Radio interface need to be disabled when antenna is not present?

Unanswered Question
Sep 5th, 2007

I have been informed within a training class that the radio interface of an access point should be disabled when an antenna is not present. The reason given was that it would protect the radio from being adversely affected (potetnial for irreparable conditions). Question: 1) Is this true? 2) If so, where can I find supporting documentation on CCO? (I have not been able to find corroboratory information.)

I have this problem too.
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rob.huffman Wed, 09/05/2007 - 10:16

Hi Vincent,

Here is a doc that speaks to this issue ( I don't see this causing irreparable damage but, better safe than sorry :)

Q. If you operate the radio but do not attach the antenna, can you damage the radio?

A. Some radio equipment manufacturers specifically warn against the operation of radios without the attachment of the antenna. Operation without the antenna can damage the transmitter. Most pieces of amateur or commercial radio equipment carry this warning because the equipment operates at a much higher transmitter power. A failure to use a proper antenna or load causes a reflected wave standing wave ratio (SWR) that can damage the final amplifier stage. This final amplifier stage is the power amplifier (PA).

For Cisco Aironet equipment, the transmitter power output is 100 milliwatts (mW) for the 350 Series and 30 mW for the 340 Series. Damage is unlikely, but possible. If you need to run the devices without antennae, turn the transmitter power down to 1.5 mW. Also, you can use a 50/52 ohm dummy load (attenuator) to be safe.

From this good Q & A doc;

Hope this helps!


vfg Wed, 09/05/2007 - 11:03

Rob - Thanx, for the information! Looks good. I associate with many field technicians that (under various circumstances) need the flexibility to move antennae. I kept getting the question, but could not provide a definitive answer (at least not without corroboration). Thanx, again.


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