Message-ID: <001301ce03c5$495bd9c0$0401a8c0@xphd97xgq27nyf>
From: "mal hamilton" <g3kevmal@talktalk.net>
To: <rsgb_lf_group@blacksheep.org>
References: <CAKvcm2edSxcESuKJR6yux7M-pBXE63rUVPbE98M-L6Mb8--cLg@mail.gmail.com>
Date: Tue, 5 Feb 2013 17:21:50 -0000
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Subject: LF: Re: My transmit converter description
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Dimitris
I do not understand how you have arrived at a 50ohm load output without a
matching transformer after the Tank circuit. The Fet Impedence is around 7
ohms and needs to be transformed to 50 ohms via a transformer, then a LPF is
necessary.
Have I missed something. Also your trailing waveform has a voltage spike
which means it is not switching at the correct time.
I have built this type of amplifier for 500 Kcs and found it worked as
specified after setting it up for spot on switching as instructed by the
designer.
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
>