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[Articles Home]  [Add Article]  

Wire Loss and Antenna Gain

Tom Thompson (W0IVJ) on May 22, 2005
View comments about this article!

The other day the discussion on 40 meters turned to the wire size used in wire antennas, and how it affects the gain of the antenna. Thanks to Roy Lewallen and his program, EZNEC, I decided to look into this. I constructed a dipole in free space and over a regular ground at 100 feet for each of the bands shown in the graph below and varied the size of the copper wire used in its construction. I also recorded the antenna gain for a lossless wire. The graph below shows the relative loss for several wire sizes and several HF bands. As you can see, the wire size has very little effect on the antenna gain unless you go to extremes.


Member Comments:
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Wire Loss and Antenna Gain  
by W4SK on May 22, 2005 Mail this to a friend!
Bigger isn't better?
 
RE: Wire Loss and Antenna Gain  
by LNXAUTHOR on May 22, 2005 Mail this to a friend!
-nice chart... it's good to know that the thin-guage wire i'm using for QRP portable ops has little, if any loss factor (especially since i use less than six feet of coax in the antenna chain - and sometimes none!)...

- wire is good! it's inexpensive, stealthy, portable, comes in a variety of flavors, sizes, coatings and colors!

- now if only someone would make flex-weave in #18 or #20...

:-)
 
Wire Loss and Antenna Gain  
by N4ABA on May 22, 2005 Mail this to a friend!
Nice bit of information, Tom, and it confirms my installation. I'm running a stealth OCF right now...26 ga. wire suspended from the peak of the house (approx 30' up) dropping down slope in a "V" to two (small) trees lower down on the property. Almost invisible, and it works much better than I had hoped. XYL would have never seen it if ice had not formed on it one day.....and the neighbors have not seen it....great stealth antenna. However, I would not dump much power into it!

73 de N4ABA Andrew
 
Wire Loss and Antenna Gain  
by WB9JTK on May 22, 2005 Mail this to a friend!
at 100 feet high and average ground ....


What about at 15 feet high ? With the antenna closer to the lossy earth would wire 'loss' be more or less significant ? This question is for 'backpacking' where we like to carry antennas that are very small and light, 22 gauge etc. and it is just tossed up in a tree, so not much height.
 
Wire Loss and Antenna Gain  
by KW4CQ on May 22, 2005 Mail this to a friend!
It would be useful to know the (EZNEC) data based on a choice of solid vs. stranded copper conductors for larger arrays such as loops, rhombics, and quads. Can EZNEC provide this information? It seems to me there would be a significant difference in ohmic coupling resistance between solid and stranded conductors.
 
Wire Loss and Antenna Gain  
by KW4CQ on May 22, 2005 Mail this to a friend!
It would be useful to know the (EZNEC) data based on a choice of solid vs. stranded copper conductors for larger arrays such as loops, rhombics, and quads. Can EZNEC provide this information? It seems to me there would be a significant difference in ohmic coupling resistance between solid and stranded conductors.
 
RE: Wire Loss and Antenna Gain  
by W6TH on May 22, 2005 Mail this to a friend!
.
It seems to me there would be a significant difference in ohmic coupling resistance between solid and stranded conductors.
------------------------------

There is a difference, but why even think about it. The outside of the wire is of importance and not the center part. Is this called skin effect?

Another thought: Why raise a antenna high to gain a db or so and loose 1, 2 or 3 db in wire feed length. Oh! I forgot, low angle of radiation.

Oh yes, forgot about tensile strength, you know where the wire stretches before the breaking point.

Hello Tom, nice article.

.:



 
RE: Wire Loss and Antenna Gain  
by W6TH on May 22, 2005 Mail this to a friend!
.

Very interesting Tom.
I am going to ad to your post some information also of value.

The skin depth in copper is about .005 centimeters for the 160 meter band, .002 centimeters for the 20 meter band, .001 centimeters for the 6 meter band, and .0003 centimers for the 70 centimeter band. It is easy to see that the spatial variation of the fields in vacuum is much smaller than the spatial variation in the metal. Therefore, for the purposes of evaluating the fields in the conductor, the spatial variation from the wave length outside the conductor can be ignored.

W6TH
.:
 
Wire Loss and Antenna Gain  
by N0AH on May 22, 2005 Mail this to a friend!
Diameter of wire impacts radials, (ON4UN LOW BAND DX'ING BOOK) so wouldn't it make sense that a larger diameter wire would impact antenna performance. Also, and this my own reasoning, as you add more power, you would need a larger wire to properly utilize it.
 
