You can also get some TO-220 non-inductive resistors of a suitable
wattage, and mount those to the heatsink. 10-watt devices should be
OK, and 50 ohms is close enough.
Those devices aren't cheap, but they're effective. I use a 100-watt
50-ohm device mounted to a heatsink with an SO-239, and it's flat to
well over 100 MHz.
73
Jim N6OTQ
