VIDEO:new bird wattmeter model #43, here i show you what a slug is and the elements this term refers to. How to install an element and why they are rated differently.These meter are super quality, and can be trusted accurate as long as the correct element has been chosen for the expected power output of the transmitter radio.
Inline between the source and the antenna or dummy load is the accepted placement of these wattmeter hence the name thruline.