[VHFcontesting] 6m Take off angles?
felasstic at yahoo.com
Thu Aug 31 15:10:53 EDT 2006
First you must know the terrain around the antennas. If it is flat, here are some general guidelines. A pair of antennas at 20' and 40' is good for intense, close-in, Sporadic E. The higher lobe that is supressed is too high angle to be refelected by most E clouds. F2 is usually best with a very low angle, so higher the better. The same is true for ground wave.
If you have any slope near your tower, N6BV's ray tracing software is needed to figure out the best heights.
k2kw-8 at adelphia.net wrote: Hi All,
I just did some reading in the archives, though I couldn't find anything that addressed my question:
What are the important take off angles for Es, F2 etc?
I am in the planning stage of putting up my 6m antenna. It will likely be a single 50' boom antenna, and likely go at the 40-60' level. I guess my main target will be DXing at the top of the cycle, though I will surely get on for the summer Es season. If I have the ability, I would put up a 2nd small boom yagi on the other tower, but right now that's not likely.
I'm comfortable with how take off angles work in HF, but clueless on 6m take off angles. I hear people talking about antennas for high and low angles, but I don't know what "high and low angles" are. What's confusing in the archives, is that people use a 2 stack at the 20' & 40' levels for high angle, yet the stack eliminates the upper lobes, so you mainly get a single lobe.
I would like to put up a stack, but I don't think that's in the cards, or the bottom antenna would be fixed (might be useful when targeting EU for example)
In running HFTA, the difference that I'm looking at is where the first null hits, and is what is a useful take off angle? The lower height has a broader first lobe, and a null in the ~13-14 deegree take off angle range based on my terrain. The higher antenna has more gain at lower angles, but the first null is in the 7-9 degree take off range.
My assumption is to have a lower antenna with a broader take off angle, but I don't want to throw away low angle gain if I don't have to.
Many thanks, Kenny K2KW/8 (now living in SW Ohio)
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