Return-Path: Received: (qmail 45603 invoked from network); 5 Feb 2004 21:05:40 -0000 Received: from unknown (HELO ptb-mxscan02.plus.net) (212.159.14.236) by ptb-mailstore01.plus.net with SMTP; 5 Feb 2004 21:05:40 -0000 Received: (qmail 35113 invoked from network); 5 Feb 2004 21:05:58 -0000 X-Filtered-by: Plusnet (hmail v1.01) X-Spam-detection-level: 11 Received: from ptb-mxcore02.plus.net (212.159.14.216) by ptb-mxscan02.plus.net with SMTP; 5 Feb 2004 21:05:57 -0000 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore02.plus.net with esmtp (Exim) id 1AoqhB-00090a-Ct for dave@picks.force9.co.uk; Thu, 05 Feb 2004 21:05:57 +0000 X-Fake-Domain: majordom Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1AoqgD-00005D-5m for rs_out@blacksheep.org; Thu, 05 Feb 2004 21:04:57 +0000 Received: from [147.197.200.9] (helo=hestia.herts.ac.uk) by post.thorcom.com with esmtp (Exim 4.14) id 1AoqgB-000054-V8 for rsgb_lf_group@blacksheep.org; Thu, 05 Feb 2004 21:04:56 +0000 X-Fake-Domain: gemini Received: from gemini ([147.197.200.44] helo=gemini.herts.ac.uk) by hestia.herts.ac.uk with esmtp (Exim 3.22 #1) id 1Aopb9-0005iB-00 for rsgb_lf_group@blacksheep.org; Thu, 05 Feb 2004 19:55:39 +0000 X-No-DNS-For: 147.197.232.252 Received: from [147.197.232.252] (helo=rsch15) by gemini.herts.ac.uk with esmtp (Exim 3.33 #1) id 1Aopb7-0001WA-00 for rsgb_lf_group@blacksheep.org; Thu, 05 Feb 2004 19:55:37 +0000 From: "James Moritz" To: rsgb_lf_group@blacksheep.org Date: Thu, 5 Feb 2004 19:55:39 -0000 Organization: University of Hertfordshire X-Bad-Message-ID: no DNS (rsch15) Message-ID: <000001c3ec22$07716120$fce8c593@rsch15> MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.2627 Importance: Normal In-reply-to: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 X-UH-MailScanner: No Virus detected Subject: LF: RE: RE: G0MRF 300w Tx & DDS VFO Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Checker-Version: SpamAssassin 2.60 (1.212-2003-09-23-exp) on post.thorcom.com X-Spam-Status: No, hits=0.0 required=5.0 tests=none autolearn=no version=2.60 X-SA-Exim-Scanned: Yes Sender: Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false X-PN-SPAMFiltered: yes X-Spam-Rating: 2 Dear Gary, LF Group, >The problem as I have specified in my e-mails is the low output. Last night >I checked back to the DDS IC & there are no substantial losses in the >signal >path, even the insertion loss of the LPF is negligable. Here are the actual >levels into 50 ohm load at the output of the DDS VFO. >137 & 274 Khz - 22mV .... There should be about 12-13dB of insertion GAIN between the DDS output and the output of the PCB due to the ERA-1SM modamp. Looking at the Analog Devices data sheet, and the schematic component values, the DDS output should be 10mA pk-pk, driving roughly 2 50R loads in parallel, i.e. 250mV pk-pk. The modamp should bring this up to about 1V pk-pk. The DC bias voltage on the modamp output pin should be 3-4V. Is it possible the modamp is in the wrong way round? If it had got turned through 90degrees, the signal would go straight from DDS to output via the 2 ground pins of the modamp. Cheers, Jim Moritz 73 de M0BMU