J Pole calculator

[BOOTY MONSTER]

J Pole calculator by dxzone.com

figgured someone here might find this useful .
to those that know about j-poles , is this calculator accurate ?

 

[Robb]

>Snicker<
I used 27.085Mhz as the freq in the formula, and got a J-pole about 26 ft high.
J Pole calculator by dxzone.com

I don't even know if it will work in that bandwidth - but it might be fun to exxperiment if you have a lot of copper tubing lying around. At 26 ft, you wouldn't need to put it up on a mast, just make a stable stand for it on your roof. The touchy and delicate part is the SO-239 - and keeping it stable and unbroken thru possible wind damage.

 

[BOOTY MONSTER]

from the looks of the home brew model it looks to me like a 239 isnt necessary . just attach the center and braid to their respective places .
no lossy coil or tuning ring either . if itll tune down good though with a 26 ft radiator it should tx and rx pretty well .

 

[W5LZ]

Is it accurate? Given that the size/diameter of the conductor used, and where the thing will be mounted always has 'some' affect on accuracy, it's accurate enough. There will always be some 'adjusting' of the feed point taps, that's normal.
One suggestion for VHF/UHF 'J'-poles is to add a sort of 'tuning adjustment' to the top of the long element. Solder a nut and bolt to the end-cap so that you can adjust the element's length. Not all that necessary, but it doesn't hurt. that tuning adjustment nut/bolt is naturally longer for the lower frequencies, maybe not as practical for 27 Mhz, and definitely a looong bolt for the lower bands. Taking a sort of 'step back' and looking at it objectively, nothing says you couldn't use a tall tower and a 'tuning stub' to make a 'J'-pole for several bands in one structure... sort of like a '18HT', huh?
- 'Doc

(18-HT = a 'Hi-Tower', now owned by MFJ. Gotta be the best "all band" HF vertical antenna around if done correctly.)
(That 'choke' isn't a bad idea for any/all antennas.)

 

[hookedon6]

i have to agree on the performance, but..... i can't even afford an 18 ht JUNIOR :headbang:headbang

 

[N9RZD]

it appears to be,
having built several , the dimensions look ok
however , i wouldnt use a jpole design much below 50 mhz
it is going to be big and gangly , and probably not very sturdy

another thing i do is use 3/4 and 1' copper
it does affect final tuning slightly , but results in higher bandwith
and makes for a much sturdier antenna


73

 

[W5LZ]

hookedon6,
Uh... me either, but it doesn't keep me from wishing. Oh well...
- 'Doc