Im building a HF linear using four PL519's. Can i use 2oz copper PCB for
the base to fit the valves too?????? as Im not very good at cutting and
messing with metal.
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Don't understand what you mean with '2 oz copper PCB' ,but any fibreglass
single or double sided PCB would be suitable , provided you don't put heavy
stuff on it like PS transformers etc. If double sided make sure both sides
make good galvanic contact at various locations.
I also like using PCB for (not too large) chassis and enclosures. Same
material screens can be readily soldered-in. Another advantage is that where
necessary components can be bonded to ground (chassis) directly.

Frank GM0CSZ / KN6WH