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 w1HBafx9029801 for ; Sat, 17 Feb 2018 12:36:44 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1en0in-0002zo-CA for rs_out_1@blacksheep.org; Sat, 17 Feb 2018 11:32:01 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1en0in-0002zX-16 for rsgb_lf_group@blacksheep.org; Sat, 17 Feb 2018 11:32:01 +0000 Received: from porthos.netcom.co.uk ([217.72.171.73]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) (envelope-from ) id 1en0ij-00075U-Lq for rsgb_lf_group@blacksheep.org; Sat, 17 Feb 2018 11:31:59 +0000 X-DKIM-Result: Domain=abelian.org Result=Signature OK DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=abelian.org ; s=default; h=Content-Transfer-Encoding:Content-Type:In-Reply-To: MIME-Version:Date:Message-ID:References:Reply-To:To:From:Subject:Sender:Cc: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=j4WKFdJWrgoXCGzY/UO5yJ6V3vPa2dioIjBWQrbxtEE=; b=xjwVUPYX3UodzWBA69wUYAQRH7 d0aClk+kyw+NHXCk4KCaySFphD4CuuIeXC4vluu4W/ZERunkBIh8xowegrphey7+hxLPbYWJvxnPQ /KOz5E/XktFXOL4+bkYukb4lrSSEXwC5Q62RbM1TLAmVkX1hg32QjijnLGbEppsaArZY=; Received: from i-194-106-52-83.freedom2surf.net ([194.106.52.83]:32775 helo=pn.abelian.org) by porthos.netcom.co.uk with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89_1) (envelope-from ) id 1en0ih-0006Tg-8I for rsgb_lf_group@blacksheep.org; Sat, 17 Feb 2018 11:31:55 +0000 Received: from [127.0.0.1] (localhost [127.0.0.1]) by pn.abelian.org (Postfix) with ESMTP id A825D400687 for ; Sat, 17 Feb 2018 11:31:54 +0000 (UTC) From: Paul Nicholson To: rsgb_lf_group@blacksheep.org References: <52dea779-7aae-aff8-1072-ad24cdcd007c@freenet.de> <4024a3ab-eb61-7801-e9ad-5715c5f49546@abelian.org> <9a7cf91a-5643-9149-28a7-ce6d282db3e9@abelian.org> <1555f07a-f2a3-fb55-c246-f52442a1a723@freenet.de> <4ac6d43f-85c7-bd05-85b9-5b64ebcfbf35@abelian.org> <2f6a408a-af27-9c9b-b116-7becd9b1c66f@abelian.org> <6eced61e-a7ce-2935-195d-4a76f375b11e@freenet.de> Message-ID: <633c1982-97fe-7d9d-7f69-07e3503147bb@abelian.org> Date: Sat, 17 Feb 2018 11:31:54 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - porthos.netcom.co.uk X-AntiAbuse: Original Domain - blacksheep.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - abelian.org X-Get-Message-Sender-Via: porthos.netcom.co.uk: authenticated_id: catchall@abelian.org X-Authenticated-Sender: porthos.netcom.co.uk: catchall@abelian.org 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: I had a bit of time to play again with the Octo, to investigate where the excess timing jitter comes from. The stereo audio injector is giving around 20nS jitter on the PPS from the neo-m8t. With the stereo card replaced by the Octo, all else the same, the jitter varies between 300nS and over 1uS. [...] Content analysis details: (0.0 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- 0.0 T_DKIM_INVALID DKIM-Signature header exists but is not valid X-Scan-Signature: 49f0f587e44d6711c57b8a4e950ba850 Subject: Re: LF: Testing Audioinjector Octo with RPi3 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit 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 I had a bit of time to play again with the Octo, to investigate where the excess timing jitter comes from. The stereo audio injector is giving around 20nS jitter on the PPS from the neo-m8t. With the stereo card replaced by the Octo, all else the same, the jitter varies between 300nS and over 1uS. A close look at the shaped PPS seen through the Octo shows some distortion or interference http://abelian.org/vlf/tmp/180217a.gif Not sure if these are additive or little step changes in gain. Here's worse example http://abelian.org/vlf/tmp/180217b.gif Always the interference is on the rising and/or falling slopes about half way. Not present on the PPS when viewed on a scope at the Octo inputs. Similar artifacts are visible on a plain old sine wave fed into an Octo input. http://abelian.org/vlf/tmp/180217c.gif For some reason on the sine wave the artifacts are always near the turning points. Meanwhile I monitored the 49.152 MHz master oscillator on a SSB receiver and it was giving a nice pure note with no obvious frequency or phase jitter. So it looks like the timing jitter on the Octo is due to its analog inputs, not the A/D conversion timing. Strangely though, there's no sign of these artifacts when there's no input to the channel. It isn't just background interference. I think the next step might be to bypass the Octo's input board and take the PPS straight to the pins of the ribbon connector. Wondering if anyone else sees this behaviour on a PPS or sine wave. -- Paul Nicholson --