Return-Path: Received: from rly-da09.mx.aol.com (rly-da09.mail.aol.com [172.19.129.83]) by air-da05.mail.aol.com (v126.13) with ESMTP id MAILINDA052-a8e4b0c3708302; Tue, 24 Nov 2009 14:42:17 -0500 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-da09.mx.aol.com (v125.7) with ESMTP id MAILRELAYINDA096-a8e4b0c3708302; Tue, 24 Nov 2009 14:42:02 -0500 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1ND1G5-0006t4-Ja for rs_out_1@blacksheep.org; Tue, 24 Nov 2009 19:41:05 +0000 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1ND1G5-0006sv-6A for rsgb_lf_group@blacksheep.org; Tue, 24 Nov 2009 19:41:05 +0000 Received: from mail-bw0-f221.google.com ([209.85.218.221]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1ND1G4-0003Sj-59 for rsgb_lf_group@blacksheep.org; Tue, 24 Nov 2009 19:41:05 +0000 Received: by bwz21 with SMTP id 21so6775641bwz.4 for ; Tue, 24 Nov 2009 11:40:58 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:date:message-id:subject :from:to:content-type; bh=gmd5KLHoYMVlsBwaFXJneX4P40r3HShW2C43iwkZeG0=; b=HMPPEDqXDb+RlT/0MFN7bY1xuFNlSCUeNM3EzKRKDPDtd/Id9523g34y4YGs8EB1ws 80VM29YtgLHsrPGshQNreUFTBp9JTAWgnaaikyVO1yaAXbm97BSMrZR1AwxPRKu1CvUw Wh3jKpbiOSPW0rS5M8oACfCQwYFRJS7gKy4vk= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:date:message-id:subject:from:to:content-type; b=gLrunHbqRwumlbnQ4Ts/ewfHptVAw30r+2CS4Nk+vqY9Dit23UINw0s5mJofrjyjXB gv2hkh8Oh9XG55F1qDy6ZD7Dw/UU51k4Bev/CAIr+r/TngyoQQc+uzwbtpcVT4rZsm8v WA2gH05KgxRMs1ZhNB9NBphVhsluBRb8KJDOE= MIME-Version: 1.0 Received: by 10.204.26.134 with SMTP id e6mr3041150bkc.87.1259091657931; Tue, 24 Nov 2009 11:40:57 -0800 (PST) Date: Tue, 24 Nov 2009 19:40:57 +0000 Message-ID: <9afca2640911241140j230515e9kcbcaffd3911ccb82@mail.gmail.com> From: Roger Lapthorn To: rsgb_lf_group@blacksheep.org X-Karma: unknown: DomainKey-Status: good (testing) X-Spam-Score: 0.9 (/) X-Spam-Report: autolearn=disabled,HTML_10_20=0.945,HTML_MESSAGE=0.001 Subject: LF: IRF510 500kHz PA stability issues - advice please Content-Type: multipart/alternative; boundary=00032555b50a02bbd80479231f54 X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=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-IP: 193.82.116.20 X-AOL-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-m209.2 ; domain : gmail.com DKIM : fail X-Mailer: Unknown (No Version) --00032555b50a02bbd80479231f54 Content-Type: text/plain; charset=ISO-8859-1 I've been using a single IRF510 FET PA stage on 500kHz and it produces around 6-7W of RF. But, when adjusting my antenna I've managed to damage several devices now. I think the stage is running somewhere towards class-E looking at the PA drain waveform on the scope and I believe either the stage is going unstable or it is running in a condition in which too much current (and heat) is taken and the device fails. Are there any simple "rules of thumb" or design/biasing/decoupling guidelines to ensure that my devices don't destroy themselves with a less than perfect load? Any simple advice would be appreciated. 73s Roger G3XBM -- ------------------------------------------------------------- http://g3xbm-qrp.blogspot.com/ http://www.g3xbm.co.uk G3XBM GQRP 1678 ISWL G11088 --00032555b50a02bbd80479231f54 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable I've been using a single IRF510 FET PA stage on 500kHz and it produces= around 6-7W of RF. But, when adjusting my antenna I've managed to dam= age several devices now.=A0 I think the stage is running somewhere towards= class-E looking at the PA drain waveform on the scope and I believe eithe= r the stage is going unstable or it is running in a condition in which too= much current (and heat) is taken and the device fails.

Are there any simple "rules of thumb" or design/biasing/deco= upling guidelines to ensure that my devices don't destroy themselves= with a less than perfect load?

Any simple advice would be appreci= ated.

73s
Roger G3XBM






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G3XBM =A0 =A0GQRP 1678 =A0 =A0 =A0ISWL G11088
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