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40m. 3el. U-Yagi

Antennas



3 Elements 40m full size U Antenna


In my last Blog I wrote about my Antenna 3 el. Yagi for 40m. >>> We now come to my projects, work is progressing, but before coming to the realization of 160 m. and resettlement of four 80m phased vertical dipoles on second tower, I put in place to change my antenna PKW 3 elements Yagi for 40m. this is a loaded antenna, which also worked well, but only in the CW portion, covering about 7000-7060, now with the new rules having he ability to use 7000-7200 I had the idea to remove the coils and extending elements of the measure physical half-wave, first of all because my tower is close to home I could not fully extend, but I reached up to 14 meters, the missed half wave phisical lenght is obtained by leaving the sides of the elements hang a wire connected to each element by crushing the alluminium tube for 2 cm, make a hole and  fixing the wires of the required length by means of cable terminals , thus forming a kind of inverted U, thanks to Donato IK2EGL through its website, where I gained various information on it; spacing of the elements for now I 've left unchanged from what was originally, now the mechanical work on the antenna is over, are about to do the resonance of the radiator and thus changing the basic measures of the radiator and reflector in proportion, the tools I use are a MFJ 259B, an Autek VA1 Vector Antenna Analyst, and a MFJ 203 Dip meter.
A final point on this antenna when there is strong wind, obvious that the dangling wires are moved by the wind causing a slight variation of the characteristics, however of small entity, in my case in this respect I feel lucky, the wind is not a constant factor in this area, however, even when the wind is present even strong, I have no trouble making DX QSO.

10 October 2010 added comments


Job is fully done, Antenna now is up and working of love, this was a very rewarding job, the antenna works very well, the results after a short trial period are flattering, gain 7/8 db, front to side 30/35 db, 20db front to back, its impedance is found to be 25 homs, and advice to everyone in a situation like mine to proceed with the improvement, in particular to the holders of the 40m antenna PKW. 3 el. loaded Yagi, after trial and error, the Antenna the was tuned at 10 m. on the ground, on frequency of 6.850 MHz, elevating it to the end position at 25 meters, the center band moves to 7080 and covering 7000/7200, indeed even more.
Here down two photos, one with data and measures, the other you see the antenna with the change, low to the ground.
Looking at the schematic of antenna is clearly seen the uneven length of aluminum tubing, which is why I had to keep a certain length setting to climb as in the original antenna, because my tower being very close to home, when I get off the antenna, i must direct it south east in a way that the elements do not touch the house gutter and allow me to go ashore without the antenna problems.
Well I think I have said all, many thanks for brouse my web site, Good Luck and Good DX' ing de IK1MNJ Enrico.

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