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Date: Tue, 12 Jun 2012 07:21:22 -0400
Message-ID: <CAMFjj71GMe8j6TB06jVm0SVgyBtz2bBLdBCrZSrN=_2sEe+BCw@mail.gmail.com>
From: Warren Ziegler <wd2xgj@gmail.com>
To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: RE: Class E etc
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Years ago, several ham friends of mine have made valve type
transmitters run in Class-D or E on 75 and 40 meters, 500kHz should be
no problem at all.

73 Warren K2ORS



On Tue, Jun 12, 2012 at 7:15 AM, M0FMT <m0fmt@yahoo.co.uk> wrote:
> Hi Ken
>
> I believe you can operate=A0some thermionic devices in higher classes tha=
n
> C=A0but they generally lack the frequency response of a modern FET. I won=
't go
> into figures but just think about it. The high efficiency output stage ha=
s
> to operate like a switch it is not actually an amplifier. The faster it
> changes state from fully on with ultra low resistance to fully off
> (which=A0means a device that will operate=A0well into the=A0VHF)=A0the hi=
gher the
> efficiency. If you have a device that is barely rated to say a couple of
> megs its not going to be much good (in terms of what we are talking
> about)=A0at 500kc/s. Remember you are trying to get the magnetic field in=
 the
> inductor to rise and collapse at a very fast rate in-order to generate a
> high electromagnetic field at the drive frequency. We are not talking sin=
e
> waves here as a scope on the drain will show. Although a scope on the out=
put
> side of the drain inductor will show quite a clean looking sine wave. Try
> it.
>
> That chart at the end of that PDF file is very clever and is the guide=A0=
I use
> to bring a PA into optimum performance.
>
> What I was trying to say is that the math is all very well but if you are
> trying to make a practical and=A0efficient CW TX for LF then=A0there is e=
nough
> empirical data from following the guide lines lines shown on the sites I
> have posted=A0that will get you a good TX. If you want a doctorate in
> theoretical physics to bamboozle you colleagues then that will detract fr=
om
> the time it takes to build a very interesting high power, efficient=A0TX
> design well within anybodies capabilities.=A0The GW3UEP design being IMHO=
 a
> very good (Scalable) example with no=A0RadCom=A0style unobtainium in the
> components listing.
>
> 73 es GL Pete M0FMT IO91UX
> From: Ken <ken.h.wright@btinternet.com>
> To: rsgb_lf_group@blacksheep.org
> Sent: Monday, 11 June 2012, 22:09
> Subject: LF: RE: Class E etc
>
> Hi Pete.
> About 40 years ago my integration was quite good, liked doing 2nd order
> differential equations, partial integration and integration by parts, the
> one thing I had big problems with was 3 dimensional integration of a poin=
t
> in free space . =A0=A0Looking at some of the sites my Class C MOSFET PA i=
s
> probably more like Class E by default. The reason I like valves is becaus=
e
> they are very forgiving devices unlike semiconductors, also the keep the
> shack and the cat warm.
>
> 73s
>
> Ken
>
> M0KHW
>
> From: owner- rsgb_lf_group@blacksheep.org [mailto: owner-
> rsgb_lf_group@blacksheep.org ] On Behalf Of M0FMT
>
> Sent: 11 June 2012 19:16
> To: rsgb_lf_group@blacksheep.org
> Subject: LF: Class E etc
>
>
> Hi Ken
>
> Ha ha Stefan, how good is=A0your Integration Ken?
>
> Here are a couple of sites that should answer your questions. You need a
> good dummy load and a good oscilloscope. Setting the conditions for the
> amplifier is to do with=A0 A/ the correct driver preferably using a FET d=
rive
> chip (like TC4422 non and TC4421 inverting) that will turn the FET fully=
=A0on
> and fully off on each cycle. Very fast rise time with accurate=A0on off t=
iming
> (mark / space). Ensuring the=A0max permitted gate voltage for the FET=A0i=
s not
> exceeded otherwise they pop, look out for transients, a diode clamp helps=
.
> B/ Setting the shunt capacitance and inductance=A0in the drain=A0circuit =
can be
> done empirically See article below. Then follow it with=A0a=A0low pass fi=
lter,
> although the output wave will be surprisingly clean.=A0Calculating the va=
lues
> is difficult as you don't necessarily know all the starting=A0parameters =
and
> in any case=A0the result is=A0going to wide of the mark. The site below w=
ill
> gives some starting values. Best to use 'Scope measurements to set the
> output conditions. You are looking for fast, very fast On / Off rise time=
s.
> Gate drive and understanding the drain circuit is the key.
> These amplifiers are capable of incredibly good efficiency well above a
> dodgy class C amp. This means the heat dissipation from the FET is very l=
ow
> at high power=A0giving cool heat-sinks!
>
> The GW3UEP (do a web search) single ended design is capable good
> efficiency=A0and high power depending upon the FET used and Drain supply
> voltage. I have modified one to run reliably at 140watts and is capable o=
f
> almost twice that into a dummy load with a heat sink that is fairly cool.
> Adjusting L and C empirically using the 'scope to get the correct drain w=
ave
> shape for max efficiency is the way to go. The article below shows you wh=
at
> you are looking for. I set my TX up into a 50 Ohm dummy load adjusting L =
and
> C to get the correct drain wave shape on the 'scope then measuring the pe=
ak
> voltage across the Dummy load.=A0I then transfer my=A0connector from the =
Dummy
> load to the input of the tuned transformer in the antenna up-lead. I adju=
st
> the coupling link to give the same peak voltage=A0across the tuner link t=
urns.
> You are not looking for maximum peak just the sames as across the dummy l=
oad
> indicating a 50ohm match.=A0This is done by either=A0adding or reducing=
=A0the
> number of turns (about two turns) along with bringing the the transformer=
 to
> resonance by measuring the peak=A0up-lead current, here you are looking f=
or
> the maximum peak.
>
> Oh yes and WIMA high voltage high value capacitors from Maplin work well.
>
> Read the articles and search info on class E amplifiers.
>
>
> For some bed time reading but ignor the math look at the Tuning Procedure
> and the pictures at the end which tell it all really.....
> http://www.cs.berkeley.edu/~culler/AIIT/papers/radio/Sokal%20AACD5-powera=
mps.pdf
>
> For design ideas
> http://www.classeradio.com/
>
> For a good practical circuit for a single ended amp=A0that =A0is a scalab=
le
> surefire design, no need to reinvent the wheel.
> http://www.gw3uep.ukfsn.org/
>
> For antennas and antenna feed methods a "look no where else site"
> http://www.strobbe.eu/on7yd/136ant/
>
> 73 es GL Pete M0FMT IO91UX
>
>
>



--=20
73 Warren K2ORS
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 WD2XGJ
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 WD2XSH/23
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 WE2XEB/2
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 WE2XGR/1