Cardboard Engineering & Science Slide Rule Calculators
The Original Mobile Apps™

October 2020 Update: Mr. Joseph Birsa, N3TTE, recently donated yet another of his vintage cardboard calculators to the RF Cafe collection. This one is the "Type B" version of the ARRL's "Lightning Calculator" series.

Long before there were smartphones and software 'apps,' engineers and scientists carried around portable 'apps' of another kind. These apps were made from printed heavy cardboard stock and typically had either a sliding section sandwiched between two outer layers, or a rotating layer on a fixed base layer. They even sported rivets to hold them together - like the original Levis dungarees. I and guys much older than me [ ;-) ] routinely carried them in our shirt pockets, securely snugged behind our plastic pocket protectors. You definitely always wrote your name on them in indelible ink since there was a tendency for those cardboard slide rules to sprout legs and walk away while you were at lunch or in the can.

These cardboard slide rule calculators used to be included on the Traditional Slide Rules page, but thanks to generous RF Cafe visitors who either sent me hard copies or high-res photos, the number has grown so large that they required their own page. You are invited to submit examples of your own collection for inclusion in the informal Cardboard Calculator Museum.

ARRL Lightning Calculator- Type B Modified

The American Radio Relay League (ARRL) sold a variety of these "Lightning Calculator" slide rules in the days before electronic calculators. This "Type B" version (copyright 1932, W.P. Koechel) calculates Ohm's Laws values for resistance, voltage, current, and power. As shown here, it indicates an alignment of 1 V, 1 A, and 1 Ω. The Lightning Calculators" were rather large at 8½" wide by 11" high. Being the size of a sheet of paper, it is surprising they did not come with holes for a 3-ring binder. There were six varieties of "Lightning Calculators," as shown in the 1939 QST magazine advertisement.

Thanks to Joe Birsa (N3TTE) for the donation - Added October 19, 2020

Varian Power Amplifier Calculator

Thanks to Neil Blaho for the donation
(copyright 1991)  Added July 6, 2017

Tecom Industries Antenna Calculations Slide Rule

Thanks to Neil Blaho for the donation
(copyright 1976)  Added July 6, 2017

Shure Brothers Reactance Slide Rule

Thanks to Neil Blaho for the donation
(copyright 1957)  Added July 6, 2017

Scientific Atlanta Antenna Communications Systems Calculator

Thanks to Neil Blaho for the donation
(copyright 1977)  Added July 6, 2017

REA Magnet Wire Co. Heavy Formvar Magnet Wire Slide Chart

Thanks to Neil Blaho for the donation
(circa 1950s)  Added July 6, 2017

JFD Mfg. Co. Stroboscopic Disc

Thanks to Neil Blaho for the donation
(circa 1950s)  Added July 6, 2017

itron Reciprocal Calculator

Thanks to Neil Blaho for the donation
(copyright 1968)  Added July 6, 2017

The Helipot Corporation Electrical Slide Rule

Thanks to Neil Blaho for the donation
(copyright 1951)  Added July 6, 2017

Naval Surface Warfare Center: Electric Field Slide Rule

Thanks to Neil Blaho for the donation
(copyright 1991)

Scientific Atlanta: Antenna Calculator Slide Rule

Thanks to Neil Blaho for the donation
(copyright 1968)

Pacific Automation Products: Copper Wire Slide Rule

Thanks to Neil Blaho for the donation
(looks a little like the Starfleet Command logo)

Flam & Russell: Radar Cross-Section Cardboard Slide Rule

Thanks to Neil Blaho for the donation
(copyright 1968)

Hughes Electron Dynamics Division: Millimeter Wave System Calculator

Thanks to Neil Blaho for the donation
(copyright 1975)

muRata: Dial-a-Bead Selector Wheel

Thanks to Neil Blaho for the donation

Instrument Specialties Company: Shielding Design Guide "sticky fingers" Slide Rule

Thanks to Neil Blaho for the donation
(copyright 1982)

Honeywell: Signal Level Conversion Slide Rule Wheel

Thanks to Neil Blaho for the donation
(Annapolis, MD, was my childhood home town)

