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The Myth Surrounding Antenna Take Off Angles

kopcicle

Sr. Member
Feb 17, 2016
2,074
3,314
273
I don't want to rehash my well known observations of a well known ....


I have a vertical that has a doughnut of silence that extends from approx 25 miles to between 125 and 175 miles. That's just because it's a vertical.

I have observed another vertical that has multiple concentric rings of silence. No surprise this coincides with the nulls at the antenna.

I know a huge sports field complex and a man lift containing yours truly and a sensitive , powered field strength meter (calibrated? you really are kidding, right?) does not an antenna range and scientific measurements make. However the lobes and nulls were found and as the angles were all that was needed I called it a day and returned the man lift before anyone noticed .

I have several horizontal wires that are better at less than optimal (says who) height and others that get better with height. It's experimentation, it's what we do.

Some general observations over the last 40 years.

Any gain you get in a desired direction or elevation is taken from somewhere else. Where are the nulls?

HF isn't Voodoo, it behaves as it should , except when it doesn't .

Any HF horizontal wire follows well understood patterns.
Multiband horizontal wires , OCFD, Fan dipole, Loops, and loaded elements do not.

Non resonant horizontal wires have two significant issues. First is when fed at voltage maximums vs frequency. Second when fed close to resonance. In the first case it's all about kilovolts wandering about. In the latter case it's passing through resonance RF getting into the shack.

Horizontal multi element beams, quads, Gizmatchy, Yagis follow well known formulas that don't work in practice. Experimentation is the key.

LPDA's Log periodic dipole arrays do follow design formulas.

EFHW (end fed half wave) Go ahead , I'll watch (and laugh)

Understand the difference between impedance , VSWR and resonance.

Low VHF and VHF are two entirely different things. 50MHz is it's own deal. once above 136MHz height wins.

Parabolas much below 1GHz are a joke .

Monopole antennas and any vertical shortened to a small percentage of a quarter wave are a radiating dummy load.

Last but not least what ever you think you prepared, engineered, built for mother nature , mother nature has something all together different in mind.

Look , it isn't rocket surgery but it is science.
...and experimentation.
 

AudioShockwav

Extraterrestrial
Staff member
Apr 6, 2005
7,660
5,604
593
Sierras Near Yosemite National Park
I agree with your mother nature conclusion.

Regardless of what we think we know about many different antennas, I don't think there is a perfect antenna for all situations , it requires you to try these antennas at different locations until you find one that works best were you are at.
Too many variables to deal with.

73
Jeff
 
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Road Squawker

Sr. Member
Jan 19, 2011
1,954
1,497
173
...edit...
This forum is a great forum, don't get discouraged by a few remarks about CB operators, it's all in good fun.

Note: Wavrider, you were right, the rotor was not a CD45, it is a M rotor #5.


Was this the "tower" thread?
Unless there is another thread that I haven't seen, ..............the identity of the rotor came from me. along with a linky to NORMS ROTOR identification page.

Its all good
 

Riverman

Old Member
Nov 12, 2013
2,682
2,677
273
I don't want to rehash my well known observations of a well known ....

I have a vertical that has a doughnut of silence that extends from approx 25 miles to between 125 and 175 miles. That's just because it's a vertical.

I have observed another vertical that has multiple concentric rings of silence. No surprise this coincides with the nulls at the antenna.

I know a huge sports field complex and a man lift containing yours truly and a sensitive , powered field strength meter (calibrated? you really are kidding, right?) does not an antenna range and scientific measurements make. However the lobes and nulls were found and as the angles were all that was needed I called it a day and returned the man lift before anyone noticed .

I have several horizontal wires that are better at less than optimal (says who) height and others that get better with height. It's experimentation, it's what we do.

Some general observations over the last 40 years.

Any gain you get in a desired direction or elevation is taken from somewhere else. Where are the nulls?

HF isn't Voodoo, it behaves as it should , except when it doesn't .

Any HF horizontal wire follows well understood patterns.
Multiband horizontal wires , OCFD, Fan dipole, Loops, and loaded elements do not.

