Highfields Amateur Radio Club
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How Long Should My Coax Cable Be?

I am often asked by new licencees: How long should the coax be to connect my radio and antenna? Well, here is a useful calculator you can use to find out the answer. ("Old hands" can use it to check their own, brain led, calculations). This calculator works for virtually all resonant antennas, some special designs may require a set length of coax, check the design specs or manufacturers' data if unsure.

To Use:

  1. Decide the route the coax will take.
  2. Measure the run, in Feet or Metres, including all the twists and turns. Don't forget any slack required for the rotator (if fitted).
  3. Allow an extra 3 Feet or 1 Metre at the radio end for repositioning the radio etc.
  4. Select the "Feet" or "Metres" button as required.
  5. Enter your measurement into the box and click the "Calculate" button.
  6. Your answer is displayed in the "Your coax length should be:" box.

    Switch to:

    Measured distance from antenna to radio in

      Your coax length should be:

    Now you have the answer, scroll down to the bottom of the page for more advice.

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Well now you know! If your radio and antenna are 30 feet apart it's no good using 22 feet of coax is it? Conversly it's no good using 50 feet and tripping over the "spare".

But you don't know if you don't ask! You're not the first and you won't be the last.



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