[600MRG] Class E Keying

[Jim Miller]

http://www.its.caltech.edu/~mmic/reshpubindex/papers/buckwalter.pdf

I think our emails crossed but here's a link to one I found. Published in
QEX!

73
jim ab3cv

On Thu, Feb 11, 2016 at 9:04 PM, Frank Lotito <k3dz at live.com> wrote:

> Jim AB3CV- Can you refer me to one or more "pulse width modulation"
> designs for keying the power supply voltage?  I assume someone has tried
> this  approach and wrote it up for publication in the popular press or
> Internet?
>
>
> 73 Frank K3DZ / WH2XHA
>
>
> ------------------------------
> *From:* jtmiller47 at gmail.com <jtmiller47 at gmail.com> on behalf of Jim
> Miller <jim at jtmiller.com>
> *Sent:* Thursday, February 11, 2016 5:48 PM
> *To:* John Langridge
> *Cc:* Frank Lotito; 600 / 630 Meter Group
> *Subject:* Re: [600MRG] Class E Keying
>
> 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
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