Chris
Ah according to my notes the peak voltage if you verge on Class E can
approach 4 times the supply.....I think that might be your problem. This is
necessary to allow a bit of headroom when tuning as "odd" reactances at the
drain will cause the peak drain voltage to soar. I use 200V devices up to
about 40 -45 volts supply and 500V above that. If you are transformer
driving I assume you have a negative voltage clamp (diode)
Alan G3NYK

----- Original Message -----
From: "OSBORN, Chris" <[email protected]>
To: "LF Group (E-mail)" <[email protected]>
Sent: 28 September 2005 10:43
Subject: LF: Advice will be gratefully received

The PA FET's in my new home brew transmitter keep exploding !

I'm using push-pull  IRF520's rated at 100 V Vds and my supply is 30
volts.
I am careful not to exceed the V gs.

The gates are driven with a toroidal transformer and the whole
circuit is just a scaled up version of my original TX, which works fine.
It generates healthy power into a 50 ohm dummy load but on
connection to the aerial circuit - bang !
The aerial system is identical to that used with the old TX !

Has anyone any ideas on what's causing the problem and how to cure
it ?

I'm running out of FET's and my nerves are somewhat frayed (shell
shock!)

73 Chris G3XIZ

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