Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-mg01.r1000.mx.aol.com (Internet Inbound) with ESMTP id DC771380000A8; Thu, 11 Oct 2012 14:18:33 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1TMMEy-0003Hi-W7 for rs_out_1@blacksheep.org; Thu, 11 Oct 2012 18:08:08 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1TMMEy-0003HZ-Be for rsgb_lf_group@blacksheep.org; Thu, 11 Oct 2012 18:08:08 +0100 Received: from smtp-out08.email.it ([212.97.34.23]) by relay1.thorcom.net with esmtp (Exim 4.77) (envelope-from ) id 1TMMEw-0007Wk-B9 for rsgb_lf_group@blacksheep.org; Thu, 11 Oct 2012 18:08:07 +0100 Received: from localhost (localhost.localdomain [127.0.0.1]) by smtp-out08.email.it (Postfix) with ESMTP id A8766C020 for ; Thu, 11 Oct 2012 19:08:02 +0200 (CEST) X-Virus-Scanned: amavisd-new at email.it Received: from smtp-out08.email.it ([127.0.0.1]) by localhost (smtp-out08.email.it [127.0.0.1]) (amavisd-new, port 10024) with LMTP id 0CpE+uFf6MG9 for ; Thu, 11 Oct 2012 19:08:02 +0200 (CEST) Received: from zv5000.localnet (unknown [95.74.75.235]) by smtp-out08.email.it (Postfix) with ESMTP id 9298CC00E for ; Thu, 11 Oct 2012 19:07:59 +0200 (CEST) From: Claudio Pozzi To: rsgb_lf_group@blacksheep.org Date: Thu, 11 Oct 2012 19:07:56 +0200 User-Agent: KMail/1.13.5 (Linux/2.6.32-5-686; KDE/4.4.5; i686; ; ) References: <50731B6C.2060506@iup.uni-heidelberg.de> <201210091526.52793.smtp01@email.it> <50745EC1.1090402@iup.uni-heidelberg.de> In-Reply-To: <50745EC1.1090402@iup.uni-heidelberg.de> MIME-Version: 1.0 Message-Id: <201210111907.56379.smtp01@email.it> X-Spam-Score: -1.9 (-) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has identified this incoming email as possible spam. The original message has been attached to this so you can view it (if it isn't spam) or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: On Tuesday 09 October 2012 19:28:33 you wrote: > Thank you Claudio, > > I will consider that when the probe is down from the roof next. There > are a few dB in reserve, i'm still far away from the RX noise. > But now it looks much better! Still some IM but only a little. Taking > into account that AFN is arround, that's a positive result. > If there would be oscillations on the output of the probe, then i would > see them across the 50 Ohm resistor in the shack, at full amplitude, right? [...] Content analysis details: (-1.9 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at http://www.dnswl.org/, no trust [212.97.34.23 listed in list.dnswl.org] 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (smtp01[at]email.it) -2.1 RP_MATCHES_RCVD Envelope sender domain matches handover relay domain 0.2 FREEMAIL_ENVFROM_END_DIGIT Envelope-from freemail username ends in digit (smtp01[at]email.it) 0.0 TVD_FW_GRAPHIC_NAME_MID BODY: TVD_FW_GRAPHIC_NAME_MID X-Scan-Signature: ebba021850e0a5d4120636e52401e975 Subject: Re: LF: active antenna output termination? Content-Type: Multipart/Mixed; boundary="Boundary-00=_szvdQPVSp+jx0bo" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.9 required=5.0 tests=FROM_ENDS_IN_NUMS 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-global-disposition: G X-AOL-VSS-INFO: 5400.1158/84666 X-AOL-VSS-CODE: clean x-aol-sid: 3039ac1d60c950770d793d72 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none --Boundary-00=_szvdQPVSp+jx0bo Content-Type: text/plain; charset="iso-8859-15" Content-Transfer-Encoding: 7bit On Tuesday 09 October 2012 19:28:33 you wrote: > Thank you Claudio, > > I will consider that when the probe is down from the roof next. There > are a few dB in reserve, i'm still far away from the RX noise. > But now it looks much