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1-1 of 1 messages
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Page 1 of 1
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el Cheapo 6M 2 Element Yagi
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by KD8LCD on June 4, 2009
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Having gotten back into Amature, I thought I'd try out 6 Meters, having no job at present I found an old FT 680rII at a decent price ( hey it will at least get me on the air) okay now I need an antenna, hum that no job at present factor is there again. Wanting to work maninly SSB and not having much space until I can get on the roof I thought how about a small 2 element yagi at least for a temp antenna.
Parts:
(Hardware supply store)
2) 10 foot sections of 1/2 inch PVC
3) 1/2 inch PVC Tee's
9) self tapping sheet metal screws 3/4 inch
(Auto Parts store)
1) 20 foot rool of 3/16 steel brake line
12) 3/4 inch hose clamps
(parts bin etc.)
1 chassis mount so-239
1 short section of mini 8 cable or the like ( even 14 ga wire will work)
My parts total was less than $26.00
The brake line could be replaced with 3/16 copper tubing like used for water/ice makers for refrigiators (the brake line is stiff though and doesnt bend as easy so thats what I used)
Making the boom and frame
From one section of PVC cut two pieces of tubing 3 feet long insert each piece into a Tee to form a 6 foot piece, from the other section cut two pieces 3 and half feet,insert each piece into a Tee to form a 7 foot piece. these will be used for the director and Reflector element mounting, now we need a two pices 13 and 3/4 inches place these in the last Tee fitting and connect the two element mounting pieces to each end, you should have now what looks like and (H) ( length from the center of each tee used to make the element mounts should be 28 and a half inches.. The unfilled section of the Tee used in the middle will be used for a short section of left over PCV to clamp to a mast.
Now for the reflector, unroll the brake line and cut off a section 117 icheces long mark of the middle of this which will be 58 and half inches.try and make the brake line as stright as possible. place the marked off section in the center of the Tee used to make the 7 foot section, using 6 of the hose clamps place 3 on each end and tigthen down with the brakeline centered on the top of the PVC tubing.
The driven element is made up of 2 section of Brake Line cut to 53 inches each. Place these on the 6 foot section of PVC butt each side up against the Tee which will leave a gap between them using the last 6 hose clamps slide 3 onto each end and align the brakeline centered on top of the PCV.
Using a short 6-8 inch section of coax strip back enough to seperate the center and ground wrap the center around one of the driven elements several times and clamp at the end butted up against the tee with one of the hose clamps, do the same for the other driven elemnt and the ground side of the coax attach the S0-239 to the other end of the coax and screw the chassis connector to middle of the plastic Tee on the driven element side with the theaded end for your PL-259 facing the reflector side so it is inline with the boom, seal up all the connections with either electrical tape or coax seal.
Use the other self tapping screws to secure the sections of PVC into the Tee fittings.Use a short section of left over PVC to insert into Tee attached to the middle of the boom. Mount to a mast using muffler clamps at least ten feet off the ground and check SWR (I used a freinds MFJ analyzer and had a low SWR below 1.8:1 from 49.00 to 52.00 and almost flat at 50.110-50.145. I made up a small bauln wraping 5 turns of coax around a coke can (almost 2 inches in diameter) then slipped plastic zip ties down between the can and around the coax coil in several places to hold the coil in shape then slide out the can. I tapped the coil to the front section of the antenna a short space down the boom from the S0-239. With no band opennings yet I havent had much time to try it out, but using a couple of beacons rotating the antenna (arm strong method) I can place the signals in a null or cancel one of them out completely I'm sure the F/B is quite low . but the forward gain should be higher then a dipole.. While typing this out I down loaded QY4 yagi program and it shows a little over 6 DB for the forward and about 8 DB on the back. Hey it's a quick easy and cheap antenna that should get you on the air. If you want to enter the info into another yagi program of plott it out for those who have the software, the 3/16 brake line comes out to .1872 inch for the diameter of the elements. Driven is 106 inches, Reflector 117 inches and boom spacing is 29.5 inches. If you do plott this out I'd be greatful to see the results..
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