From owner-qrp-l@Lehigh.EDU Thu May 1 21:45:48 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 VAA17989 for ; Thu, 1 May 1997 21:45:46 -0400 (EDT) Received: from Lehigh.EDU ([127.0.0.1]) by fidoii.cc.Lehigh.EDU with SMTP id <35235-54090>; Thu, 1 May 1997 21:45:25 -0400 Received: from nss2.CC.Lehigh.EDU ([128.180.1.26]) by fidoii.cc.Lehigh.EDU with ESMTP id <35214-58958>; Thu, 1 May 1997 21:44:29 -0400 Received: from mailhost.cyberhighway.net (qmailr@mailhost.cyberhighway.net [205.139.62.187]) by nss2.CC.Lehigh.EDU (8.8.5/8.8.5) with SMTP id VAA134252 for ; Thu, 1 May 1997 21:44:16 -0400 Received: (qmail 958 invoked from network); 2 May 1997 01:44:41 -0000 Received: from ts1-05.eug.cyberhighway.net (HELO ?206.26.237.21?) (206.26.237.21) by mailhost.cyberhighway.net with SMTP; 2 May 1997 01:44:41 -0000 Message-Id: <199705020144.VAA134252@nss2.CC.Lehigh.EDU> Date: Thu, 1 May 97 18:42:55 -0700 Reply-To: russ@natworld.com Sender: owner-qrp-l@Lehigh.EDU Precedence: bulk From: Russ Carpenter To: "Low Power Amateur Radio Discussion" Subject: Confessions of a Terrain Junkie Mime-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" X-To: "QRP-L List" X-Listprocessor-Version: 8.1 beta -- ListProcessor(tm) by CREN Status: RO In the aftermath of the QRPTTF, several members of the QRP-L were kind enough to praise the signals from my in-the-field operation (in spite of the general slothfulness and ineptitude of the operator). This seems like a good time to share some insights. It turns out that locating an antenna in just the right terrain can have a remarkable impact on signal strength. I first got interested in this subject about four years ago, after reading Les Moxon's inscrutable but intriguing book "HF Antennas for all Locations." Chapter 10, entitled "The Antenna and Its Environment," fired my imagination. Sloping terrain can produce surprising gain at low angles of radiation. According to Moxon, with ideal terrain (a steep slope, at least 1,000 feet high, terminating in a plain or ocean) there can be 6dB of gain from the foreground reflection and another 6dB of gain from the distant reflection. After reading Moxon's book, I trooped all over Oregon looking for the perfect mountain. The best part of this quest was that it was an excellent excuse to take some great hikes to obscure mountaintops, many of which had been lookout sites in the old days. My search, however, was based largely on theory. Two things have since happened that have convinced me that Moxon's ideas about terrain are valid. First, Brian Beezley published software called "TA," which performs ray tracing analysis for specific antennas in actual terrain. Second, I've been getting some outstanding results from very humble antennas placed in steep terrain. By now, I've done ray tracing analyses of quite a collection of ridges and mountaintops and have tested many of them in outdoor ham events, like QRPTTF, Field Day, QRP Afield, and so on. For me, this emphasis has transformed a fine hobby (QRP radio) into the hobby from heaven. Now, I've got the perfect excuse to stick some radio gear in a pack, hop up to the top of some steep terrain, and put out a pretty nice signal in a contest environment. Here's some practical advice: 1. The places with ideal terrain almost never have trees in the right place (or trees at all). So it's important to develop a self supporting, portable antenna. For me, this means a multiband inverted V supported by a lightweight mast. 2. As Moxon states, with steep terrain horizontal polarization is much better than vertical. Vertical polarization cannot take full advantage of the gain from near and far reflections. Another reason why an inverted V, placed broadside to the cliff, makes sense. 3. Living on the West Coast, I look for east-facing, convex cliffs which terminate in large, flat areas. Interestingly, the vertical radiation coming off the ends of the inverted V, and reflecting off the "flat terrain" of a ridge line, works just fine for the relatively short north and south distances needed to cover the West Coast. Meanwhile, the inverted V is radiating horizontally polarized waves into the "foreground zone" of the cliff, and producing low angle, killer signals to the east. 4. TA generates vertical radiation profiles which, in turn, can be ported into the VOA Area propagation software (using a utility program you can get from Brian). You can then plot maps of the country, or the world, showing where your peanut whistle signal will go. Thus, TA will tell you about the elevation impacts of terrain, while VOA will dramatically show you the azimuth impacts. A far cry from the days when I was wandering around looking at mountains with nothing but Moxon's words echoing in my head. 5. The tops of mountains and ridges are exposed to weather. So if the weather looks dubious, you need to take shelter that can stand up to fairly exciting conditions. So that's it--Terrain 101. The secret to life. Russ Carpenter, AA7QU McKenzie River, Oregon