RE: Wire Loss and Antenna Gain  
by W6TH on May 22, 2005 Mail this to a friend!
.
I believe power has a great effect in regards to the high standingwave and temperature rise especially in open wire lines.

However I also believe that the frequency has a greater effect to wire diameter size, but do not want to start a argument. In regards to gain, no comment; I am stopping at this point.

.:
 
RE: Wire Loss and Antenna Gain  
by WM5Z on May 22, 2005 Mail this to a friend!
I disagree with your findings. The larger the diameter the less losses there are because of the skin effect and ohms law. Though you probably would not see the difference at most HF frequencies. The higher frequencies, say 15, 12 and 10 would begin to see the difference. At UHF and above there most definately would be a visable difference.

One other observation will be in usable bandwidth of the antenna. The larger the wire, the broader will be the bandwidth.

My recommendation is to use the largest conductor size possible. Even in a stealth antenna. This can be done by using small wire sizes seperated with spreaders. I have used popsicle sticks painted white so that they "dissapear" in the air as spreaders and glued together like an "X" and hung 4 wires. I used enameled 22 Ga. wire and noone ever said they could see the antenna. For 40 meters, I had 6 spreaders on each leg. The first and last legs were 6' from the ends, and the other 4 spreaders were spaced to keep the wires from touching. With that setup, I was able to keep operating on 40 and 15 and I was able to compete with the big boys locally.

Steve/WM5Z
 
RE: Wire Loss and Antenna Gain  
by N6AJR on May 22, 2005 Mail this to a friend!
How does this figure in on the Fan Dipole..

actually if its a wire too small, it breaks, and a wire too large it sags due to weight but a middle sized wire is great.

Better yet FREE wire has more gain than wire you pay for, and wire in home brew antennas is more effective than store bought wire antennas.

If you want to make broader band width use several wires ( your choice of size) in a "cage" dipole, ( the original fan dipole??)

So for 80 m use 3 wires , 1 wire at 64 feet long per side, 1 wire at 66 feet long per side, and 1 wire at 68 feet per side long, run these on the same popsicle stick top, middle and bottom.

When you tune the 80 m bands you use more of the long one at the low end and more of the short one at the high end. and a bit of power goes to all three all the time but to the radio it looks like a wire that is 6 inches in diameter and has super bandwidth.

I don't know how to model antennas, and find most yards where antennas go have rain gutters of metal, other antennas and masts, chicken wire in the stucco and such so a perfect model realy isn't possible.

I prefer basics, common sense, good plans , and some majic whiffle dust to make mine work well.

73 tom N6AJR
 
RE: Wire Loss and Antenna Gain  
by W6TH on May 22, 2005 Mail this to a friend!
,

From what I gather, is the number 20 wire has less loss on 10 meters than the same wire for 80 meters. Is the what I see?

.:
 
RE: Wire Loss and Antenna Gain  
by W6TH on May 22, 2005 Mail this to a friend!
.
Ok, aside from the chart, I would enjoy having the words "radiation resistance" more thoroughly explained. Is this saying, loss due to resistance of the wire, resistance of some sort or the mismatch of the antenna feed point. The words radiation resistance has been so abused, that it is hard to determine what was in the mind of Roy Lewallen and EZNEC, clear definition is needed.
. Tom can you give me some idea of the explanation of "Radiation Resisitance" in this particular case?

From what I see, this antenna of yours seems to be excellent and of high efficiency, which interests me to no end.

Give me any formular of your choice and I will get a better understandint of radiation resistance in this particular case.
Thanks.

73 W6TH
.:
 
RE: Wire Loss and Antenna Gain  
by KD5DFM on May 22, 2005 Mail this to a friend!
you don't think a stranded wire had more skin effect then just a solid wire ? stranded wire has much more skin effect due to its a wire around other wires multiplied ;-) to me it would be significant , am i right OR wrong ?

>There is a difference, but why even think about it. >The outside of the wire is of importance and not the >center part. Is this called skin effect?
 
RE: Wire Loss and Antenna Gain  
by W6TH on May 22, 2005 Mail this to a friend!
.
Tom W0IVJ,

My server Earthlink will cut me off at midnight as they have some work to do. I am shutting down my electric here tonight as I want to disconnect several of my 220 volt ac boxes. This property is being sold and want it to pass inspection.

I will return in 4 or 5 days, to the internet and EHAM, I hope I won't be missed, HI HI.( I hear ya, Good riddance, eh? )

73 W6TH
.:
 
RE: Wire Loss and Antenna Gain  
by N0TONE on May 22, 2005 Mail this to a friend!
Thanks for the numerical confirmation.

