[600MRG] Class E Keying

[John Langridge]

Hi Frank,

I can't really comment much on what you have provided above but...

There is option for what you are using now that will work well.

I will be referencing the GW3UEP shaped keying circuit on his basic IRF540
amp and have placed a copy of the schematic on my website as it was not
explicitly linked on Rog's parent site:
http://njdtechnologies.net/wp-content/uploads/2016/02/GW3EUP-keyed-pa.gif

So lets say you wanted to key the base GW3UEP amp, which you already own,
in order to achieve improved harmonic performance on CW. In your case, you
would implement the portion of the circuit at the top right of the
schematic built around the IRF9530 on the positive power lead input to the
amp.  Your driver could be any signal source and you simply key the
positive lead with a signal applied to the input.  The rise and fall times
are controlled and lead to a really nicely shaped waveform.

I have this particular keying method in my arsenal of 630-meter CW
transmitters, using Rog's homebrew VFO design based around a binary counter
feeding the input of the amp and I just key the power lead.  It works very
well and its very clean.  You might get better stability from a commercial
signal generator.  My VFO does tend to drift around a little but is often
pretty stable within a CW session.

That's one option.  I am sure you will get other recommendations.

73!

John KB5NJD / WG2XIQ..

On Thu, Feb 11, 2016 at 2:56 PM, Frank Lotito <k3dz at live.com> wrote:

> I am looking for suggestions on methods to key Class E RF Power Amplifiers
> for ON / OFF keying, be it at regular CW speeds, or QRSS speeds.  I assume
> this topic has been discussed in the popular literature, or special
> interest bulletin boards such at the 600mrg bulletin board.  Improper
> keying may generate key clicks with its resulting plethora of emissions on
> either side of the carrier.  This may be a moot point point for the QRSS
> mode, maybe not.
>
> ..........
>
> I found the 1997 May / June QST 2-Part article by Lau, et. al.  The
> article presents a drain (B+) keying circuit for the Class E amplifier's
> 120 VDC drain supply voltage.  For a specified power level a little simple
> theory gives the relationship that the (approximate) equivalent resistive
> load on the DC power supply at key down varies as the square of the ratio
> of drain voltage.  For example, double the design's drain voltage, the
> equivalent power supply resistance is 4 times that of the lower voltage
> design. Higher drain voltage designs may have an advantage as in the 1997
> QST article's power supply keying design if higher voltage components and
> semiconductors are available.
>
> ...................
>
> Besides voltage and current concerns, including the problem of obtaining
> appropriate RF current rated amplifier tuning capacitors, there is the
> matter of controlling the shape (rise and fall) of the keying waveform.
> This is mandatory to minimize key clicks.  Not easily done when the
> equivalent DC load resistance is only a few ohms.  The Lau design presents
> a method to shape the rise and fall times of the keyed power supply drain
> voltage.
>
> ...................
>
> Anything else out there published on keying Class E RF Power Amplifiers
> (the popular literature, or on an individual's or company's web site?)  I
> am assuming other designs might be more suitable for the more common 24 VDC
> systems. Your suggestions are welcome.
>
> .................
>
> 73 Frank Lotito  K3DZ / WH2XHA
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