IRF840?

Dino_24 · Post by **Dino_24** » Wednesday 12th Nov 2008, 4:38

I was considering an IRF520 in my cobra 29, but what about an IRF840? I know this mosfet is capable of around 125 watts max and I certainly wouldn't expect THAT much, but would the 29 produce sufficient voltage to obtain any noticeable results?

Rick · Post by **Rick** » Thursday 13th Nov 2008, 3:39

You would turn it on, as the input capacity is hi, and a very hi impedance at 27 MHz.

Dino_24 · Post by **Dino_24** » Thursday 13th Nov 2008, 9:51

Thanks for the reply. I'm a genuine novice when it comes to electronics and I've not had a whole lot of experience with MOSFETs. If the resistance is high at 27MHz, would that mean that the FET would become less efficient, producing more heat than RF power?

Rick · Post by **Rick** » Friday 14th Nov 2008, 3:09

I do not like getting to technical, but there is not that easy to answer.

Impedance is not Resistance.

Impedance is more complex than resistance because of the effects on a tune circuit.

You may find this article may help you understand impedance.
http://forum.ecoustics.com/bbs/messages ... 31527.html