Post by Night Ranger on Dec 8, 2012 0:14:27 GMT -5
I just successfully built an 11 meter j-pole with a long piece of 14 gauge insulated wire, an 8 foot piece of RG-58 coax, a small piece of PVC pipe with a whole drilled in each end as an end insulator, and a section of 450 ladder line.
I found a PDF on the Internet with the details for making a 10 meter J-pole for 28.400 MHz. I converted the dimensions for 27.205 MHz. It took me about 30 minutes to make the new calculations and build it. Next I hung it from a tree limb in a medium sized magnolia tree. I was expecting to tune an inch or two here and there to get the SWR right, but to my amazement the SWR on the first check was;
1.1:1 on channel 1
1.1:1 on channel 20
1.2:1 on channel 40
This is the original PDF design for 10 meters;
www.shadowstorm.com/cb/pdf/10mjpole.pdf
..and here are the new measurements for 27.205 MHz
Length of single piece of 14 gauge stranded and insulated wire = 17 feet 3 inches.
(I cut the wire longer than 17 feet 3 inches so I could twist the extra wire back around through the PVC insulator just like you do with the end of a dipole through an egg insulator)
Length of 450 ladder line matching section = 8 feet 2 inches. Be sure to short the two sides of the 450 ladder line together at the bottom end only.
Make the coax connection to the 450 ohm ladder line 7 inches up from the bottom of the ladder line.
For the RG-58 RF choke I used 6 turns of RG-58 coax at a diameter of 4 inches.
By the time I finished the antenna the time was 11:30 p.m., and the locals had already signed off for the night. I'll try to hang it in a higher tree and get some signals reports tomorrow. I built this antenna to talk to the locals since all my other antennas are horizontal polarization for skip.
...And yes I climbed the tree at night. I have a homemade portable wooden box with two 500 watt halogen flood lights attached. I pointed the lights at the tree, plugged them up, and started climbing.
Night Ranger
I found a PDF on the Internet with the details for making a 10 meter J-pole for 28.400 MHz. I converted the dimensions for 27.205 MHz. It took me about 30 minutes to make the new calculations and build it. Next I hung it from a tree limb in a medium sized magnolia tree. I was expecting to tune an inch or two here and there to get the SWR right, but to my amazement the SWR on the first check was;
1.1:1 on channel 1
1.1:1 on channel 20
1.2:1 on channel 40
This is the original PDF design for 10 meters;
www.shadowstorm.com/cb/pdf/10mjpole.pdf
..and here are the new measurements for 27.205 MHz
Length of single piece of 14 gauge stranded and insulated wire = 17 feet 3 inches.
(I cut the wire longer than 17 feet 3 inches so I could twist the extra wire back around through the PVC insulator just like you do with the end of a dipole through an egg insulator)
Length of 450 ladder line matching section = 8 feet 2 inches. Be sure to short the two sides of the 450 ladder line together at the bottom end only.
Make the coax connection to the 450 ohm ladder line 7 inches up from the bottom of the ladder line.
For the RG-58 RF choke I used 6 turns of RG-58 coax at a diameter of 4 inches.
By the time I finished the antenna the time was 11:30 p.m., and the locals had already signed off for the night. I'll try to hang it in a higher tree and get some signals reports tomorrow. I built this antenna to talk to the locals since all my other antennas are horizontal polarization for skip.
...And yes I climbed the tree at night. I have a homemade portable wooden box with two 500 watt halogen flood lights attached. I pointed the lights at the tree, plugged them up, and started climbing.
Night Ranger
..When I first put up my directional dipole, I built it in the front yard. I live on a busy residential side street, so there's always an audience. One passer-by actually stopped and helped me "walk" the mast and antenna up! Then he asked all about the rest of them along side the house...2 cups of coffee later he was on his way. The array never fails to draw some attention when I'm working on it.. 
