Max power for RG58 coax cables?

Discussion in 'General Technical Questions and Answers' started by KE3FG, Mar 17, 2009.

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  1. K2WH

    K2WH Premium Subscriber QRZ Page

    And the frequency of operation. Using this cable at 900 mhz and 100 watts will eventually melt the coax.

    Bill
    K2WH
     
  2. KC8VWM

    KC8VWM Ham Member QRZ Page

    I wouldn't recommend using an amp with such cable.

    It might "work" but the question is for how long?

    A bad SWR on a rainy day is all it takes.

    Try to use "rated" feedline. I usually "overrate" feedlines as a safety margin.

    73
     
  3. N7SGM

    N7SGM Ham Member QRZ Page

    KL7AJ - ERIC
    K7KBN - PAT

    Thanks guys for your replies to my uneducated response! I mean that in a sincere way. I simply don't understand some concepts with the appropriate wiring gauge used in ham radio electronics. While it remains somewhat abstract to me, I want to learn more about it. I base my opinions solely on my electrical wiring background with little or no knowledge of radio circuits.
    Thanks for keeping me straight! :)

    73 de Bob
     
  4. AB8ZL

    AB8ZL Ham Member QRZ Page

    The reason most people recommend 12 or 14 gage wire for an antenna is to make them mechanically sound, not for any electrical reasons. Higher gage (smaller) wire will brake to easily especially when ice, wind or broken tree branches are considered.
     
  5. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    ::Yep, that's why I said, "at HF."

    I've melted RG58/U on 2 meters with about 450 W. Oops.:p
     
  6. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    ::It wouldn't matter much. It's a very short length and as such cannot dissipate much power even if it were very thin wire (as long as it's a good conductor like silver, copper, aluminum or gold). Also, you can increase the conductivity of any crappy old wire (even if it were steel or iron) if you can silver plate it, since only the outer .001" (or much less) of wire actually conducts all the current at radio frequencies -- the "core" performs no function other than to support the skin.

    Power semiconductors (especially transistors, power ICs and hybrid circuits) routinely use about #24AWG to conduct several amperes internally -- you just can't see the wire, because it's inside a sealed device. That works fine because wire lengths are very short, resulting in almost no voltage drop even at high currents, and the connections are welded, so they will not "melt" until the wire itself does.

    WB2WIK/6
     
  7. KL7AJ

    KL7AJ XML Subscriber QRZ Page


    Hi Bob:

    No problem! By the way, you'll notice that nobody expressed any particular horror at my light bulb experiment. :) Guess we have a lot more adventuresome crowd on here than I thought. HI

    Eric
     
  8. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    ::I can make a regular 40W 48" fluorescent lamp light up with no power source evident at all. I just have to walk up the hill to my local SWBC station KVOH (1.2 MW e.r.p. on HF) holding the tube end in one hand. As soon as I get within about 200 yards of the antennas, the bulb lights up. It's pretty cool at night.

    WB2WIK/6
     
  9. KL7AJ

    KL7AJ XML Subscriber QRZ Page

    We used to do that at HIPAS all the time. But a fluorescent lamp doesn't actually require any real power to light....just a lot of field voltage. The incandescent lamp, however, requires a real, genuine 100watts!

    Eric
     
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