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View Full Version : Slide Rules and the Difference Between an Amateur and a Collector

KD5RFT
05-22-2009, 11:23 AM
WHY is this miserable transformer worth that kind of money? But, more importantly, WHY are bidders willing to pay this kind of money for it????

Perhaps that's the difference between an amateur and a collector -- we're digging for old stuff to actually use it.

I was sniped many times looking for an all-purpose slide rule at a usable price. I settled on the compliment of the N600-ES (http://sliderulemuseum.com/Pickett/P079_Pickett_N600-ES_LogLog_SetWithS187.jpg) (6" slide rule -- used in the Apollo missions) and the N4-ES (http://sliderulemuseum.com/Pickett/S090_Pickett_N4-ES.jpg) (12" 34 synchro-scales).

Both of these can be had today at a reasonable price. A new N600-ES (without box/manual) runs for \$30 new in plastic with soft leather case. A used N4-ES with hard leather case (no box/manual) runs \$40 - \$60 depending on condition and what day of the week the close lands on. I recommend either of these, even for a beginner as you start with the base scales and work your way up to doing different types of problems and your own creative ways to work even more.

The 6" N600-ES has the most functionality to both price and size/weight ratio (the latter is probably why it went to the moon). I consider the N4-ES to be the most functional 12" general-purpose slide rule and especially like that it features four base-10 log-log scales and a second base scale to use them as base-e.

A general purpose slide rule performs a variety of calculations such as multiplication, division, exponents / arbitrary roots, trigonometry, and features constants such as pi or e and more specialized calculations depending on the rule. Combinations of two to three of these calculations can often be performed in a single step. The slide rule does this by converting the numbers into a logarithmic base which can then be manipulated by additive or subtractive distances.

With a little finesse, you can also work addition and subtraction on a slide rule, but precision is often too low to be practical. A slide rule is best used in combination with pen-paper for solving equations, addition/subtraction, and as a decimal counter when performing a series of calculations. An addiator or decimal counter were also used in the past.

A logarithmic based calculator is naturally well suited for amateur radio calculations. (among many others)

Curious? -- try a virtual slide (http://www.antiquark.com/sliderule/sim/) rule and some basic instruction (http://www.antiquark.com/sliderule/sim/sr-calcs-by-example.html).

Why a slide rule instead of a calculator? A modern calculator is high precision.. anywhere from 8 to 32 significant figures and beyond with arbitrary precision. A slide rule has a general accuracy of 3-4 significant figures or better as you're interpolating the remaining figures. This often translates into tenths of a percent. This is accurate enough for most applications. A slide rule also won't crash if the result is extremely large or small unless you drop it, requires no batteries, and is resistant to EMP (http://en.wikipedia.org/wiki/Electromagnetic_pulse).

It's also fun and has some advantages over a calculator in certain problems where higher precision is not a concern. Because you're actively looking for reasonable answers when performing calculations at each step, you're less prone to certain types of errors that could go undetected when examining a single result. You're focused not only on what steps to perform and in what order, but also the interaction between the numbers and what's a reasonable result at each step. I consider this a great teaching tool. Your result is also not only a single figure, but a graph all of the other possible results if you were to manipulate one of the last variables.

As an example, if you solved for what interest rate would be required to double a quantity of money in 20 years, you could view at a glance how long it would take similar interest rates to reach the same goal. The same could be done with a calculator by plugging in different values, it could be graphed on a graphing calculator, and you could also make a spreadsheet.

A slide rule is a unique and simple device suitable for working a variety of problems. I also enjoy spreadsheets.

73,
Nick KD5RFT
RF Turkey

WD4CHP
05-22-2009, 12:04 PM

I have my Dad's slide rule that he used as a meteorologist in the Air Force.

It is a 20 inch K&E Polyphase Slide Rule. White ivory or plastic mounted on wood.

It has the standard scales.

A,B,C1,C,D,K,S,L AND T.

It also has a 20 inch and a 50 cm scale.

The *Equivalents and settings chart on the back is perfect.

There are 2 patent numbers.

2,086,502 and 1,934,232

SN 906766

I don't have the instruction sheet but I have the leather case.

KD5RFT
05-22-2009, 12:11 PM

I have my Dad's slide rule that he used as a meteorologist in the Air Force.

It is a 20 inch K&E Polyphase Slide Rule. White ivory or plastic mounted on wood.

...

I don't have the instruction sheet but I have the leather case.

Very nice.

73,
Nick KD5RFT
RF Turkey

K8ERV
05-22-2009, 12:11 PM
Hard to beat for ratio/proportions

TOM K8ERV Montrose Colo

WD4CHP
05-22-2009, 12:21 PM
Thank you

I used one of the links and identified it as a <N4053-5>.

KD5RFT
05-22-2009, 12:30 PM
Thank you

I used one of the links and identified it as a <N4053-5>.

