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Are antennas altered in the presence of carbon fiber masts?

Discussion in 'Amateur Radio News' started by KX4O, Mar 13, 2021.

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  1. KX4O

    KX4O XML Subscriber QRZ Page

    Opinions vary on how carbon fiber composites conduct RF currents... inspiring an experiment.

    The VHF tests in the video below reveal carbon fiber antenna masts behave just like any conductor at radio frequencies. I test several items including the Carbon6 portable mast from SOTABEAMS. Long story short, carbon fiber supports have their utility for the radio aficionado with the caveat to treat them as a conductive structure and plan accordingly.

    carbon6.jpg

     
    CS7ATM, AF5SB, W1SRR and 15 others like this.
  2. AK5CT

    AK5CT XML Subscriber QRZ Page

    I know I skipped through the video some, but from what I saw, carbon fiber and steel do affect it, wood and fiberglass do not, and if a Deer is playing an electric guitar next to your antenna , you should be OK. :)
     
    K5DBJ, K9AEE, N7KO and 15 others like this.
  3. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    Good experiment!
     
    VE2CYV, M1WML and AJ6KZ like this.
  4. NU4R

    NU4R XML Subscriber QRZ Page

    THIS is typically where I step in and talk about my experience with the Boeing 787.

    But, as of late, I'm sick to death of being cut off at the knees by all the aviator wannabees every single time I politely point something out.
     
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  5. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    ??
     
    M1WML and AJ6KZ like this.
  6. W6TOM

    W6TOM Ham Member QRZ Page

    A good practical demonstration, thanks!!!
     
    M1WML likes this.
  7. AJ6KZ

    AJ6KZ Ham Member QRZ Page

    Did you park a 787 next to your antenna?
     
    NN0M, K4BMW and M1WML like this.
  8. N1IPU

    N1IPU Ham Member QRZ Page

    Now I am curious. Just started to mess with carbon composites and took Burt Rutans course some 20 years ago. Not much about RF out there when related to carbon fiber.
     
    M1WML likes this.
  9. WB6MPH

    WB6MPH XML Subscriber QRZ Page

    I have a little experience with carbon fiber and solar panels. I worked on a solar race car in 1987. One of the many flexible solar panels wasn't insulated properly on the rear side. After it was glued on and in the sunshine, someone noticed that the panel was shorted out. We found some carbon fibers lying around and put some voltage across them. They glowed red hot like an infra-red heater, so yeah, they are very conductive, though have more resistance than a copper wire. I would expect some absorption of RF, which would change the capacitance-reactance compared to a fiberglass pole.
     
    AA5BK, N7KO, KC5JSR and 7 others like this.
  10. KI5AAI

    KI5AAI Ham Member QRZ Page

    I use to fly an OV-1 Mohawk....I do not even think we had plastic on that thing LOL.
     
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  11. N9AMI

    N9AMI Ham Member QRZ Page

    Didn't need a video to prove this.
     
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  12. KX4O

    KX4O XML Subscriber QRZ Page

    That's correct even though evidence of misunderstanding from the vendor itself begins at 0:10. Consider the video a demonstration to help spread the word.
     
    Last edited: Mar 14, 2021
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  13. K6CLS

    K6CLS Ham Member QRZ Page

    ... Can't just say "carbon fiber", because it depends on the fabric, layup, epoxy, etc. I've made coupons with varying RF and DC conductivity.

    There's a lot of carbon black tinted pultruded fiberglass products available, that would fool most people, oh yeah looks like carbon fiber...
     
    K1HOP, KC1MRN, AK5B and 3 others like this.
  14. AC1CP

    AC1CP XML Subscriber QRZ Page

    I'm no rocket scientist but the first thing that came to mind was carbon based resistors. Sure they offer resistance but that implies flow. So why wouldn't a carbon fiber material have properties like a low value resistor?
     
    AK5B, M1WML and KX4O like this.
  15. W4FID

    W4FID XML Subscriber QRZ Page

    A common situation is using some of the easily available fiberglass 4 foot section poles for quick/temporary antenna support. Go up 20 or 24 or maybe 28 feet, with the pole as the center support of a simple wire dipole like a 102 foot non resonant one. Not much weight or wind resistance so probably get by without even guying the pole. Feed the dipole with ladder line hanging down the mast. Especially good for field day, RVs, etc. A carbon fiber mast would be a lot stronger so maybe get a little taller one or get by without guys where the fiberglass mast wound be more of a concern. The article and video is about VHF. AT HF -- WILL THE CARBON FIBER MAST BE A PROBLEM?
     
    W1LJ and K9AEE like this.

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