Thank you all for your replies.
The author stated schotkky diodes there but no type. I tried bat84 and burned one of them (the low one) at 10W. I then tried the 1n5711 and again burned it out. Each time the diode burnt I sensed high vswr on the transceiver.
I checked the diodes with a multimeter (the diode function).
Instead of placing series resistors with the diodes, could you please suggest higher voltage/current diodes? I am not sure I can find that fast diodes (<30MHz) at that current/voltage.
I like the single scale feature of this simple meter as well as the passive circuit.