Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-da03.r1000.mx.aol.com (Internet Inbound) with ESMTP id 576CB380000A5; Sat, 12 May 2012 15:56:43 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1STIOq-0003KU-Kd for rs_out_1@blacksheep.org; Sat, 12 May 2012 20:54:44 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1STIOq-0003KL-6G for rsgb_lf_group@blacksheep.org; Sat, 12 May 2012 20:54:44 +0100 Received: from mail-ob0-f171.google.com ([209.85.214.171]) by relay1.thorcom.net with esmtps (TLSv1:RC4-SHA:128) (Exim 4.77) (envelope-from ) id 1STIOn-0004sB-Pa for rsgb_lf_group@blacksheep.org; Sat, 12 May 2012 20:54:43 +0100 Received: by obfk16 with SMTP id k16so11468076obf.16 for ; Sat, 12 May 2012 12:54:39 -0700 (PDT) X-DKIM-Result: Domain=gmail.com Result=Good and Known Domain DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; bh=cbL+SOuuWUAf7ENCZCjodHcQm4cpEHNoaSsCWplWNW8=; b=FSS3rKrEJwqt8/f4AtVi20TnD5tNM0TsmAHtIIH3PIIrWsjGJ0cgvvHc5bEtlAj98N 05T/unW+H+vsgUCgC/JrmuPRl+nre+PQy6dqXTqiJANf+u4+syQU5Le5V+oLN5/5BHVw MNELkVdNVBuiwCvGI/+zBKGxrFjIDOv5R8xcs9HmLMSHP/3zW+D/8ebLTgEdgE/tsCVG japnbOPuPz67kG/QAewrYfSQzAkC7Hs47tEAv1YxCvVvc+0l1QTKu81xXNCT9ThlpLtG 8PPuk0OPNsX6sPNDVWJdP199B83rFQpAQ6HFIe879BkaGqjgpLJVBYLIZzNa1FLT7HCO Dg0A== MIME-Version: 1.0 Received: by 10.50.181.164 with SMTP id dx4mr1419169igc.1.1336852479558; Sat, 12 May 2012 12:54:39 -0700 (PDT) Received: by 10.231.60.134 with HTTP; Sat, 12 May 2012 12:54:39 -0700 (PDT) In-Reply-To: <7C951166FE1F4075974968A9E1393368@GaryPC> References: <99F3BE8C10254B3AAC3A81BA16DA2584@computereebf79> <3333EC45C262400BA932E210F3241223@JimPC> <7C951166FE1F4075974968A9E1393368@GaryPC> Date: Sat, 12 May 2012 20:54:39 +0100 Message-ID: From: Andy Talbot To: rsgb_lf_group@blacksheep.org X-Spam-Score: -0.7 (/) 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: If you use a DDS of the AD9850/51, and probably the AD9832 type, there is a very neat way of amplitude keying them. Place an NPN transistor in series with the D/A current setting resistor, and a small resistor in teh emitter to give some neg feedback and key that. Using a low pass filter on the drive waveform allwos a gentle ramp rather than a hard on-off. More details are somewhere on the Analog Devices web site [...] Content analysis details: (-0.7 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.7 RCVD_IN_DNSWL_LOW RBL: Sender listed at http://www.dnswl.org/, low trust [209.85.214.171 listed in list.dnswl.org] 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (andy.g4jnt[at]gmail.com) -0.0 SPF_PASS SPF: sender matches SPF record 0.0 T_DKIM_INVALID DKIM-Signature header exists but is not valid X-Scan-Signature: c0336009bd9bab526ca27d297ea7579a Subject: Re: LF: IEEE488 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=none 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-SCOLL-SCORE: 0:2:479469824:93952408 X-AOL-SCOLL-URL_COUNT: 0 X-AOL-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-m242.1 ; domain : gmail.com DKIM : pass x-aol-sid: 3039ac1d404b4faec07b6c76 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none If you use a DDS of the AD9850/51, and probably the AD9832 type, there is a very neat way of amplitude keying them. Place an NPN transistor in series with the D/A current setting resistor, and a small resistor in teh emitter to give some neg feedback and key that. Using a low pass filter on the drive waveform allwos a gentle ramp rather than a hard on-off. More details are somewhere on the Analog Devices web site Not that gentle amplitude ramoing s a particularly good idea when used for driving switching PAs Andy 'jnt On 12 May 2012 20:28, Gary G4WGT wrote: > Hi Martin, LF, > > I have used relay keying using qrs.exe to key the output from my DDS VFO & > it was a very simple, stable & reliable method. The DDS VFO remained on all > the time. seems to me the way to go. > > 73, Gary - G4WGT. > > ----- Original Message ----- From: "James Moritz" > > To: > Sent: Saturday, May 12, 2012 7:14 PM > Subject: Re: LF: IEEE488 > > >> Dear Martin, LF Group, >> >> Provided you were happy with simple on/off keying, i.e. QRSS rather than >> DFCW or the various mFSK modes, there is no need to interface the sig gen to >> the PC. You could just connect the sig gen output via a relay or other bit >> of gating circuitry, set the generator to the frequency you want and key the >> relay with the QRSS software... Actually, for most types of TX, a better >> idea is to leave the generator going constantly and key the PA stage. I used >> to use an old Racal generator in this way. >> >> Cheers, Jim Moritz >> 73 de M0BMU >> > >