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 v4TICW06028733 for ; Mon, 29 May 2017 20:12:33 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1dFP4w-0005Yk-6r for rs_out_1@blacksheep.org; Mon, 29 May 2017 19:07:42 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1dFP4v-0005Yb-Oa for rsgb_lf_group@blacksheep.org; Mon, 29 May 2017 19:07:41 +0100 Received: from mail-lf0-x22b.google.com ([2a00:1450:4010:c07::22b]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) (envelope-from ) id 1dFP4s-0001uN-IO for rsgb_lf_group@blacksheep.org; Mon, 29 May 2017 19:07:40 +0100 Received: by mail-lf0-x22b.google.com with SMTP id h4so38053101lfj.3 for ; Mon, 29 May 2017 11:07:38 -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 :cc; bh=nYABwLxMr6t5P37LVzKT79fmzF1jFTHYD3IIXeYyUJI=; b=Bi+Ru/QsntZUNpEYxXQBj6HTPeQrHwNKccWfWEhXHLV/c6AdNXhMi3TmH4+eP/v//V 1uQ1xtihJqNbUWi0dA8l8Zt98czLbF55un/B2nSxoskcdVQfvgpCRADE9kOsWFPGNEDA EqRM8Qv7xMagTJdYnW2MuHp60d04SDHrvVSgDGS+0q9dDq+2OcbRW5WRiTQdxMhRKKkw pSiA+kOIYU0qbwcbaNFxgUhCw3mSi2xknHnAi3v+Jp0lwG6+rhbcOo1VgvOXuoH3dGoY ym4s26b4rgl+E6C5cGs6+jOb4AMA1pxviMxe4SEjwQ8TPJPF2GCTaZseyaRiUijLd/vr cerA== 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:cc; bh=nYABwLxMr6t5P37LVzKT79fmzF1jFTHYD3IIXeYyUJI=; b=IeeYGekHraynrt/Ob2U5DcjwNpG2lqM29W9RlBuNeIzym/lx0RYs5/sVxpkK8voe/X ptlW9WY8oLeWXy2FkADBQ7QT2U04dkEp172vYAMNTIu0z5iwHIOFzEwasg73B3ppV5IF H/TW+4SNN2/8RjL0cb4lCaJ5ub6vphfdnzJ4sTdfHHraQRDpG+bWn+rM7T9PGJAN4wtO pp1m1zkSWIOZCWuCfUtBh8VSPfGBHHQZ2QAxD5QwQSFziskBJc7aSqRp3Fh5ei5Yr+U1 gGDDSMveqI4TrKXNHnly2qwQJ+bjdR5JnAgAEhmptgbrQHaEjFvZpMR3TrHy2/NAP4Me PegQ== X-Gm-Message-State: AODbwcDY6nHfyF3+nK61ICqgH5nW4lueplhIoLk7gZcY2A1NzpvjRhxf 7mbZqmyuvNl9aEXIMG+wORSa/QWxVg== X-Received: by 10.46.22.4 with SMTP id w4mr3490010ljd.109.1496081256604; Mon, 29 May 2017 11:07:36 -0700 (PDT) MIME-Version: 1.0 Received: by 10.25.156.13 with HTTP; Mon, 29 May 2017 11:07:36 -0700 (PDT) In-Reply-To: <15c5552ac1b.marcocadeddu@tin.it> References: <15c5552ac1b.marcocadeddu@tin.it> From: Andy Talbot Date: Mon, 29 May 2017 19:07:36 +0100 Message-ID: To: rsgb_lf_group@blacksheep.org Cc: dead.fets@gmail.com X-Scan-Signature: 9b15d9defc5ae6fa811529a4cbe8c306 Subject: Re: LF: Re: I: Fw: For today the FETs survived... Content-Type: multipart/alternative; boundary="f403045fc0f8daea3f0550ad8fcc" 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: RO X-Status: X-Keywords: X-UID: 11824 --f403045fc0f8daea3f0550ad8fcc Content-Type: text/plain; charset="UTF-8" Yes. As you'll see in my original write up, I originally forgot that the peak of the fundamental sine component of a square wave is GREATER than the peak by a factor of 4 / pi and initially my PA delivered a lot more power (1.6 times) than it was supposed to. So if the square wave has a peak value of 1, its fundamental sine component has a peak value of 4/pi or around 1.27. The RMS of the resulting sine is SQRT(2) less than this giving a Peak square to RMS-sine ratio of 0.9.. If you specifye peak-peak of the square wave, a further factor of 2 applies, leading to the 0.45 ratio described before. Incidentally, this same ratio appears in that equation for flux in a magnetic code, V = 4.44.F.N.A.B The magic number 4.44 is actually SQRT(2) * pi and comes about from the same sort of sine to square transform. Andy On 29 May 2017 at 18:48, marcocadeddu@tin.it wrote: > > uhuh... a slightly silly misleading assumption... Vdc are the same of > Vrms before FETs make their work! > > Thank you Andy for pointing out it!! > With this approach calculation changes a bit and probably with the > right Xfmr the PA can give higher satisfaction :-) > > Hopefully the FETs will survive and this time I'm ready to burnout the > antenna hi > > Will keep you both updated, thank you once more Andy > > 73 Marco, IK1HSS > ----Messaggio originale---- > Da: andy.g4jnt@gmail.com > Data: 28-mag-2017 21.18 > A: "marcocadeddu@tin.it", > > Cc: > Ogg: LF: Re: I: Fw: For today the FETs survived... > > First thing I noticed is that your turns ratio on the output > transformer > doesn't look right. > You quote "* ... with primary winding of 15 turns and secondary of 12 > turns...*" > > 180V DC in a half bridge is 180V peak-peak square wave. > The fundamental sine part of that is 4/pi * 180 = 229V pk-pk > so is 229V /[2.SQRT(2)] = 81V RMS > > To a good approximation RMS(fund) from a half bridge is Vrms(fund) = > 0.45VDC > > For 500 Watts out, Rload = 81 ^ 2 / 500 = 13 ohms > > So to match to 50 ohms you need a turns ratio of SQRT(50/13) = 1.9: > 1 so > call it 2:1 Keeping 12 turns on the secondary means you need 6 turns > on > the primary > > When operating at reduced voltage, the power out will vary exactly as > the > square of the voltage. > Recalculating from first principles for a 12V supply: > > 12V DC = 12V pk-pk = 12 / [2.SQRT(2)] * 4/pi = 5.4V RMS (fundamental) > in 13 ohms should give 5.4^2/13 = 2.2 Watts > > check using ratio of voltages, squared : > > (12V/180V) ^ 2 * 500W = 2.2 Watts which is the same as above. > QED > > Your 15:12 ratio result sin a load impedance of (15/12)^2 * 50 = 78 > ohms > > At 40V DC == 18V RMS(fund) that will give 18^2/78 = 4.1 watts which is > actually LESS that you are seeing - the 2* discrepancy is odd, but the > low > power is in the area of what you measured.. > > Andy G4JNT > > > > On 28 May 2017 at 19:34, marcocadeddu@tin.it > wrote: > > > Hi Chris, > > > > I tried to post this message on the reflector but apparently I had no > > success.. > > As promised I keep you updated but as you can read in the > > attachment the first trials were not enocouraging... > > Andy, may I ask you to read my report? your interpretation and > > suggestion are welcome! > > > > 73, Marco IK1HSS > > > > > > -----Original message----- > > > > From: "marcocadeddu@tin.it" marcocadeddu@tin.it > > Date: Sun, 28 May 2017 17:01:33 +0200 > > To: rsgb_lf_group@blacksheep.org > > Subject: For today the FETs survived... > > > > Hi LF, > > > > hope that also the toroids of Chris survived! > > My FETs survived, but they are not working as expected :-( > > Attached the report on my attempt to duplicate the half bridge of > > Andy.. > > Has anyone suggestions before I try to cook all connecting to the > > 180Vdc supply? > > > > Thank you > > 73 Marco IK1HSS > > > > > > -- > > This message has been scanned by E.F.A. Project and is believed to be > > clean. > > > > > > > > > > > > > > > > ---------- Forwarded message ---------- > > From: "marcocadeddu@tin.it" > > To: > > Cc: > > Bcc: > > Date: Sun, 28 May 2017 17:01:33 +0200 (CEST) > > Subject: For today the FETs survived... > > Hi LF, > > > > hope that also the toroids of Chris survived! > > My FETs survived, but they are not working as expected :-( > > Attached the report on my attempt to duplicate the half bridge of > > Andy.. > > Has anyone suggestions before I try to cook all connecting to the > > 180Vdc supply? > > > > Thank you > > 73 Marco IK1HSS > > > > > > -- > > This message has been scanned by E.F.A. Project and is believed to be > > clean. > > > > > > > > > > > > > --f403045fc0f8daea3f0550ad8fcc Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Yes.
As you'll see in my original write up, I orig= inally forgot that the peak of the fundamental sine component of a square w= ave is GREATER than the peak by a factor of 4 / pi and initially my PA deli= vered a lot more power (1.6 times) than it was supposed to.

<= /div>
So if the square wave has a peak value of 1, its fundamental sine= component has a peak value of 4/pi or around 1.27.=C2=A0 The RMS of the re= sulting sine =C2=A0is SQRT(2) less than this giving a Peak square to RMS-si= ne ratio of =C2=A00.9.. =C2=A0 If you specifye peak-peak of the square wave= , a further factor of 2 applies, leading to the 0.45 ratio described before= .

Incidentally, this same ratio appears in that eq= uation for =C2=A0flux in a magnetic code, =C2=A0 V =3D 4.44.F.N.A.B
The magic number 4.44 =C2=A0is actually SQRT(2) * pi =C2=A0 =C2=A0 and c= omes about from the same sort of sine to square transform.

Andy

On 29 May 2017 at 18:48, mar= cocadeddu@tin.it <marcocadeddu@tin.it> wrote:

uhuh... a slightly silly misleading assumption... Vdc are the same of
Vrms before FETs make their work!

Thank you Andy for pointing out it!!
With this approach calculation changes a bit and probably with the
right Xfmr=C2=A0 the PA can give higher satisfaction :-)

Hopefully the FETs will survive and this time I'm ready to burnout the<= br> antenna hi

Will keep you both updated, thank you once more Andy

73 Marco, IK1HSS
----Messaggio originale----
Da: andy.g4jnt@gmail.com
Data: 28-mag-2017 21.18
A: "marcocadeddu@tin.it&quo= t;<marcocadeddu@tin.it&g= t;,
<rsgb_lf_group@blackshee= p.org>
Cc: <dead.fets@gmail.com><= br> Ogg: LF: Re: I: Fw: For today the FETs survived...

First thing I noticed is that your turns ratio on the output
transformer
doesn't look right.
You quote "* ... with primary winding of 15 turns and secondary of 12<= br> turns...*"

180V DC in a half bridge is 180V peak-peak square wave.
The fundamental sine part of that is=C2=A0 4/pi * 180 =3D 229V pk-pk
so is 229V /[2.SQRT(2)] =3D 81V RMS

To a good approximation RMS(fund) from a half bridge is Vrms(fund) =3D
0.45VDC

For 500 Watts out, Rload =3D=C2=A0 81 ^ 2 / 500 =3D=C2=A0 13 ohms

So to match to 50 ohms you need a turns ratio of SQRT(50/13) =3D 1.9:
1=C2=A0 =C2=A0 =C2=A0so
call it 2:1=C2=A0 Keeping 12 turns on the=C2=A0 secondary means you need 6 = turns
on
the primary

When operating at reduced voltage, the power out will vary exactly as
the
square of the voltage.
Recalculating from first principles for a 12V supply:

12V=C2=A0 DC =3D 12V pk-pk =3D 12 / [2.SQRT(2)] * 4/pi =3D 5.4V RMS (fundam= ental)
in 13 ohms should give 5.4^2/13 =3D 2.2 Watts

check using ratio of voltages, squared :

(12V/180V) ^ 2 * 500W =3D 2.2 Watts which is the same as above.
QED

Your 15:12 ratio result sin a load impedance of (15/12)^2 * 50 =3D 78
ohms

At 40V DC =3D=3D 18V RMS(fund) that will give 18^2/78 =3D 4.1 watts=C2=A0 w= hich is
actually LESS that you are seeing - the 2* discrepancy is odd, but the
low
power is in the area of what you measured..

Andy=C2=A0 G4JNT



On 28 May 2017 at 19:34, marcocadedd= u@tin.it <marcocadeddu@tin.it= >
wrote:

> Hi Chris,
>
> I tried to post this message on the reflector but apparently I had no<= br> > success..
> As promised I keep you updated but as you can read in the
> attachment the first trials were not enocouraging...
> Andy, may I ask you to read my report? your interpretation and
> suggestion are welcome!
>
> 73, Marco IK1HSS
>
>
> -----Original message-----
>
> From: "marcocadeddu@tin.it= " marcocadeddu@tin.it > Date: Sun, 28 May 2017 17:01:33 +0200
> To: rsgb_lf_group@blac= ksheep.org
> Subject: For today the FETs survived...
>
> Hi LF,
>
> hope that also the toroids of Chris survived!
> My FETs survived, but they are not working as expected :-(
> Attached the report on my attempt to duplicate the half bridge of
> Andy..
> Has anyone suggestions before I try to cook all connecting to the
> 180Vdc supply?
>
> Thank you
> 73 Marco IK1HSS
>
>
> --
> This message has been scanned by E.F.A. Project and is believed to be<= br> > clean.
>
>
>
>
>
>
>
> ---------- Forwarded message ----------
> From: "marcocadeddu@tin.it= " <marcocadeddu@tin.it>
> To: <rsgb_lf_group@= blacksheep.org>
> Cc:
> Bcc:
> Date: Sun, 28 May 2017 17:01:33 +0200 (CEST)
> Subject: For today the FETs survived...
> Hi LF,
>
> hope that also the toroids of Chris survived!
> My FETs survived, but they are not working as expected :-(
> Attached the report on my attempt to duplicate the half bridge of
> Andy..
> Has anyone suggestions before I try to cook all connecting to the
> 180Vdc supply?
>
> Thank you
> 73 Marco IK1HSS
>
>
> --
> This message has been scanned by E.F.A. Project and is believed to be<= br> > clean.
>
>
>
>





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