I made a directional coupler. I used the 'Wainwright' 50 ohm strips - these are
strips of PC board with the the correct width of track for 50 ohms and with glue
on the back - and stuck them to a sheet of aluminium. Another track suitably
close gives and terminated at one end gives a coupler with around 30dB of
directivity, and a coupling factor that increases at 6dB/octave. G4DGU had one
made out of PCB many years ago: that one had N connectors for the mainline, and
happily handled 1kW at 432MHz.
Strips around 10cm long spaced about 1 cm centre to centre give a coupling of
about 40dB at 30MHz, decreasing at 6dB/octave. You can then use an attenuator
prior to the spectrum analyser.
73
Peter G3RZP
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