Return-Path: Received: (qmail 9342 invoked from network); 11 May 2000 07:55:02 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by teachers.core.plus.net.uk with SMTP; 11 May 2000 07:55:02 -0000 Received: from majordom by post.thorcom.com with local (Exim 3.02 #1) id 12pngm-0001xp-00 for rsgb_lf_group-outgoing@blacksheep.org; Thu, 11 May 2000 08:47:20 +0100 Content-Transfer-Encoding: 8bit Received: from bob.dera.gov.uk ([192.5.29.90]) by post.thorcom.com with esmtp (Exim 3.02 #1) id 12pngg-0001xS-00 for rsgb_lf_group@blacksheep.org; Thu, 11 May 2000 08:47:14 +0100 Received: by bob.dera.gov.uk; (8.8.8/1.3/10May95) id IAA20145; Thu, 11 May 2000 08:50:20 +0100 (BST) X-Priority: 3 X-MSMail-Priority: Normal Received: (qmail 2312 invoked from network); 11 May 2000 08:43:01 -0000 Received: from gauntlet.mail.dera.gov.uk (172.16.9.10) by baton.dera.gov.uk with SMTP; 11 May 2000 08:43:01 -0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Received: by gauntlet.mail.dera.gov.uk; id HAA25200; Thu, 11 May 2000 07:31:21 GMT Received: from unknown(146.80.11.40) by gauntlet.mail.dera.gov.uk via smap (3.2) id xma025184; Thu, 11 May 00 07:31:00 GMT Received: from frn-gold-1.dera.gov.uk (unverified) by mailguard.dera.gov.uk (Content Technologies SMTPRS 4.1.5) with ESMTP id for ; Thu, 11 May 2000 08:51:27 +0100 Received: by FRN-GOLD-1 with Internet Mail Service (5.0.1460.8) id <2J00B35S>; Thu, 11 May 2000 08:45:36 +0100 Message-ID: <3617AC3245C2D1118A840000F805359C017528CF@pdw-mercury-1.dera.gov.uk> From: "Talbot Andrew" To: rsgb_lf_group@blacksheep.org Subject: LF: 1Hz Bandwidths Date: Thu, 11 May 2000 08:45:32 +0100 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.0.1460.8) Content-Type: text/plain; charset=iso-8859-1; format=flowed Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: > James Moritz wrote: > > > Dear Andy & Group, > > With a 1Hz Bandwidth, isn't it rather difficult to find the > signals > > in the first place? How do you tell if what you are receiving is a > > signal or not? It seems to me that some radically different > > operating procedures will have to be devised to exploit extreme > > narrow band techniques such as these! > > It has to be assumed you know the operating frequency beforehand to the required accuracy - being able to adjust to within 1 Hz should be trivial at these frequencies where it is even difficult to pull a crystal that far off frequency. You will know a signal is there when the demodulator or display responds in the correct manner. Alberto Wrote: >Spectran presently applies a Hamming window to the incoming data. >If you think it would be useful to use a rectangular one, perhaps >selectable with a push-button, it is an easy change to the program I don't think a rectangular window will offer much extra value in a crowded band like 137kHz ( ! ) the sidelobes of other signals could cause visual QRM offsetting the 1.8 times bandwidth advantage. I've played with many window types and come to the conclusion that the Hamming or Hanning windows are the best compromise every time. By the look of Spectrogram, it also uses one of these. Andy G4JNT -- The Information contained in this E-Mail and any subsequent correspondence is private and is intended solely for the intended recipient(s). For those other than the recipient any disclosure, copying, distribution, or any action taken or omitted to be taken in reliance on such information is prohibited and may be unlawful.