[TowerTalk] Re: Can takeoff angle be too low?

[n4kg@juno.com]

N4KG responses inserted following appropriate paragraphs.
Previous discussion omitted for brevity.

On Mon, 18 Dec 2000 Pete Smith <n4zr@contesting.com> writes:
> Wait a second....
> 
> N6BV's original data made certain assumptions about the antenna on 
> either end of the path.  In about October 98, he revised the data,
based 
> on assuming isotropic antennas at each end of the path.  These tended 
> in general to give more weight to lower-angle modes.   (N4ZR)

	As one would expect.  A more complete understanding
	would be obtained by calculating the path loss for each
	mode (waveangle) supported by the ionopshere and then
	applying the energy radiated at the various angles by
	antennas of different heights from the minimum to 
	maximum height typical of amateur installations. 
	It is a LOT of work, but would be a more accurate
	representation of amateur signals.  de N4KG

> In both cases, my understanding is that only the best mode 
> was counted, even in cases where there were 4 or 5 different ones, 
> some within a few dB of the best  one.  (N4ZR)
> 
     Which leads to the mis-assumptions so prevalent today, 
     that higher angles DO NOT PROPAGATE,  EVER,
     since the data was misrepresented by omission.
     de N4KG

> If you assume low dipoles and/or tribanders on the other end of a 
> W1-4/EU path, then a high antenna may have a null right where the 
> European  antenna is concentrating its energy.  There will be times 
> when (with these antennas) signal strength will be significantly better

> at a higher angle  (with more hops) than at a lower one.  The result 
> could very well be a  perceived (and real) advantage to the lower 
> antenna at those times.  (N4ZR)

	As has been reported by MANY observers but
	dismissed by interpreters of incomplete or 
	inaccurate computer models, many of whom
	have not made their own OBSERVATIONS. 
	de N4KG
	 
	(Note that HF Broadcast stations in Europe
	are NOT representative of the typical DX
	station with low antennas that we are trying 
	to hear in contests.)	de N4KG
> 
> Try to apply the same principle in W9 or W5 and it probably doesn't 
> prove out, because those high angle modes are not present for much 
> of the  time, and when they are the signal level is less.  (N4ZR)
> 
	Ah,  N2IC/0 and WE9V, among others, have reported
	Low antennas beating out stacks during mid day.
	Even KL7Y or KL7RA (I forgot which) has reported
	their LOW 10M antenna was BEST at certain times.
	de N4KG

> Because their vertical lobes are wider, stacks probably average 
> better than a single Yagi, more of the time.  (N4ZR)

	A LOW antenna has a wider vertical lobe than stacks.

	Stacks have a wider lobe than the high antenna alone.
	Is the pattern of a pair of 8.5 dBi stacks any wider
	than a single 10.5 dBi antenna at the average height
	of the stack?  I suspect not.  de N4KG

	As an antenna is raised, each single degree that the
	low side of the lobe is lowered, the upper side of the 
	lobe is lowered by THREE degrees, narrowing the lobes.
	de N4KG
> 
> What am I saying?  Everyone is right, depending on his situation.  
> There is no one right answer.  There's no substitute for individual 
> analysis,  taking your terrain and propagation into consideration.
> (N4ZR)
	
	AMEN !

	As has been said MANY times by MANY reporters
	(with MANY antennas) :
	
	You can NEVER have TOO  MANY antennas !

	Because of the NULLS in the vertical pattern of
	Horizontally Polarized Antennas, it is IMPOSSIBLE
	for any SINGLE Antenna to cover ALL the angles
	that are supported by the ionosphere in spite of
	the never ending desire to find the OPTIMUM height
	for one single antenna!   de N4KG

	TWO antennas positioned such that the Low antenna
	fills in the first NULL of the High antenna is a BIG
	improvement over a single antenna at any height.

	Simple translation:  NO  SINGLE  ANTENNA can cover 
	ALL the angles supported by the ionosphere.  de N4KG

	The land limited amateurs don't want to hear this
	and keep the dream of finding an "optimum" height
	alive.

	SO, how about all you guys with Stack Matches
	and 4 high stacks ( or even 2 high stacks) making
	some observations and reporting your findings?

	Please include data on your foreground / terrain,
	time of year, and sunspot data.  Note that the 
	antenna with the LEAST received signal is often 
	the BEST indicator of arrival angle due to the 
	narrow range of deep NULLS.

	de  Tom  N4KG

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