MaverickNH
NES Member
I got around to building a DBJ-2 Roll-up 2m/70cm J-Pole Antenna yesterday. It’s wasn’t hard at all. The most difficult part was cutting the sheath of RG58 and RG316 off without cutting the ground braid. The trick was in a video - you bend the coax and just glide a blade over the sheath where it’s stretch and it pops open - kind of like surgery, where you stretch skin between fingers and cut.
Tuning is accomplished by moving the wire bridge at the bottom of the ladder line up/down and/or moving the coax feedpoint attachment up/down. I only tried the former as it was easier. Moving it up brought the SWR dip up from ~143 MHz to ~145 MHz but also raised the SWR low a bit. My RigExpert meter only goes to 230 MHz so I didn’t test 70cm. Maybe jiggering the feedpoint can broaden the range but I didn’t try.
I was shooting for 145.18 MHz (the average 2m Winlink gateway frequency) as I plan to use the J-Pole for digital work using an HT or IC-705. The final antenna will get a Velcro cable tie and a zip-tie hang loop at the top with some slick arborist line attached to a baby sock filled with lead shot, for tossing over low tree branches. I hope my wife doesn’t notice I raided her memento collection from our kids! The antenna is light enough to pull up with a telescopic carp pole - I got a long one and discarded the upper sections.
Tuning is accomplished by moving the wire bridge at the bottom of the ladder line up/down and/or moving the coax feedpoint attachment up/down. I only tried the former as it was easier. Moving it up brought the SWR dip up from ~143 MHz to ~145 MHz but also raised the SWR low a bit. My RigExpert meter only goes to 230 MHz so I didn’t test 70cm. Maybe jiggering the feedpoint can broaden the range but I didn’t try.
I was shooting for 145.18 MHz (the average 2m Winlink gateway frequency) as I plan to use the J-Pole for digital work using an HT or IC-705. The final antenna will get a Velcro cable tie and a zip-tie hang loop at the top with some slick arborist line attached to a baby sock filled with lead shot, for tossing over low tree branches. I hope my wife doesn’t notice I raided her memento collection from our kids! The antenna is light enough to pull up with a telescopic carp pole - I got a long one and discarded the upper sections.
