K6TU.Net
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Charlie
Jun 20, 2015, 7:15:33 PM6/20/15
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OK, I registered for K6TU.net propagation site. This is the site that did the propagation study for FT5ZM and others.
The first thing I did was have K6TU generate a set of terrain profile radials every one degree around the compass. All this was done by filling in my tower lat and long into a simple web form and sending it in. A few minutes later, K6TU emailed to me a link to the radial file. It was orders of magnitude easier than doing it the old fashioned way. I didn't have to load a USGS DEM map, or do any merging of USGS maps, or even use Microdem to draw the radials.
The pick the coordinates of my tower, I used Google Earth. The coordinates have to be entered in decimal degrees. There is a conversion link on K6TU if your coordinates are in a different format.
Once I downloaded the new radials from K6TU, I used HFTA to print out a 0 degree azimuth terrain profile from the K6TU site and compared it to the 0 degree terrain profile printed manually for the same tower, to make sure they matched. The shape of the terrain profile features is nearly identical, but there is a slight difference in the elevation of some features. I have known for some time the USGS map I have been using is not generating an elevation for my tower site that matches the elevation shown on Google Earth or paper topo maps. The HFTA elevation I have been using for my hilltop tower is 20' lower than Google Earth.
I always figured this was because the resolution of the USGS DEM data points is 30 meters and my hilltop must be falling between data points. However, when I look at the terrain profile generated by K6TU, it shows my tower base elevation to be exactly what Google Earth shows it to be, 884' ASL. Thus, the new K6TU elevations seem more accurate than what I have been using. Not sure what to make of this, K6TU is supposed to be using the same USGS reference I am using. Obviously something is different, more in favor of the K6TU data.
The other thing is that I now have a radial for every degree of azimuth with the new system, compared to every 5 degrees on the old system. Likely I could change the setting in Microdem and get 1 degree resolution on the old system, but the HFTA manual instructions were followed and they specified 5 degrees. I will rerun all my towers now with the new system. It is easy enough to do.
OK that addresses the terrain profiles. The next thing I did was create a data file that incorporates 360 azimuth radials into a special format for use by VOACAP for propagation studies. I had a slight bit of trouble with this, but finally got it done.
After this file was created, I uploaded it to the K6TU.net site and incorporated the data into a VOACAP propagation prediction. You can use K6TU to do these predictions without going to the trouble of creating a terrain file, you can enter manual parameters into a web form and do the same thing. These VOACAP predictions are interesting but truthfully I never have used them for DXing. Some expeditions and contesters plan their schedules by these things, but generally I have a feel for which bands might be open and when.
What I have not done yet is draw a graph showing my elevation pattern gain around the compass rose from the new 1 degree HFTA radial files. So far, I have not found where to do that graph on the K6TU site. One might have to download the data to an Excel file to do it. I might have overlooked it. Not too worried about that, it was more something interesting to look at. I already know what it shows :-) Terrain enhancement in some directions, even steven in some, and degradation in others. It is what it is anyway. Bring on the DX, we can still work it even if the signal is not rock crushing in some directions.
73 Charlie N8RR
The first thing I did was have K6TU generate a set of terrain profile radials every one degree around the compass. All this was done by filling in my tower lat and long into a simple web form and sending it in. A few minutes later, K6TU emailed to me a link to the radial file. It was orders of magnitude easier than doing it the old fashioned way. I didn't have to load a USGS DEM map, or do any merging of USGS maps, or even use Microdem to draw the radials.
The pick the coordinates of my tower, I used Google Earth. The coordinates have to be entered in decimal degrees. There is a conversion link on K6TU if your coordinates are in a different format.
Once I downloaded the new radials from K6TU, I used HFTA to print out a 0 degree azimuth terrain profile from the K6TU site and compared it to the 0 degree terrain profile printed manually for the same tower, to make sure they matched. The shape of the terrain profile features is nearly identical, but there is a slight difference in the elevation of some features. I have known for some time the USGS map I have been using is not generating an elevation for my tower site that matches the elevation shown on Google Earth or paper topo maps. The HFTA elevation I have been using for my hilltop tower is 20' lower than Google Earth.
I always figured this was because the resolution of the USGS DEM data points is 30 meters and my hilltop must be falling between data points. However, when I look at the terrain profile generated by K6TU, it shows my tower base elevation to be exactly what Google Earth shows it to be, 884' ASL. Thus, the new K6TU elevations seem more accurate than what I have been using. Not sure what to make of this, K6TU is supposed to be using the same USGS reference I am using. Obviously something is different, more in favor of the K6TU data.
The other thing is that I now have a radial for every degree of azimuth with the new system, compared to every 5 degrees on the old system. Likely I could change the setting in Microdem and get 1 degree resolution on the old system, but the HFTA manual instructions were followed and they specified 5 degrees. I will rerun all my towers now with the new system. It is easy enough to do.
OK that addresses the terrain profiles. The next thing I did was create a data file that incorporates 360 azimuth radials into a special format for use by VOACAP for propagation studies. I had a slight bit of trouble with this, but finally got it done.
After this file was created, I uploaded it to the K6TU.net site and incorporated the data into a VOACAP propagation prediction. You can use K6TU to do these predictions without going to the trouble of creating a terrain file, you can enter manual parameters into a web form and do the same thing. These VOACAP predictions are interesting but truthfully I never have used them for DXing. Some expeditions and contesters plan their schedules by these things, but generally I have a feel for which bands might be open and when.
What I have not done yet is draw a graph showing my elevation pattern gain around the compass rose from the new 1 degree HFTA radial files. So far, I have not found where to do that graph on the K6TU site. One might have to download the data to an Excel file to do it. I might have overlooked it. Not too worried about that, it was more something interesting to look at. I already know what it shows :-) Terrain enhancement in some directions, even steven in some, and degradation in others. It is what it is anyway. Bring on the DX, we can still work it even if the signal is not rock crushing in some directions.
73 Charlie N8RR
Larry R Fravel
Jun 20, 2015, 10:59:27 PM6/20/15
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"If
you aim at nothing, you will hit it every time." - Zig
Ziglar
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