Saturday, May 26, 2007

Propagation planning

Contest University was organized by Tim Duffy (K3LR) and a handful of other top contesters. Tim's accomplishments are well known. You can get a glimpse of his efforts on his web site. In addition to all this planning, Tim also pulled moderator duty for the Friday Hamvention Antenna Forum. Even if the term hero doesn't seem apt, I believe his efforts, and the efforts of those he worked with, can easily be characterized as heroic. Thank you, guys.

Check in at Contest University was Wednesday evening with the activities scheduled to begin bright and shiny Thursday morning. Each of the 150 students received a sizable bundle of materials and collateral including a binder containing slides for all presentations, an Icom shirt, and a cloth bag stuffed with magazines, catalogs, and other gifts. Each student was also presented with their personalized schedule.
Just as with regular college classes, Contest University filled classes on a first-come-first-served basis. Those who responded to the class selection email quickly were likely to receive the class assignments they wanted; those who waited may not have. It seemed like the fairest way to accomplish seat assignments. I received the message requesting me to complete this form at 11:15 PM and had made my choices ten minutes later. I took some ribbing from Tim Duffy for this. My late night diligence resulted in me being the very first of the students to respond thereby winning me first dibs on all the classes I selected. Those who waited were not so lucky. Just as with contests, you snooze you lose. {grin}
Classes were held in three rooms: the banquet room, and two nearby meeting rooms. Breakfast was served in the banquet room while Tim Duffy briefed attendees on the schedule. Based on the selection process described above, students would split into the two smaller meeting rooms for morning classes. We would reconvene in the banquet room for lunch and more classes. After lunch, we would split again receiving the remainder of our instruction in those smaller meeting rooms.

Dean Straw (N6BV), Senior Assistant Technical Editor for the ARRL, was top of my schedule with Propagation: What To Look Forward To. Though I had done very little propagation planning for previous trips, I was quite keen to hear this presentation. Allow me to explain.
Most the the antennas I have used on 100 Pound DXpeditions have been verticals or dipoles, neither with any appreciable gain in a particular direction. (The notable exception to this was my trip to Deer Isle, Maine (NA-055) where Dave Bushong (KZ1O) and I deployed a Force-12 C3SS tribander atop a rugged military mast.) Because I do not typically have a directional antenna, there is no need to have a plan for where to point it. On Montserrat, for example, we erected the 17m vertical and just worked everybody we could hear. There was no plan to turn it to the East for European sunrise or to later turn it West for a different opening. Propagation planning was limited to band selection.
Things are about to change for me. I have ordered a small Mosley beam which I intend to use on my St. Kitts trip for CQ WW SSB in October. With a 17 dB front-to-back ratio, I must now point the antenna if I hope to hear anybody. If there is an opening to Europe and I am pointing towards South America, I'll miss it. So, I must now know (a) which band should I be on, and (b) where should the antenna be pointed?
Dean Straw's presentation focused on the propagation tables included with the ARRL Antenna Book (which he helps edit). If you don't already own this book, buy it now. Highly recommended. Anyway, the tables are published as pages within PDF files on the CD bundled with the book. There are two files for each covered geographic region: one for summary predictions between that place and Europe, the Far East, South America, Africa, Asia, Oceana, and North America, and one for detailed predictions between that spot and another covered region such as W1, W6, KL7, and so on.
In addition to this division by geography, the tables are also organized by month, sunspot activity, and band. For example, there is a page in the summary document for KP2, in October, and a low sunspot count.

Yes. The numbers are small in the snapshot above.
The numbers in the table represent anticipated S-unit readings. It is assumed that both stations are running 1500 watts and have 3-element yagis at 100 feet. You then discount values from there. I am running only 100 watts so I subtract 3 S-units from each value in the table. Additionally, I must subtract more S-units because I am not using a 3-element yagi, nor is it at 100 feet. Dean Straw presented a whole page of rules for discounting these table values to match them to different operating conditions.

I have begun doing the planning for St. Kitts with these tables by dropping the published values into a spreadsheet and discounting the numbers using Dean's rules. It has been time-consuming to create a model for this, but I hope to work out a solid operating plan for the whole contest over the next few weeks. Of course, I'll publish it in a place where it can be viewed once I am finished.

This was just one of the classes (the very first one!) at CU. I will try to discuss more of them in future blog entries.

2 Comments:

Blogger Steve Weinert said...

Scott - do you have ideas for OS-X based Propagation Prediction and also Antenna Modeling options?

73

Steve
K9ZW

May 26, 2007 11:03 PM  
Blogger David said...

I'd argue that it makes sense to have an idea of what the propagation is to other parts of the world even if you're only using a non-directional antenna because it helps you to be aware of short openings to other parts of the world. As an example, I'm going to Cayman next month with a Buddistick (sort of a "20 pound dxpedition", if you will), and I used Hamcap (sorry, it won't work under OS/X) to plot the expected propagation globally so that I can see, for example, when I might be able to work JAs or other more difficult areas. Even though I can't "beam" there, it does mean that if I'm operating at the right time, I'll ask NA and EU to stand by and at least listen. The result of the plot is available at my website if you're interested.

May 27, 2007 8:28 PM  

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