Re: K3s driving a KPA1500 - how much drive power is nominal for 1500 watts? #kpa1500
Bob McGraw - K4TAX
Re dummy load. First measure it with an ohm meter. It should measure 50 ohms +/- 5% or better. Then measure it with your antenna bridge from the lowest to highest frequency you intend to use. An MFJ-259 or other known accurate bridge is suitable. Make sure you use a known good, short length, low loss coax as a jumper. The bridge should show 50 ohms and an SWR value of less than 1.2:1. Higher values indicated some value of reactance. A good dummy load will be resistive at all frequencies and show no reactance. The R value is resistance and the reactance is the “j” part of the impedance. Ideally it should be zero as measured on a VNA.toggle quoted messageShow quoted text
I’ve found that both the air cooled loads and the “gallon of oil” types will change values as they heat. Heat one with some RF and measure it again while hot. If you find it to be different when hot than when cold, just be forewarned what you have to consider when making power measurements.
It doesn’t take an expensive or precision load. It just takes knowledge and knowing what you are dealing with.
On Feb 5, 2020, at 9:26 PM, Mike VE3YF <mike@...> wrote: