Return-Path: Received: (qmail 10507 invoked from network); 21 Jan 2001 15:35:37 -0000 Received: from unknown (HELO warrior-inbound.servers.plus.net) (212.159.14.227) by excalibur.plus.net with SMTP; 21 Jan 2001 15:35:37 -0000 Received: (qmail 1863 invoked from network); 21 Jan 2001 15:29:55 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by warrior with SMTP; 21 Jan 2001 15:29:55 -0000 X-Priority: 3 X-MSMail-Priority: Normal Received: from majordom by post.thorcom.com with local (Exim 3.16 #1) id 14KMH4-0004Vx-00 for rsgb_lf_group-outgoing@blacksheep.org; Sun, 21 Jan 2001 15:19:22 +0000 Received: from hestia.herts.ac.uk ([147.197.200.9]) by post.thorcom.com with esmtp (Exim 3.16 #1) id 14KMH3-0004Vs-00 for rsgb_lf_group@blacksheep.org; Sun, 21 Jan 2001 15:19:21 +0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Received: from [147.197.200.44] (helo=gemini) by hestia.herts.ac.uk with esmtp (Exim 3.16 #4) id 14KMGs-0006T0-00 for rsgb_lf_group@blacksheep.org; Sun, 21 Jan 2001 15:19:10 +0000 Message-ID: <22624.200101211519@gemini> From: "James Moritz" Organization: University of Hertfordshire To: rsgb_lf_group@blacksheep.org Date: Sun, 21 Jan 2001 15:22:57 +0000 MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 8bit Subject: LF: Receiving VA3LK X-Mailer: Pegasus Mail for Win32 (v3.11) Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: Dear LF Group, I monitored VA3LK's frequency again using the same set-up as before, and got rather similar results as in the previous two nights. The QRN level seemed rather high, adding about 5-10dB to the noise floor, however, Larry's signal also seemed to be a few dB stronger, so copy was still fairly good. As before, there were several periods of good copy, interspersed with fades where only odd dots or weak traces of signal were visible. The periods of good copy were 2220-2240, 0040-0150, 0225-0320, 0345-0400, 0715- 0745, 0825-0840. The signals seen around dawn are getting quite weak, but the noise level also drops off at this time. I have yet to see anything before about 2200 in the evening. >From the other reports that are coming in, it would seem that most people equipped for QRSS operation should be able to detect Larry's signals; the important thing compared to the "faster" QRSS is to obtain high resolution and accurate frequency calibration of the receiver, so you know where to look for the signal. Here are some details of the methods I am using: I am currently using a W&G SPM19 level meter with external homebrew preselector and demodulator, and DL4YHF's "Spectrum Lab" spectrogram software. This setup has the advantage of very good frequency stability, but I think most synthesised receivers would be able to maintain the +/- a couple of Hz per night which is probably required. The frequency error of 2Hz on the soundcard seems to be something of a standard.... the easiest way to calibrate the frequency within a fraction of a Hz is to look at the Loran lines; in my QTH, (SE England), there are lines at 137.78785, 137.79171, 137.79528 kHz. G4CNN has produced lists of frequencies from other Loran chains. I believe Loran uses a caesium clock for a reference, so they should be pretty accurate. They had to come in handy for something! The transmit frequency does not seem to have drifted measurably. The spectrogram software needs to have higher resolution than the 0.3Hz that seems to be optimum for 3s/dot QRSS. Spectrum lab goes down to 0.042Hz (11k sample rate, divided by 4, 65k point FFT, average of 2 FFTs selected in the "spectrum" menu). It also has an input monitor 'scope display, so you can check the A/D converter is not being overloaded by the QRN. The brightness and contrast controls can be set for high contrast (about 20dB for the full colour spectrum), which is good for readability, but less contrast is better for monitoring the general signal level. The spectrum width is set to 5Hz or 10Hz - another reason to calibrate the frequency carefully. I find that the receiver generates a weak spurious signal at it's center frequency; it is worth checking for this kind of thing during the day. I set the timebase for about 35 mins per screen (can't remember actual figure), and setting the image capture to once every 30 minutes means I can go and get some sleep sometimes! I have been using a large single turn loop antenna, which I mentioned before on the reflector, which seems to work quite well and gets rid of most of the Loran lines. But I think the TX inverted L would work well too. Cheers, Jim Moritz 73 de M0BMU