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 Engineer Jobs LinkedIn Crosswords Engineering Humor Kirt's Cogitations RF Engineering Quizzes Notable Quotes Calculators Education Engineering Magazine Articles Engineering software RF Cafe Archives RF Cascade Workbook 2018 RF Symbols for Visio - Word Advertising Magazine Sponsor RF Cafe RF Electronics Symbols for Visio RF Electronics Symbols for Office Word RF Electronics Stencils for Visio Sponsor Links Saturday Evening Post NEETS EW Radar Handbook Microwave Museum About RF Cafe Aegis Power Systems Anritsu Alliance Test Equipment Amplifier Solutions Anatech Electronics Axiom Test Equipment Berkeley Nucleonics Bittele Centric RF Conduct RF Copper Mountain Technologies Empower RF everything RF Exodus Advanced Communications Innovative Power Products ISOTEC KR Filters Lotus Systems PCB Directory Rigol San Francisco Circuits Reactel RFCT TotalTemp Technologies Triad RF Systems Windfreak Technologies Withwave LadyBug Technologies Wireless Telecom Group Sponsorship Rates RF Cafe Software Resources Vintage Magazines Thank you for visiting RF Cafe!
RF Cascade Workbook 2018 - RF Cafe

Temperature Rise in Rigid Waveguide
January 17, 1964 Electronics Magazine Article

January 17, 1964 Electronics

January 17, 1964  Electronics Cover - RF Cafe[Table of Contents]

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

Here is a chart you don't see every day - "Temperature Rise in Rigid Waveguide." The company, Engineering Antenna Systems, of Manchester, New Hampshire, that published the chart in a 1965 edition of Engineering magazine, does not exist anymore. They were probably bought by someone else, but I could not even find an honorable mention of them in a Google search. Given the very low attenuation of properly sized and installed waveguide, it is hard to imagine a temperature rise of 500°F; however, when megawatts are pumped into it even a couple tenths of a decibel of attenuation per 100 feet results in a lot of power loss. Noted is how attenuation - and therefore temperature rise - is greater for frequencies at the lower end of the waveguide's operational range. Temperature rise numbers are for natural convection in free air (no forced air, heat sink, or liquid cooling).

Temperature Rise in Rigid Waveguide

Temperature Rise in Rigid Waveguide, January 17, 1964 Electronics Magazine - RF CafeBy T. J. Vaughan

Manager of Engineering Antenna Systems, Inc.

Manchester, N. H.

Designers of waveguide components must be concerned with the temperature increase above ambient due to the average power.

Knowing the average power in watts, the temperature rise above ambient of the waveguide can be quickly determined from the graph. The heat is generated because of the power lost due to the attenuation of the guide. The calculations are based on a 2:1 aspect ratio and material emissivity of 0.5.

By plotting, attenuation of that waveguide is the bracketed figure on the right. Because the attenuation varies for different materials available, the most common material used for the respective waveguide size have been selected from: WR 2300 to WR 650 Aluminum 6061 T6; WR 430 to WR 284 Commercial Aluminum; and WR 187 to WR 90 Brass.

Data - The temperature rise plot represents averages: on the 30°F and 70°F plots, for example, the slash line shows how the temperature varies within a waveguide size as a function of frequency. For example, in WR-975, operating 755 to 1120 Mc, attenuation varies from 0.115 db/100 ft at 1120 Mc to 0.18 db/100 ft at 755 Mc. For the higher temperature this represents a worst case since natural convection was assumed, for example even the smallest amount of forced convection will drop the temperature.

For any given waveguide size, from the operating frequency the attenuation per unit length can be determined from manufacturer supplied charts or available handbooks. Once attenuation is known, temperature rise can be determined for the average power in question from the above chart.

Example: WR-975 at a frequency of 755 Mc and an average power of 100 kW. From charts or handbook the attenuation is 0.18 db/100 ft. Laying a straightedge on the chart at this attenuation gives a temperature rise of 35°F above ambient.

This data, confirmed by myself in the 0.08 db/100 ft and 1 megawatt region and by MIT-Lincoln Laboratory in 0.3 db/100 ft and 50 kW region, can be useful to those who are unaware that with the high average powers now available (and required in satellite communications) there can be a serious temperature problem. This could limit the system noise temperature on a low noise tracking system.



Posted August 28, 2018

PCB Directory (Manufacturers)
ConductRF Phased Matched RF Cables - RF Cafe
Triad RF Systems Amplifiers - RF Cafe
KR Electronics (RF Filters) - RF Cafe
RF Cascade Workbook 2018 by RF Cafe

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

These Are Available for Free


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...

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: