Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on lipkowski.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=5.0 tests=FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS,HTML_MESSAGE,RCVD_IN_DNSWL_MED, SPF_PASS,T_DKIM_INVALID autolearn=ham autolearn_force=no version=3.4.0 X-Spam-DCC: : mailn 1480; Body=2 Fuz1=2 Fuz2=2 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by lipkowski.org (8.14.4/8.14.4/Debian-8+deb8u1) with ESMTP id v3JC43cQ016196 for ; Wed, 19 Apr 2017 14:04:04 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1d0oGu-0001CK-Bo for rs_out_1@blacksheep.org; Wed, 19 Apr 2017 12:59:44 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1d0oGn-0001CB-Lz for rsgb_lf_group@blacksheep.org; Wed, 19 Apr 2017 12:59:37 +0100 Received: from mail-yw0-x230.google.com ([2607:f8b0:4002:c05::230]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) (envelope-from ) id 1d0oGj-000220-Tf for rsgb_lf_group@blacksheep.org; Wed, 19 Apr 2017 12:59:36 +0100 Received: by mail-yw0-x230.google.com with SMTP id j9so9274292ywj.3 for ; Wed, 19 Apr 2017 04:59:32 -0700 (PDT) X-DKIM-Result: Domain=gmail.com Result=Good and Known Domain DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to; bh=Hw8akSRs+Tmv6hHu9qlZfkTsrbj3Gqr4WQzgzR6L0Jc=; b=nBg/Hz35l8ywazIUMhE59XWrMYKM1oAGvWhkL/BAriOBGvLioOh1eOfs0ZtB3Db4Fq kdGr5kbpTP98Cv0xQgcWlaPeKYw9I0A+G4xdNTpklUyKwcjgVtnqdfieZnLgj750BFgi Cnx5LzDPHbj5Maugy0bSjxv3uS6j0j+s5qh6sg52pSqbT3MooLlEFNpNPwy0aH44OuyB sOCsWLMZ7yTBsAVvOB3AVUlOo04YjqG0n6iuhW9FWmeVDYAeGHOjAdh3AQqZ5P3uVmv4 4JmYhIUnhn2qTBGSvLNHeGFyjwfxyGTFPhYSOfFzdyqqczqUVlmr1Ta8reOYGXGrSWpr X7fg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to; bh=Hw8akSRs+Tmv6hHu9qlZfkTsrbj3Gqr4WQzgzR6L0Jc=; b=Klz2o1VTcuiEa10KPCtb7+rQDmv5Oyu3kmWpN5HhVYinD71arZ7crI1X0qLZe9suVo 11nP9bu/g/Luzbfjng1NsT2T04wLx86c0t+3BH/sPTKWz4RXEkENZetsRAhe+n9RZ7KD vntl4NMBaymZfcHRlAGAd0/s5qfC+Hnp9hm08TitkqP7DnplScwXmL2mmqHlBFJARjmJ PZDP+Z3gphka5iGIpeVZ23eytqTrObkwA4/BRwTa8uN/qyFJFas3H1MjZUZVwvT6tehH qHfkE9TAK6gYy/lSmg13VulOLeKZGI+EulgapgY0vs9MK94qd5Wa0V30mBjHadZllPqr 2g6g== X-Gm-Message-State: AN3rC/5sjJ0NrBongVQm/2/4tvoOgvHc2Bb+NS0BCez8+sQRO/caQ4nZ S58Zgb1bZZaJWcUO+Sa9DsD2aiJJEF/L X-Received: by 10.129.88.8 with SMTP id m8mr1851527ywb.62.1492603170772; Wed, 19 Apr 2017 04:59:30 -0700 (PDT) MIME-Version: 1.0 Received: by 10.129.173.1 with HTTP; Wed, 19 Apr 2017 04:59:30 -0700 (PDT) In-Reply-To: <58F722C9.5010003@posteo.de> References: <15b72b3360e.marcocadeddu@tin.it> <731997437.20170416124847@gmail.com> <58F525B4.9090008@posteo.de> <1229336941.20170418125840@gmail.com> <58F60567.20001@posteo.de> <58F63C48.4020006@posteo.de> <58F722C9.5010003@posteo.de> From: Andy Talbot Date: Wed, 19 Apr 2017 12:59:30 +0100 Message-ID: To: rsgb_lf_group@blacksheep.org X-Scan-Signature: 94b4899eb522d3cd83a8c4d63d16b91e Subject: Re: LF: A transductor for power regulation? Content-Type: multipart/alternative; boundary=001a11493038c8e3e9054d83c15d 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-Scanned-By: MIMEDefang 2.75 Status: O X-Status: X-Keywords: X-UID: 11392 --001a11493038c8e3e9054d83c15d Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable The easiest way to think of a transformer , I believe, is to accept it has "infinite" (oar at least arbitrarily high) inductive reactance, and that part of it can be ignored. So an open circuit on the secondary is transformed to an open circuit on the secondary; ditto a short circuit. And any impedance by N squared. A practical "very high" Xl is ensured by using high Ue ferrite, and using enough turns that your ferrite is not degraded by saturation. As soon as that "infinite" inductance begins to drop, it appears in parallel with the pri / sec and contributes to the transformed load impedance. Which lowers it with shunt inductive reactance. Even worse is when the ferrite is driven into saturation, and the AC component drives it around the B-H hysteresis curve. This dissipates energy in the core, and dissipated energy appears [electrically] to be added resistance. Whether it appears in parallel or in series is moot; it is there, and dissipating. A tapped inductor, or two coupled inductors may have an incidental impedance transforming action , but if the inductance, or Xl, is significant and enters the matching or load impedances - it is NOT a transformer It is a pity that transformers and inductors both have the same circuit symbols, and similar wound construction in some cases. So trying to control a transformer with DC saturation is very definitely not on. But controlling a saturable inductor very definitely is acceptable. If that inductor happens to be part of a matching network, or be tapped, or have two windings - you have to study , calculate and think what it is going to actually do Andy G4JNT On 19 April 2017 at 09:41, DK7FC wrote: > Hi Andy, > > Yes yes, i agree, and that's what i don't fully understand yet. Last nigh= t > i played a bit with the transductor that is laying arround here in a > cupboard. It didn't take much time to build up a 1:1 transformer. I took = my > small MF PA and a 50 Ohm dummy load. I watched the sine wave across the R > with a scope. About 50W were passed through the transformer. Then i start= ed > to run a DC current into the saturating coil. The amplitude on the dummy > load decreased but the PA consumed even more current! Not a good working > point. > But then, how is this transformer working? It looks like it can only work > in a series resonant circuit, as you say. So it is not really a transfrom= er. > Actually i built something similar a few months ago, when i wanted to > increase the resonance frequency of a HV mains transformer (antenna C =3D= 480 > pF switche in parallel to the HV winding). The idea was to saturate the t= wo > outher legs of the tripple leg transformer which has its windings on the > center leg... > > 73, Stefan > > > Am 19.04.2017 08:59, schrieb Andy Talbot: > > Stefan > your idea of saturating the transformer is, I think, flawed. If you > reduce mu-r of the core by saturating with DC, the primary winding will > have vastly reduced inductance and appear as a near short circuit to the > transmitter - not what you want > > The idea of saturable reactors applies to resonant inductors, where you > use the DC to change the inductance. So it could be applied to a class= D > transmitter with a tank arrangement, to retune the tank circuit to adjust > for match, or control amplitude. > > Andy G4JNT > > On 18 April 2017 at 17:18, DK7FC wrote: > >> Hi all, >> >> I'm just thinking about transductors and find them them quite fascinatin= g >> again. I read a bit Wikipedia and thought about the use as a steerable >> transformer. >> Imagine you have a hard switching class D PA, H bridge or so. The output >> is a constant voltage source and it is no problem to connect no load, as >> long as a proper type of low pass filter is used. >> Then imagine a simple 1:1 ferrite transformer, 50 Ohm to 50 Ohm. The >> transformer has a 3rd winding for a DC current (to compensate the AC >> component transformed from the RF windings, 2 cores must be used, which = are >> in parallel for the RF and anti-serial for DC). >> Then i can saturate the transformer with the DC so the =E7=9A=B4 falls d= own to 1. >> With this arrangement i could build a linear PA out of a switch mode PA, >> even a fast one, which avoids key-clicks, at least in QRSS-3 (you rememb= er >> the mode) or OP32 or even EbNaut on LF? >> Sounds like an interesting experiment at least. The question is how warm >> the transformer would become when the RF output current is permanently >> reduced to 50%. >> Has someone ever tried that on LF/MF? >> >> 73, Stefan >> >> > --001a11493038c8e3e9054d83c15d Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
The easiest way to think of a transformer =C2=A0, I believ= e, is to accept it has "infinite" =C2=A0(oar at least arbitrarily= high) inductive reactance, and that part of it can be ignored. =C2=A0 So a= n open circuit on the secondary is transformed to an open circuit on the se= condary; =C2=A0ditto a short circuit. =C2=A0 And any impedance by N squared= . =C2=A0 A practical "very high" Xl is ensured by using high Ue f= errite, and using enough turns that your ferrite is not degraded by saturat= ion.