MegaPhase: Watts & Voltage Conversion Slide Rule

Thanks to Joe Cahak for the donation
(copyright 2009)

HP: HP 9000 Series 200 Memory Configuration Wheel

Thanks to Joe Cahak for the donation

HP: HP 9000 Series 300 Memory Configuration Wheel

Thanks to Joe Cahak for the donation

HP: Reflectometer & Mismatch Error Limits Calculator

Thanks to Joe Cahak for the donation
(copyright 1976)

AILTECH: Noise Slide Rule

Thanks to Joe Cahak for the donation
(copyright 1973)

Amphenol RF Division: Smith Chart Slide Rule

Thanks to Joe Cahak for the donation

Andrew: Heliax Slide Rule

Thanks to Joe Cahak for the donation

inmet: Gain Equalizer & Conversion Calculator

Thanks to Joe Cahak for the donation
(copyright 1999)

Concise: Chemical Element Slide Rule

Thanks to Joe Cahak for the donation
(copyright 1968)

Microwave Development Labs (MDL): Rigid Waveguide Data Calculator

Thanks to Joe Cahak for the donation
(copyright 1995)

Miteq: Mixer Spur Analyzer Calculator

Thanks to Joe Cahak for the donation

Rogers Corporation: High Frequency Substrate Selector

Thanks to Joe Cahak for the donation
(copyright 2010)

Roos instruments: RF & Reactance Calculator

Thanks to Joe Cahak for the donation
(copyright 1995)

Tektronix: Time Domain Reflectometer Slide Rule

Thanks to Joe Cahak for the donation
(copyright 1972)

Control Components: Valve Sizing Calculator

Thanks to Joe Birsa (N3TTE) for the donation
(copyright 1986)

Ohmart Corporation: Radiation Measurement Calculator 

Thanks to Joe Birsa (N3TTE) for the donation
(copyright 1991)

Daniel Industries, Inc.: Air-Gas Orifice Flow Calculator

Thanks to Joe Birsa (N3TTE) for the donation
(copyright 1977)

The Ballentine Rule: dB <--> Ratio Conversion | Volts <--> dB Power Level

Thanks to Gary Steinhour for the donation
(copyright 1953)

EM Laboratories: U.S. ↔ Metric Conversions

Thanks to Gary Steinhour for the donation
(copyright 1975)

Tel-Instrument Electronics Corp.: AC Power Slide Rule

Thanks to Gary Steinhour for the donation
(copyright 1964)

FXR (now Microlab/FXR): Smith Chart Slide Rule

Smith Chart Side

Slide Rule Side
Thanks to Gary Steinhour for the donation)

APN-85 Pressure Reduction Computer

I. Sea-Level Reduction (left), II. Altimeter Setting (right)
These were used by air traffic controllers back in the Stone Age This particular model was auctioned off when the Bedrock Airport closed
Thanks to Don Hicks for the donation

M/A-COM: VSWR Calculator

(copyright 1983)

Sage Wireline/Wirepac Calculator

Sage Wireline/Wirepac Calculator
(copyright 1992)

I have a spreadsheet available for the Wireline Calculator.

GE Mobile Radio Range and Transmitter Power Calculator

GE Mobile Radio, Range and Transmitter Power Calculator
(copyright 1977)
Thanks to Alan Kealey for the donation!

Andrew Microwave Antenna System Computer

Andrew Microwave Antenna System Computer
(copyright 1994)

Classic Format Slide Rules

Pickett N600 ES Log-Log Slide Rule

Pickett N600 ES Log-Log Slide Rule
(this is the same model that went to  the moon w/the Apollo astronauts)

K&E Model N4080-3 Log Log Duplex Trig

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
(wooden frame & bar w/metal ends)

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

Pickett N1010-T Slide Rule

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)
Send me an e-mail if you want a PDF file of a partial (10 pages) copy of the instruction manual.
[Buy the complete manual set here]

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."

K&E Beginner's Slide Rule

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

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

Other Interesting Slide Rule Configurations

Gong Se He Ying
Metalworking calculator for Iron materials

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
(352 feet long, 300 pounds)

Soviet Slide Rule Watch

Soviet Slide Rule Watch

Projection Slide Rule

Projection Slide Rule