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What should be the DC resistance of an external Wi-Fi antenna (when measured between center and shield of the SMA connector)?

In case of:

  1. DIY "Pringles" antenna
  2. Consumer grade antenna, connected to external USB WiFi adapter

I believe there should be no difference between #1 and #2, right?

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1  
Do you mean impedence? Are you looking for a 50 ohm antenna? – Thomas O Nov 13 '10 at 12:33
No I mean really DC resistance, not at the 2.4GHz. (I believe it should be 50Ohm at band of interest but not necessary at DC). – mazurnification Nov 13 '10 at 12:39

2 Answers

up vote 8 down vote accepted

Do you mean the resistance across the coaxial connector, from the center pin to the ground?

Depending on the type of antenna, it should either be infinite (Most antennas, including pringles cantenna, which uses a simple 1/4 wave antenna), or a dead short (Some odd types, like a folded dipole).

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Yes That is the case, I have edited the question to include that info. Is there a quick way to tell which type I am facing (I am trying to find a quick way to tell if my antenna is broken). BTW Thanks for the answer. – mazurnification Nov 13 '10 at 12:33
2  
Not really. RF Impedance is significantly different than DC resistance. – Connor Wolf Nov 13 '10 at 12:41
up vote 3 down vote

Agree with the answers above. Just wanted to add that the zero-ohm type is not so uncommon these days. This could be a very popular PIFA antenna. You will not measure exactly zero ohm with PIFAs, loops or folded dipoles, the DC resistance would be a couple of ohms.

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