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Do I have a Short in my CB Antenna??

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daysand

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Jun 11, 2004
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I have a old CB Antenna from Radio Shack model # 21-989.

I was about to put a PL-259 connector onto the Antenna Coax.
I was checking to see if the Coax was in good shape and when I checked the Coax with a Continuity checker, there was a direct connection between the Coax Lead and the Grounding shield.

I was very supprised.

I would think there should NOT be a direct connection between the Coax Lead and the Grounding shield.

Could this be a Short in the Coax, as I would think???
or
Could it be possible that this type of Magnetic Mount CB Antenna, would have the Lead and Ground connected?
 

SCPD

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If it is a base-loaded antenna it is probably DC grounded and showing a DC short would be normal
 

LtDoc

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It can seem confusing but a 'short' at DC may not be a 'short' at radio frequencies. If that's a typical base loaded antenna, that 'coil' on the base also contains an impedance matching coil. If such a coil is measured with a typical ohm meter or continuity tester it will show a short, which is normal.
- 'Doc
 

kb2vxa

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"If it is a base-loaded antenna it is probably DC grounded and showing a DC short would be normal."
More detail needed for clarity, depending on the "base load" it could be continuous or open.

I don't know what kind of antenna that is but here's a rule of thumb. Most shortened mobile antennas are loaded 1/4 wave, series fed and will read open (infinity ohms) from ground to active element. Most base antennas, that is with radials are shunt fed 1/2 wave (advertized as 5/8 wave) and will show only a few mil-ohms and look like a short on an ordinary meter. A half wave dipole (no radials) like the classic Shakespeare Big Stick will read open.

Logic says if you want to read the coax do so without anything connected to it. Just remember a DC meter won't give a clue about RF characteristics or condition.
 
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