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World of Ham Radio 1997
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1997-02-01
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3KB
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56 lines
LOOP ANTENNA CALCULATOR
by GEORGE CSAHANIN JR.
WB2DYB
7 JULY 1986
THIS PROGRAM WILL CALCULATE THE VARIOUS PARAMETERS OF THE W5QJR SMALL LOOP
AS DESCRIBED IN JUNE 1986 QST. THE FORMULAS ARE FROM TED HART'S BOOK ON SMALL
LOOPS. THIS VERSION WILL CALCULATE THE CAPACITY, VOLTAGE, Q, BANDWIDTH. ETC.
FOR THIS FINE ANTENNA. TED HAS NOTED THAT THE ACTUAL BANDWIDTHS ARE GREATER
THAN THE FORMULAS CALCULATE, AND IN FACT I HAVE FOUND THIS TO BE TRUE WITH MY
LOOP. MY BANDWIDTH IS ABOUT 2.2 TIMES WHAT THE FORMULA SHOWS IT TO BE. AT ANY
RATE THIS IS A FINE ANTENNA, AND WORTH A SHOT IF YOU HAVE A SPACE PROBLEM. MY
INSTALLATION IS IN MY ATTIC, WHERE IT ACTUALLY PERFORMS NECK& NECK WITH MT
DIPOLE, OR VERTICAL. IN FACT MY FIRST QSO ON IT WAS ON 40 METERS FROM MY QTH
IN TEXAS TO JAPAN! THE THING DIDN'T EVEN HAVE IT'S MOTOR DRIVE YET, IT WAS
JUST SITTING ON THE BOOKSHELF NEXT TO ME IN THE SHACK, BAREFOOT, 100 WATTS,
AND THIS JA7 CAME BACK TO ME. NOISE IMMUNITY ISN'T WHAT IT IS CRACKED UP TO
BE. IT ISN'T WORSE, JUST NOT BETTER.
TED HART SELLS A CAPACITOR, WHICH I RECOMMEND. I GOT A STEPPING MOTOR FROM
HERBACH & RADEMAN FOR $3.50. IT HAS LARGER STEPS, BUT I HAVE NOT HAD ANY
PROBLEM WITH IT YET. WITH THE CAPACITOR THAT I GOT FROM TED, MY 3 FOOT
DIAMETER LOOP (WHICH I DID HAVE TO PRUNE A BIT) TUNES FROM 6.950 MHZ TO 14.250
MHZ. I GAVE UP PRUNING FURTHER, AS THIS DID ALL I NEEDED. IF YOU DO ANY
SNOOPING AROUND THE INTERNATIONAL BROADCAST BANDS WITHIN THIS IS A GREAT FIND.
AS FOR MOUNTING, I HAVE IT HUNG FROM THE 2X4'S IN THE ATTIC WITH NYLON ROPE.
IF YOU ARE AN ANTENNA EXPERIMENTER, OR IF YOU JUST HAVE A PLAIN OLD SPACE
PROBLEM, TRY THIS ONE. FOR THE COST OF THE CAPACITOR, SOME SOLDER, AND SOME
COPPER TUBING IT WILL PROVE ITSELF TO YOU. AS FOR THE FORMULAS, AND THIS
PROGRAM WHICH IS WRITTEN FIRST IN BELIEVE IT OR NOT, COMMODORE BASIC,
TRANSLATED TO MBASIC, AND FORTHER REFINED UNDER BASICA, THEN COMPILED WITH
TURBOBASIC, TRY THEM. IF YOU NEED THE BASIC FILE DROP ME A NOTE THRU THIS
AMATEUR RADIO BBS, OR THRU COMPUSERVE, OR DEEP THOUGHT IN AUSTIN, I'LL GET IT
FOR YOU. THIS PROGRAM IS NOT FOR SALE, AND IS FREE FOR THE USE OF ALL ENGAGED
IN NOT FOR PROFIT ACTIVITIES, RELATIVE TO NEWLOOP.EXE, OR NEWLOOP.BAS
GEORGE
512-331-9568 HOME
512-476-3636 WORK
PS- ALSO I HAVE INCLUDED NULOOP FROM ANOTHER SOURCE. IT DOES THE SAME, BUT DO
NOT BE CONFUSED BY THE DIFFERENCE IN TUNING CAP RESULT. MINE IS SHOWING TUNING
CAP MINUS THE DISTRIBUTED CAPACITANCE. NULOOP ALSO WANTS DIMENSION IN LENGTH
OF A SIDE FOR AN OCTAGON, NEWLOOP(MINE) WANTS LOOP DIAMETER.
GEORGE 72060,3640/75706,577