A 30w dummy load really can’t handle 100w

Or at least that’s what I found out a few days ago… I was doing some tests on a bidirectional coupler (more about that project in a future post) and I didn’t pay enough attention so I cranked up the power of my transmitter to 100w. And, of course, after a few seconds I got the smell of burned electronics in my shack.
That’s when I decided to go through my junkboxes and find the resistor I once bought to build myself a decent dummyload.
These are the results:

The resistor is an RFP 250-50 TC so this should handle up to about 250w.
SWR between 160m and 6m is max 1.04:1. I have not tested any higher frequencies because my antenna analyser only goes up to 54 MHz.
The heatsink is salvaged from an old telephone switchboard (made by Bell Telephone in 1980).