Non resonant horizontal wires have two significant issues. First is when fed at voltage maximums vs frequency. Second when fed close to resonance. In the first case it's all about kilovolts wandering about. In the latter case it's passing through resonance RF getting into the shack.

Horizontal multi element beams, quads, Gizmatchy, Yagis follow well known formulas that don't work in practice. Experimentation is the key.

LPDA's Log periodic dipole arrays do follow design formulas.

EFHW (end fed half wave) Go ahead , I'll watch (and laugh)

Understand the difference between impedance , VSWR and resonance.

Low VHF and VHF are two entirely different things. 50MHz is it's own deal. once above 136MHz height wins.

Parabolas much below 1GHz are a joke .

Monopole antennas and any vertical shortened to a small percentage of a quarter wave are a radiating dummy load.

Last but not least what ever you think you prepared, engineered, built for mother nature , mother nature has something all together different in mind.

Look , it isn't rocket surgery but it is science.
...and experimentation.

Cool. The CliffsNotes version of www.w8ji.com. :ROFLMAO:

My buddies loved CliffsNotes back in college. For just $1.50 they could learn everything they needed to know about Moby Dick or The Scarlet Letter in 20 or so pages without having to read the books. :p
 
Last edited:

Justme

Sr. Member
Jan 28, 2008
591
722
103
70
The Netherlands
Theory and practice.
I'm using an OCF for 160 to 6 meters, yes it is working fine there, i used to have a 5 element beam up, that worked better and a 12 element for 2 and 23 element for 70, getting too old to maintain it so i took them down.( ere on a slanted roof)
A 77 Foot vertical L fed with MFJ 998 legal limit autotuner at the bottom, from 160 to 20, after that it is pretty useless but will tune fine there.
An Imax 2000 for 10/12/15/18.
So i can chose on all bands for horizontal/vertical polarisation.
Worked the world on all bands with that, mostly 100-200 watts.
For 2/70 now an Diamond X510N at 43 feet above streetlevel, 5 meter long gain 6 dBd at the transceiver on 2, 8.9 dB gain dBd for 70 at the transceiver.
Repeater range 160+ km's or 100 miles, made direct qso's without conditions up to 250 KM's in SSB running 50 watts SSB from the FT 991A.
Living in a pancake flat country has it's advantages...
The 77 feet vertical has 3000 feet of radials under it, worked on 160 all continents.
That from the edge of the city with a lot of land 100 x 25 feet, and understanding neigbours i could use to dig radials in...
For the rest patience, conditions, propagation, and noise fighting in the neighbourhood killing off noise sources, and operator practice.
I can't change conditions, i can improve my antenna setup even on a limited plot.
Low band Dxing from ON4UN helped setting up the low band antenna.

Why 160? not because it was easy, i love challenges and going against the grain.
 
Last edited:

TheBlaster

Well-Known Member
Jun 29, 2020
270
278
73
For a vertical omni on DX I imagine a broad wide angle take off from 5-35 degrees would be ideal. Peak gain i.e. a dB or 2 is not likely to be the reason for not getting through... or them, back.

Until the last moment of the QSB, so say 73 a little earlier !

I found feed point at 7.5 - 10 Meters above ground is the height for me when my verticals start motoring on 11m. For Sporadic E, I am finding 5 meters works ok. (until you were not heard, lol, then you wish it was 10m)
 

Road Squawker

Sr. Member
Jan 19, 2011
1,954
1,497
173
This is all baloney. I have kept a very close eye on my antennas and none of them have ever taken off...edit...

I can assure you that some of them do take off.
Mine did at about 2:30 Fri the 13th when hurricane Charlie made landfall about 1/2 mile from me.
 
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TheBlaster

Well-Known Member
Jun 29, 2020
270
278
73
This is all baloney. I have kept a very close eye on my antennas and none of them have ever taken off. I did have one convert to plasma once...., but that is a different story

On your linear there is a knob, turn it down : )

(I am thinking of coronal discharge)

Vapourizing your antenna does tend to reduce its performance.
 
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