Return-Path: Received: from rly-df10.mx.aol.com (rly-df10.mail.aol.com [172.19.156.23]) by air-df05.mail.aol.com (v125.7) with ESMTP id MAILINDF051-5834a9ab52b33c; Sun, 30 Aug 2009 13:21:52 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-df10.mx.aol.com (v125.7) with ESMTP id MAILRELAYINDF106-5834a9ab52b33c; Sun, 30 Aug 2009 13:21:49 -0400 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Mho5J-0008QA-G1 for rs_out_1@blacksheep.org; Sun, 30 Aug 2009 18:20:57 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Mho5J-0008Q1-3U for rsgb_lf_group@blacksheep.org; Sun, 30 Aug 2009 18:20:57 +0100 Received: from smtp825.mail.ird.yahoo.com ([217.146.188.235]) by relay1.thorcom.net with smtp (Exim 4.63) (envelope-from ) id 1Mho4S-0006G2-7V for rsgb_lf_group@blacksheep.org; Sun, 30 Aug 2009 18:20:04 +0100 Received: (qmail 12640 invoked from network); 30 Aug 2009 17:20:45 -0000 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=btopenworld.com; h=Received:X-Yahoo-SMTP:X-YMail-OSG:X-Yahoo-Newman-Property:Message-ID:From:To:References:In-Reply-To:Subject:Date:MIME-Version:Content-Type:Content-Transfer-Encoding:X-Priority:X-MSMail-Priority:X-Mailer:X-MimeOLE; b=caud2zo0gnEjN9ZZkuQaWqDmygt3EaHW6U7ALXeRvDSDDrCo9blm8D38mX6jScDSwPs+rhNDqXeWcrwwIyKpFEVJlSMmen0yTIEq6JhMgpefsCaL2Xzu5nG4ByVeiIMcxeJWuNe3+fAifucnRhmGjyuBV1na6nLtduzmUjsl9Do= ; Received: from unknown (HELO JimPC) (james.moritz@86.177.108.28 with login) by smtp825.mail.ird.yahoo.com with SMTP; 30 Aug 2009 17:20:45 -0000 X-Yahoo-SMTP: qKIhhNCswBB2TTHr2BORWcGGR2mpopxhCcunGIxpCKQYiG07Q7UOhNo- X-YMail-OSG: DimpQKkVM1mCsPt4l9L8VMNeMxUnxfWa6nb2zClIp3s94po2eHFyIEoJGWrDPXGXqJCs5QDS8AGx.RmhqQtk1AAI7ObKKcA2ioeVb44NiMjqCp6u8Ks5.7XuANq6FxLJE1jjFQLRTGa0JXGnRc7ThRhI4w1MLuEogufEfkEgvKGTKws4M0mgIDM1xftAroveD8TV_H0Jx1zfIK1Kwi2kGFhV8rO1B9lymoPzzzDmjj2C2SLdGeQ- X-Yahoo-Newman-Property: ymail-3 Message-ID: From: "James Moritz" To: References: <92C6FA2037874B9888C28DDBF9096246@JimPC> <9afca2640908300531w1393b476y7a06b102a9db9076@mail.gmail.com> In-Reply-To: <9afca2640908300531w1393b476y7a06b102a9db9076@mail.gmail.com> Date: Sun, 30 Aug 2009 18:20:45 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Windows Mail 6.0.6001.18000 X-MimeOLE: Produced By Microsoft MimeOLE V6.0.6001.18049 X-Karma: unknown: DomainKey-Status: good (testing) X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,none Subject: LF: Re: FT-817 at LF/MF Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=original 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=0.1 required=5.0 tests=MISSING_OUTLOOK_NAME 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-IP: 193.82.116.20 Dear Roger, LF Group, Re: using the FT-817 and long wire for receiving the WSPR beacons - I have an FT-817 also, which I mostly use with a converter for VLF - MF reception due to its poor sensitivity at low frequencies. I just did a quick sensitivity check on mine - the following figures are for 10dB SNR using the 500Hz CW filter: 4.5MHz (the output frequency of my converter): "IPO on" (ie. preamp off) -117dBm "IPO off" (preamp on) -125dBm Sensitivity is much the same over the HF range. 502kHz: IPO on -105dBm IPO off -108dBm 137kHz: IPO on -89dBm IPO off -80dBm So sensitivity is about 20dB down on 500k, which is more or less passable, but a bit disastrous at 137k where it is around 30 - 40dB down depending on whether the preamp is selected or not. The un-tuned wire will also be a contributing factor - at low frequencies, it will have a high capacitive impedance with a huge mismatch to the low impedance RX input. You can expect to lose a further 20dB or more at 500k, and 30dB or more at 137k, compared to having some sort of antenna tuner. These figures are not unusual for the situation of using a "random" wire with typical amateur HF rigs with general coverage RX, so it is not surprising people often get reasonable results at 500k using this sort of setup for receive, but 137k usually needs a bit more sorting to get useful reception Cheers, Jim Moritz 73 de M0BMU