[Boatanchors] RF current sensor

[Dave Brown]

In my post on this yesterday I mentioned using perhaps a 4k7 resistor 
across the output winding on the 1 turn primary, N turn secondary rf 
current transformer. That is waay too high (maybe I was, at the time!)

Assuming the 1 turn primary is in a nominal 50 ohm system , the load 
resistor on the secondary should be no more than 100 ohms-and should 
ideally be a lot less, but that depends on the meter sensitivity and 
how many turns on the toroid and such things. Start with it around 47 
ohms not 4k7, and go up or down from there.

The sensitivity pot can be 4k7 or even higher, especially if you have 
a very sensitive meter movement. Use a shottky diode if you need to 
see low power levels-they have a lower turn-on knee voltage than the 
nominal 0.7 volts for ordinary silicon diodes like the 1N4148 etc.

73
Dave, ZL3FJ