From: Dimitrios Tsifakis <[email protected]>
To: [email protected]
Sent: Tuesday, 5 February 2013, 9:28
Subject: Re: Re: LF: My transmit converter description

Hi Eike,

you are right, the drain voltage waveform is not perfect! I have since
corrected the duty cycle on the gate to be exactly 50%. I have also
added two 200 V zener diodes from the drain to the source. This will
clamp the voltage to 400 V which is quite safe for a 500 V FET. The
zener diodes together with the fuses, I think, make this design pretty
bullet proof.

73, Dimitris

PS Nothing wrong with your english :-)


2013/2/5 Eike Katzera <[email protected]>:
> Hi Dimitros,
> the pulse shape in this picture does not look good:
> http://people.physics.anu.edu.au/~dxt103/472/nltt/vk1sv-drain.jpg
> The reason seams to be the duty cycle at the gate. Please try to change R5
> to a 100k potentiometer and trim it to a clean single Pilse an the drain. I
> solved the same problem tha way in my PA, wich killed my IRF540.
> Kind regards
> Eike DL3IKE
> PS: sorry for my english ;)
> Gesendet: Dienstag, 05. Februar 2013 um 08:45 Uhr
> Von: "Victor van Kooten" <[email protected]>
> An: [email protected]
> Betreff: Re: LF: My transmit converter description
> Looks very nice Dimitris,hope to see/hear you soon,
>
> 73
>
> Victor
>
>>>> Dimitrios Tsifakis <[email protected]> 05/02/2013 01:50 >>>
> Hello group,
>
> My transmit converter is now finished and tested - it survived two
> sessions of 50% duty cycle WSPR transmissions on 475 kHz and the
> results are great. I thought others may find this useful, so I have
> put a write-up on my web page:
>
> http://people.physics.anu.edu.au/~dxt103/472/nltt/
>
> It is a 50 W class-e PA designed for 50 ohm impedance, so there is no
> need for an impedance transformer. Doesn't get simpler than that :-)
> The driving circuit is based on G3XBM Roger's design with the
> difference of a 10 MHz OCXO LO and the addition of a beefy MOSFET
> driver.
>
> 73, Dimitris VK1SV
>
>
>
>