Return-Path: Received: from rly-mf01.mx.aol.com (rly-mf01.mail.aol.com [172.20.29.171]) by air-mf07.mail.aol.com (v126.13) with ESMTP id MAILINMF071-9424b279a17189; Tue, 15 Dec 2009 09:16:15 -0500 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-mf01.mx.aol.com (v125.7) with ESMTP id MAILRELAYINMF018-9424b279a17189; Tue, 15 Dec 2009 09:15:53 -0500 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1NKY9B-00053K-Ui for rs_out_1@blacksheep.org; Tue, 15 Dec 2009 14:13:05 +0000 Received: from [83.244.159.144] (helo=relay3.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1NKY9B-00053B-GD for rsgb_lf_group@blacksheep.org; Tue, 15 Dec 2009 14:13:05 +0000 Received: from smtp819.mail.ird.yahoo.com ([77.238.189.19]) by relay3.thorcom.net with smtp (Exim 4.63) (envelope-from ) id 1NKYAr-00043Q-67 for rsgb_lf_group@blacksheep.org; Tue, 15 Dec 2009 14:14:51 +0000 Received: (qmail 56428 invoked from network); 15 Dec 2009 14:14:43 -0000 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=btopenworld.com; h=Received:X-Yahoo-SMTP:X-YMail-OSG:X-Yahoo-Newman-Property:Message-ID:From:To:References:In-Reply-To:Subject:Date:MIME-Version:Content-Type:Content-Transfer-Encoding:X-Priority:X-MSMail-Priority:X-Mailer:X-MIMEOLE; b=ryAq1gMiOJ+SSMfuzwJDZwDYOVQmtThGs4dKyLZrxTmpmNdEu+4NupmocEGp/hb6vqQnOzOWrJzyIeJdX69FvURYL7MFpwmzIM4Tja2tENKalyA5Bsj5KjLLiPREiQ3fXLO1IiP9AlMf9kCoJ5LAXkbuDQgNivWlDUWf5IW6rlg= ; Received: from unknown (HELO JimPC) (james.moritz@86.179.135.6 with login) by smtp819.mail.ird.yahoo.com with SMTP; 15 Dec 2009 14:14:42 -0000 X-Yahoo-SMTP: qKIhhNCswBB2TTHr2BORWcGGR2mpopxhCcunGIxpCKQYiG07Q7UOhNo- X-YMail-OSG: E_uvkJYVM1mjiddVgel2yKD_9qH7cEGtMlD38AXI6sBIb46jfinmpIaQtQ.ICpMLaxrJIrunjDgBHJMscJCkOUreceO9H4zc7y093yhHcy9xpDG0kyHyt0J5KYnH8gtjfyEyMRvP4S5t3py69Aqi1Cf153mfqkPAFJlq61c4eI8ZcFPw.DZAaVkd27vIJP_II.tPXzhGgwwQaDN3ZwwxrzUl7cJZl9adXKFObIdGMWoEEiT7or0gZsiPQTEh34.Jlnt1hE4AtqlHHvmfFIKTn_jDvhfvdDytedxuFaUdZ7qsRhti X-Yahoo-Newman-Property: ymail-3 Message-ID: From: "James Moritz" To: References: <38A51B74B884D74083D7950AD0DD85E828AC77@File-Server-HST.hst.e-technik.tu-darmstadt.de> In-Reply-To: <38A51B74B884D74083D7950AD0DD85E828AC77@File-Server-HST.hst.e-technik.tu-darmstadt.de> Date: Tue, 15 Dec 2009 14:14:43 -0000 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Windows Mail 6.0.6002.18005 X-MIMEOLE: Produced By Microsoft MimeOLE V6.0.6002.18005 DomainKey-Status: good (testing) X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,none Subject: LF: Re: "Gain" between qrss3 and qrss10 / PA design Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=original 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=0.1 required=5.0 tests=MISSING_OUTLOOK_NAME 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 Dear Stefan, LF Group, A much better choice of circuit topology for QRO transmitters using an off-line rectified mains PSU of about 330V is the half- or full bridge, voltage-mode class D, as used in the "Decca" PAs, and G4JNT's off-line design. Here the peak voltage across each MOSFET is only equal to the DC supply voltage, so cheap 500V Mosfets designed for off-line SMPSUs are ideal. The class E and push-pull current-mode class D designs are better for relatively low voltage supplies, say < 40V. The limitation on TX power that can be used at LF with a vertical antenna is the antenna voltage, roughly Iant * XCant. In my experience, corona breakdown becomes a problem in the 10 - 20kV range with a wire antenna. So to use high power, and so achieve high antenna current and ERP, you need high antenna capacitance. Also, the voltage will be increased if the antenna loss resistance is low. I found that, with an 10m high inverted L antenna of about 50m of wire in total, I could run 1.2kW reliably, provided care was taken to eliminate sharp ends, narrow spacings, etc. in the antenna and tuner. This resulted in up to 5A antenna current, and about 17kV on the antenna wire. Even so, I have to increase the antenna height in order to approach 1W ERP. At 500k, the antenna impedance is much lower, and efficiency also usually higher, so TX power is less of a problem. In my experience, DX contacts using QRSS30 are quite practical, given a large supply of strong coffee! But with longer dot periods, good propagation does not last long enough to complete even a minimal QSO. Cheers, Jim Moritz 73 de M0BMU ----- Original Message ----- From: "Stefan Schäfer" To: Sent: Tuesday, December 15, 2009 12:44 PM Subject: AW: AW: LF: "Gain" between qrss3 and qrss10? Yes, you are right. But i mean i USA, where the voltage is 110V, you get about 155V and thus the 900V FET would have 6 times more. For a class e mode PA, 4x the voltage can be reached when SWR is correct(!) so there would be a goog savety factor. 73, Stefan / DK7FC