Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by klubnl.pl (8.14.4/8.14.4/Debian-8+deb8u2) with ESMTP id w09B6x9r026411 for ; Tue, 9 Jan 2018 12:07:00 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1eYrXU-0006Mb-CJ for rs_out_1@blacksheep.org; Tue, 09 Jan 2018 10:53:52 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1eYrXT-0006MS-KJ for rsgb_lf_group@blacksheep.org; Tue, 09 Jan 2018 10:53:51 +0000 Received: from mout.perfora.net ([74.208.4.197]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) (envelope-from ) id 1eYrXQ-0004bE-3y for rsgb_lf_group@blacksheep.org; Tue, 09 Jan 2018 10:53:50 +0000 Received: from [192.168.1.127] ([72.224.254.201]) by mrelay.perfora.net (mreueus002 [74.208.5.2]) with ESMTPA (Nemesis) id 0LsS5u-1f1Q0F0Llo-011yMr for ; Tue, 09 Jan 2018 11:53:43 +0100 To: rsgb_lf_group@blacksheep.org References: <923db48e-ca8e-67d5-e70d-3c9695277b97@n1bug.com> From: N1BUG Message-ID: <2e4b6c93-746c-f933-93cd-69973f902ae4@n1bug.com> Date: Tue, 9 Jan 2018 05:53:39 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-Provags-ID: V03:K0:r6RzHb/ZJ7W9xQp8mLRANjVFK6vxUgE89adleWOF3gHgdyfGYbH sY+pkjCocafr+iOFeEMZvQ7/PtQqD/r7bEz4NunNA1JQg+Bz4/2mQU1B56Y1dxWsdeAF2EP JGJfppgNT/HeiEQj+rgupZOjAmQcIeFnDhzi+7RcRJDUVFD8Un9/RXrSd3kbwA5ojlFoL6P jLvXWMM1M+8Ng+O8KWDBQ== X-UI-Out-Filterresults: notjunk:1;V01:K0:X9LpUhoa9hg=:wLCZZ9+gvH5/y9XuaxsSS7 J5owYdUi1hoIutPwFz6/cJZ/r+dwqXK1v2Vu8EzWoI+snq5Yhd4/JT0CaUGzBmW6aZKOPI27K hc8HUfhAdnLiZD22y8Qd8ZOQ/KTiY0+RNMhTKy5529eNAhxAJ1v+PD/2BrnQlbWNYU8wOmQDj N/6Y160bWXLHVe6A4olybd52mHFDy2vK6exRqhMU4vqqg7xbJkgoSlz2cwxiR6g1Uarmqy975 ROckxIBtb7T/ClEK7UQAgJ1He+0As7cC3KgTqljWV7gV4FXG2UN6pnJW1jFlbxse55kYKexNS HVs7U201a8YZbhf6MxpTHeys4HBEq//f9w0oZ8pCaaGpL6+XCEXp/0YwIX9Fn3CVWOgDOJ44Z bNa0IMH+QQtDb4Oe7EbP3MMpMuuw1ffZLu4RM9Lr5bGE4FD54rzrDd5PsAQBvKstMke/Ve8+A FyjpOV28KdzypK6Q4SzVX3U+1lQnx77fQmfNh87PfpyGOi+BT+J2PNA1s7D8YMLf5jr1rjNyK 0lhaAIzGZHhps7QYKT7pJkzXMgdC1XDOljhF94GPmI0BVzTpyPTaKnBs36cU3pgqGz9oBCsZ3 28bHLrNbdiyUy47OuoHJKqGx0LoRaYPqDsThbDT966zL+xWcD+3YSqA8nvCM5UdN2sCvu1bAS WY/TJlFYgo0c/qCGruoNFMkeYWMeQgCaXJ5Sl/eoL3Ukufry96KZ7uPxSsdc15xX8ChhxAN1z a69FoU4E/7Dbv/OcoEqFk1onV55NWxWSQ01mu/74ZCrZg9042L3nquNqWS4= X-Spam-Score: 1.1 (+) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has NOT identified this incoming email as spam. The original message has been attached to this so you can view it or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: Thanks Andy. I need more time to get my head around that equation. I'm still struggling with a near vertical learning curve on all of this. I never worked with ferrite (except in RFI suppression) until very recently. To start with I don't know what figure to use for N turns on this 16:1 transformer with 4 x 10 turn windings. There must be beginner level articles somewhere that walk one through this stuff, but I haven't yet found them. [...] Content analysis details: (1.1 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- 0.0 HTML_MESSAGE BODY: HTML included in message 1.1 MIME_HTML_ONLY BODY: Message only has text/html MIME parts X-Scan-Signature: 11963a33d604c33786d8f1de94ce267f Subject: Re: LF: Progress? with the PA Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: 8bit X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: * X-Spam-Status: No, hits=1.0 required=5.0 tests=HTML_30_40,HTML_FONT_BIG, HTML_MESSAGE,MIME_HTML_ONLY 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

Thanks Andy.

I need more time to get my head around that equation. I'm still struggling with a near vertical learning curve on all of this. I never worked with ferrite (except in RFI suppression) until very recently. To start with I don't know what figure to use for N turns on this 16:1 transformer with 4 x 10 turn windings. There must be beginner level articles somewhere that walk one through this stuff, but I haven't yet found them.

For that matter I'm not sure how to calculate Vrms on something that isn't a sine wave.

All I can say at the moment is the core is a EPCOS / TDK B64290L674X830

N30 material with a ui of 4300, 36 x 23 x 15 mm.

I'm still interested in understanding the issues with this PA as a learning exercise but am preparing to move on to something else for on air use.

Paul N1BUG



On 01/07/2018 12:34 PM, Andy Talbot wrote:
What core ?
What  dimensions ?

Does it obey the fundamental equation for saturation in a core ?
Vrms = 4.44 .F . N . A . B

F Hz,   N turns,  A core area area in m^2   B Tesla

Keep B < 0.1 and  ferrite saturation should be fine

And if it is saturating, you need more turns, not less

Andy  G4JNT



On 7 January 2018 at 17:26, N1BUG <paul@n1bug.com> wrote:
http://n1bug.com/n1debug/ASB_LF_Amp-20171223.jpg

Recall that last week I had increased turns on the output transformer from 3x5 to 3x10. That reduced heating of the FET but did not help to stabilize the PA. It would put 12 to 14W into the antenna before oscillation started.

Today I changed it to 4x10 turns so it is now a 16:1 transformer. This has made a big change! The PA will now put more than 30 watts into the antenna before oscillation starts with 13V on it. For the first time I noticed some slight warming of the transformer. I think it is the core heating up, not the wire.

If I put 19V on it, I briefly see almost 50 watts into the antenna but the transformer becomes hot very quickly and within just 3 or 4 seconds, power begins to drop rapidly.

At this point I guess either:

The core is not suitable material or not big enough...

or

Maybe it needs fewer turns (but this may lead to too much heat in the FET again?) At 30W output with 13V, that FET is already running quite warm with 4x10 turns.

At least I finally found something that makes a change!

73,
Paul N1BUG