Specifications
Physical : 9.50 inch diameter, 4 antenna elements with BNC mounts Inputs : discrete antenna select lines, ( N-E-S-W ) TTL levels Power : not required ( switching signals only ) RF Output : BNC connector
General Description
The PicoDopp MiniAntenna board is an "evolved" legacy from the original Doppler DF "hobby" website. It is a fully integrated PC board antenna for VHF Doppler DFs, using a modified version of the Joe Moell wideband Doppler antenna design. The PicoDopp MiniAntenna is fabricated on a circular, 9.5-inch diameter thru-plated board that serves as a ground plane for the antenna elements. SMT components and stripline methods are employed on the board, to ensure good performance to 1000 MHz. The user must provide a mounting method, interconnecting cables, and ( if desired ) an enclosure or radome for the MiniAntenna.
The small physical size of the MiniAntenna makes it very convenient to install on a vehicle, and also convenient for storage. However, the reduced size of the antenna also causes reduced RF sensitivity for weak signals, especially at frequencies below 400 MHz. If weak signal performance is critical, especially below 400 MHz, the user should consider this deficiency before purchase. Operation with signals of moderate to high strength has been tested down to 100 MHz, with user reports of operation at even lower frequencies.
PicoDopp Connections
The figure below shows the PicoDopp connections for the MiniAntenna.
Technical Description
The MiniAntenna employs stripline PCB techniques and SMT components, to achieve good RF performance to 1000 MHz and beyond. SMT Agilent PIN diodes are employed ( HSMP3890 ) for antenna switching.The Joe Moell Doppler antenna design employs PIN diodes at each end of each antenna feedline, to eliminate ( wideband ) frequency sensitivity of the antenna. This would be caused by "resonant" antenna feedlines that ( without double-ended switching ) would cause load impedances ( observed by each antenna ) that vary radically, for large changes of signal frequency.
More Info and Inquiries
Download links to schematic diagrams and pictorials for the PicoDopp MiniAntenna are provided below. For additional information about the PicoDopp MiniAntenna board, inquire directly by e-mail to the development engineer : Bob Simmons
PicoDopp MiniAntenna schematic diagrams and board pictorials can be downloaded here :
PicoDopp MiniAntenna schematic ( 9 Kb GIF file )PicoDopp MiniAntenna pictorial ( 20 Kb GIF file )