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Extra math questions

Feb 21st 2018, 09:00


Joined: Nov 22nd 2017, 08:39
Total Topics: 0
Total Posts: 0
On page 4-29 of the Extra book they show fig 4-25
If you go to the last equation and plug it in should their be a syntax problum.? If so how do you correct it?
Feb 21st 2018, 09:32


Super Moderator

Joined: Apr 4th 1998, 00:00
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Total Posts: 0
I worked Equation 4.15 and calculated 97.7 pF. I prefer to use a HP Scientific Calculator with RPN notation. Conventional algebraic calculators are hard to use with something this complicated.

It may be best to take things step by step and write down all the intermediate numbers and re-enter them, rounding them off to save time and reduce the chance for error. It takes a lot of practice to enter in a complex calculation with a lot of parenthesis and get the right answer without syntax errors. Be sure to read the instructions. Algebraic calculators have different procedures for complex math. Don't expect a new calculator to work like the old one.

Zak Lau W1VT
ARRL Senior Lab Engineer
Feb 22nd 2018, 15:49


Joined: May 20th 2014, 01:06
Total Topics: 0
Total Posts: 0
Good on you for asking! I teach Extra upgrade classes, so I have an idea of what is happening here.

How you enter this into your calculator depends on which calculator you have. For most, it is easiest to start with the product of L and C. For that, you should obtain 2.00E-15. Next, take the square root; to three digits this is 4.47E-08. Multiply this by 2π; you'll have 2.81E-07 to three significant digits. Take the reciprocal of this to obtain 3.56E+06, or 3.56 MHz, in agreement with the text.

Remember, you will only see a few questions (likely four) involving computation on the exam. Do not let computational problems stress you out. GL es 73

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