As soon as that "infinite" inductance beg= ins to drop, it appears in parallel with the pri / sec =C2=A0and contribute= s to the transformed load impedance.=C2=A0 Which lowers it with shunt induc= tive reactance.

Even worse is when the ferrite is = driven into saturation, and the AC component drives it around the B-H hyste= resis curve.=C2=A0 This dissipates energy in the core, and dissipated energ= y appears [electrically] to be added resistance. =C2=A0 Whether it appears = in parallel or in series is moot; =C2=A0it is there, and dissipating.
=

A tapped inductor, or two coupled inductors may have an= incidental impedance transforming action , but if the inductance, or Xl, i= s significant and enters the matching =C2=A0or load impedances - it is NOT = a transformer

It is a pity that transformers and i= nductors both have the same circuit symbols, and similar wound construction= in some cases.

So trying to control a transformer= with DC saturation is very definitely not on.=C2=A0 But controlling a satu= rable inductor very definitely is acceptable.=C2=A0 If that inductor happen= s to be part of a matching network, or be tapped, or have two windings - yo= u have to study , calculate and think what it is going to actually do


Andy =C2=A0G4JNT

On 19 April 2017 at 09:41,= DK7FC <selberdenken@posteo.de> wrote:
=20
Hi Andy,

Yes yes, i agree, and that's what i don't fully understand yet. Las= t night i played a bit with the transductor that is laying arround here in a cupboard. It didn't take much time to build up a 1:1 transformer. I took my small MF PA and a 50 Ohm dummy load. I watched the sine wave across the R with a scope. About 50W were passed through the transformer. Then i started to run a DC current into the saturating coil. The amplitude on the dummy load decreased but the PA consumed even more current! Not a good working point.
But then, how is this transformer working? It looks like it can only work in a series resonant circuit, as you say. So it is not really a transfromer.
Actually i built something similar a few months ago, when i wanted to increase the resonance frequency of a HV mains transformer (antenna C =3D 480 pF switche in parallel to the HV winding). The idea was to saturate the two outher legs of the tripple leg transformer which has its windings on the center leg...

73, Stefan


Am 19.04.2017 08:59, schrieb Andy Talbot:
Stefan=C2=A0
your idea of saturating the transformer is, I think, flawed. =C2=A0 =C2=A0If you reduce mu-r of the core by saturating with DC, the primary winding will have vastly reduced inductance and appear as a near short circuit to the transmitter - not what you want

The idea of saturable reactors applies to resonant inductors, where you use the DC to change the inductance. =C2=A0 =C2=A0So it could be applied to a class D transmitter with a tank arrangement, to retune the tank circuit to adjust for match, or control amplitude.

Andy =C2=A0G4JNT

On 18 April 2017 at 17:18, DK7FC <selber= denken@posteo.de> wrote:
Hi all,

I'm just thinking about transductors and find them them quite fascinating again. I read a bit Wikipedia and thought about the use as a steerable transformer.
Imagine you have a hard switching class D PA, H bridge or so. The output is a constant voltage source and it is no problem to connect no load, as long as a proper type of low pass filter is used.
Then imagine a simple 1:1 ferrite transformer, 50 Ohm to 50 Ohm. The transformer has a 3rd winding for a DC current (to compensate the AC component transformed from the RF windings, 2 cores must be used, which are in parallel for the RF and anti-serial for DC).
Then i can saturate the transformer with the DC so the =E7=9A=B4 falls down= to 1.
With this arrangement i could build a linear PA out of a switch mode PA, even a fast one, which avoids key-clicks, at least in QRSS-3 (you remember the mode) or OP32 or even EbNaut on LF?
Sounds like an interesting experiment at least. The question is how warm the transformer would become when the RF output current is permanently reduced to 50%.
Has someone ever tried that on LF/MF?

73, Stefan



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