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(john.rabson@numeo.fr@217.67.155.178) by smtp.qtxt.dns-iol.com with SMTP; 9 Sep 2010 10:41:46 +0200 Mime-Version: 1.0 (Apple Message framework v1081) From: John Rabson X-Priority: 3 In-Reply-To: <7304C3CD17394F5B81C72D1A36628D0A@IBM7FFA209F07C> Date: Thu, 9 Sep 2010 10:47:29 +0200 Message-Id: References: <4C8686CF.9060100@iup.uni-heidelberg.de> <4C86A124.907@iup.uni-heidelberg.de> <7304C3CD17394F5B81C72D1A36628D0A@IBM7FFA209F07C> To: rsgb_lf_group@blacksheep.org X-Mailer: Apple Mail (2.1081) X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: Re: LF: 137.5kHz WSPR Tuesday evening - reports appreciated Content-Type: multipart/alternative; boundary=Apple-Mail-3-772171181 X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.9 required=5.0 tests=HTML_30_40, HTML_FONTCOLOR_UNSAFE,HTML_MESSAGE autolearn=no version=2.63 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false x-aol-global-disposition: G x-aol-sid: 3039ac1d60944c889e32655b X-AOL-IP: 193.82.116.20 X-AOL-SPF: domain : blacksheep.org SPF : none --Apple-Mail-3-772171181 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=iso-8859-1 Chris, I think your formula and Stefan's are equivalent but just expressed differ= ently. You use (Vpk * 0.707), square ithe result and divide it by the resistance= . He takes Vpk, squares it and then divides the result by 2 at the same time= as dividing by the resistance. (0.707 squared =3D 0.5) The mistake I have sometimes made is to read the peak to peak value from= the oscilloscope screen and forget to divide it by 2. Like Andy, I have sometimes obtained raw figures that suggest slightly ove= r 100% efficiency. Very careful checking of the various meters has resolve= d this. 73 John F5VLF On 9 Sep 2010, at 10:11CEST, Chris wrote: > Hi Stefan, > I thought the power was the RMS voltage squared (i.e. peak voltage X 0.7= 07) divided by the resistance. > Chris, G4AYT. > ----- Original Message ----- > From: Stefan Sch=E4fer > To: rsgb_lf_group@blacksheep.org > Sent: Tuesday, September 07, 2010 9:31 PM > Subject: Re: LF: 137.5kHz WSPR Tuesday evening - reports appreciated >=20 > Roger, >=20 > For measuring the output power take a 50 Ohm dummy load (50, not 55 Ohms= or so) and measure the peak voltage with an oscilloscope. Type this into= the excel file and calculate the output power (P=3D(=FB)^2/(2*R)). >=20 > 73, Stefan >=20 >=20 > Am 07.09.2010 21:32, schrieb Andy Talbot: >>=20 >> Take a look at G3NYK's Class E design page http://www.alan.melia.btinte= rnet.co.uk/classepa.htm >> =20 >> Don't even try biassing the FET with a pot. You must use a squarewave= drive- preferrable from a proper MOSFET driver like an ICL7667 or TC4426= type, or at a push a stack of paralleled 74C drivers will do.=20 >> =20 >> I measured somewhere between 85 - 103% efficiency for a 20 Watt design= running from 12V on 1.9MHz. Its very difficult to measure PA efficiency= properly at low frequencies as the HP432 power meter doesn't go below 10= MHz Judging by how not-hot the device got, looks to be around 90%. = See the next RadCom for more details. >> =20 >>=20 >> Andy >> www.g4jnt.com >>=20 >>=20 >> On 7 September 2010 20:08, Roger Lapthorn wro= te: >> Stefan/Mal, >>=20 >> Clearly my design was not working in class E properly as the PA was dis= sipating a fair amount of heat and it was taking about 0.8A to produce 40V= p-p output from a 13.8V supply which is about half as efficient as it sho= uld be. I took a PA design start from a design program I found on the net= by Tonne Software called "Class E" and the values seemed to be close to= optimum when I adjusted caps and L up and down a