One one of my large lots I tried some antenna experiments on wire size. I would built two identical dipoles, one with 1/4" soft-drawn refrigeration tubing, and one with the thinnest wire I could keep in the air.

With dipoles at the same height and orientation, I could never actually measure any difference, either on RX or TX.

Tried this on many bands, and with dipoles both high and low.

The only time I started seeing a difference is when I started my short dipole experiments. Once a dipole got less than about an eighth wave long, it seemed to get lossy, unless I started using fat conductors.

W2FMI did a great series on short verticals, and he covered this topic fairly well. At "resonant length", the wires size matters very little. Once you start geting an antenna "very short", then diameter begins to have a significant effect.

AM
 
RE: Wire Loss and Antenna Gain  
by W6TH on May 22, 2005 Mail this to a friend!
,
Notuned


What did you use for the detection of your receiving data? How did you record it, use a diode detector through a field strength meter or such? How far was the distance between antennas? did your line radiate power? More information please.

I tried many like you and Tom did and no change. Made a two element Yagi and placed it on a polar recorder, took E and H plane patterns, the yagi made of aluminum. Made another of wood and used wire, number 14 for the elements and took similiar patterns, no change. Gamma match used on both. The wood was 2X2 pine.

.:
 
RE: Wire Loss and Antenna Gain  
by AA4PB on May 22, 2005 Mail this to a friend!
The efficiency of the antenna is determined by the radiation resistance vs the loss resistance. For a 1/2 wave dipole, the radiation resistance is so high compared to the loss resistance that changing from say a #14 wire to a #10 wire will have no significant impact on the antenna efficiency.

A larger diameter element will have a broader bandwidth but again, on the HF bands even the larger wire is so small in terms of wavelength that it has little impact on the bandwidth. If you go from #14 wire to a 3-foot diameter wire then you will see a significant impact on the lower HF bands. A "cage dipole" simulates this by using multiple wires around a system of spreaders.
 
RE: Wire Loss and Antenna Gain  
by W6TH on May 22, 2005 Mail this to a friend!
.
AA4PB


The efficiency of the antenna is determined by the radiation resistance.

You may have the answer I want. How and where do you measure the Radiation Resistance?

Tell me yours and I will tell you mine. You first.

.:
 
RE: Wire Loss and Antenna Gain  
by AA4PB on May 22, 2005 Mail this to a friend!
The resistive portion of the feed impedance is the radiation resistance plus the loss resistance. As I recall the radiation resistance of a 1/2 wave antenna is somewhere around 377 ohms. Since the loss resistance in a wire dipole is only a few tenths of an ohm it is quite small compaired to the radiation resistance and so a tenth or so one way or the other won't have much of an effect. I'm not sure there is a way to directly measure radiation resistance. If you have a good estimate of the loss resistance, you can always measure the R in the impedance and subtract out the loss resistance.
 
RE: Wire Loss and Antenna Gain  
by AA4PB on May 22, 2005 Mail this to a friend!
As I understand it, radiation resistance is sort of an imaginary thing. Its the amount of resistance that would disipate the same amount of power as the actual antenna disipates thru radiation.
 
RE: Wire Loss and Antenna Gain  
by W6TH on May 22, 2005 Mail this to a friend!
.
Ok, you have hit the nail on the head. I also calculate and with the resistance and the inductance and so forth.

I wonder how close this EZNEC will be, pretty accurate I presume.

Thanks
.:
 
RE: Wire Loss and Antenna Gain  
by AB6CV on May 22, 2005 Mail this to a friend!
Where does my wet string show up in there?

Mike
 
RE: Wire Loss and Antenna Gain  
by WA9SVD on May 22, 2005 Mail this to a friend!
Mike,
Wet Strings and spaghetti only work on 6 Meters... (If there's Sporadic "E")
 
RE: Wire Loss and Antenna Gain  
by K8MHZ on May 23, 2005 Mail this to a friend!
The National Electrical Code has something to say about this.

"Antenna conductors for transmitting and receiving stations shall not be of a size less than given in table 810.52"

The table shows that using a span of less than 45 feet, #14 is the legal minimum. Spans over 45 feet must use either #10 hard drawn copper or #12 copper clad steel, bronze or other high-strength material.

You will find this and other laws pertaining to amateur radio installation in the National Electrical Code, Article 810.51 through 810.71

And yes, we DO have to abide by the NEC to have a legal station. All the laws we have to abide by are not in FCC Part 97.

