From owner-qrp-l@Lehigh.EDU Thu Oct 23 12:12:12 1997 Received: from fidoii.CC.lehigh.EDU (fidoii.CC.lehigh.EDU [128.180.1.4]) by oucsace.cs.ohiou.edu (8.8.5/8.8.5) with ESMTP id MAA27508 for ; Thu, 23 Oct 1997 12:12:11 -0400 (EDT) Received: from Lehigh.EDU ([127.0.0.1]) by fidoii.cc.Lehigh.EDU with SMTP id <35039-71666>; Thu, 23 Oct 1997 12:00:47 -0400 Received: from nss4.cc.Lehigh.EDU ([128.180.1.13]) by fidoii.cc.Lehigh.EDU with ESMTP id <34880-34544>; Thu, 23 Oct 1997 11:28:36 -0400 Received: from server1.maxwell.com (server1b.maxwell.com [199.120.55.3]) by nss4.cc.Lehigh.EDU (8.8.5/8.8.5) with ESMTP id LAA60064 for ; Thu, 23 Oct 1997 11:28:24 -0400 Received: from inferno.scubed.com (inferno.scubed.com [192.31.66.42]) by server1.maxwell.com (8.8.7/8.7.2) with SMTP id IAA14817 for ; Thu, 23 Oct 1997 08:28:19 -0700 (PDT) Received: from [192.31.66.158] by inferno.scubed.com (S3.4/s3-sgi-5) id PAA18563; Thu, 23 Oct 1997 15:22:31 GMT Message-Id: Date: Thu, 23 Oct 1997 09:29:07 -0600 Reply-To: ji3m@maxwell.com Sender: owner-qrp-l@Lehigh.EDU Precedence: bulk From: ji3m@maxwell.com (James R. Duffey) To: "Low Power Amateur Radio Discussion" Subject: Propagation on 40M; The Band Goes Long, But in Which Direction? (long) Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" X-Sender: ji3m@192.31.66.42 X-Listprocessor-Version: 8.1 beta -- ListProcessor(tm) by CREN Status: RO I have been following the discussions on 40 m propagation and the band "going long". Couldn't resist putting in my $0.02 worth. Propagation is a fairly well understood physical phenomena. For references I suggest the chapter on propagation in the ARRL Handbook and deVoldere's discussion on propagation in is "Tips and Techniques for Low Band DXing". After you read these you will better understand why you are hearing the stations you are on the bands. To first order, much of the propagation phenomena we see on the low bands can be understood by the position and activity of the Sun. Signals are reflected by ionized atoms in the ionosphere. These atoms are ionized by the Sun's energy and during high solar activity times can be supplied by the Sun. The density of ionization will be largest directly under the Sun's position on the earth. That is "nadir" for those of you in the satellite business. Therefore, as an approximation, the "best" or "most likely" propagation path will be a straight line that connects your station, the subearth position of the Sun, and the station you are talking to, with the Sun's subearth position at the midpoint of the path. Around the equinnoxes, March and September, the band will open to the east in the morning, to the south in midday and to the west in the evening. In the summer when the sun is farther north, the band opens to the north east in the morning, the south in midday and to the north west in the afternoon and evening. In the winter, when the sun is farther south, we get openings in the morning to the southeast, still to the south in the midday and to the southwest in the evening. As the day ends, the sun's subearth position moves further west from your QTH which makes the midpoint of the propagation path further away, which makes the stations you can talk to further away, which is what we call the band going long. Now this is an oversimplifiation and the area ionized by the sun is not a spot, but a rather large patch, so there are a lot of straight lines that can be drawn from your station through this patch to the station you are communicating with. Also the portion that remains ionized is often big enough to support twin reflections which can also lengthen the path. The ionization rate is faster than the recombination rate so there is some skewing of the path to the east. In addition, on 40M absorption by lower ionospheric layers pretty much eliminates long DX during the day. In the summer Europe is good in the morning, in the winter propagation favors the Carribbean at the same time. Hawaii and the South Pacific are nice in the evening, with winter afternoons and evenings favoring Australia and New Zealand. Particularly good DX paths can be found around Sunup and Sundown. On the other hand, 15M and sometimes 10M are often open to South America at midday even when the sunspot activity is low. Propagation to South America is particualrly good around the equinoxes. All of this is included in simple propagation prediction programs such as MiniMuf. I suggest acquiring one and "fiddling around with it" to better understand why the bands behave the way they do. I hope that this simplified propagation explanation is of benefit to list readers. For the whole story read the references I have given above and discover all the fine (and not so fine) points I have glossed over. - Duffey KK6MC/5 James R Duffey KK6MC/5 DM65 30 Casa Loma Road Cedar Crest, NM 87008