Actually, it doesn't. Slap a flat plate over the end of a zero length waveguide and the SWR is infinite. Insert whatever you want in front of that and the SWR may measure something different, but it's still infinite:-) On 9/14/2016 1:11 PM, Michael Walker wrote: > inserting an SWR meter changes the SWR... > hopefullyby a neglible amount.* >