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Patrick,

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.

73,

Steve

aa8af

"Patrick Cummins" <pcummins@misnet.com>

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>

cc:

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

rewriting

the whole darned thing.

-----Original Message-----

From: Patrick Cummins <pcummins@misnet.com>

To: fpqrp-l@mpna.com <fpqrp-l@mpna.com>

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
*

an

*>auto tune balanced antenna matcher. I put this idea down on my "this
*

could

*>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?)
*

to

*>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
*

5).

*>My problem is that I may need to compute square roots of some values and
*

I

*>don't remember how to. (So much for my early math education, but I have
*

been

*>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
*

look

*>at how we used to compute it. (Which may really have been an
*

implimentation

*>of newtons method.) Anyway, if any one can remember how could you please
*

let

*>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
*

and

*>purchasing a C compiler or other software that does is not an option for
*

me

*>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
*

*>pcummins@misnet.com
*

*>
*

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