This weekend is the EUHFC contest. No DX, only EU. It’ll be hard enough with A=27 and K=5. Stupid solar flares! Anyway the question arose: should I leave the tower as it is now, with 2 out of 3 sections up, or should I crank it up all the way? Here’s the deal:
- Case 1: tower up 2/3: tribander at 15m, rotary dipole 40m at 17m
- Case 2: tower up 3/3: tribander at 21m, rotary dipole 40m at 23m
I think I have always used case 1 except last year but I’m not sure anymore. So what should I do? I talked it over quickly over MSN with Wim ON4BHQ and later on with Denis K7GK. The latter suggested doing a quick analysis with HFTA. HFTA is a computer program that comes with the ARRL Antenna Handbook, and it’s written by N6BV. I knew I played with HFTA in the past, but I got stuck. To run the program you need to know your terrain profile. Back then, a few years ago, it seemed for Belgium (Flanders?) this data was only available commercially. Since I refuse to pay for data collected by the government (presumably?) or at least paid for with tax money (guess so), I didn’t go any further with HFTA.
Now K7GK suggested I’d use the standard flat terrain. Worth a shot. It took me a while to see it but I needed to lower my ‘ASL’ in the flat terrain data file. I’m at 46m above sea level here and then I needed to enter that number in foot, not meters. Here are the plots, case 1 is blue and case 2 is in red:
Actually I was quite surprised to see this. The program calculates all the data for different statistical take off angles and awards a “figure of merit” to the situation. It seems the lower height is much better for 10m and 15m, as expected. The difference on 20m is marginal.
The biggest difference of course is on 40m but not really a problem since I experienced over the last couple of weeks that with the 40m dipole at 17 meters above the ground, EU in a 1500 km range is LOUD. I tried to draw a circle on Google Earth with a 1500 km radius but it seems GE doesn’t support this. Anyway 1500 km spans deep down EA to high up in Scandinavia, and far enough in UA. Usually in EUHFC I set the beam at 90° and park it there. Let’s hope the announced T-storms stay away. The current A-index is already enough of a burden.