small amount, but the di= ssipation seems miles off what a good class E design should take. The IRF5= 10 gate voltage is set just below 3V with a resistive pot. The drive is no= t a square wave though, so I suppose this could be part of the issue? >>=20 >> Stefan, if you have a better class E PA circuit for 137kHz suitable for= around the 10-20W out region I'd be interested in seeing it. I would pref= er to use toroid inductors because of size. I have several T106-2 cores to= hand as well as several 16mm diameter 3C90 cores. >>=20 >> I'm still learning..... and not too proud to ask for help from those wi= th more experience. >>=20 >> 73s >> Roger G3XBM >>=20 >>=20 >>=20 >>=20 >>=20 >> 2010/9/7 Stefan Sch=E4fer >> Hello Roger, >>=20 >> Maybe you can send us a circuit with its values. I have built class E= PA for 2200/160/80/40/30/17/10m and have some experience. If you are usin= g a IRF510 and stay in the QRP range (< 10 W) at 137 in a class E stage yo= u wouldn't even need a heat sink at all if well dimensioned! >>=20 >> See the infos at http://www.classeradio.com/ This is most useful if yo= u are starting with that design. On 137 kHz problems are much smaller than= on HF :-) >>=20 >> Best 73, Stefan/DK7FC >>=20 >> Am 07.09.2010 20:17, schrieb Roger Lapthorn: >>> Just hit a bit of a snag and blew up my (last) IRF510 PA because of to= tally inadequate heatsink. So, I'm on 137.5kHz WSPR but only with about 1W= from the simpler PA at present, so ERP low uWs. I need to get some heats= ink and more FETs! >>>=20 >>> Any reports (now less likely) still appreciated. >>>=20 >>> [Mal - it started out as a Class E design attempt but hadn't been opti= mised, so I guess this counts as class D. ] >>>=20 >>> 73s >>> Roger G3XBM >>>=20 >>>=20 >>>=20 >>> On 7 September 2010 17:34, Roger Lapthorn wr= ote: >>> My 137.5kHz WSPR TX transverter is now working fine, so I'll be on-air= with WSPR tonight (Sept 7th) from 5.30pm - 11pm UK time.=20 >>>=20 >>> After my success on QRSS3 with G3XIZ I'm hopeful he'll now decode my= WSPR signal tonight, assuming Chris can take a listen. If anyone else wit= hin, say, 100km of Burwell, Cambs JO02dg cares to take a look for the WSPR= beacon (running around 35% TX time) I'd be most grateful.=20 >>>=20 >>> Not sure if anyone else has had this problem, but I was using the smal= l 16mm 3C90 cores (cream colour) as the PA bifilar output transformer and= I had all sorts of issues with the darn thing overheating and even one cr= acking. I replaced this with a choke wound on a T106-2 core and made the= output network work in class D/E and now everything is working very predi= ctably. The larger diameter 3C90 cores seem fine in the step-down transfor= mer matching the "in the air" loop. >>>=20 >>> The WSPR beacon is now going ON..... >>>=20 >>> 73s >>> Roger G3XBM >>>=20 >>>=20 >>> --=20 >>> http://g3xbm-qrp.blogspot.com/ >>> http://www.g3xbm.co.uk >>> http://www.youtube.com/user/g3xbm >>> G3XBM GQRP 1678 ISWL G11088 >>>=20 >>>=20 >>>=20 >>> --=20 >>> http://g3xbm-qrp.blogspot.com/ >>> http://www.g3xbm.co.uk >>> http://www.youtube.com/user/g3xbm >>> G3XBM GQRP 1678 ISWL G11088 >>=20 >>=20 >>=20 >> --=20 >> http://g3xbm-qrp.blogspot.com/ >> http://www.g3xbm.co.uk >> http://www.youtube.com/user/g3xbm >> G3XBM GQRP 1678 ISWL G11088 >>=20 >=20 --Apple-Mail-3-772171181 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=iso-8859-1
Hi Stefan,
I= thought the power was the RMS voltage squared (i.e. peak voltage X 0.707)= divided by the resistance.
Chris, G4AYT.
----- Ori= ginal Message -----
=
Sent:=  Tuesday, September 07,= 2010 9:31 PM
Subject: R= e: LF: 137.5kHz WSPR Tuesday evening - reports appreciated

