RE dummy load.
ok found plans for bigger dummy load..but need supplier of non inductive
50r
resistor..needs to take full legal load for long as possible..( or 300w
continous)intend to use ARRL suppy dummy load design..
UK supplier would be nice but anywhere will do..
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Suggest you check with Mainline Electroniscs - Leicester.
They probably still have T0220 packaged non-inductive resistors of
25 -50 -100 Ohms.
You might have to use a number to make up a package of 50 Ohms which can
absorb 300 Watts.
These resistors are fine well up to 300 MHz.
You obviously need a substantial heatsink to get rid of the heat.

A US manufacturer of these resistors is Caddock (their UK agent is/was
Rhopoint Ltd -Oxted , Surrey ,tel: 01883-717988)

Their Cooltab TO220 power film resistors ,model MP820 -20 Watts come in a
range of 1 Ohm to 10 kOhms .

Good Luck

Frank GM0CSZ / KN6WH