RF amplifier - why typically 4:1 transformer on input

[Al (astral highway)]

Originally Posted by Argus25

http://www.communication-concepts.com/rf-transformers/

CCI also make great amplifier modules & kits.

Thank you, Argus25. That's brilliant.

Thanks also for the circuit diagram of the 1.4MHz RF amplifier; I like the design and will investigate.

[mole42uk]

Originally Posted by MrBungle

It's quite surprising the current you can switch with them. If RDS(on) is low you can sling ridiculous amounts of current. It wasn't unusual to have RC PWM speed controllers switch 120A or so in a little box an inch square with a tiny heat sink

We used to manufacture a PWM speed controller for electric flight model aeroplanes with about ten BUZ11 and no heat sink at all! ISTR it was quite efficient.