Ralph, First, check you dimensions. The calculated dimensions are: Radiator (Long) = 19.44 inches (I would cut to 19.75 and trim down to bring the resonance up Stub (short) = 6.48 inches (I would cut 6.5 ") Feed point = A touch less than 5/8 inch FROM THE TOP ( not the middle) of the bridge on the bottom of the radiator and stub Bridge length = a touch less than 5/8 in between the inside edges (not the middle, or outside) of the radiator and the stub
J-poles need to be choked, and I usually do this by taking 5 loops of the coax about 5 inches in diameter, and zip tying the loops with three or 4 zip ties. That choke needs start immediately below your lightning arrestor, directly before the feed point. Finally the braid of the coax needs to be connected to the stub, and the center connector to the radiator. If all of your dimensions are correct, adjust SWR by moving the feed point up and down. I usually make this part easier by using 12 guage ground wire from the SO-239 chassis to the stub, and from the SO-239 center conductor to the radiator, and taking one loop around each. Once I have SWR right, I clamp and solder the ground wire. On a 440 J-pole a tiny bit deviation in the feed point length goes a long way, and the distance from the bridge HAS to be exactly the same on both the radiator and the stub. Once you have a reasonable SWR you can trim a little off the radiator to get you center freq where you want it. Unless you missed the measurements when you cut the thing, or you did not choke the feed, I will lay dollars to donuts your problem is that the feed point is not the same distance from the bridge on the radiator and the stub. On a longer J-Pole (i.e. a lower freq) this difference doesn't matter much, when your wavelength is <28 inches, small differences get big results. Ron Judging by personal experience, the next public health crisis after COVID 19 is likely to be cirrhosis. Ron Bosch "..any man who may be asked what he did .. to make his life worthwhile, I think can respond with a good deal of pride and satisfaction" 'I served in the United States Navy." John F. Kennedy When I was young and bold and strong, Oh, right was right, and wrong was wrong! My plume on high, my flag unfurled, I rode away to right the world. ‘Come out, you dogs, and fight!’ said I, And wept there was but once to die. But I am old; and good and bad Are woven in a crazy plaid. Dorothy Parker "The best lack all conviction, while the worst are full of passionate intensity" Wm Butler Yeats "Believing with you that religion is a matter which lies solely between man and his God, that he owes account to none other for his faith or his worship, that the legislative powers of government reach actions only, and not opinions, I contemplate with sovereign reverence that act of the whole American people which declared that their legislature should "make no law respecting an establishment of religion, or prohibiting the free exercise thereof", thus building a wall of separation between church and State." Thomas Jefferson "Fix reason firmly in her seat, and call to her tribunal every fact, every opinion. Question with boldness even the existence of a god; because, if there be one, he must more approve the homage of reason, than that of blindfolded fear." Thomas Jefferson in a letter to Peter Carr A Government founded upon justice, and recognizing the equal rights of all men; claiming no higher authority for existence, or sanction for its laws, than nature, reason, and the regularly ascertained will of the people; steadily refusing to put its sword and purse in the service of any religious creed or family, is a standing offense to most of the Governments of the world, and to some narrow and bigoted people among ourselves. Frederick Douglass On Tue, Apr 21, 2020 at 2:52 PM ralph phillips via BVARC <[email protected]> wrote: > Having problems with my home brew 440 mhm jpole...will not tune better > than a SWR 1.9. Books and articles no help. Will velocity factor or > resistance change dimensions for steel vs aluminum?? > > Get Outlook for Android <https://aka.ms/ghei36> > ________________________________________________ > Brazos Valley Amateur Radio Club > > BVARC mailing list > [email protected] > http://mail.bvarc.org/mailman/listinfo/bvarc_bvarc.org >
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