better! Still some IM but only a little. Taking > into account that AFN is arround, that's a positive result. > If there would be oscillations on the output of the probe, then i would > see them across the 50 Ohm resistor in the shack, at full amplitude, right? case 1, Oscillation: you are right case 2, instability: appear as overshoting or ringing response at step or pulse. See the attached image. Sometime instability became self-oscillation if load impedance change a little, e.g. no oscillation if the load is a pure resistance and strong oscillation if the load have some reactance. 73 Claudio ik2pii p.s. See also the M0BMU preamplifier schematic output transistor in "Bandpass Receiving Loop Antennas". > > Am 09.10.2012 15:26, schrieb Claudio Pozzi: > > The emitter follower transistor have a very low output impedance, no > > problems for receiving purpose but... if you use a long coaxial cable > > you connect a capacitance of about 100 pF/meter between output and > > ground. The circuit can become unstable and oscillate, I found that a 27 > > or 33 ohm resistor in series to the output help to kill the oscillation > > and the signal loss is a little less than 6 dB (voltage, 3dB power). > > > > I's a good practice to put a few ohm resistor in series at the low > > impedance output devices (OP-AMP, emitter follower, 74HCxxx buffers etc) > > driving a capacitive load to prevent oscillation. > > > > 73 > > > > Claudio, ik2pii -- Claudio Pozzi - Happy Linux User - http://www.qsl.net/ik2pii -- Caselle da 1GB, trasmetti allegati fino a 3GB e in piu' IMAP, POP3 e SMTP autenticato? GRATIS solo con Email.it http://www.email.it/f Sponsor: Vuoi fare un regalo davvero originale? Su MisterCupido.com troverai centinaia di IDEE REGALO per tutte le tasche! Consegne in tutta Italia in soli 2-3 giorni Clicca qui: http://adv.email.it/cgi-bin/foclick.cgi?mid=12387&d=11-10 --Boundary-00=_szvdQPVSp+jx0bo Content-Type: image/gif; name="ringing.gif" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="ringing.gif" R0lGODdhzACEAIAAAAAAAP///ywAAAAAzACEAAAC/4yPqcvtD6OctNqLs968+w8mwEiW5omm6sq2 7gvH8kynChDm+s73Cy7yCYfE4gOIQBqXzOZHaYA6p9RqQyq1ardNLPcLNnrD5HJubE6rMei1++1o w+d0uZheya7tRJwefxPwZ8Y35AcYcVgX2CX4g5jkyFhWKKQYOeh2ebAJVunT6ZiV+RUaKln1yYME ZYoaWcoZ5DV6F8TEOhtIO4kri7kbfHvWC/vrkQusuyxLupPcLKwcTTxs/coBHbU9Tf3rXI0N1Iot egtOUandsT7O7P06stTODb+thI+eWGysv1+Pipy4eDfkGToW8Nw7LAY3fDrlEKE2eviuNHwmMSNA c/8IRVy08DDgxx8lHgGc2NHdRpI1TpgkeDJlPVIm8vAbtu7INZQz+3UEtVNjwmM5QaiC5q+iT6JC i/ZQyjQqzKEYr8X5qVNmzK1U/WUz1lNqV6xPbjJwegUs1bVIya5Sy3Nq27dW44yEADWs3rHlLMFt ulSSV5t1ddDjCjXZ4K8b4yb+BrRwOIFyA3Ocp7WyWIhlJYc4rNke56eZH3e7XFUt3YGNy3UavZoy OV6nw7n9/NMVbXt9crv+PTuy6tS7ebtqtFK3tNvIzE5efu+llpzKnQtnbrRvdTWntk+3jrtWLU3a y8fyHP7R4i3d+4ZRlV3Pevbu59sajtE+Ifdw4Gf/h4QXgMkJSKAn4BWIYG/oJcggaQs2CCFuD0ZI IWP4VYghOwdmyCFhF3YIYjobhkjiWSOWiKJvKa4Y4IQslujfizCeKCOIMdZoI404Znjjjjzq6COF PQYpJJBENjjkkUgaqSSCSTbpJJNH1FRESy2JQYOH2Fl4UJX3rbZlRF6OqaCDHzZHZpdlgrmSbX6l +aaZYWqgn4hwXpfanBnUOQGfEvj5j5xtsnYBoC2uGSeb9bkoZaFfJprnoGuB9CielrrJH1qBqskp pIZZd8lghmaF6KUSfgjboZ2aGumn6OXVZ6WCstrZmbD+Kauis2Kqj6i5trrrqXr6emewwAorqXSx /xara7P/ncmonlx6amyt0jrK7LHaWpssmqVWiymv1Drr6rfI8sctreGS6+21lGZb7qriqnsuuPWe O2qj75q7bbvdagjvuv0CDO209D4rL77jDozwwunm65GVM2ApsQyeQgwld/pmDMiTHAPo8ceIhCwy HiSXPMfJKL+h8sp7bOyyxtHGvMjMNPcH881ktKzzezn3fF7BQKf8s0MlCWJoQ6wsRkKUNhs2DsQG NY10oRgjJ7QlUVdNJdJUH310FH7IM3XZVXs9dtlqp+2S2HfdeXU6W5M9d91in53EIWMLtjfdd5vN 9dJ3Bz441u5C/fXehAde0khkixK133Q3vvXiZ3mbHbYTPGejuN+Le84JQ5P3TTreg2Mu+OVLv71q 3H3ajfrfdhcUuuxun9757KrbbjpmT5+xeu5ur1143rUPfzvyeIOdOuCZ+/I7FakP/VvHVFNfPfYE bq699EV3r/n34EOf9fg7i28+3BWvz3777r8Pvw3pz0//BgUAADs= --Boundary-00=_szvdQPVSp+jx0bo--