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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 typing 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:


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Slide Rule & Calculator Museum

Slide rules have come in different formats over the years. The most familiar is probably the  3-part model with a fixed outer frame and a sliding inner rod, and a sliding clear window with a reticle line etched into it for aligning numbers (the cursor). While far from being any type of "collection," I do have a couple nicely preserved models. The ones from Keufel & Esser (K&E) are at the top of the table below. The Beginner's slide rule model is very basic with graduations on one side and some conversions on the other. The best of all is the Pickett N600-ES Log-Log that is in new condition and actually still has the box, leather case, instructions and certificate. The Pickett N600-ES is the slide rule model that went to the moon* with the Apollo astronauts (not the one I own, of course).

Simulated Pickett N909-ES Slide Rule - online & interactive - excellent!Finally, a few of the cardboard calculators I have are at the bottom. Probably only the VSWR Calculator from M/A-COM can be considered collectible. My good friend Patrick Fitzgerald bestowed it upon me when I went to work for him at General Electric right out of college. I can recall some of the older engineers still using slide rules there when I arrived in the 1980s. In fact, the first algebra textbook I had in a community college right out of high school in 1976 had a section in it on how to use a slide rule. The Sterling 684 plastic slide rule that I bought at the bookstore is show below. Shortly thereafter, the HP-35 hit the market and the world changed forever (now that was truly a disruptive technology).

April 2016 Update: *According to the Smithsonian National Air & Space Museum, the N600-ES did not actually make it to the moon because it was aboard Apollo 13, which experienced a system failure that required the crew to do a U-turn and execute manual maneuvers to get home safely.

June 2015 Update: Thanks to generous RF Cafe visitors who either sent me hard copies or high-res photos of their Cardboard Slide Rule Calculators (which I have dubbed The Original Mobile Apps™), the number has grown so large that they required their own page.

 ◊ Here is my collection of vintage Cardboard Slide Rule Calculators.

Here is the definitive source: International Slide Rule Museum
      - Slide Rule Library Archive of books, manuals, instructions and ephemera.
      - Instructions on how to use a slide rule.
 ◊ Or, try the Slide Rule Guy
 ◊ See the The Quick and Easy "Lawrence" Slide Rule Instruction Book
 ◊ The Slide Rule Universe - great resource
 ◊ Visit the Oughtred Society (William Oughtred - inventor of the slide rule in 1622)
 ◊ Buy new-in-the-box, mint condition slide rules
 ◊ Virtual Slide Rules: Standard slide rule - EngCom.net,  Pickett slide rule - Antiquark.com
 ◊ Here is a website on vintage instruments (slide rules and other instruments of math, drafting, science, and music)

Pickett N600-ES Log-Log Slide Rule

Pickett N600-ES Log-Log Slide Rule - the same model that the Apollo astronauts took to the moon with them

Original Pickett N600-ES Log-Log Slide Rule in the Box - RF Cafe

Original Pickett N600-ES Log-Log Slide Rule Box - RF Cafe

Original Pickett N600-ES Log-Log Slide Rule Eye-Saver-Insert - RF CafeOriginal Pickett N600-ES Log-Log Slide Rule Guarantee - RF CafeOriginal Pickett N600-ES Log-Log Slide Rule Mesage - RF Cafe

1968 Pickett Catalog (Slide Rule Museum) - RF CafePickett N600-ES Log-Log Slide Rule (ES stood for the 'eye saver' yellow color)
(this is the model that was aboard the Apollo 13 mission and according to Buzz Aldrin, the one he took to the moon aboard Apollo 11). According to information from Pickett, my N600-ES was manufactured sometime between March and June 1959. See "The Great Pickett Slide Rule Apollo Conundrum."

K&E Model N4080-3 Log Log Duplex Trig

K&E Model N4080-3 Log Log Duplex Trig S/N 467192, Copyright 1947

K&E Model N4080-3 Log Log Duplex Trig, S/N 467192, Copyright 1947 Slide Rule
(wooden frame & bar w/metal ends)

K&E Model 4081-3 Slide Rule

K&E Model 4081-3 Slide Rule S/N 087105

K&E Model 4081-3 Slide Rule, S/N 087105
(wooden frame & bar w/metal ends)

Sterling 684 White Plastic Slide Rule

Sterling 684 White Plastic Slide Rule

Sterling 684 White Plastic Slide Rule
(I bought this for my first algebra class in 1976)

Skala Wilcza 32 Wooden Slide Rule

Skala Slide Rule - markings on leather case include "SP-NIA"  "PRACY" "WARSZAWA" "WILCZA 32"

Skala Slide Rule LogoSkala Wilcza 32 Wooden Slide Rule (Poland)
Thanks to Alan Kealey for the donation!

Pickett N1010-T Slide Rule

Pickett N1010-T Slide Rule - RF Cafe

Pickett N1010-T Slide Rule
(found in my father-in-law's basement)

Cleveland Institute 515-T Slide Rule


Cleveland Institute 515-T Slide Rule, made by Pickett (front)

Cleveland Institute 515-T Slide Rule, made by Pickett (case)

Cleveland Institute 515-T Slide Rule, made by Pickett (rear)

Cleveland Institute of Electronics 515-T Slide Rule (made by Pickett)
Thanks to Mr. Joe Hernandez (KN2A), the complete set of four Cleveland Institute 515-T manuals is now available here.

Cleveland Institute 515-T Slide Rula Advertisement, August 1967 Electronics World - RF Cafe

This advertisement appeared in the August 1967 edition of Electronics World magazine. The unique slide rule, leather case, and 4-course instruction booklet was "...deliberately underpriced at less than $25."/p>

K&E Beginner's Slide Rule

K&E Beginner's Slide Rule Model 4058C

K&E Beginner's Slide Rule Model 4058C

K&E Beginner's Slide Rule, Model 4058C
(all-wood frame & bar)

Lawrence Slide Rule Instruction Book

Lawrence Slide Rule Instruction Book

Lawrence Slide Rule Instruction Book
(copyright 1952)

Cleveland Institute of Electronics

Cleveland Institute of Electronics, Slide Rule Product Feature, January 1965 Popular Science

Cleveland Institute of Electronics Slide Rule Product Feature
January 1965 Popular Science

Other Interesting Slide Rule Configurations

From the International Slide Rule Museum website

Gong Se He Ying
Metalworking calculator for Iron materials

Slide Rule Wallpaper

Slide rule wallpaper

Slide Rule Wallpaper
Click on the image to open it in a new window, then right-click on it and choose Set as Background

Texas Magnum Slide Rule

Texas Magnum - World's Longest Slide Rule

Texas Magnum, World's Longest Slide Rule
(352 feet long, 300 pounds)

Soviet Slide Rule Watch

From the International Slide Rule Museum website

Soviet Slide Rule Watch

Projection Slide Rule

From the Slide Rule Guy website

Projection Slide Rule

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