Return-Path: X-Spam-DCC: paranoid 1480; Body=2 Fuz1=2 Fuz2=2 X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on lipkowski.org X-Spam-Level: X-Spam-Status: No, score=-0.7 required=5.0 tests=BAYES_00,DNS_FROM_AHBL_RHSBL, RATWARE_GECKO_BUILD,SPF_PASS autolearn=no version=3.1.3 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by paranoid.lipkowski.org (8.13.7/8.13.7) with ESMTP id u9BL2RnC020076 for ; Tue, 11 Oct 2016 23:02:27 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1bu49T-00023N-6E for rs_out_1@blacksheep.org; Tue, 11 Oct 2016 21:59:55 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1bu49S-00023C-Te for rsgb_lf_group@blacksheep.org; Tue, 11 Oct 2016 21:59:54 +0100 Received: from mout02.posteo.de ([185.67.36.66]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.87) (envelope-from ) id 1bu49R-0001w4-EG for rsgb_lf_group@blacksheep.org; Tue, 11 Oct 2016 21:59:53 +0100 Received: from submission (posteo.de [89.146.220.130]) by mout02.posteo.de (Postfix) with ESMTPS id E302520A26 for ; Tue, 11 Oct 2016 22:59:52 +0200 (CEST) Received: from customer (localhost [127.0.0.1]) by submission (posteo.de) with ESMTPSA id 3stqBJ4DqBzyRB for ; Tue, 11 Oct 2016 22:59:52 +0200 (CEST) Message-ID: <57FD52C8.1010401@posteo.de> Date: Tue, 11 Oct 2016 22:59:52 +0200 From: DK7FC User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; de; rv:1.9.1.8) Gecko/20100227 Thunderbird/3.0.3 MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org References: <57FD3F9F.80409@lineone.net> In-Reply-To: <57FD3F9F.80409@lineone.net> X-Scan-Signature: 4e3b1488273adbbe9757d6bdd5adf219 Subject: Re: LF: Audio link Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit 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-Scanned-By: MIMEDefang 2.56 on 10.1.3.11 Content-Length: 1509 Status: O X-Status: X-Keywords: X-UID: 9017 Hi Hugh, Maybe there is some improvement when trying 2 isolation transformers and grounding the TP cable in the center? The other solutions will not work well i think, because the dynamic range is not high enough. 73, Stefan Am 11.10.2016 21:38, schrieb LineOne: > To avoid having laptop running in the shack, which occasionally > produces some QRM, I can send received audio from the shack to a > desktop computer in the house on a twisted telephone pair. This works > but any wire connection between shack and this desktop introduces some > spurious signals on 136khz even if I use an audio isolating transformer. > > I bought a cheap digital baby alarm, disconnected the microphone and > padded down the input to the sender's microphone pads including a > potentiometer to adjust the input. Audio seems to reach the house OK > but I think the automatic gain control in the sender has a strange > effect with some sort of attack time allowing the start of, say, an > Opera signal to be seen but not the whole of a pulse. The background > noise does come up slightly between signals also. Nevertheless I can > hear the audio normally and did send a decent Opera report for G3XDV > this evening. WSPR doesn't seem to decode at all but I will persevere > tonight before abandoning the project. Has anyone else tried these > baby alarms nad managed to overcome the agc? > > My next attempt is likely to be a 36kHz PWM laser link which will take > some time to build. > > 73, Hugh, M0DSZ >