73,

Mark K8MHZ
 
RE: Wire Loss and Antenna Gain  
by K8MHZ on May 23, 2005 Mail this to a friend!
Here is how I (think) I understand radiation resistance.

When we speak of impedance, we mean the total amount of dissipation of energy. Included is capacitive and inductive losses, heat losses due to the resistance of the wire, and the 'loss' of energy that turns into radio waves and escapes the antenna.

Since neither capacitive nor inductive reactance produces an impedance that is the result of transforming electricity into our desired forms of energy, they are obviously figured as separate constituents of the equation. Only resistive impedance is turned into watts, or power.

When we pump RF through a feedline into an antenna, the energy has several choices. It can be turned into heat on the feedline or antenna (IR squared losses. True power, just not where we want it), it can be reflected back into our rigs and create heat there too!,(High SWR), it can be absorbed due to reactance and not turned into heat or RF, or it can be turned into radio waves that leave the antenna.

The radiation resistance can be calculated if you know all the other numbers in the formula. Just do the math and whatever the difference is equals radiation resistance.

The concept of radiation resistance is similar to internal resistance on in a battery. You just can't hook up an ohmeter to it and measure it. You have to charge it and measure current and volts to calculate the internal resistance.

Now, that being said, here is what I am not totally clear on. Shouldn't a 50 ohm antenna be more efficient than a 377 ohm antenna just due to the fact that lowered resistance means more watts, mathematically??

73,

Mark K8MHZ
 
RE: Wire Loss and Antenna Gain  
by WA6BFH on May 23, 2005 Mail this to a friend!
I don’t see any correlation of the question with the answer!

All antennas exist as an L/C circuit. Wire size would affect the L vs. C, or C vs. L ratio. It would also affect resistance, because as Vito alluded, a larger surface area lowers resistance pursuant to that surface area in an “AC” circuit.

Gain is not effected if though you are talking about a simple half-wavelength dipole! If it’s a half-wave dipole its aperture does not (significantly) change because you use slightly fatter wire! It’s still a have wave dipole -- it has unity gain!

It may be a more efficient dipole, wasting less energy, but that’s not gain! Expand its aperture size, by phasing additional half-wave’s etc; that will improve its gain!
 
RE: Wire Loss and Antenna Gain  
by WB2WIK on May 23, 2005 Mail this to a friend!
I think "radiation loss" is a misleading term. An antenna can only do two things with power applied: Dissipate, or radiate. Radiation loss is what we'd like to have, at 100%, so that dissipation loss is zero.

But, regardless of the wording, I understood the article.

What surprises me is that the chart implies the wire antenna is more efficient, or less lossy, at higher frequencies, irrespective of operating frequency. I don't see why or how that would be. As we increase frequency, we use less of the conductor (skin depth becomes shallower), so wouldn't this tend to increase "loss" with frequency?

WB2WIK/6
 
RE: Wire Loss and Antenna Gain  
by AD5X on May 23, 2005 Mail this to a friend!
"Shouldn't a 50 ohm antenna be more efficient than a 377 ohm antenna just due to the fact that lowered resistance means more watts, mathematically??"

Assuming you keep the power the same, a 377 ohm antenna system is generally more efficient than a 50 ohm system, assuming you have real resistive losses in the system (and who doesn't have some loss?). For a given power, the current will be less in a high impdeance system than in a low impedance system. Therefore, you'll have less I-squared-R losses with the higher impedance.

Phil - AD5X
 
RE: Wire Loss and Antenna Gain  
by NL7W on May 23, 2005 Mail this to a friend!
I agree with Steve's (WB2WIK) comments. Shouldn't losses increase with frequency? If this isn't the case, this is certainly revealing. If we've missed something, please explain. 73.
 
RE: Wire Loss and Antenna Gain  
by K8MHZ on May 23, 2005 Mail this to a friend!
<An antenna can only do two things with power applied: Dissipate, or radiate.>

It can also reflect the power applied to it back into the transmitter. (Reverse electromotive force)

That makes three things.

It can also waste it through L/C impedance. (The reason why I x Z does not always = E, and I x R does.)

That makes four, and that is all that I know...er...theorize.

