Re: Fw: Computing square roots, help needed


From: Steve Lawrence (Steve.Lawrence@ITWFEG.COM)
Date: Sat Jan 05 2002 - 10:05:39 CST

My recollection of the formula that converges on the SQRT( N ), using only
basic math:

        ((N/Guess) + Guess) / 2 = NewGuess

Iterate, using "NewGuess" for subsequent passes, until the difference
between two consecutive "NewGuess" computations are within some acceptable
epsilon error. If I recall correctly, the initial guess can pretty much
be anything convienent: "2" for example.


"Patrick Cummins" <>
Sent by: owner-qrp-l@Lehigh.EDU
01/04/2002 11:32 AM
Please respond to pcummins

        To: "Low Power Amateur Radio Discussion" <qrp-l@Lehigh.EDU>
        Subject: Fw: Computing square roots, help needed

Guy and Gals
     I am sending this in this manner because i goofed up the address and
this is the only way i could figure out how to get it out without
the whole darned thing.

-----Original Message-----
From: Patrick Cummins <>
To: <>
Cc: qrp-l@Lehigh.EWU <qrp-l@Lehigh.EWU>
Date: Friday, January 04, 2002 10:20 AM
Subject: Computing square roots, help needed

>Hi guys and gals:
> I am sending this to both lists I monitor to see if someone out there
>can help me. A few months ago someone mentioned it would be neat to have
>auto tune balanced antenna matcher. I put this idea down on my "this
>be interesting list" and it has finally surfaced onto my "see if this is
>possible list". My intentions are to use a microPIC controller (16F84?)
>tune either a Zack Lau balanced tuner as shown in QRP Classics or Charles
>Lofgren's Z matcher as shown in the ARRL antenna compendium (vols 3 and
>My problem is that I may need to compute square roots of some values and
>don't remember how to. (So much for my early math education, but I have
>using either a slide rule or a calculator since about the mid 50's.)
> I could implement newtons method to solve it but would also like to
>at how we used to compute it. (Which may really have been an
>of newtons method.) Anyway, if any one can remember how could you please
>me know the method. I should note that the micro pic stuff I have, the
>simulator, emulator, and assembler do not have the square root function
>purchasing a C compiler or other software that does is not an option for
>at this time.
>And now a word from the immortal bard -- "Song of the open road with
>appologies to Joyce Kilmer"
>I never think that I shall see
>a billboard lovely as a tree,
>Indeed unless the billboards fall
>I'll never see a tree at all.
> -- Ogden Nash --
>(I also like his " Candy is dandy, but liquor is quicker " )
>72 and oo
>Patrick S. Cummins, W5PSC

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