VHF-UHF Antenna Analyser |
This RF Wheatstone bridge can measure accurately the SWR & Impedance (MFJxxx uses this model of RF bridge)
For best result use SMD resistors(2x100 or 3x150ohms in parallel connection)
The FR4 pcb was replaced with a "ugly" construction. Now the maxium frequency is >500MHZ with very good precision.
For antenna connector use only N or SMA types. SO-239 introduce high errors of SWR measurements and is suitable only for HF range.
Optimal input power is 1-2W. For short test i use 5W delivered from an FM handy, without any SMD resistor burned...
Use short connections, quality connectors, SMD resistors and Schottky diodes.
Inside of my RF bridge
YO4SAZ construction
WK5JST UHF Aerial Analysers (pdf)
GM3VLB HF Version (pdf)