Are antennas altered in the presence of carbon fiber masts?

The N9TAX antenna used in the test has a reasonably effective choke at the feed point that I've verified suppresses common mode tendencies by about 10 dB. I guess I could add another one 1/4 wave down for the coup de grâce, but that will have to wait for another time.

 

References mentioned in the video...

• https://apps.dtic.mil/dtic/tr/fulltext/u2/a140261.pdf
• https://www.haigh-farr.com/

 

some resins use metallic adjuncts (JB Weld) and are slightly conductive.

 

Everything is slightly conductive!

According to the manufacturer though, it is not:

https://www.jbweld.com/faqs

But I've never measured it myself. Have you?

73.

 

Again not an expert on materials or chemistry. To me the clay acts like a binder and to hold it's shape. Have you seen where they use graphite a form of carbon from a pencil and play around with making a resistor on paper?

 

one guy mentions "However, carbon fibers are also composited with other materials, such as with graphite to form carbon-carbon composites, which have a very high heat tolerance." from https://www.researchgate.net/post/Is-carbon-fiber-and-graphite-fiber-means-the-same

This is just what I find on the web as I have no expertise in the subject matter.

 

JB Weld comes in a number of different "flavors." I use a lot of their KwikSteel in my lapidary work and I believe it has powdered steel suspended in it---so it must be at least somewhat conductive. The basic JB Weld 2-part epoxy is likely what the company was referring to unless I am mistaken.

 

yes I have run DC and RF tests on a variety of materials, layups, etc. About 15 years ago we were trying to get GPS reception (and APRS transmitter) to work in a high power model rocket. Best place to mount the tracking stuff is in the nose cone. But we found that the GPS reception was unreliable in a certain manufacturer's carbon fiber nose cones. So we ran a bunch of tests. Turned out to be a whole bunch of factors, not just RF attenuation..

The DC conductivity of the carbon fiber airframe parts was an issue for mounting control circuitry, switches, etc. Easily solved with careful mounting and cardstock insulation.

And, yes the (high temperature) JBWeld was conductive enough to interfere with the motor initiator, leads accidentally touched the epoxy used for the motor mount, oops. We also experimented with high temp ceramic epoxy (very $$$$ aerospace stuff!), turned out to be too brittle and didn't wet out the fabric.

Sorry I do not have the report handy. But yeah, this emphasizes my point that there are quite a few variations in the materials, and some times it matters.

(In the end we went with a conventional fiberglass nose cone, good enough is good enough! If it doesn't survive a few Mach 3+ flights, then just call it a consumable and get another one.)

 

Interesting. But it needs tidying up. The massive dip with the wood stick is dismissed as unimportant, largely because we don't expect it to have this impact. It seems to have been down to bad body/hand positioning. So until all the materials are introduced without a human body affecting the results, we can't be entirely satisfied with the result.

 

I have to guess some tower manufacturer is looking at carbon fiber. Whole new can of worms regardless considering UV and grounding. Still prepeg tubes are easy to work with and stronger by far. Most what would be needed is off the shelf these days.

 

[QUOTE = "WB6MPH, post: 5796547, membre: 837383"] J'ai une petite expérience avec la fibre de carbone et les panneaux solaires. J'ai travaillé sur une voiture de course solaire en 1987. L'un des nombreux panneaux solaires flexibles n'était pas correctement isolé à l'arrière. Après avoir été collé et au soleil, quelqu'un a remarqué que le panneau était en court-circuit. Nous avons trouvé des fibres de carbone qui traînaient et les avons mises sous tension. Ils brillaient en rouge comme un radiateur infrarouge, alors oui, ils sont très conducteurs, bien qu'ils aient plus de résistance qu'un fil de cuivre. Je m'attendrais à une certaine absorption des RF, ce qui modifierait la capacité-réactance par rapport à un pôle en fibre de verre. [/ QUOTE]
Voilà un test pratique plus efficace que du Blabla...
Chris.

 

A carbon fiber mast would indeed require a UV resistant coating of paint, preferably in a light color (white) for best UV resistance. As for lighting: a direct hit will make the mast explode.

 

That would be OK as long as the guitar had plastic strings otherwise the RF burns would be ruination for your calouses. Oh wait, never mind the deer's hooves wouldn't feel it.

 

Any non (or very low) conductive materials with a dielectric constant greater than one should be easily noticed with an S11 test like this... hence not surprised to see an effect. That said, I did expect the dip to move down in frequency as is the case with insulated wire and antennas placed inside a PVC pipe. It didn't, but went with the data as shown.

Yeah... the hand. Should have held it at the bottom to remove that variable. This was my forth take with three cameras and was getting anxious to finish. Next time. At least the antler test with hand gives some hand to hand comparison.

Fair enough. The other two references introduced in the video make the question of CFC conductivity rhetorical, but I hope this demonstration inspires others to confirm it for themselves.

 

Properly bonded I don't think it will explode. Aircraft composites use many method but usually a copper mesh in the outer layers.