It's quite a beauty (http://sliderulemuseum.com/KE/L001_K&E_N4053-5_755410.jpg). (here's the link for anyone else who wants to take a look)

73,
Nick KD5RFT
RF Turkey

WA6MHZ
05-22-2009, 01:24 PM
I was at an old engineers house just as it was being torn down. There was countless, priceless artifacts being bulldozed, and I only had a few minutes to grab some things before the Dozer leveled the place. Amongst the debris was an unbuilt Heathkit (Worth a fortune) and, there, in the old man's desk, was a Slide Rule!

I nabbed it figuring I had struck GOLD in this antique Slide Rule.

But, upon logging onto Ebay, I found this model was very common and only going for about \$10

It got tossed into MY desk, where maybe someone will find it 20 years from now. Maybe THEN it will be worth more than \$10!

WF7A
05-22-2009, 02:03 PM
As a pilot and flight instructor, I used the trusty E6-B (circular) slide rule computer for calculating courses, true airspeed, and fuel consumption. Of course there are plenty of electronic and avionic ones that'll perform the same calculations much faster and more accurately, but when the power goes out you can't beat a manual slide rule. :)

http://en.wikipedia.org/wiki/E6B

W4HAY
05-22-2009, 02:30 PM
You forgot the most important attribute of the slide rule, especially for us OFs: It makes you think. At our age, keeping the ol' noodle agile is important to slowing down our rate of decline.

The '58 vintage K&E Log-Log-Duplex-Decitrig I bought my Freshman year at N.C. State still hangs beside my desk. It gets constant use, especially when designing vacuum tube circuits.

KO0M
05-22-2009, 02:39 PM
I'm a Slide Rule Amateur, learned to use it in the fifth grade (1960's-ish) and using "Scientific Notation", when I was younger (before battery-powered calculators) I could do complex multiplication and division in my head.

The first LED watch, the "Pulsar" cost over \$400 bucks back in 1972, the handheld calculators came shortly after and, Texas Instruments sent the Slide Rule into obsolescence.

.

N9XV
05-22-2009, 02:39 PM
The E6-B is a lot of fun when you finally master it. I had one as a kid and wondered if I would ever be able to comprehend it. Now at 46, I love that thing. Its a great example of the power of simplicity!:D

KI6DCB
05-22-2009, 03:09 PM
[Frederick] Post Versa-Log II here (Model 1460); nice slipstick.

W7KKK
05-22-2009, 04:07 PM
Interesting side story~
I remember when I got out of the Army I went to work for a type 2 Cal Lab and learned to use a slide rule in 1972.
I then entered a 4 year apprenticeship on a sub base and was required to buy one for the classes there. I think it was a double log if I remember right and yellow for easier reading.
Shortly after being employed there HP came out with the HP-35 I think it was. We had them in the cal lab just as I was leaving. There were an amazing device at the time and cost the government some \$600 if I remember right.
I ask the instructors if you could use one of the new calculators in the classes as an electronics mechanic and was told no. I wanted to know why not and why we were being denied the use of the newest technology and fought the issue.
We had to take math challenge tests to get into the electronics trade and were not really being tested on our math skills but rather our ability to use math to solve a problem. If you did not know the formula and how to apply it and enter it into the calculator you were still stuck.
They even threatened at one point to fire me if I did not quit making such a fuss over the use of calculators in the apprenticeship. I told them to go ahead and try and I would sue the hell out of them and that I was not going to shut my mouth. I had just done 6 years in the Army and I was through taking orders let alone from Navy!
Old school thinking was all it was and they knew it. It took a few months but I won and from that point on you were allowed to have these marvelous devices in the classroom.
The HP-35 is long gone. I still have the slide rule and don't know why. It's just a memory and I don't even know now if I know how to use it anymore.
For years now you have been able to buy a calculator that will exceed what that first true scientific calculator could do for \$10-20 almost anyway. I think I paid \$425 for mine back when but it was worth it at the time. I used it for many years while running tests on equipment.

K0RGR
05-22-2009, 06:20 PM
I'm going to have to call out a search party to see if my dad's old slide rule from the 1930's can be found. I used it on both my General and Extra exams back in the 60's and early 70's. Of course, Dad had to teach me how to use it, first, including how to use logarithms. Dad's had his old Colorado callsign, W9YDW, on it. And yes, Colorado was in the 9th district in 1935.

When I was in school, the circular slide rule was king until the well-heeled started showing up with these electronic calculators that used 'reverse Polish notation'. After a couple years, the Japanese had taken over the market and you could buy a barrel of good scientific calculators for pocket change.

K8ERV
05-22-2009, 06:54 PM
Long ago I visited a factory in Japan. There was a big Nikon optical comparator. It was run by a small and very old Jap man. He was doing his calculations on an abbacus. I have a pix somewhere.

