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11 meter j pole w/300ohm twinlead

dxing440

Active Member
Apr 10, 2011
161
10
28
I recently built a jpole for 11meter from 300ohm twinlead and 12g copper wire. Radio with 30 watts had a 1.3 swr and about 1.7swr on 10 meter, and have made many dx contacts. 1/2wave`s are a bit long on 11/10 meter about (27ft).

BUT curiosity wants to know if anyone has built a 1/4wave jpole .Or can someone help with calculations to build such, like radiating length, stub length, and feedpoint locations? Like i said" curious about 1/4wave" (about 14)ft

Any thoughts? Thanks
 
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Wiskey Six

Member
Nov 7, 2010
1
0
11
I have been thinking about doing the j-pole for 11m also. What were the spec you used? Did you use a particular site for a reference.

I have see a few out there but I was unsure about the figure that I got. The long side about 26' long, short side about 30" long, and about a 9" seperation. I dont know if this is right.
 

Marconi

Usually if I can hear em' I can talk to em'.
Oct 23, 2005
7,161
2,200
343
Houston
I recently built a jpole for 11meter from 300ohm twinlead and 12g copper wire. Radio with 30 watts had a 1.3 swr and about 1.7swr on 10 meter, and have made many dx contacts. 1/2wave`s are a bit long on 11/10 meter about (27ft).

BUT curiosity wants to know if anyone has built a 1/4wave jpole .Or can someone help with calculations to build such, like radiating length, stub length, and feedpoint locations? Like i said" curious about 1/4wave" (about 14)ft

Any thoughts? Thanks

440, I think you can feed an end fed 1/2 wave radiator with the top end of a 1/4 wave element working against a 1/4 wave ground element like the bottom of the J-Pole, but I don't think a 1/4 wave element would work the same on top...in place of the 1/2 wave radiator.

The voltage nodes where the lower tuning element connects to the radiator are the exact opposite and are not compatible. IMO, a voltage node connected to another voltage node will work, but a voltage node connected to a current node will not.

You might consider to fold over the top half of the 1/2 wave element, or use a top hat if antenna length was a problem.
 

dxing440

Active Member
Apr 10, 2011
161
10
28
I have been thinking about doing the j-pole for 11m also. What were the spec you used? Did you use a particular site for a reference.

I have see a few out there but I was unsure about the figure that I got. The long side about 26' long, short side about 30" long, and about a 9" seperation. I dont know if this is right.

Hey whiskey6 try this site.NYLO's NOTEPAD Antenna Page
 
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Captain Kilowatt

Professional Amateur
Staff member
Apr 6, 2005
16,992
11,415
823
59
Nova Scotia,Canada
All a J-Pole is is a half wave vertical fed at the bottom end thru a 1/4 wave matching stub. The feed impedance of an end fed half wave antenna is extremely high and the shorted 1/4 wave stub transforms this into something near 50 ohms. There is no such thing as a 1/4 wave J-Pole as you cannot feed a 1/4 wave vertical at the end with another 1/4 wave stub. You would feed a 1/4 wave at one end and place another 1/4 wave at the opposite end and thus have a dipole.
 
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towerdog

one-niner-seven
Nov 18, 2009
644
128
53
NC
looks like a good tree antenna, I might just build one after i move.......depending on presence of tree
 

W5DMG

Member
Mar 20, 2012
5
0
11
62
I can not remember where I read this, but remember reading where someone with an Imax 2000 built a 10 meter j-pole and compared the 2, and said the j-pole out performed. For some reason I doubt that the j-pole would out perform it.
 

IMD262

Well-Known Member
Apr 26, 2005
1,099
287
93
NY
I can not remember where I read this, but remember reading where someone with an Imax 2000 built a 10 meter j-pole and compared the 2, and said the j-pole out performed. For some reason I doubt that the j-pole would out perform it.

I've read about someone's Sirio Gainmaster that " will whoop the snot out of a 3 element all day long i don't care what the propagation is but it will give a 4 element a run for its money. ", do you think I believe it???
 

Robo

Member
Nov 25, 2012
11
0
11
Hello,

im new here, if you want to make the J-pole make 1 out of aluminum its lighter. If made 1 out of coper pijp 15mm, but it is to heavy. I have made it for 2 mtrs, but i was not happy whit this antenna. So i made a slim-jim antenna that antenna is lighter end bether for 2 mtrs, its made out of aluminum pijp 10mm en its on a mast of 5,50 mtrs read somthing about the slim-jim then you no what i mean. Btw QTH is Holland greets 73.
 

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