73,

K8MHZ
 
RE: Wire Loss and Antenna Gain  
by WB2WIK on May 23, 2005 Mail this to a friend!
>RE: Wire Loss and Antenna Gain Reply
by K8MHZ on May 23, 2005 Mail this to a friend!
<An antenna can only do two things with power applied: Dissipate, or radiate.>

It can also reflect the power applied to it back into the transmitter. (Reverse electromotive force)

That makes three things.<

I disagree. The antenna itself can only do two: Dissipate, or radiate. "Wasting" power is also dissipating it. Phase shifting does not create dissipation. If there is reflected "power," that may eventually be dissipated in the transmission line, assuming there is one; however, this isn't something the antenna actually *does.*

WB2WIK/6




 
RE: Wire Loss and Antenna Gain  
by WA6BFH on May 23, 2005 Mail this to a friend!
My goodnes!

Lets say that I am going to make a Dipole for the 3 cM band, actually two dipoles.

For one I will use #18 wire, for the second I will use 3/4 inch copper tube.

What do you think will happen?
 
RE: Wire Loss and Antenna Gain  
by W8JI on May 23, 2005 Mail this to a friend!
Now, that being said, here is what I am not totally clear on. Shouldn't a 50 ohm antenna be more efficient than a 377 ohm antenna just due to the fact that lowered resistance means more watts, mathematically??
73, Mark K8MHZ>>>


http://www.w8ji.com/radiation_resistance.htm

explains it.

Everything in the graph looks sensible to me. 80 meters would have more loss because the wire is longer, so the series loss resistance is higher.

Stranded wire does not have more "surface area" at radio frequencies. It actually has less surface area carrying current. That's why the lowest loss transmission lines for a given physical size use solid center conductors and solid shields or foil inside the shield. Stranded wire, for a given physical outer size, has more resistance on any frequency but is gradually worse as frequency is increased.

Good article.

73 Tom
 
Radiation Resistance  
by K7PEH on May 23, 2005 Mail this to a friend!
AA4PB says:

"As I understand it, radiation resistance is sort of an imaginary thing. Its the amount of resistance that would disipate the same amount of power as the actual antenna disipates thru radiation."

And, K8MHZ (I like this call) says:

"The radiation resistance can be calculated if you know all the other numbers in the formula. Just do the math and whatever the difference is equals radiation resistance. "


Radiation resistance is not imaginary but a real physical attribute of a given antenna (and, it's surroundings of course). For a given antenna in a given location at a given frequency, it is a physical constant of the antenna system.

Of course, it is not a real resistor in the sense of a carbon resistor or something but think about that carbon resistor. It dissapates the energy via I-squared R loss as heat. Heat is not that much different than radiation (though, this is usually convection style heat rather than infrared style heat, they are both changes to the system by energy moving to more random states). Both radiation and heat is a representation of increase in entropy.

Radiation resistance of an antenna is calculated using Poynting's equation and the current flow equation for the antenna. It is actually very simple. You compute the average energy flow out of the antenna (the radiation) by the energy capacity of the E and H fields. This comes from the Poynting relation of E x H (E cross product H). The formula itself is expressed as one-half times the surface integral of the cross product of E and H* where H* means complex conjugate.

To perform this cross product analytically (using formulas) you need a representation for both E and H. One thing about these formula representations is that they are frequency dependent. You want to compute the time average power over one half full cycle (pi) which usually leads to an integral (using calculus). This is actually a rate of energy change and this gives you the power in watts. You can compute the average in this manner since the function itself is an even function and the average is either the average of the positive side or the average of the negative side.

Then, you compute the average current-squared which is also a full cycle time average over the formula representation of the current squared. This is also an integral.

When you have computed the average power from the Poynting vector integral formulation and you have computed the average of the current-squared integral, you divide the average power by the average current squared and this gives you the radiation resistance of the antenna.

Now, of course I have said nothing of the surrounding environment and that does come into play and makes real havoc with the cleanliness of this analytical computation. So, when you factor in the ground loss formulation and the presense of other conductors and so on you have a more complicated, albeit, also numerical problem. At this point you are not solving it analytically but rather numerically and this is what programs like NEC help you do.

phil
K7PEH
 
Wire Loss and Antenna Gain  
by AA5KV on May 23, 2005 Mail this to a friend!
Good article. I've always wondered about that. 73
 
RE: Wire Loss and Antenna Gain  
by WA6BFH on May 24, 2005 Mail this to a friend!
I don’t understand the statement about 80 Meter antennas being longer. In the topic model we are talking about a simple half-wavelength dipoles, right?

In that regard, all antennas under discussion are the same length no matter what band they are resonant on. They are one half-wavelength long!

This reminds me of the guy that says he is going to put a “long wire” up in his yard for 80 Meters. You ask him how long it is, and he answers 50 feet. On 80 Meters that is not a long wire, it’s not even a ¼ wavelength!
 
