The DBJ-2 Roll Up J Pole Antenna

On Jan 27, 2016, Edison Fong will discuss the design of the DBJ-1 and DBJ-2 antennas. These are roll-up J-pole antennas that are designed to work on both VHF and UHF amateur bands. A typical J-pole will only transmit well on one band or the other. Actually, a VHF roll-up J-pole can have good SWR on UHF due to 3rd harmonics, but the takeoff angle is too high to be of practical use in normal situations. However, through the use of tuning and detuning stubs and careful sectioning of the twin lead line, it is possible to construct a dual band roll-up J-pole antenna whose SWR does not exceed 1.7 across either band and with a low takeoff angle on both bands.

Ed's Briefing Charts
QST Article (March 2007)

Edison teaches RF wireless communications at UC Santa Cruz, and his graduate students build these antennas as part of their instruction. The antennas are sold on eBay, and proceeds are used to buy the materials for the antennas and pay labor costs for the graduate students. The DBJ-2 comes with male BNC connector. Also in the package is a 6ft piece of RG-58 with BNC connectors to extend the antenna and several connectors that will allow conversion to other connector types. The DBJ-2 can be purchased from Ed on eBay.