[TowerTalk] Takeoff angles HF VS VHF / F2 VS Es DE K0FF

[n4kg@juno.com]

N4KG comments / questions intersperced below.

On Mon, 21 Aug 2000  "Tom Rauch" <w8ji@contesting.com> writes:
> 
> > Lets talk apples to apples and oranges to oranges or the newbies 
> will get
> > totally confused. On F2 skip, which is the predominate mode on HF 
> a low angle is almost always better than a high angle for long distance
> > communication. I can demonstrate this clearly in my own shack on 
> 20M any time with the 2 different 20M beams.
> 
> I agree with that. My 150 foot high 5 element 20 meter antenna 
> was a real smoker into Europe and even the Caribbean from Ohio. 
> The only time a lower antenna was better was when the band was 
> really stretched out and I wanted to work in close.   

	And how do you KNOW that the peak was not at the
	SECOND lobe (around 20 degrees) instead of the first?

	As I have said too many times on this reflector, my
	TH7 at 40 ft is almost ALWAYS better to Africa on
	20M in the afternoons than my Telrex 3L20 at 80 ft.
	It is OFTEN stronger to Europe in the early afternoons
	on 20M.  MANY others (K4AB, N4NO, AA4NU, NN4T)
	and others in the literature who have BOTH high and low
	antennas have observed the same phenomenon. N4KG
> 
> The same thing applies on 160 meters, except at even closer 
> distances. My ground mounted verticals clearly beat my horizontal 
> antennas even though some are 300 feet in the air!
> 
> They are about equal at distances from 100 miles to maybe two 
> hundred miles, but beyond that the vertical is better a large 
> percentage of the time. The wave angle is clearly very low even on 
> 160 meters and even at reasonably short distances.
> 
> The exception is at or just after sunrise during days when the band 
> has a strong sunrise peak, or during geomagnetic storms.

	Interesting.  I OFTEN observe that my 130 ft high 80M dipole
	is better than my vertical to Western and Central Europe.
	Only the Scandanavians are regularly stronger (RX and TX)
	on my vertical or elevated GP.   N4KG
> 
> Tilting the antenna can't possibly have much effect unless the 
> antenna is very directive in the elevation plane. Look at the 
> ***free-
> space pattern**** of the antenna, and the vertical plane HPBW. 
> Only when the tilt is enough degrees to appreciably change the 
> energy down at the angle to earth or up at the sky at the desired 
> angle will tilting have an effect.
> 
> Tilting a large collinear vertical has an affect, if vertical  pattern
is 
> narrow enough. Tilting an antenna with a wide freespace vertical 
> antenna moves the straight up null to an angle more in the direction 
> of top tilt but does little else to pattern.
> 
 
> 
> 73, Tom W8JI
> w8ji@contesting.com

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