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J-Pole's
- Thread starter NorthStar
- Start date
NS, I have no personal experience with J-poles, but I do know there are a lot of arguments even on the Internet about how difficult they are and the problems with them to build and use. On the other hand I have heard the term applied to some of the best antennas I believe are out there working, so you just have to be careful. Some think they are hot and some not.
To me it looks like and antenna with a lot of RF business going on near the botton as usual, but without a ground plane I suppose they do work the feed line and the mast pretty good. Now the fact that a 1/4 wave feeder is working a parallel ground element and this ground element is feeding the radiator at a voltage node at some height above the feed point may make this antenna even less disruptive with currents on the feed line and/or mast and maybe no ground plane is needed at all.
How is that for stradlin' the fence.
To me it looks like and antenna with a lot of RF business going on near the botton as usual, but without a ground plane I suppose they do work the feed line and the mast pretty good. Now the fact that a 1/4 wave feeder is working a parallel ground element and this ground element is feeding the radiator at a voltage node at some height above the feed point may make this antenna even less disruptive with currents on the feed line and/or mast and maybe no ground plane is needed at all.
How is that for stradlin' the fence.
NorthStar said:
If you're interested in building any antenna at all, get the FCC Antenna Book and leaf through it. I would imagine there are plans and guidles in it on just about anything buildable. I have one and I can't find the fleeping thing to see what's there and don't remember if there is even a j=pole in it but there should be since lots of people say they built one.
73
A J-pole antenna does not need a groundplane to work well. It is not a 3/4 wave antenna like many think it is but rather an end-fed 1/2 wave antenna that uses a 1/4 wave matching stub to transform the high feedpoint impedance of a half wave down to 50 ohms.I have built a few of them and they work well especially the extended super J antenna. I built one from 3/4 and 1/2 inch copper pipe with 1/4 inch copper tubing for the phasing line and ran it for several years on the tower.It worked really well. Extended J-pole info It is really a normal J-pole with another 1/2 wave stacked on top and fed in phase.
Qrn,,,,are you talking about the "super j" from the ARRL manual? I have also built a few of them, they actually work very well.There is alot of good stuff in the manuals everybody should have a few to play with.
Yes mrcoily,that is the one.I built two of them,one from stainless whips and rod and the other from copper pipe.Both worked very well indeed.
Northstar, the ARRL Handbook has build instructions with diagrams and dimensions for a 2m J Pole. If you go with that, you'll have no problem putting one together. If you don't have the ARRL Handbook, I have it on CD and could probably email you that section as a PDF.
Marconi said:
I built it for 2m. I can't imagine it for 11m.It would have to be really strong or guyed.The super J is 1 1/4 wavelengths long or about 44 feet high for 11m. :shock:
QRN said:
That's why Avanti made the Sigma IV the way they did! So it could support itself. :twisted:
I can see that after hearing your claims sometime back when things were good, but all that good stuff is all gone now.
You are right on the money young man and I will argue right along with you until I am forced to change my feeble mind.
And if the good Lord permitts me I will be there in the desert with you guys, my Sigma and my Starduster, making you all sweat big time. I have a few tricks up my sleeve that all these years of experience has brought to me.
You are right on the money young man and I will argue right along with you until I am forced to change my feeble mind.
And if the good Lord permitts me I will be there in the desert with you guys, my Sigma and my Starduster, making you all sweat big time. I have a few tricks up my sleeve that all these years of experience has brought to me.
Yea yea, but wait until you see my modified I-10K with 5/8 long radials bent down at 45 degrees! :twisted: :twisted: :twisted: