Return-Path: Received: from mtain-da04.r1000.mx.aol.com (mtain-da04.r1000.mx.aol.com [172.29.64.76]) by air-db02.mail.aol.com (v127_r1.1) with ESMTP id MAILINDB021-85ee4b7aed7d60; Tue, 16 Feb 2010 14:09:49 -0500 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-da04.r1000.mx.aol.com (Internet Inbound) with ESMTP id E830B3800036E; Tue, 16 Feb 2010 14:09:45 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1NhSmD-00060C-Td for rs_out_1@blacksheep.org; Tue, 16 Feb 2010 19:08:05 +0000 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1NhSmD-000603-5D for rsgb_lf_group@blacksheep.org; Tue, 16 Feb 2010 19:08:05 +0000 Received: from mail.gmx.net ([213.165.64.20]) by relay1.thorcom.net with smtp (Exim 4.63) (envelope-from ) id 1NhSm8-0003XR-5z for rsgb_lf_group@blacksheep.org; Tue, 16 Feb 2010 19:08:05 +0000 Received: (qmail invoked by alias); 16 Feb 2010 19:07:46 -0000 Received: from p5DD3484B.dip.t-dialin.net (EHLO Clemens04) [93.211.72.75] by mail.gmx.net (mp038) with SMTP; 16 Feb 2010 20:07:46 +0100 X-Authenticated: #17214767 X-Provags-ID: V01U2FsdGVkX1/1eJwRSTL1BL77pTbPrR5ScKTN6PjaAeOrhxMKrn Z6EStxqJOXX3xc Message-ID: <006501caaf3b$53ddb350$0201a8c0@Clemens04> From: "Clemens Paul" To: References: Date: Tue, 16 Feb 2010 20:07:39 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.3598 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3350 X-Y-GMX-Trusted: 0 X-FuHaFi: 0.46000000000000002,0.46999999999999997 X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: Re: LF: RE: PA matching oddity Content-Type: multipart/alternative; boundary="----=_NextPart_000_0061_01CAAF43.B0831250" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.8 required=5.0 tests=HTML_30_40,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: 3039ac1d404c4b7aed794d03 X-AOL-IP: 193.82.116.20 ------=_NextPart_000_0061_01CAAF43.B0831250 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Andy,Rik, after thinking a while over the transformer of Andy's PA and referring= to http://www.g4jnt.com/pamatch.gif I'm sorry to say that I'm still quite (say 99,9%) sure that it is a conventional 1:9 (Z) tra= nsfomer. Here are some crucial points which exclude *absolutely* the above desi= gn to be an autotransformer,(1:16 or whatever). 1.) Autotransformers provide no dc isolation, i.e. you have a dc path= from the primary to secondary side. There is no such dc path here. 2.)In a bootstrap design the braid of one coax end is connected to the= center conductor at the start of the same coax (1:4) or of the next coax se= ction (1:9 or higher). This is not the case in this design.The center of the secondary is now= here connected with a braid. BTW there is no reason to worry about the theoretical 900W limit in li= near mode. If the PA is slightly overdriven you get easily one 1dB more power on= the fundamental frequency which is about 1133W so you have enough margin for losses of= the low pass filter losses etc. It's very unlikely that this PA which was used as industrial RF heater was designed to be superlinear. 73 Clemens DL4RAJ ----- Original Message -----=20 From: Andy Talbot To: rsgb_lf_group@blacksheep.org Cc: ukmicrowaves@yahoogroups.com Sent: Tuesday, February 09, 2010 10:43 PM Subject: Re: LF: RE: PA matching oddity BINGO - Tnx Rik, thats it, convincing. Sorted So my thing IS 1:4 turns ratio, (1:16 Z ratio) just as the calcula= tions said it needed to=20 be, and is indeed, effectively, an auto transformer. Otherwise known= as a bootstrapped coaxial=20 transformer, but just configured with different reference points to co= nfuse everyone. Your=20 second reference, the Semelab paper, (UKuW see below) gives the answe= r. Look at page 10, the 1:9 Ruthroff UnUn . With just two bits of= coax, which are then=20 bootstrapped up on top of the input to give a 3:1 ratio (for 1:9 imped= ance). Add another turn,=20 so three windings are bootstrapped on top of the primary, rearrange= the grounding points and=20 there, in all its glory, is my mystery. The reference / grounding points can be shifted as the mosfet PA ha= s two separate, non=20 magnetically linked cores. This is is just normal push-pull HF PA pra= ctice, and being so normal=20 in its concept, completely hides hides a big real advantage - it enabl= es the designer to float=20 just whatever ternainals need to be floated for balanced / unbalanced= operation, and even to=20 provide DC isolation, Any conductor passing through the core allows= one end to be completely=20 Rf decoupled from the other end, so that's how balanced operation is= permitted with the basic=20 Ruthrof design shown in the paper. On the same page, a single length of coax is shown giving 1:2 transf= ormation by the same=20 bootstrapping arrangement, and when the transmision line is shown as= a twisted pair rather than=20 coax, then wrapped on a torroid, it becomes the 1:4 balun beloved of= HF antenna constructors.=20 A natural progression that helps illustrate the concept of a loop of= coax giving one turn more=20 than it appears to. It all falls out. ... life is worth living again ... ... can retire happy ... Andy www.g4jnt.com ... now, next job, how to sort out the world financial crisis ... On 9 February 2010 19:53, Rik Strobbe = wrote: Andy, have a look here : http://www.polyfet.com/HFE0503_Leong.pdf http://www.semelab.com/rf/documents/Push-Pull%20Circuits%20and%20W= ideband%20Transformers.pdf 73, Rik ON7YD - OR7T ----------------------------------------------------------------------= ------ Van: owner-rsgb_lf_group@blacksheep.org [owner-rsgb_lf_group@black= sheep.org] namens Andy=20 Talbot [andy.g4jnt@googlemail.com] Verzonden: dinsdag 9 februari 2010 18:10 Aan: rsgb_lf_group@blacksheep.org; ukmicrowaves@yahoogroups.com Onderwerp: LF: PA matching oddity ----------------------------------------------------------------------= -------- Eingehende eMail ist virenfrei. Von AVG =FCberpr=FCft - www.avg.de Version: 9.0.733 / Virendatenbank: 271.1.1/2677 - Ausgabedatum: 02/0= 9/10 08:35:00 ------=_NextPart_000_0061_01CAAF43.B0831250 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Andy,Rik,
 
