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 Ham Member QRZ Page

    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 grĂ¢ce, but that will have to wait for another time.
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  2. KX4O

    KX4O Ham Member QRZ Page

  3. K6CLS

    K6CLS Ham Member QRZ Page

    some resins use metallic adjuncts (JB Weld) and are slightly conductive.
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  4. N7EKU

    N7EKU Ham Member QRZ Page

    Everything is slightly conductive!

    According to the manufacturer though, it is not:

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

  5. AC1CP

    AC1CP Ham Member QRZ Page

    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?
  6. AC1CP

    AC1CP Ham Member QRZ Page

    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

    This is just what I find on the web as I have no expertise in the subject matter.
  7. AK5B

    AK5B Ham Member QRZ Page

    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.
    K6CLS likes this.
  8. K6CLS

    K6CLS Ham Member QRZ Page

    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.)
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  9. MW1CFN

    MW1CFN Ham Member QRZ Page

    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.
    AK5CT likes this.
  10. N1IPU

    N1IPU Premium Subscriber QRZ Page

    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.

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