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Coil Antenna's ... Are there really any differences?

70cst

70cst

Well-Known Member
Dec 4, 2009
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I have read various threads about coil antennas for mobile applications so I ask...are there really that much differences between the coils and if so what makes it so?

And...for mobile applications would a mobile radio see a difference between lests say a Wilson 5000 or a Sirio 5000 verses a coil designed antenna.
Thanks again...
 
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Some difference.
The coil antennas, like a Viper or Predator, have a larger open coil above its base - as compared to the Wilson 5000 or a Sirio 5000 that has an enclosed coil at the base.

A larger diameter coil, like the Viper or Predator, means there are less coil turns used and less loss due to coil loss. Less capacitive loss too; but we aren't talking about much loss. It all adds up - though. Since we are talking about antennas that are ALL less than a 1/4 wave in length, there isn't a LOT of difference. But some.

Are they better for that reason? Yes; because they minimize loss. But not better than a 1/4 wave. Anything less than a 1/4 wave is a compromise. The closer the antenna in question in length to a 1/4 wave antenna, then the better off you are. Because less coil is needed to make up for the distance in length. So, less capacitive and inductive ('coil') loss with the Viper and Predator type of antenna . . .


EDIT:
The Viper/Predator with a long whip will also have better bandwidth. Something that may be important if the operator uses a radio for both 10m and 11m. The 6 1/2 ft Sirio has a usable bandwidth of 1.2mHz and the 5 1/2 ft Wilson has .8mHz bandwidth. The Viper/Predator is better; but I am not sure how much. Perhaps someone has put a Predator10k on a MFJ-259B analyzer and checked its 2:1 VSWR. I don't have a Predator; or I would check it myself.
 
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Here is one of my "Most Favorite Threads". Worth the time to read the whole thread - some great info:

http://www.worldwidedx.com/cb-antennas/82388-my-first-attempt-mobile-antenna.html

This page in particular gives you an idea of bandwidth and antenna length. Look at these antennas that were mostly hand-built - except for a K-40 and a 1/4 wave steel whip used in there for comparison. Also note the diameter/width of some of these coils and the amount of turns they have.

Page 11, post #103:

http://www.worldwidedx.com/cb-antennas/82388-my-first-attempt-mobile-antenna-11.html
 
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Again...thanks for the LINKS. What is it they say...Reading is a dangerous think :laugh:
 
70cst said:
That is very ineresting info ...
Click to expand...

ditto. i figured there would be some differences between the antennas based on the size of the coils, # of turns, etc... but that was just conjecture on my part (i'm the farthest thing from an engineer you can imagine).

i was kinda surprised to see that the skipshooter held it's own against some of the other coil antennas, if i understood the chart correctly (the 7' skipshooter or a 102" whip are my daily driver antennas). now i don't feel so bad when i go to the local meeting spot and everyone and their brother has coil antennas (they always ask me why i don't have one too).

i'd have to agree that the MM is a pretty hefty antenna. got one for my good friend for his birthday many years ago, and the thing is on his daily driver. still going strong after all these years, although it's looking a little worn and dirty. that thing has gone to the beach, through drive-throughs, even through car washes in the bed of his truck and it's still going strong.
 
The simple fact is that the only reason for a coil in an antenna is to shorten it. The amount of wire/conductor in that coil has no direct correspondence to the 'length' that antenna was shortened. The amount of wire/conductor used, and it's shape and spacing, does correspond to the amount of inductance required to make that antenna resonant. It also contributes (the size) to the amount of power the coil is capable of withstanding. The spacing between turns of that coil has more affect on that power handling ability than the 'size' of the wire/conductor (because of arcing).
The only radiation ability a coil contributes is related to uit's 'height', how 'tall' it is, it has nothing to do with the amount of wire/conductor making up that coil. If the thing is one foot long/tall then it will only radiate as much energy as a one foot long conductor.
The shape of the conductor making up that coil, round, flat, vertical flat/horizontal flat, does have an effect on how much inductance the coil produces. Flat vertical conductor contributes nothing to vertical polarization, flat horizontal conductors contribute nothing to horizontally polarized radiation. Round conductors don't contribute to either polarization. The only affect the 'shape' of the conductor has is with the interaction between coil turns and wind resistance of the coil. All the advertising about that sort of thingy is pure advertising hype (sorry 'bout that).
The 'shape' of a coil can have/make a difference in how much inductance that's produced by that coil. Short wide coils are more efficient than tall skinny coils. That's easily proved by formula and experience.
There's a huge difference between efficiency, being practical, and 'looks'. What may be 'gained' in one of those is always lost in one of the other. It just depends on what you are after, and what you can do. To me, that 'practical' aspect is a biggy. That means that the 'looks' of an antenna has least to do with why I may use it. I still want it to be as efficient as possible and still 'fit' the practical aspects. 'Where'/'how' you use an antenna is also going to determine what it looks like and how 'big' it is. The backyard is totally different than the car/truck. That car/truck is always going to be a compromise sort of situation, right? So, you figure out what's gonna 'work' for you and then use it.
- 'Doc


One aspect of HF mobile operation is that the bigger and uglier, the better... within reason, of course.
 
