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radiation patterns of different types of antennas

freecell said:
"Am signals radiate out in sine wave form"

initial radiation is in the form of an electric field.
Click to expand...

Okay, after reading about the E and H plane, and looking at your previous post, I just have a couple more clarification questions...

It looks like the E plane and H plane are on a 90 degree axis of each other.
Is that in fact the case, or is it radiating not on a axis but instead all around the antenna.

Also when the radiation hits the end of the conductor (antenna) what happens? Does the radiation pattern continue straight upward, or does it return back into the transmitter if it is not at the 90, 180,270,360 degree point? ( I was under the impression that this was what contributed to SWR, the returning of wave energy)
 
And fortunately, some of us with those misconceptions are 'righter' than others with misconceptions.
Freecell - it would help a lot if you would cite the particular circumstances for your version of those 'misconceptions', they do not hold true for all circumstances, but only the ones you find convenient for your explanation of why others are wrong and you are right. There are a couple of them in that stuff above that are very easy to see.
- 'Doc
 
Just saying "wrong" without any further supporting material is argumentative and non-productive. For the purposes of the way the original question was asked, I think he got the answers he was looking for.

First, I didn't say everything that was going on with the coil because it wasn't an important part of answering the question asked. But since you want to bring it up, I'll quote the W8JI link (which has been presented here before by me and others):

"The flawed viewpoint is current goes in one end, winds its way around through the physical length of wire in the coil, and after a time delay caused by the copper path length current appears at the other end."

Which is exactly what I said in simpler terms. W8JI goes on to explain what really happens quite well, but it is quite technical. The way I described it works just fine in trying to help someone just starting to understand antenna theory.

Pertaining to helically wound antennas, I don't know where you're getting your material from. Long, skinny coils used in antennas have terrible Q and are terribly inefficient compared to better designs. A helically coiled antenna is just a long skinny coil. Here's another good reference: Topband: How Helically Wound Verticals Really Work

loose coiling of excess feedline defeats the counterpoise effect called for in most mobile installations where body metal is at a premium
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Yeah especially if you're installing this antenna on a corvette or some other fiberglass body. If you need the shield of the coax to provide additional counterpoise on any sheet metal bodied vehicle, you're doing it wrong.

"Also does the length of the coax effect the antenna output- it must."
it does if the feedpoint swr is anything but 1:1, especially in the case of a transmitter source with a fixed impedance.
Click to expand...

The question was asked from a practical standpoint and answered correctly from a practical standpoint.
 
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Also when the radiation hits the end of the conductor (antenna) what happens? Does the radiation pattern continue straight upward, or does it return back into the transmitter if it is not at the 90, 180,270,360 degree point? ( I was under the impression that this was what contributed to SWR, the returning of wave energy)
Click to expand...

I think the thing you're missunderstanding here is that the entire antenna radiates. RF doesn't shoot straight out the end of the antenna like water coming out of a high pressure nozzle. If RF is returning back through the coax to the transmitter, it is because of some type of impedance mismatch at the feedpoint of the antenna. That's what typically causes high SWR.
 
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well now...

I think that I need to go back to school to refresh, or just simply learn a little or a lot more about Antenna theory.

Where can I go to learn starting back at the basics and working up through a moderate scientific understanding?

Thanks y'all
 
moleculo wrote:

"Pertaining to helically wound antennas, I don't know where you're getting your material from. Long, skinny coils used in antennas have terrible Q and are terribly inefficient compared to better designs. A helically coiled antenna is just a long skinny coil. Here's another good reference: Topband: How Helically Wound Verticals Really Work"

the reference link provides no support for your argument. a single HWMA can exceed 70% efficiency if it is not "very short" and proper attention is given to the ground. as we're talking about 27 mhz. as indicated in the original posters reference to popular wilson antennas, how 'bout we stick to the subject. the topband article is a discussion of low freq. hf antennas and you can bet the physical dimensions are an appreciable fraction of what they would be at full length.

