to be Estonian, you might think of something entirely different than most RF Cafe visitors do when we hear the word "getter." In fact, you probably capitalize the word since it is the name of a pop singer from your country, Getter Jaani. If you are a child living in Japan, you would probably think of Getter Robo, an anime from a popular cartoon series. I suspect just about everyone who visits RF Cafe knows getter as the silvery deposit Getter Jaani (Estonian pop singer) - RF Cafe(typically barium) that resides inside vacuum tubes for the purpose of helping to maintain the vacuum and to absorb pesky random molecules that No 3 Shin Getter Robo 1 Action Figure - RF Cafemight otherwise cause electrical noise in the circuit. This article from a 1958 edition of Radio-Electronics magazine discusses the purpose of getter. BTW, I had never heard of either of the other two Getters due to OGS (old guy syndrome).

Notes on the Getter

Getter inside 12AU7 vacuum tube - RF Cafe

Getter inside 12AU7 vacuum tube. (RF Cafe photo)

By Norman V. Becker

In high-gain audio circuits, tube noises such as hiss and frying are some of the most troublesome things encountered. They can be eliminated only by selecting tubes which are inherently quieter or by reducing stage gain with negative feedback. In the latter instance gain might have to be reduced by such a factor as to defeat the original purpose.

Hiss is created by DC resistance paths existing between various elements inside the tube. These leakage paths may be as high as 1,000 megohms and would not upset normal tube operation if they remained constant. But like a bad carbon resistor, they create noises of their own through random and erratic changes of resistance.

Leakage paths of this sort are primarily located on the top mica support wafer, where the support rods are punched through. If the wafer is contaminated by impurities, it becomes a highly unstable conductor, connecting tube elements through very-high-resistance paths. Unfortunately, contamination of the wafer during tube manufacture is almost unavoidable. Before sealing the tube envelope, as much air as possible is exhausted by vacuum pumps, but a small percentage of oxygen and other gasses remain inside.

This is where the getter comes into the picture. A small square loop of wire usually located at the top of the tube, part of it coated with an explosive substance similar to that used in photoflash bulbs. High-frequency radio waves penetrate the sealed envelope and heat the getter to a temperature high enough to fire this coating. This miniature explosion burns up the remaining atmospheric gasses inside the tube and, at the same time, splatters a mirror-like silver coating over a portion of the inner surface (a familiar sight in glass tubes). Some of this splatter falls on the mica wafer, making it slightly conductive.

To reduce contamination of this sort, certain premium tubes are manufactured in which the space between getter and wafer is materially increased. In other types two top wafers are used - the upper one insulated from the lower - and act as an umbrella to receive most of the splatter. Another method is to punch oblong slots in the wafer. These openings effectively lengthen DC leakage paths and thereby reduce noise.

In designing high-gain input stages for microphones and low-output pick-ups, it is desirable to use premium tubes whenever possible. Special manuals describing these types are published by tube manufacturers, giving electrical data, physical dimensions, recommended applications, etc. In many instances premium tubes are directly interchangeable with standard types which you might now be using. In addition to reducing hiss, premium tubes are less microphonic, have lower hum and are generally more dependable - and are more expensive.



Posted June 12, 2023
(updated from original post on 1/20/2014)

Innovative Power Products Resistors Terminations
Crane Aerospace Electronics Microwave Solutions: Space Qualified Passive Products

LadyBug RF Power Sensors

Exodus Advanced Communications Best in Class RF Amplifier SSPAs