Re: LF: Re: My transmit converter description

["mal hamilton" <g3kevmal@talktalk.net>]

Pete

I have built and used class E amps for years and have always succeeded in getting a rounded off  trailing edge presentation on the scope.

If the amp is aligned properly as per Sokai instructions the perfect Drain wave is achievable otherwise the voltage spikes present will kill the Fet eventually. If it is used in a QRP rig of a few watts with a hefty FET I expect you will get away with it but then it is not really class E.

g3kev

 

 

----- Original Message -----

From: M0FMT

To: rsgb_lf_group@blacksheep.org

Sent: Tuesday, February 05, 2013 1:22 PM

Subject: Re: LF: Re: My transmit converter description

Hi Mal and group

 

The Drain wave trailing edge spike is shown clearly in this PDF on microwave Class e amps although microwave the principle applies to MF as well. In the PDF, Nathan O. Sokal author, has produced a IMHO cool chart to track the changes necessary to produce the near perfect Drain wave. To save reading the whole thing scroll to the end of the article and see the chart.

I have played with the drain wave on one or two HB amps and the chart works as advertised.... no sums just cut and try!   http://www.cs.berkeley.edu/~culler/AIIT/papers/radio/Sokal%20AACD5-poweramps.pdf

73 es GL Pete M0FMT IO91UX

From: mal hamilton <g3kevmal@talktalk.net>
To: rsgb_lf_group@blacksheep.org
Sent: Tuesday, 5 February 2013, 12:16
Subject: LF: Re: My transmit converter description

Dimitris
Your 'scope shot of the signal after the low pass filter shows a Voltage
spike which should not be there for a class E amplifier. This needs to be
smoothed out otherwise you wil eventually Zap the PA Fet.
You need to adjust L2 to correct this problem.
de Mal/G3KEV

----- Original Message -----
From: "Dimitrios Tsifakis" <dtsifakis@gmail.com>
To: <rsgb_lf_group@blacksheep.org>
Sent: Tuesday, February 05, 2013 12:50 AM
Subject: LF: My transmit converter description


> 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
>