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Thread: Is RG316 coax enough for 65 watts in the 2M band?

  1. #1

    Default Is RG316 coax enough for 65 watts in the 2M band?

    The specs for the cable seem to indicate that it is but a buddy of mine says I should be using RG58. Any thoughts?

  2. #2
    Super Moderator 5B4AJB's Avatar
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    When your SWR goes high, you will find out

  3. #3

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    From a voltage and dielectric standpoint, that coax is rated for 900Vrms. Assuming the worst case scenario of a complete mismatch providing an infinite SWR, the maximum the RF voltage applied to the coax should be half that value, or 450Vrms. This will ensure that under total signal reflection (standing wave sees 2x the voltage you put in), the voltage of the standing wave never exceeds the operating voltage of the coax. That should come out to about 4,050watts. Obviously, the coax is not going to handle that for heat dissipation reasons, but high SWR and arcing isn’t going to be the coax killer.

    The loss of this cable at 2m googles to around 14dB per 100’. This means if you put 65w through 100 feet of this cable, you would have about 2.5w make it to the other end in a perfectly matched system. The other 62.5w goes toward heating the coax. With that much loss, you wouldn’t even get a decent swr reading at the input end as the reflected wave encounters the same loss on the return trip.

    Summary: That cable on 2m loses .6 watt a foot (at 65w in) to heating the coax. Absolutely terrible. Pick a different cable!
    Last edited by brandon lind; Thu 17th Oct 2019 at 15:23.

  4. #4

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    Thanks guys. I'm only using about 12' of cable but it still sounds like I should go with something else.

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