TOM K8ERV Montrose Colo

AF6LJ
05-22-2009, 07:18 PM
I still have my slide rule packed in the garage. When I first took electronics in JC it was required in spite of the fact I was one of the few who had a calculator. (TI SR-10)
A few years later it came in very handy for both calculating decibels and for correcting RF power readings. (to compensate for losses in my workstation setup.)
By then I had an HP-41 CVX still the power correction was faster than my program in the 41 that did the same thing.
At that time I was doing so much work with decibels that within a year I had memorized all the ratios and could estimate the DB values within a DB :)

The slide rule allows you to see relationships between numbers in a way no other instrument will allow.

An amazingly powerful tool.

N7RJD
05-22-2009, 07:39 PM
Texas Instruments sent the Slide Rule into obsolescence.

Ah yes, when the TI - 30 was the king of the scientific calculators. Wasn't long before it was out done and ended up being king of the cheap and affordable scientific calculators.

N7RJD
05-22-2009, 07:41 PM
Long ago I visited a factory in Japan. There was a big Nikon optical comparator. It was run by a small and very old Jap man. He was doing his calculations on an abbacus. I have a pix somewhere.

TOM K8ERV Montrose Colo

Now you're speaking my language.

I've never used a slide rule (probably a bad thing to admit in this thread) but used to play with an abacus from time to time. Grew up going into China Town in SF and was always intrigued by some of the guys that could work the abacus faster than most could work a calculator.

K8ERV
05-22-2009, 09:26 PM
Yes, but some people cheat.

TOM K8ERV Montrose Colo

AG3Y
05-22-2009, 09:34 PM
I have two Post Versalogs around here somewhere. One is the standard size, that I got during my training at the old DeVry Tech in Chicago. The other one is a "shirtpocket" sized one that is only about 4 or 5 inches long! It is a real beauty! They are both made of plastic bonded to bamboo.

Then I also have a couple of plastic K & E sliderules that are nearly as functional, but not as "sexy" as those old posts ! I still resort to a spreadsheet or calculator if I want to do some figuring, without making a big mistake.

73, Jim

K9CN
05-22-2009, 10:37 PM
There has been some real progress in the world, and, for practical work, I miss slide rules about as much as I miss typewriters, pay telephones, TELEX and paper correspondence.

Still, there was a bit of an art and skill to using a slide rule that I oddly miss and find appealing.

As HAY points out, it required you to think. You had to keep track of the decimal point, which more or less forced you to have at least an "order of magnitude" idea of what the appropriate result should be. That served as a practical check on your work and helped avoid truly monumental blunders.

After I switched over to a calculator (TI SR-51A) my Junior year in engineering school, I found it MUCH easier and faster to punch in numbers and get a result than I ever did with the old slip stick. I also found it much easier simply to accept whatever answer popped up, however absurd -- even if a simple keystroke error made the result off by a factor of 1000 or more.

Now I doubt many of us would seriously go back to using slide rules for "real" work any more than we'd seriously consider horseback as a viable means of commuting to a downtown office job. But I still have the K&E LogLog Decitrig Duplex my old man gave me for Christmas too many decades ago. As with CW, tube rigs and straight razors, there's still a certain charm in doing things the old way.

WA4BRL
05-22-2009, 11:07 PM
I started learning to use a slide rule just as the scientific calculators were coming out (HP-35 and others). My high school physics teacher gave me a most valuable technique for any computing method:

Knowing the first significant digit and the order of magnitude keeps track of the decimal point for slide rule work and identifies obvious keystroke errors on calculators.

K9UDX
05-23-2009, 11:32 AM
I showed up at a VE session (within the past couple of years) with my trusty K&E slide rule in its leather case hanging from my belt. The VEs (with a big grin on their faces) said I had to remove the batteries.

It might be worth only a few dollars on Ebay, but it is priceless to me. It got me through two chemistry degrees in the middle of the last century. It is still fun (and challenging) to do some of the arcane calculations one can do with the LogLog Decitrig slide rule.

W9JEF
05-23-2009, 06:09 PM
The previous engineer was showing me the ropes at the radi station that had just hired me. We were checking transmitter power (volts times current times efficiency). While he was still tapping away at his calculator, I already had the whole ballpark of acceptabe plate current in view. Same with phase angles and current ratios.

Like someone up the thread said, it
shows relationships between numbers.

The ARRL offers a circular L/C/F calculator, that also computes coil winding. Based on optimum plate tank Q, with that, and my trusty old slide rule, calculated L and C values for my homebrew linear, and antenna tuner values for my HF turnstile.

4Z5TO
05-23-2009, 07:15 PM
Get yourself one of these too...

http://en.wikipedia.org/wiki/Curta
http://www.vcalc.net/cu.htm