RF Cafe Software

RF Cascade Workbook 2005 - RF Cafe
RF Cascade Workbook

Calculator Workbook
RF Workbench
Smith Chart™ for Visio
Smith Chart™ for Excel
RF & EE Symbols Word
RF Stencils for Visio

About RF Cafe

Kirt Blattenberger - RF Cafe WebmasterCopyright
1996 - 2016
Webmaster:
Kirt Blattenberger,
 BSEE - KB3UON

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 Internet was still largely an unknown entity at the time and not much was available in the form of WYSIWYG ...

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

Try Using SEARCH
to Find What You Need. 
There are 1,000s of Pages Indexed on RF Cafe !

Electronics World Cover,TOC,and list of posted Popular Electronics articles QST Radio & TV News Radio-Craft Radio-Electronics Short Wave Craft Wireless World About RF Cafe RF Cafe Homepage RF Cafe in Morse Code Google Search of RF Cafe website Sitemap Electronics Equations Mathematics Equations Equations physics Manufacturers & distributors Engineer Jobs Twitter LinkedIn Crosswords Engineering Humor Kirt's Cogitations Engineering Event Calendar RF Engineering Quizzes AN/MPN-14 Radar 5CCG Notable Quotes App Notes Calculators Education Magazines Software,T-Shirts,Coffee Mugs Articles - submitted by RF Cafe visitors Simulators Technical Writings RF Cafe Archives Test Notes RF Cascade Workbook RF Stencils for Visio Shapes for Word Thank you for visiting RF Cafe!

-27 °F in Alpena, Michigan, February 28, 2014

-27 °F (-31 °C) was the low temperature in Alpena, Michigan this morning, February 28, 2014. That was the official measurement at the airport, which is typically a few degrees warmer than here on Long Lake, about 15 miles north of there. I knew from the star-filled sky last night that it was going to be frigid. Without a cloud cover to insulate the Earth, radiative cooling can be quite pronounced, especially in low humidity conditions as found in the desert and frozen-solid, ice-covered ground. Our daytime highs and nighttime lows have consistently been 15 to 20 degrees below the long-term averages since we arrived nearly three months ago - a brutal introduction to northern Michigan. The summer had better better be nice and cool.

-27 °F in Alpena, Michigan, February 28, 2014 - RF Cafe

Stefan-Boltzmann Law: P = Aεσ T4

Where: P (watts) is the radiated power from a body of area A (m2), at temperature T (K).

ε is emissivity, a dimensionless number between 0 and 1 that determines the
   efficiency of a body to radiate and absorb energy. A black body has an emissivity
   of 1. Soil, asphalt and human skin have emissivity of about 0.95. The emissivity of
   the clear night sky is approximately 0.74 at 0 °C.

σ is the Stefan-Boltzmann constant, 5.67x10−8 Wm−2T−4

Here is a short tutorial of nighttime radiative cooling, with examples.

 

 

 

 

Posted  February 28, 2014