Hugh.

Quick and dirty way....
Fire up a 100W jap rig on 160 into a 50 ohm load. At full welly of 100W you
should read 1.4A into the load. If the tx has a power meter or you have an
external one in line then you can set it to exactly 100W. Most rigs give
about 110 or 120 flat-out. If it were 120W you should read 1.55A so you
won't be far out.
I just calibrated mine against a thermocouple ammeter which I checked with
50Hz and a DMM.

Dave  G3YXM.

But how can I calibrate it - how do I know that an indicated Amp really is
an Amp.
My DVMs, being intended for mains current measurement, don't have the
frequency response.
How have other people done it ?  Any ideas ?
73
Hugh M0WYE