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!
Windfreak Technologies Frequency Synthesizers - RF Cafe

Innovative Power Products Passive RF Products - RF Cafe

Axiom Test Equipment - RF Cafe

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

Exodus Advanced Communications Best in Class RF Amplifier SSPAs

Letters from Our Readers
May 1969 Electronics World

May 1969 Electronics World

  Table of Contents 

Wax nostalgic about and learn from the history of early electronics. See articles from Electronics World, published May 1959 - December 1971. All copyrights hereby acknowledged.

This letter to the editor column from a 1969 issue of Electronics World got my attention because of the submission by reader Walter T. Stevenson. He mentions having discovered that semiconductors, in his case a transistor, could have their junction conductance modulated by ambient light sources, in his case a fluorescent light. Evidently some of the early transistors were shipped on a substrate where the die was potted with a translucent epoxy compound that permitted some light penetration. At least one manufacturer switched to an opaque compound as a result of Mr. Stevenson's report.

I remember the first I experienced the phenomenon was as a technician working at Westinghouse Oceanic Division in an engineering lab. I was doing a lot of prototype circuit fabrication mounting, wire bonding, and testing semiconductor die on bare substrates. While testing circuits I noticed that the readings would be different depending on whether my workbench light was on or off. The engineers had never seen that, either, since we were all new at it. The final items were packaged in light-tight enclosures and tested prior to delivery to the customer for evaluation, so we never shipped with bad data.

BTW, does anyone else remember when owning one of the Xcelite "99" tool kits on the page was a status symbol?

Light Modulation of Semiconductor Junctions

Transistor Beta Variation

To the Editors:

Transistor Beta Variation Due to Light - RF CafeMaybe I can bail Rufus Turner out of his problems on those 2N2712's ("Transistor Beta vs Source Resistance," Nov. issue and Feb. "Letters" column).

The early ones were molded with a brown translucent epoxy, and would admit radiated light from overhead fluorescent lights. This, naturally, garbaged up apparent beta when a large base resistor was used. I had no end of trouble with this in a design several years ago until I found out what was causing it and used black paint on them. The manufacturer was shocked when I complained, but their tests verified it. As a result, they sent me a new batch molded in black epoxy, and I finished the design job. Black epoxy has been standard in the industry since.

I hope this gets the monkey off Rufus' back. He's an old timer in this game - I've enjoyed his articles for years.

Walter T. Stevenson, Instructor, Technical Electronics A.V.T.S.

Kansas City, Kansas

* * *

Ferrite Cores for C-D System

To the Editors:

We refer to "Unique Capacitor-Discharge Ignition System" on page 45 of your January, 1969 issue. As an authorized distributor of Ferroxcube parts we are in a position to supply the cores for T1 and T2 transformers. Price for K3-005-01-3E and 266T125-4C4 cores is $3.50 for both. Please send check with the order.

Hugh A. Martin, Sales Mgr.

Elna Ferrite Labs, Inc.

Box 395

Woodstock, N. Y. 12498

Also, equivalent Indiana General cores are listed in the Newark Electronics (500 N. Pulaski Rd., Chicago, Ill. 60624) catalogue. Incidentally, wire size for T2 should be #38 rather than #28. Although we did manage to wind a T2 with the heavier wire, there was no room for a mounting bolt. -Editors

* * *

Transistors Made of Glass

To the Editors:

Reference is made to the article "Transistors Made of Glass" by A. H. Seidman in your February, 1969 issue. In Fig. 1A on page 68 a glass device connected in parallel with a resistive load and a constant voltage source is shown, and it is claimed that the device controls the voltage appearing across the load resistor.

This diagram tends to be somewhat misleading since from basic electrical circuit considerations we know that the voltages appearing across elements in parallel are always the same and therefore eo will always be equal to the e.m.f. of the voltage source. This apparent source of difficulty may be overcome simply by placing a resistor in series with the 60-Hz source.

Robert Mauro, Ph.D.

u. S. Army Electronics Command Fort Monmouth, N. J.

Thanks to Dr. Mauro for pointing out our somewhat oversimplified simplified diagram.-Editors

* * *

SCA FM Stations

To the Editors:

Are there any FM stations currently operating in New York City using SCA (subcarrier authorization) and what subcarrier frequencies do they use?

Martin sanders

Brooklyn, N. Y.

According to a list we just received from Music Associated, 65 Glenwood Road, Upper Montclair, N. J. 07043, there are five FM stations in New York City now using SCA transmissions for one purpose or another. These are WHOM (41 and 67 kHz subcarrier), WPIX (67 kHz), WNCN (32.5 kHz), WRFM (41 and 65 kHz), and WNYC (32.5 kHz). The list, which i-8 available for $1 from the company, shows about 550 U.S. FM stations using SCA, mostly operating on a 67-kHz subcarrier frequency -Editors.



Posted January 29, 2018

Crane Aerospace Electronics Microwave Solutions: Space Qualified Passive Products

About RF Cafe

Kirt Blattenberger - RF Cafe Webmaster

Copyright: 1996 - 2024


    Kirt Blattenberger,


RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The World Wide Web (Internet) was largely an unknown entity at the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps while tying up your telephone line, and a nice lady's voice announced "You've Got Mail" when a new message arrived...

Copyright  1996 - 2026

All trademarks, copyrights, patents, and other rights of ownership to images and text used on the RF Cafe website are hereby acknowledged.

All trademarks, copyrights, patents, and other rights of ownership to images and text used on the RF Cafe website are hereby acknowledged.

My Hobby Website: AirplanesAndRockets.com

My Daughter's Website: EquineKingdom


everythingRF RF & Microwave Parts Database (h1)