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Author Topic: AN INEXPENSIVE 2 ELEMENT 10 METER BEAM.  (Read 8240 times)
K0YNE
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« on: November 25, 2009, 10:00:54 PM »

I AM REPRODUCING DIMENSIONS ABOUT A 2 ELEMENT 10 METER BEAM, DON'T KNOW THE AUTHORS CALL OR NAME. FOUND IT ON THE INTERNET.

DESIGNED FOR SHORTNESS AND TRANSPORTABILITY.
FREQUENCY CUT FOR 28.400 MHZ.

THE DRIVEN ELEMENT CAN BE MADE IN ONE PIECE 17 FEET AND 3 INCHES LONG. THAT IS IF YOU ARE GOING TO HAVE A GAMMA MATCH TO ATTACH TO THIS DRIVEN ELEMENT.

OR YOU CAN CHOSE TO DRIVE IT AS A DIPOLE, AND INSULATE EACH ELEMENT SIDE FROM THE BOOM ATTACHMENT.
NO POWER LIMITING, SINCE  RG 58 OR RG8 TYPES OF COAX WILL BE HOOKED DIRECTLY TO EACH HALF
OF THE "DIPOLE TYPE " CONFIGURATION OF THE DRIVEN ELEMENT.
EACH DRIVEN SIDE WOULD BE 8 FEET AND 7 1/2 INCHES LONG .
DIPOLES MAYBE BE LENGTHENED OR SHORTNED TO GET THE LOWEST SWR.

TOTAL LENGTH OF BOOM IS 48 INCHES.

THE REFLECTOR IS 18 FEET AND 1/2 INCHES LONG..

TEXAS TOWERS OFFERS A VARIETY OF TUBING SIZES, AND 3/4 INCH  BY SIX FEET
2 PIECES FOR MIDDLE OF BOOM ,DRIVEN AND REFLECTOR .

NOW, 1/2 TUBING SLIDES INTO THE 3/4 INCH BOOM PIECES ON EACH END MAKING THAT
NUMBER OF PIECES TO BE 3 TOTAL.

NOW YOU HAVE TO FINISH THE LENGTHS  OUT TO THE ABOVE MENTIONED DIMENSIONS.

LASTLY FOR THE ELEMENTS, 3/8 INCH SLIDES INTO THE 1/2 INCH PIECES, FILLING THE
TOTAL DIMENSION OF DRIVEN AND REFLECTOR.

NOW YOU WILL NEED 1 PIECE OF 3/8 INCH TUBING BY 6 FEET LONG TO COMPLETE THE
YAGI ELEMENTS. YOU WILL ALSO NEED A COUPLE SIZES OF HOSE CLAMPS TO CLAMP THE SECTIONS
TOGETHER, BUT FIRST SPLITTING THE ENDS OF THE 3/4 INCH PIPE AND THE HALF INCH PIPE
SO THEY CAN THEN COMPRESS TOGETHER TO MAKE A GOOD BOND.

SINCE ALL OF THE TUBING IS UPS SHIPABLE, 6 FEET MEETS UPS SHIPPING STANDARDS OKAY AND
HELPS REDUCE THE COST.

U CLAMPS CAN BE USED TO MOUNT THE ELEMENTS TO A 1 INCH BOOM PIPE.
A SADDLE MAY HAVE TO BE MADE TO KEEP THE ELEMENTS STABLE.

NOT MANY TOOLS REQUIRED TO DO THIS JOB, A DRILL AND BIT AND A GOOD HACK SAW.
MAYBE A SCREW DRIVER TO ATTACH THE COAX CABLE, SHIELD AND CENTER CONDUCTOR TO THE RESPECTIVE SIDES, OR IF LEFT IN ONE PIECE, THE DRIVEN ELEMENT CAN BE DRIVEN BY THE FAMOUS
GAMMA MATCH. THE GAMMA MATCH USES A 24 INCH GAMMA ROD. A SIMPLE GAMMA MATCH WITHOUT A HOME BREW CAPACITOR IS OFTEN ENOUGH FOR 100 WATTS.
THE GAMMA TUBE COULD BE MADE FROM 1/2 INCH TUBING. THE SPACING IS 4 INCHES MEASURED FROM THE CENTER TO CENTER OF BOTH THE GAMMA ROD AND THE DRIVEN ELEMENT TO WHICH IT IS BEING ATTACHED . THE GAMMA TUBE'S ONE END IS EVEN WITH THE OUTER EDGE OF THE BOOM,  AND THE INSULATED SUPPORT FROM THE DRIVEN ELEMENT TO THE GAMMA TUBE IS  4 INCHES CENTER TO CENTER OF EACH PIECE. NOW BUILDING A SHORTING STRAP NEAR THE END OF THE GAMMA TUBE, AND SPACING THIS STRAP 4 INCHES ALSO. SO ON THE STRAP THAT IS INSULATED NEAR THE BOOM AND THEN THE SHORTING STRAP NEAR THE END OF THE 24 INCH GAMMA TUBE. RUST PROOF MATERIAL IS DESIRED FOR BEST CONTACT OVER TIME.

NOW THE COAX END MUST BE SPLIT OUT TO REVEAL THE INNER CONDUCTOR THAT WILL START WITH
24 INCHES EXPOSED. INSERT THE CENTER CONDUCTOR, OBSERVING THAT NO STRANDS OF WIRE WILL TOUCH THE INNER GAMMA WALLS.  NOW ATTACH THE SHIELDED BRAID WIRE TO THE BOOM .
THE COAX CONDUCTOR INSERTED INTO THE GAMMA TUBE WILL LIKELY HAVE TO BE PRUNED SEVERAL TIMES, AS THE SWR IS READ THRU THIS PROCESS. THE SHORTING STRAP ON THE FAR END SHOULD BE ADJUSTED FIRST TO CHECK FREQ AND SWR.  28.400 IS THE DESIGN FREQUENCY. SO A LOT OF PRUNING AND SLIDING THE SHORTING STRAP BACK AND FORTH TO FIND THE LOW SWR SPOT AND THE FINAL PRUNED LENGTH OF THE COAX CONDUCTOR.
SEAL THE ENDS OF THE GAMMA TUBE TO PREVENT MOISTURE ENTERING. SILICON WORKS WELL.

*****NOTE, I INCLUDED A 1/2 TUBE FOR THE GAMMA TUBE SHOULD IT BE USED.
FURTHER TUNING CAN BE DONE WITH AN  ANTENNA ANALYZER THAT A FRIEND MAY HAVE.
 

SOME DETAILS MAY HAVE NOT BEEN MENTIONED, BUT USE GOOD JUDGEMENT WHEN INSTALLING AND STAY AWAY FROM ELECTRICAL WIRES.. BE SAFE
K0YNE PAUL
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