on the other hand, a 1/4 wave HWMA at say HALF the full physical length of a quarter wave (4.5 feet) @ 27 mhz. presents much less loss and higher efficiency than say an 80M HWMA for mobile application simply because the 80M HWMA is "very short" for the operating frequency in question, and in addition would not be much more than 10-15% efficient, best case scenario. and what is "terrible Q"?. within 3 db. markers the bandwidth of the 27 mhz. model referenced above is in excess of 700 khz..

if we ditch the fixed pitch and use a stepped-pitch tesla design in winding the HWMA using multiple (4) elements @ 3/8 wavelength we can also eliminate the need for link coupling at the feedpoint to achieve a match to 50 ohm feedline and present less than or equal to a 2:1 VSWR at the band edges across 1.7 - 2.2 mhz. of bandwidth and produce a stronger far field ground wave signal than a full size 1/4 wave whip.

that's how HWMA's REALLY Work.
 
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freecell said:
"Antenna gain occurs due to multiple current nodes which must be separated by distance."

does not apply to single monopole designs.

"A 5/8 electrical wavelength antenna fashioned with a loading coil that is physically 1/4 wave long will have the same exact gain as a 1/4 wavelength antenna minus the 5/8th's coil losses."

wrong.

some have a few "misconceptions" of their own.
Click to expand...

I'd just love to see further explaination here.

After you prove me wrong I'm going to wind up a 160 double extended zepp on a plastic garbage can and take over the world.
 
The original question was:

Also if you need a coil antenna is it better to be coiled (or loaded)- I assume these are the same thing- at the bottom, like the Wilson mag mount, or middle like the Wilson 5000 trucker on a 10 inch shaft before the coil, or top loaded like many of the fiberglass whips?
Click to expand...

Nothing I said is incorrect at answering that question.

Wilson publishes that their coil Q on the Wilson 5000 is 864, as tested by Dr. Dwight Heim. There is no way a helical wound HF antenna like a Firestik or Silverload comes anywhere close to that Q. For purposes of the, "which is better" question most people are usually asking from an efficiency perspective, not a bandwidth perspective. Of course a helical wound coil has good bandwidth - as you pointed out - that's one of the characteristics of a lossy antenna design, and also of a helical wound antenna. That doesn't mean it radiates any better.

...produce a stronger far field ground wave signal than a full size 1/4 wave whip
Click to expand...

Groundwave propagation on 11 meters???? REALLY???? :unsure:
 
"Wilson publishes that their coil Q on the Wilson 5000 is 864, as tested by Dr. Dwight Heim."

Heim is an advertising tool. this is so clear to anyone who has bothered to notice that he doesn't specify whether the "Q" is loaded or unloaded. the omission of information always lends itself well to advertising purposes.
while the unloaded "Q" (out of circuit) may well be as he claims, the truth of the matter is that when the inductor is part of an LC (filter) circuit exerting a profound effect upon bandwidth the loaded "Q" is typically one fifth of that figure.

furthermore, "Q" is only one of several factors that determine antenna efficiency. case in point, a 160 meter antenna (approximately 136' @ quarter wave) that has been helically wound and reduced to a fraction of its physical size to adapt it to mobile operation is much less efficient than a quarter wave for 27 mhz. that has been physically reduced to only half its full physical quarter wave dimensions.

so much for the helical 160 double extended zepp on a plastic garbage can.
 
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Get copies of the ARRL Antenna Book and the RSGB Antenna Book. If you're not familiar with RF, then get books that cover the subject and at least become conversant with the terminology.

There's no quick way to learning these things. Many of those who've answered the OPs question have 20 years or more experience in radio/antenna work (I've been licensed 50 years come November). And I'm still learning.

Antenna experimentation is still a wide-open field. Play around with different antennas. Find out what works, what doesn't, and (most important): WHY?

Take voluminous notes.
 
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"Groundwave propagation on 11 meters???? REALLY?"

GROUND-WAVE PROPAGATION CURVES FOR FREQUENCIES
BETWEEN 10 kHz AND 30 MHz. over 11 different types of signal-path soil conditions.

the propagation curves in this recommendation are calculated based on the assumption that both the transmitting and the receiving antennas are at ground level.

http://www.itu.int/dms_pubrec/itu-r/rec/p/R-REC-P.368-8-200503-S!!PDF-E.pdf
 
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