Envelope-to: dave@picks.force9.co.uk Delivery-date: Sun, 12 Feb 2006 23:26:39 +0000 Received: by ptb-mxcore01.plus.net with spam-scanned (PlusNet MXCore v2.00) id 1F8Qc3-0007s5-3x for dave@picks.force9.co.uk; Sun, 12 Feb 2006 23:26:39 +0000 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore01.plus.net with esmtp (PlusNet MXCore v2.00) id 1F8Qc2-0007ru-V7 for dave@picks.force9.co.uk; Sun, 12 Feb 2006 23:26:39 +0000 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1F8QbP-0008LK-LJ for rs_out_1@blacksheep.org; Sun, 12 Feb 2006 23:25:59 +0000 Received: from [193.82.59.130] (helo=relay2.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1F8QbO-0008LB-K5 for rsgb_lf_group@blacksheep.org; Sun, 12 Feb 2006 23:25:58 +0000 Received: from smtp808.mail.ukl.yahoo.com ([217.12.12.198]) by relay2.thorcom.net with smtp (Exim 4.51) id 1F8ROi-0003hc-7r for rsgb_lf_group@blacksheep.org; Mon, 13 Feb 2006 00:17:01 +0000 Received: (qmail 91398 invoked from network); 12 Feb 2006 23:25:52 -0000 Received: from unknown (HELO lark) (alan.melia@btinternet.com@213.122.18.199 with login) by smtp808.mail.ukl.yahoo.com with SMTP; 12 Feb 2006 23:25:50 -0000 Message-ID: <003401c6302b$aa9d4b80$67b0fea9@lark> From: "Alan Melia" To: rsgb_lf_group@blacksheep.org References: <1f8.1b254c1a.3120f5b3@aol.com> Date: Sun, 12 Feb 2006 23:06:32 -0000 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 5.00.2615.200 X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2615.200 Subject: Re: LF: Fast QSB and SXV ripples Content-Type: text/html; charset=windows-1252 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-PN-SpamFiltered: by PlusNet MXCore (v2.00) Content-transfer-encoding: 8bit
Hi Markus. I cannot believe a 10ms "delay" even if one path had managed to get through the E layer and up to the F layer and back the timing is not enough. HOWEVER dont forget that is an FSK signal with two frequencies almost 100Hz apart. Could it be a selective sideband fade artifact ?? I am not sure how to interpret your plots but the other thing we have found is that SXV transmit with the FSK on  a "subcarrier" on the upper sideband of their nominal frequency. This I think is why they are not always that stable (the subcarrier frequency drifts) and have been seen to drift up and down by 10s of Hz, but that effect is usually fairly slow.
 
There was no significant aurora so it was not backscatter from the auroral curtain which is seen in the States as a broadening of a single frequency (QRSS) line.
 
 As the signal is changing phase rapidly could there be some interaction with the sample rate (like we get looking at the patterns produced by PSK31)....can you reprocess at a different rate and get the same effect?
 
Cheers de Alan G3NYK
----- Original Message -----
From: MarkusVester@aol.com
To: rsgb_lf_group@blacksheep.org
Sent: 12 February 2006 20:33
Subject: Re2: LF: Fast QSB and SXV ripples

Dear Alan,

thanks a lot for commenting on this riddle. Yes the two hop versus one hop pattern is probably the most common source of multipath fading. But what keeps unresting my mind is that 10 millisecond figure: how would such a long delay fit into the picture, how can you fold up an extra 3000 km inbetween ionospheric layers and ground?

I am aware that the group velocity in a dispersive medium may be slower than c, showing in the upward "hook" in ionograms near cutoff. But this is at several MHz, could it be so pronounced at LF?

I found myself fantasizing about horizontal detours, like reflections from ionospheric irregularities (whatever these may be) or terrestial features like a mountain range or a coastline. There is a fascinating article by Peter Dana on the "Raymondville Ghost", a focused reflection of LORAN groundwave signals from a Mexican mountain bluff:
http://www.pdana.com/PHDWWW_files/Rghost.pdf .

Lots of questionmarks in this posting...

Have a nice evening,
73 de Markus, DF6NM

In einer eMail vom 12.02.2006 01:29:53 Westeuropäische Normalzeit schreibt alan.melia@btinternet.com:

Hi Markus I gave up watching SXV as I could not make any sense out the levels at the best of times. I think the complication is the the Adriatic and the mountains. Bob Brown NM7M recounts some strange results at dawn on a 50kHz signal signal skirting the rockies in a QST article.  What happens if you factor in interference between a one-hop and  a two-hop signal ?  My calculation suggest things move a lot quicker. It is difficult to do it properly as the higher angle 2-hop signal penetrates the ionosphere further. It has been very quiet recently and there is very little absorbtion at night for these higher modes. I think this is why the longer paths often show slower smoother changes, because the higher modes are attenuated out of the picture.
 
Cheers de Alan G3NYK