Hi Kenny;
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.
Fred
k2kw-8@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.
Any thoughts?
Many thanks, Kenny K2KW/8 (now living in SW Ohio)
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