WiFi Antenna Cable Length

[wjackson]

We have some 1300 units and we have used some prebuilt antenna cables.

Trouble is they are way too long.

I have heard that the cables must be of a certain length or multiples of a certain length otherwise you get feedback issues.

Can anyone enlighten me on this issue please as I would like to make the cables as short as possible without compromising the performance.

[fabianoleso]

Hi,

I Know that a good choises for Cisco devices are:

- Cable LMR 600 100 - 150 foot (4.4 - 6.6 dB)

- Cable LMR 400 20 -50 foot (1.3 - 3.4dB)

For this type of cables you can visit this site: http://www.timesmicrowave.com

[wjackson]

We have the LMR 400 type cable, but its not the type im after its the distance related issue:

i.e:

Can I make the cable to length or are there specific lengths of cable that have to be met?

[rikrasmussen]

The issue is the loss of rf signal in the cable, which is expressed in db loss per 100 feet. The longer the cable, the more loss. Generally, the larger the diameter, the less loss per foot. So, longer runs require larger cable. At the frequencies we are working with, cable loss is significant.

[wjackson]

OK

so If I make a 19ft cable and compare it against the standard 50ft cable.

the only difference will be the loss etc from the length and connectors.

There are no issues with tha cable not being a standard length?

[Rob Huffman]

Hi William,

There are no issues with the cables not being a standard length. For what you are describing (19ft) a good choice would be this Cisco pre-made cable;

AIR-CAB020LL-R

Cable Length

20 ft (6 m)

Transmission Loss

1.3 dB

From this doc;

http://www.cisco.com/en/US/tech/tk722/tk809/technologies_tech_note09186a00801c12c2.shtml

Because of the inherent loss from poor connectors I probably wouldn't make my own custom length cables unless you have the proper equipment. But you can order custom length cables (professionally made) from many sources, such as;

http://www.hyperlinktech.com/web/cable_feed600.php

http://www.cellantenna.com/cable/customcable.htm

Hope this helps!

Rob

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[rikrasmussen]

Correct. You do not have to use multiples of a particular length. Do use as short a cable as possible. Install lightning surge suppresors and ground adequately.