RE: Wire Loss and Antenna Gain  
by N8CPA on May 24, 2005 Mail this to a friend!
According the ARRL antenna book, larger conductor diameter makes for shorter radiating elements,due to factor K. Factor K is the ratio of signal wavelength to conductor diameter in electrical degrees. The traditional dipole formulae, 468/L for a Wl/2; and 234/L for Wl/4 elements, includes a K factor for 12 gauge wire. In addition, because of skin effect, the conductor need not be solid, but can be hollow.

It has been a while since I read that, but it explains why HF beams are so short compared to the wavelengths of the signals they radiate. Those tubes are fairly large in diameter, but very thin compared to the wavelength.

Steve
 
RE: Wire Loss and Antenna Gain  
by WB2WIK on May 24, 2005 Mail this to a friend!

>RE: Wire Loss and Antenna Gain Reply
by W8JI on May 23, 2005 Mail this to a friend!

Everything in the graph looks sensible to me. 80 meters would have more loss because the wire is longer, so the series loss resistance is higher.<

Duh. That's right. I understand, and now everything in the graph looks sensible to me, too.

WB2WIK/6
 
RE: Wire Loss and Antenna Gain  
by W8JI on May 24, 2005 Mail this to a friend!
RE: Wire Loss and Antenna Gain Reply
by WA6BFH on May 24, 2005 I don’t understand the statement about 80 Meter antennas being longer. In the topic model we are talking about a simple half-wavelength dipoles, right? >>

Right, but the PHYSICAL LENGTH is different.

In that regard, all antennas under discussion are the same length no matter what band they are resonant on. They are one half-wavelength long!>>

For those who understand it is distributed resistance or ohms-per-foot, the graphs make perfect sense.

For those who think a conductor's resistance is defined as ohms-per-wavelength nothing will make sense and you will even be able to build 30dB gain Rhombics because that long long wire will hardly have any series resistance feeding the next section down the pipeline.

;-)

73 Tom
 
Wire Loss and Antenna Gain  
by W0IVJ on May 24, 2005 Mail this to a friend!
If you look at the graph, you will see that the 80 meter antenna has more loss for a given wire size than the 10 meter antenna. This is because it is longer as Tom, W8JI , has stated.

As the wire size gets smaller, the amount of change between the 80 and 10 meter dipoles is larger, ie, the loss difference between 80 and 10 is greater for #30 wire than it is for #10 wire. This is because the skin depth is greater on 80 than on 10, which causes the 80 meter antenna to "run out of wire" since the current density penetrates further. The skin depth for a given conductor at a given frequency is where the current density is 37% of where it was on the surface of the conductor. This reduction of current density follows the same curve as a dicharging capacitor. Since the cross sectional area of a conductor controls its current carrying capacity, the lower frequency loses more of its conductor for a small wire size than a higher frequency. This results in a greater difference in loss as a function of frequency as the diameter of the wire decreases. If you could view the wire end on, the current density would look like a donut, if the wire was large enough, except the hole would not be sharply defined, but rather it would be fuzzy as the current density gets smaller and smaller as it approaches the center, but never reaches zero.

It is true that as the conductor diameter increases, the bandwidth between the 2:1 SWR points increases. But, the difference is not as much as one might think. For example, an 80 meter dipole in free space has a 2:1 SWR bandwidth of 220 kHz when constructed with #10 wire and a bandwidth of 200 kHz when constructed with # 20 wire. There is a lot of difference between those two wire sizes but only a 10% difference in bandwidth. BTW #30 has a bandwidth of 180 kHz and 1 inch diameter conductor has a bandwidth of 290 kHz.

I hope this clarifies a few points.

73,

Tom W0IVJ
 
RE: Wire Loss and Antenna Gain  
by WA6BFH on May 25, 2005 Mail this to a friend!
I guess then that I am learning a new realm of physics. In “long antennas”, which seems to be arbitrarily defined by the statement ‘well a half-wave on 80 is 133 feet, that’s pretty long isn’t it’, I guess that makes a 40 meter half-wave only ‘sorta long’.

By this standard, should I consider that putting up a “FULL SIZE” half-wave is not worth the effort. Perhaps I should just put up coiled antennas? They are pretty short but, oh yea darn, they do represent a lot of resistance huh? Maybe I should just give up this hobby, or any thought of physics. In the light of our times, I will just take a more moderate approach -- I will give up the concept of resonance, and all that it entails!

