Re: Max cable length for Aironet 350

michael.spence · ‎01-27-2006

I have a 350 bridge installed with a 100 ft antenna cable. I need to move the bridge, because of an alignment problem. To move it I will need to use an antenna cable longer than 100 ft, so if I can use a longer cable what is my signal loss? Does Cisco reguire only certain lengths for the antenna cables?

scottmac · ‎01-28-2006

More information is needed.

100' of cable is already pretty extreme. Are you using the Cisco cabling?

If it's ever worked, how was the signal strength and quality?

What is the distance between the antennas of the two (or more?) sites?

What kind of antennas (at what gain) are you using?

Losses for most cable at 2.4GHz are pretty high. IF you have the spec sheet for your cable (or can look it up), find the spec for loss, under the column for 2GHz ... for every 3db of loss, you're losing half the power. A common spec for high-quality coax is ~12-18db per hundred feet.

For 12 db, that 's half of half of half of half - if your AP is sending 100mw, that's 100(start) / 50 / 25 / 12.5/ 6.25mw reaching the antenna. There are also other losses from connectors, so-called lightning arrestors, and some other factors. You're doing good to get 4mw into the antenna's radiator.

Adding more cable and connectors to that will take it down even more.

You can go to lower-loss cable (or Heliax, from Andrew Corp) or add an amplifier, but then your system is no longer Certified according to the FCC rules (to guarantee that you are within government specifications). You'd need someone authorized to perform the proper testing and provide you with a certificate of compliance.

Provide some more details and we can offer some more specific details.

Good Luck

Scott

michael.spence · ‎01-31-2006

I am using Cisco cabling. The only other problem, and reason for moving the antenna is that the two antennae are out of alignment. The distance between the antennae is not that great, maybe 200yrds at most. I am using a Cisco Air-ANT1728.

I will need to go to at least a 150 foot cable to get the antennae back in alignment. Moving the antenna on the remote bridge will not help the situation. I appreciate all your help.

michael.spence · ‎01-31-2006

I believe the part number on the cable was ANT-CAB100ULL-R.

scottmac · ‎01-31-2006

Extending the cable to 150 feet is probably a bad idea. If you have no other choice then give it a shot, but the cable losses are going to be pretty significant.

As an alternative, would it be possible to move the AP closer to the antenna and extend the LAN cabling?

If possible, I think you'll find this to be a better solution.

Good Luck

Scott

michael.spence · ‎02-13-2006

Thanks for your input. I am really concerned about signal loss as well. I will look at moving the AP.