[600MRG] Class E Keying

[Jim Miller]

I would think at the 5-10ms rise/fall time needed for good shaping that a
PWM approach would work on the drain supply line.

73

jim ab3cv

On Thu, Feb 11, 2016 at 4:12 PM, John Langridge <kb5njd at gmail.com> wrote:

> 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
> > _______________________________________________
> > 600MRG mailing list
> > 600MRG at w7ekb.com
> > http://w7ekb.com/mailman/listinfo/600mrg_w7ekb.com
> >
> _______________________________________________
> 600MRG mailing list
> 600MRG at w7ekb.com
> http://w7ekb.com/mailman/listinfo/600mrg_w7ekb.com
>