Act162This said:
ditto. i figured there would be some differences between the antennas based on the size of the coils, # of turns, etc... but that was just conjecture on my part (i'm the farthest thing from an engineer you can imagine).

i was kinda surprised to see that the skipshooter held it's own against some of the other coil antennas, if i understood the chart correctly (the 7' skipshooter or a 102" whip are my daily driver antennas). now i don't feel so bad when i go to the local meeting spot and everyone and their brother has coil antennas (they always ask me why i don't have one too).

i'd have to agree that the MM is a pretty hefty antenna. got one for my good friend for his birthday many years ago, and the thing is on his daily driver. still going strong after all these years, although it's looking a little worn and dirty. that thing has gone to the beach, through drive-throughs, even through car washes in the bed of his truck and it's still going strong.
Click to expand...
I found it interesting that the Wilson 5' Silver load is a good antenna as well, where as the Firsstik basically sucks. Just confirms what I always thought (to myself that is).
 
now i'm also kinda curious - one of the locals here has a large, flat-coil antenna made by a friend in seattle. it looks a lot like the other flat-coil antennas, except it has a really wide piece of flat stock wound loosely about four times, instead of the others like the MM with a larger number of thinner, more tightly wrapped coils.

power-handling wise, i suspect they are similar in power-handling, but i wonder if one is truly better than the other.

bandwidth-wise, i'm assuming it shouldn't matter since he is not running an export radio, and spends most of his time or ch. 6 or 11 and hardly any on SSB.
 
binrat said:
I found it interesting that the Wilson 5' Silver load is a good antenna as well, where as the Firsstik basically sucks. Just confirms what I always thought (to myself that is).
Click to expand...

my 5 foot silverload was so crappy no matter what i tried that i went ahead and unwraped it and sank a 4 foot whip into the top making a 1/4 wave whip that doesnt destroy everything it hits. now its useful and works good. my wilson1000 didnt quiet keep up with my sirio5000 but my wilson5000 beats them both and almost stays with the 102" and is the quitest antenna i have but has better receive then the 1000 or the sirio
 
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This is what I am finding out...we have many different opinions based on experience. There are those who like the Wilson 5000 better than the Sirio 5000 and vice versa. We have some who say the coli antennas beat the heck out of the 5000 style antennas. We have some say there is little difference between antennas. So it comes down to what best fits your mounting location, your radio, your match, and so forth. The more I read the more I am learning there is no super magic CB antenna. JMHO Please note...my opinion is subject to change...(y)
 
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70CST,

I have used an assortment of antennas, and antenna types. Some little cheap antennas are very poor performers, but even they will suprise you when conditions favor them. As has been said, the bigger/uglier, generally the better. However, I can mount any of my assortment and drive down the road. From one spot in the road to the other the antenna will be better. The only absolutely consistent thing with regards to mobile antennas I've experienced is the bigger/uglier/better they are, the more my wife complains about how redneck and tasteless I am riding down the road with that stupid ugly thing on my vehicle.

I have a friend who spent a few hundred dollars which he really didn't have trying to find the greatest antenna made. In the end those big super antennas sit in the corner collecting dust, and he is running the one he started with. Why he doesn't just run a 1/4 wave whip if he wants to maximize his mobile eludes me... I suspect it is because it isn't exotic/cool enough. It's just big/better/ugly.
 
antenna comparisons

70cst said:
I have read various threads about coil antennas for mobile applications so I ask...are there really that much differences between the coils and if so what makes it so?

And...for mobile applications would a mobile radio see a difference between lests say a Wilson 5000 or a Sirio 5000 verses a coil designed antenna.
Thanks again...
Click to expand...

First, copper has a better signal to noise ratio than aluminum or stainless. But, unless your radio was tuned by 1 of 2 different technicians and your noise floor of your radio as measured with a signal generator is down to .01uv like mine, you would never notice the difference with a noise floor of .3uv, which is average on a stock rig.
Copper is weak and breaks easily. Stainless is extremely strong, heavy, and picks up a lot of noise(unless it is coated in plastic which helps eliminate noise. Aluminum is a little bit stronger than copper but picks up more noise. If you built 1 design antenna out of the three different metals, they would probably transmit in an identical manner. The only difference would be you would hear weaker stations better with the copper version. The best aluminum mobile antenna I have tested was a predator 10k. The only problem is that it is kinda flimsy and easy to break.all my homemade antennas that I build for personal use incorporate stainless steel where structural integrity matters most, then I use copper wire wrapped tightly around an insulator then thick shrink tubing to cover the copper. Basically the oldest designs are some of the the best antennas. Hustler Wilson k40 utilize the best materials they all use a copper coil with a stainless steel shaft and whip. If only they made them custom for big trucks so the top of the whip comes even with the top of the trailer. I use a Wilson 5000 roof mount on my Chevy Tahoe with 15'2" of lmr 240, swr is 1.15:1 r equals 49 x equals 0, and it gets out about 40 miles barefoot with a Magnum S-9.
 
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