I can put up 80 Meter center fed dipoles that are only 30 feet long. It fits between the two trees I have on my property, and that’s what’s important, right! I can put up an 80 Meter mono-pole that is fabricated from a 10 foot piece of pipe, and no coils to wind! As long as I am accepting that there is no resonant cycle, that I have cast aside the idea of efficiently pumping energy into the air by use of an efficient tuned radiator, it is so freeing! I may build a multi-element Sterba for 80. I can just keep that 10 foot dimension {psssst I will secretively to myself call it resonant}. Shoot, I won’t have to worry about I-R squared losses of even properly phased antennas, it will simply be irrelevant! Maybe I will phase a bunch of 10 foot long 80 Meter half-waves. Do I have to phase them at ‘true’ alternating quarter-wavelengths?

Or maybe some of you out there should just shift to “DC” for your signal generator, or transmitter if you prefer that term. Hook up one pole of your “DC” source to your antenna, and the other pole to ground. One constraint though, DON’T BREAK THAT CIRCUIT!!! Just leave it hooked up all the time. If you break the circuit, at least for the instance of instantaneous current flow, it will look like an “AC” circuit!
 
RE: Wire Loss and Antenna Gain  
by NL7W on May 25, 2005 Mail this to a friend!
Tom (W0IVJ),

Thanks for explaining the enlightening graphs! It does make sense now. These losses (like beauty) are more than just skin deep...

Thanks again for thinking this through to its logical conclusion. 73.

Steve, NL7W
 
RE: Wire Loss and Antenna Gain  
by W8JI on May 26, 2005 Mail this to a friend!
RE: Wire Loss and Antenna Gain Reply
by WA6BFH on May 25, 2005 Mail this to a friend!
I guess then that I am learning a new realm of physics. In “long antennas”, which seems to be arbitrarily defined by the statement ‘well a half-wave on 80 is 133 feet, that’s pretty long isn’t it’, I guess that makes a 40 meter half-wave only ‘sorta long’.

By this standard, should I consider that putting up a “FULL SIZE” half-wave is not worth the effort. Perhaps I should just put up coiled antennas? They are pretty short but, oh yea darn, they do represent a lot of resistance huh? Maybe I should just give up this hobby, or any thought of physics. In the light of our times, I will just take a more moderate approach -- I will give up the concept of resonance, and all that it entails! >>

That's a good idea!

A good starting point would be getting a fim grasp on the fact that loss resistance is a linear progression with PHYSICAL length of a conductor, and has nothing to do with the "wavelength".

The interaction between radiation resistance and loss resistance is complex. We certainly can't understand a complex interaction until we get a handle on the more basic concept of distributed resistance.

73 Tom
 
RE: Wire Loss and Antenna Gain  
by WA6BFH on May 26, 2005 Mail this to a friend!
Tom, I am well acquainted with the resistance as seen by and within the I squared R losses of antennas! I build VHF antennas with boom lengths of multiple wavelength size. It is only practical to decide when to stop; when I squared R makes any further addition of elements a waste of time, as my earlier series of posts SHOULD explain!

Pursuant to ‘big antennas for HF’, we obviously have some disagreements about the practical gain that might be achieved by multi-wavelength aperture HF antennas. While I have never yet built a Ham version of ‘such an HF antenna of my dreams’ I have seen and used them many times on Short-wave Broadcast or Maritime circuits -- both Sterba‘s, and Rhombic‘s.
 
RE: Wire Loss and Antenna Gain  
by W8JI on May 28, 2005 Mail this to a friend!
Pursuant to ‘big antennas for HF’, we obviously have some disagreements about the practical gain that might be achieved by multi-wavelength aperture HF antennas. While I have never yet built a Ham version of ‘such an HF antenna of my dreams’ I have seen and used them many times on Short-wave Broadcast or Maritime circuits -- both Sterba‘s, and Rhombic‘s.>>>

There are very few, if any, Sterba's in commercial applications. That's because the Sterba is a series distribution array that places the resistive losses and phase errors of each section in series with the next section. That limits gain and bandwidth.

Virtually all commercial arrays use distributed or "branched" feed systems that place elements in parallel. Distributed feed greatly reduces phase errors and resistive losses in large arrays.

Aperature or more correctly effective aperature is a function of gain and frequency, and not physical size. The high distributed losses in HF long wire arrays cause the effective aperature to be significantly less than we might expect when looking at physical size. This is because each progessively more remote section of the antenna is fed from current that passes through earlier sections. Ground losses below the antenna and resistive losses in the antenna eat up power, just as the dipole chart in the article shows. The LONGER the conductor is physically, the more problematic conductor losses (and earth losses below the conductor) become.