after thinking a while over the trans= former of=20 Andy's PA and referring to
I'm sorry to say that
I'm still quite (say 99,9%) sure= that it=20 is a conventional 1:9 (Z) transfomer.
 
Here are some crucial points which&nb= sp;exclude=20 *absolutely* the above design
to be an autotransformer,(1:16 or whatever).
1.) Autotransformers provide no= dc isolation,=20 i.e. you have a dc path from
the primary to secondary side.=
There is no such dc path=20 here.
2.)In a bootstrap design the = braid=20 of one coax end is connected to the=20 center
conductor at the sta= rt of the=20 same  coax (1:4) or of the next  coax section (1:9 or=20 higher).
This is not the case in this design.<= STRONG>The=20 center of the secondary is nowhere connected
with a braid.=
 
BTW there is no reason to worry about= the=20 theoretical 900W limit in linear mode.
If the PA is slightly overdriven you= get=20 easily one 1dB more power on the fundamental
frequency which is about 1133W so you= have enough=20 margin for losses of the low pass filter
losses etc.
It's very unlikely that this PA which= was used as=20 industrial RF heater
was designed to be superlinear.
 
73
Clemens
DL4RAJ
 
 
 
 
----- Original Message -----
From:=20 Andy Talbot
Sent: Tuesday, February 09,= 2010 10:43=20 PM
Subject: Re: LF: RE: PA match= ing=20 oddity
=
BINGO -  Tnx Rik, thats it, convincing.  So= rted
 
So my thing  IS 1:4 turns ratio, (1:16 Z ratio)  = ;just as=20 the calculations said it needed to be, and is indeed, effe= ctively,=20 an auto transformer.  Otherwise known as a bootstrapped coaxial= =20 transformer, but just configured with different reference points&nbs= p;to=20 confuse everyone. Your second reference, the Semelab paper= , (UKuW=20 see below)  gives the answer.  
 
Look at page 10,   the 1:9 Ruthroff &n= bsp; UnUn=20 .   With just two bits of coax, which are then= =20 bootstrapped up on top of the input to give a 3:1 ratio (for 1:9=20 impedance).   Add another turn, so three windings are = ;=20 bootstrapped on top of the primary, rearrange the grounding points= and there,=20 in all its glory, is my mystery.   
 
The reference / grounding points can be shifted as the mosfet= =20 PA  has  two separate, non magnetically=20 linked cores.  This is is just normal push-pull HF PA= practice,=20 and being so normal in its concept, completely hides hides = ;a=20 big real advantage - it enables the designer to float just what= ever=20 ternainals need to be floated for balanced / unbalanced operation,= and even to=20 provide DC isolation,   Any conductor passing through the= core=20 allows one end to be completely Rf decoupled from the other end= , so=20 that's how balanced operation is permitted with the basic Ruthrof de= sign shown=20 in the paper.
 
On the same page, a single length of coax is shown giving= 1:2=20 transformation by the same bootstrapping arrangement, and when the= transmision=20 line is shown as a twisted pair rather than coax, then wrapped on a= torroid,=20 it becomes the 1:4 balun beloved of HF=20 antenna constructors.   A natural progression that he= lps=20 illustrate the concept  of  a loop of coax giving one turn= more than=20 it appears to.
 
It all falls out. 
... life is worth living again ...
... can retire happy ...
 
... now, next job, how to sort out the world financial crisis= ...=20

On 9 February 2010 19:53, Rik Strobbe <= Rik.Strobbe@fys.kuleuven.be>=20 wrote:
Andy,<= /FONT>
 
have a look here :
 
 
73, Rik  ON7YD -= =20 OR7T
 
Van: owner-rsgb_lf= _group@blacksheep.org [owner-rsgb_lf_group@blacksheep.= org] namens Andy Talbot [andy.g4jnt@googlemail.com]
V= erzonden: dinsdag 9=20 februari 2010 18:10
Aan: rsgb_lf_group@blacksheep.= org; ukmicrowaves@yahoogroups.com
Onderwerp:= LF: PA=20 matching oddity

 


Eingehende eMail ist virenfrei.
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