RF workbench

Posted on Feb 6, 2014

Focus on measuring low-level, HF circuits with a return loss bridge ” topics such as using the bridge for antenna matching are omitted and readily found on the web. This web page contains minimal text and just relies on simple diagrams and photographs to transfer ideas and knowledge. Information regarding wideband bridge network function may be found elsewhere on this and other web sites and

RF workbench
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in EMRFD. Equipping for a 50 measurement environment in 2010 greatly improved my design capacity. The 50 terminated oscilloscope makes a sensitive and accurate detector for return loss measurement. Discussion about using a 50 oscilloscope termination is on the RF Workbench 1 web page. Above left ” The RLB and measurement set up from EMRFD. Occasionally, you may see bridges using a different balun transformer wiring as shown to the right of this figure. Above ” All the needed parts to home build a return loss bridge. For some, the parts investment might seem substantial, but what hobby isn`t expensive If you consider the cost of commercially manufactured bridges, a homebrew solution seems a bargain. Recycled parts and a home-built chassis are inviting cost-containment techniques. See the web site of Jim, K8IQY for an example of a homebrew RLB chassis. Jim, a Manhattan style construction wizard, builds the nicest looking gear ” he puts me to shame. Above ” A completed bridge. I used 1% tolerance 49. 1 ohm resistors and an FT50-43 ferrite toroid for the bifilar wound transformer. Inductance = 38. 4 uH. Many builders use the FT37-43 ferrite core. I prefer using 2 colors of enamel coated wire to avoid confusion when building stuff with transmission line style transformers and all I had in 2 colors was 24 gauge wire The bigger size ferrite toroid better accommodates the 24 gauge wire, plus photographs better. Above ” Measure the...

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