<= /div>Roger,

For measuring the output power take a 50 Ohm dummy load= (50, not 55 Ohms or so) and measure the peak voltage with an oscilloscope= . Type this into the excel file and calculate the output power (P=3D(=FB)^= 2/(2*R)).

73, Stefan


Am 07.09.2010 21:32, schrieb Andy= Talbot:
Take a look at G3NYK's Class E desi= gn page h= ttp://www.alan.melia.btinternet.co.uk/classepa.htm
 
Don't even try biassing the FET with a pot.  You must use a= squarewave drive- preferrable from a proper MOSFET driver like an ICL7667= or TC4426 type, or at a push a stack of paralleled 74C drivers will= do. 
 
I measured somewhere between &n= bsp;85 - 103% efficiency for a 20 Watt design running from 12V on 1.9= MHz.  Its very difficult to measure PA efficiency properly at low fre= quencies as the HP432  power meter doesn't go below 10MHz  =   Judging by how not-hot the device got, looks to be around 90%. = ;   See the next RadCom for more details.
 
=
On 7 September 2010 20:08, Roger Lapthorn <rogerlapthorn@gmail.com> wrote:
Stef= an/Mal,

Clearly my design was not working in class E properly as th= e PA was dissipating a fair amount of heat and it was taking about 0.8A to= produce 40V p-p output from a 13.8V supply which is about half as efficie= nt as it should be. I took a PA design start from a design program I found= on the net by Tonne Software called "Class E" and the values seemed to be= close to optimum when I adjusted caps and L up and down a small amount,= but the dissipation seems miles off what a good class E design should tak= e. The IRF510 gate voltage is set just below 3V with a resistive pot. The= drive is not a square wave though, so I suppose this could be part of the= issue?

Stefan, if you have a better class E PA circuit for 137kHz= suitable for around the 10-20W out region I'd be interested in seeing it.= I would prefer to use toroid inductors because of size. I have several T1= 06-2 cores to hand as well as several 16mm diameter 3C90 cores.

I'm= still learning..... and not too proud to ask for help from those with mor= e experience.

73s
Roger G3XBM





2010/9/7 Stefan Sch=E4fer <schaefer@iup.u= ni-heidelberg.de>
Hello Roger,

Maybe you can send us a circuit with its val= ues. I have built class E PA for 2200/160/80/40/30/17/10m and have some ex= perience. If you are using a IRF510 and stay in the QRP range (< 10 W)= at 137 in a class E stage you wouldn't even need a heat sink at all if we= ll dimensioned!

See the infos at http://www.classeradio.com/  This is mo= st useful if you are starting with that design. On 137 kHz problems are mu= ch smaller than on HF :-)

Best 73, Stefan/DK7FC

Am 07.09.201= 0 20:17, schrieb Roger Lapthorn:
Just= hit a bit of a snag and blew up my (last) IRF510 PA because of totally in= adequate heatsink. So, I'm on 137.5kHz WSPR but only with about 1W from th= e simpler PA at present, so ERP low uWs.  I need to get some heatsink= and more FETs!

Any reports (now less likely) still appreciated.
[Mal - it started out as a Class E design attempt but hadn't been opt= imised, so I guess this counts as class D. ]

73s
Roger G3XBM
=


On 7 September 2010 17:34, Roger La= pthorn <rogerlapthorn@gmail.com> wrote:
My 137.5kHz WSPR TX tran= sverter is now working fine, so I'll be on-air with WSPR tonight (Sept 7th) from 5.30pm - 11= pm UK time. 
=
After my success on QRSS3 with G3XIZ I'm hopeful he'll now decode my= WSPR signal tonight, assuming Chris can take a listen. If anyone else wit= hin, say, 100km of Burwell, Cambs JO02dg cares to take a look for the WSPR= beacon (running around 35% TX time) I'd be most = ;grateful. 
Not sure if anyone else has had this problem, but I was using the small 16mm 3C90 cores (cream colour) as the PA= bifilar output transformer and I had all sorts of issues with the darn th= ing overheating and even one cracking. I replaced this with a choke wound= on a T106-2 core and made the output network work in class D/E and now ev= erything is working very predictably. The larger diameter 3C90 cores seem= fine in the step-down transformer matching the "in the air" loop.

= The WSPR beacon is now going ON.....

73s
Roger G3XBM


-- 
http://g3xbm-qrp.blogspot.com/
http://www.g3xbm.co.uk
http://www.youtube.com/use= r/g3xbm
G3XBM   GQRP 1678    ISWL G11088



-- 
http://g3xbm-qrp.blogspot= .com/
http://www.g3xbm.co.uk
http://www.= youtube.com/user/g3xbm
G3XBM   GQRP 1678   = ; ISWL G11088


-- http://g3xbm-qrp.blogspot.com/
http://www.g3xbm.= co.uk
http://www.youtube.com/user/g3xbm
G3XBM=    GQRP 1678    ISWL G11088



=3D --Apple-Mail-3-772171181--