Are antennas altered in the presence of carbon fiber masts?

I would think there is something to this other than just radiating feed line as magnetic loop antennas are fed this way and do perform remarkably. There does appear to be some validity to using trees as antennas from military reports I have seen on the topic. For instance one report says "Signal field •strength received from the toroid by itself in air is about 15 dB lower than that from the toroid coupled trees, which proves the role of the trees as radiating elements." This was lifted from this report https://apps.dtic.mil/dtic/tr/fulltext/u2/742230.pdf which is PERFORMANCE OF TREES AS RADIO ANTENNAS IN TROPICAL JUNGLE FORESTS -(PANAMA CANAL ZONE EXPERIMENTS). If a tree can be used as an antenna by coupling via a toroid then I would certainly think a carbon fiber pole would prove much more effective. Sorry I don't have one with which to try. Perhaps someone here will do it and report back to us.

 

The resistivity of drinking water is somewhere between 20 Ohm and 2 kOhm and highly depends on dissolved salts. So I don't think a tree will be an efficient conductor. Your comparison with a loop antenna is very off the scale since a loop antenna requires an extremely low resistance in the loop.
As for carbon fiber: its resistivity is also too high to be an efficient antenna. Besides that, you never know how long the strands are in a mat, how dense the mat layup is and in which direction. So in worst case, when the strand direction is 45 degrees compared to the rod, the electrical length of lowest resistance might be much more than the physical length of the rod.

 

I took a course in composites at Reno, it seems like carbon is a conductor when you don't want it to be and an insulator when you need it to be.

 

That was an awesome course all the same. I applied it to boats at the time but its moved a great deal forward since then. I am still concerned about the state of the art with carbon in several areas though. I wonder if we will see some spectacular failures in the years ahead.

 

It's all about the coupling method at the feedpoint.

Check out the "electrolyte fluid stream", ie seawater antenna, developed and demonstrated by Daniel KA6FRY for primarily military and maritime applications.

The key invention seems to be the so called "current probe" donut at the base. Would be more fun to see it operating on HF, though, would take a much bigger pisser !



More from the linked article cited above,

"The technology could possibly be used on land with salt-supplemented water, replacing large unsightly antenna towers with fountains. Another use for a seawater antenna could be as an emergency antenna system for watercraft.

In the future, Tam (KE6FRY) said the technology will be able to use the salt solution in human bodies to turn body parts into communications antennas.

"My vision for the future for Navy warfighters is to design a small antenna using your own finger as an antenna element. For women, I can design earrings, a necklace and a bracelet. For men, a necktie and a belt," Tam said.

Using human body parts as communications antennas will give warfighters a winning edge by dramatically reducing the weight they have to carry."

 

I hear that dog tags radiate really good in the giga hertz range.

 

So how is the radiator lenght controlled? It seems to me that at some random point the seawater stream starts to break down in droplets. And if that point is random and influenced by wind, you'll end up with a radiator that changes length constantly and randomly.

 

How can you hear anything up that high? It's not for you, it's for dogs!

 

I had the same thought; but realize it's a contingency antenna, not an optimum one. And the effect of stream breakup, ie length, is inverse to operating frequency. It matters much more at UHF then lower HF.

Perhaps stream dynamics could be mitigated by a fairly fast acting active closed-loop servo control on stream pump output based on feedback from a resonate dip in SWR, or the electronic black-box equivalent in variable match at the coupling. Again, the current probe donut coupler UNUN may be broad-banded enough to handle an average amount of that at lower frequencies.

 

The water stream antenna would be much more efficient if they were to employ a laminar flow nozzle. Then the stream would act as a solid rod for a much greater distance.
http://hackedgadgets.com/2012/04/09/diy-laminar-flow-water-fountains/

 

Hmmm, interesting idea, but not clear to me that the unturbulated flow has better radiation... We'll have to run some tests!

 

I am designing a new beam antenna with a really strong fiberglass boom, with fiberglass supporting radials. I have been using the design
on PVC for about a year but it is time to upgrade the antenna. Specially designed for 15 and 25 degrees take off angles for short and long path.
It is a beautiful and graceful beast...lol. I may even market this new design. It handles the legal limit great. You will need room to put it up.
Performs super great at a height of 10 meters but works just fine at 5 meters.

 

good job.... and... I think, what about the use of this poles as radiant element?
I use a telescopic fiber glass fisshing with steel roope iner 5m hight as radiant element, is light and easy to carry in the back pack, but the automatic roller to colect the roope sometime fails.

 

Back in the early 90's, I acquired some carbon fiber rods. I have successfully used them to make antenna for 10m, 2m, and 470cm. Not as efficient as aluminum but very broad band. The 2m version is really 2m/470cm and I used it at my current QTH for a 2m/470cm cross band repeater.