That isn't my data, that's information well known in HF BC engineering circles. There are IEEE papers on the subject, as well as data released by General Dynamics.

The effective aperature of a 3 WL per leg V beam at HF is barely larger than the effective aperature of a dipole because of losses in the antenna and earth below the antenna. Effective aperature is another way of expressing gain at a given frequency, not size.

73 Tom
 
RE: Wire Loss and Antenna Gain  
by K6IOU on May 28, 2005 Mail this to a friend!
To: K8MHZ

With all due respect, you have been taken in by some very common myths about SWR.

Reflected power is "NOT" returned to the rig and generate heat. Also, power that is used in reactance is ALL returned with no loss. Reactance is 'lossless'.

The power that is reflected at the antenna due to an impedance mismatch is reflected back down the feedline creating the SWR. When it reaches the rigs tuner or tank circuit, it is all re-reflected back toward the antenna. Eventually after enough back-and-forth trips it is radiated through the antenna. The only losses are the resistive losses in the feedline.

The feedline losses can be considerable with coax. With open wire or window line the losses are reduced enough to become unimportant [with reasonable line lengths].

For more info and some interesting reading see following:

http://members.dslextreme.com/users/w6wqc/antenna.html

DON
K6IOU

 
RE: Wire Loss and Antenna Gain  
by K8AI on May 31, 2005 Mail this to a friend!
>W8JI
>For those who think a conductor's resistance is defined >as ohms-per-wavelength nothing will make sense and you >will even be able to build 30dB gain Rhombics because >that long long wire will hardly have any series >resistance feeding the next section down the pipeline.

I love it... "ohms-per-wavelength"

Yep, just like transducer gain being in proportion to physical length.

Curt, K8AI
 
RE: Wire Loss and Antenna Gain  
by W4JLE on May 31, 2005 Mail this to a friend!
Some folks enjoy picking fly crap out of pepper

"Gee Joe that new antenna with the skinny wire is really worse than the #6 wire you used to run. Normally you are 40 over 9, with the new antenna your only 39.2 over 9"

I suggest that those that worry about such things make their antennas only from litz wire, that will take care of the skin effect. Good for at least another .0006dB

Play enough with eznec, losses because of wire size, and pretty soon you will conclude no antenna works.

And oh my goodness don't forget all the reflected power lost due to high SWR.

(I never have less than a 9:1 SWR on my feed line and I do that intentionally)
 
Wire Loss and Antenna Gain  
by KC8YYO on June 1, 2005 Mail this to a friend!
As you say the wire size is of no oconsequence. In basic electronics/physics I was taought that electricity travels on the outside of the wire Not in the wire. So ahenceforth RF is not to much differant, so it will travel on the outside of the wire. In affect if you have small wire and many of them you will see better preformace unless its a hi load situation where you need to adjust the wire size to carry the load. What it all really boils down to is surface area.
 
RE: Wire Loss and Antenna Gain  
by KE4ZHN on June 5, 2005 Mail this to a friend!
Perhaps if I were to use some 36" pipe for dipole elements...I may pick up .000001 of a db! lol
 
RE: Wire Loss and Antenna Gain  
by N0SP on June 5, 2005 Mail this to a friend!
To Tom, W8JI...
Tom, you're really wasting your time responding to BFH's rants. I sigh when I see them, (seldom wade through them anymore) then wince when I think if you spending good time responding to them. They will never end. How many times have people on here reminded him of long-ago-published engineering practices and proven theory?? He'll never know them, never learn them, and never understand them since his time is fully taken up with this endless bloviating of inane tripe... radio effluvium.
By the way, this was a great article... thanks IVJ.
73
Dennis
 
Wire Loss and Antenna Gain  
by K8KAS on June 8, 2005 Mail this to a friend!
While you guy's jaw about nothing, I'll just increase the drive to my Henry 8K and have fun. Your worries about tenth's of a db are a JOKE. If you have spent anytime on a real antenna range looking at pattern and field strength numbers you realize how hard it is to obtain real improvements in simple antennas.
 
Wire Loss and Antenna Gain  
by KA5FAP on June 8, 2005 Mail this to a friend!
The chart shows bigger is better as far as I can tell. The vertical axis is db loss. The chart indicates 10-14ga have the lowest loss as the frequency moves up.
 
Wire Loss and Antenna Gain  
by KA5FAP on June 8, 2005 Mail this to a friend!
The chart shows bigger is better as far as I can tell. The vertical axis is db loss. The chart indicates 10-14ga have the lowest db loss for all frequencies.
 
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