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 vAAKalnI024584 for ; Fri, 10 Nov 2017 21:36:48 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1eDFwj-0003fR-4V for rs_out_1@blacksheep.org; Fri, 10 Nov 2017 20:30:37 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1eDFwi-0003fI-7A for rsgb_lf_group@blacksheep.org; Fri, 10 Nov 2017 20:30:36 +0000 Received: from rhcavuit02.kulnet.kuleuven.be ([2a02:2c40:0:c0::25:130] helo=cavuit02.kulnet.kuleuven.be) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) (envelope-from ) id 1eDFwe-0005N3-Nw for rsgb_lf_group@blacksheep.org; Fri, 10 Nov 2017 20:30:34 +0000 X-KULeuven-Envelope-From: rik.strobbe@kuleuven.be X-KULeuven-Scanned: Found to be clean X-KULeuven-ID: 88D6912809B.A3373 X-KULeuven-Information: Katholieke Universiteit Leuven Received: from icts-p-smtps-1.cc.kuleuven.be (icts-p-smtps-1e.kulnet.kuleuven.be [134.58.240.33]) by cavuit02.kulnet.kuleuven.be (Postfix) with ESMTP id 88D6912809B for ; Fri, 10 Nov 2017 21:30:24 +0100 (CET) Received: from ICTS-S-EXMBX23.luna.kuleuven.be (icts-s-exmbx23.luna.kuleuven.be [10.112.11.58]) (using TLSv1.2 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by icts-p-smtps-1.cc.kuleuven.be (Postfix) with ESMTPS id 8678640AD for ; Fri, 10 Nov 2017 21:30:24 +0100 (CET) Received: from ICTS-S-EXMBX27.luna.kuleuven.be (10.112.11.62) by ICTS-S-EXMBX23.luna.kuleuven.be (10.112.11.58) with Microsoft SMTP Server (TLS) id 15.0.1320.4; Fri, 10 Nov 2017 21:30:24 +0100 Received: from ICTS-S-EXMBX27.luna.kuleuven.be ([fe80::291a:cc4f:6953:698a]) by ICTS-S-EXMBX27.luna.kuleuven.be ([fe80::291a:cc4f:6953:698a%25]) with mapi id 15.00.1320.000; Fri, 10 Nov 2017 21:30:24 +0100 X-Kuleuven: This mail passed the K.U.Leuven mailcluster From: Rik Strobbe To: "rsgb_lf_group@blacksheep.org" Thread-Topic: LF: PA problem Thread-Index: AQHTWmJpyXQDHC+Ik0GMqONVBYc8sA== Date: Fri, 10 Nov 2017 20:30:24 +0000 Message-ID: <1510345776321.99412@kuleuven.be> References: <22d6c712-43af-3a5d-099e-adb285f086a1@n1bug.com> <7d1279b6d1a84b692d281d48901f2b23@xs4all.nl> <5A03089B.6060600@posteo.de>, In-Reply-To: Accept-Language: nl-BE, en-GB, en-US Content-Language: nl-BE X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.112.50.1] MIME-Version: 1.0 X-Spam-Score: -0.0 (/) 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: Hello Paul, I just had a look at the circuit (http://qrp-labs.com/ultimate3/u3mods/lfamp.html). One end of the output transformer connected is to the +13.8V should be "cold" (no RF). As already mentioned regulated power supplies often behave strange to reverse (RF) currents. To rule out any hickups of the power supply I would suggest to run the PA on a large (car) battery or an unregulated power supply (just transformer + rectifier + large C of at least 10000uF). Now the voltage at one end of the output transformer should be (almost) pure DC. If the PA run fine (expected output power and efficiency) now you should focus on AC decoupling the power supply (proper shoke with serveral uF of good caps at both ends). [...] Content analysis details: (-0.0 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RP_MATCHES_RCVD Envelope sender domain matches handover relay domain X-Scan-Signature: bf9cd6b3d49c805062abf73a1027fea8 Subject: Re: LF: PA problem Content-Type: text/plain; charset="iso-8859-1" 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=TO_ADDRESS_EQ_REAL 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 Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by klubnl.pl id vAAKalnI024584 Hello Paul, I just had a look at the circuit (http://qrp-labs.com/ultimate3/u3mods/lfamp.html). One end of the output transformer connected is to the +13.8V should be "cold" (no RF). As already mentioned regulated power supplies often behave strange to reverse (RF) currents. To rule out any hickups of the power supply I would suggest to run the PA on a large (car) battery or an unregulated power supply (just transformer + rectifier + large C of at least 10000uF). Now the voltage at one end of the output transformer should be (almost) pure DC. If the PA run fine (expected output power and efficiency) now you should focus on AC decoupling the power supply (proper shoke with serveral uF of good caps at both ends). 73, Rik ON7YD - OR7T ________________________________________ Van: owner-rsgb_lf_group@blacksheep.org namens N1BUG Verzonden: vrijdag 10 november 2017 19:44 Aan: rsgb_lf_group@blacksheep.org Onderwerp: Re: LF: PA problem Hi Stefan, Your answer is not late at all. After working very hard on antennas the past days I am just now getting back to the little PA. About RF choke in the supply line: This is something I don't understand about most of the LF/MF PA designs I have looked at. I don't see such a choke in any of them! If I do see one, it is just a few uH. Why don't all LF/MA PAs need a big choke in the +DC lead? So today I put in a new FET. I set the bias so it draws 10 mA at idle. Several people suggested I start there. With my Fluke DMM between the power supply and the PA I got 20 watts RF output but efficiency was very poor. The FET was generating a lot of heat! I removed the DMM but left everything else exactly as it was. Now I had only 17 watts RF output but the FET was running cold. This is very similar to results I obtained some days ago. So I started to probe around with the scope. I see a somewhat distorted sine wave at the gate, a much greater amplitude distorted sine wave at the drain, same at the PA RF output. I see a nice clean sine wave at the other side of the LPF. But I see a lot of RF (36 volts peak to peak) at the +13.8V power connection to the PA! Surely it is not supposed to put 36V peak to peak RF on the power supply!? That seems crazy to me. So either it does need a big choke there, or something is wrong with it. I didn't do any experiments with different bypass capacitors yet. I do not see any signs of oscillation with my 100 MHz scope but who knows. 73, Paul N1BUG On 11/08/2017 08:37 AM, DK7FC wrote: > Hi Paul, > > My answer may be a bit late. > > It sounds to me like a EMC issue. A RF choke is needed in the supply > line. 1 mH may be a good choice. And i would add a 1000 uF electrolytic > capacitor with a low internal resistance (the good ones :-) ) near the > Drain, in parallel to the 1 uF capacitor. > > A few more arguments: It is not ideal to drive a class E with a linear > signal. It is better (regarding efficiency) to use a hard keying by > using a MOSFET driver such as ICL7667, TC4422 or so. A class E is not a > design for linear modes, it is for a constant output power, good for > QRSS/DFCW, CW, WSPR, OPERA, EbNaut... > > I would recommend to build a class D PA. You can use the existing > components. A class D is much less critical regarding matching (SWR) and > the efficiency can be in a range of > 90% at LF as well... > > 73, Stefan