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New Member

interference from cordless phone - i think - can different antennas help

at a recent installation that has a Panasonic cordless 'system' (base station and 5 handsets) we are experiencing intermittent disconnections.

Since i'm suspecting the phones i intend to do a test tomorrow of an FTP with no phones in use and then one with phones operating, etc. to confirm our suspicions.

If that is the case, is there anyway of using a better antenna system or will the power of the phones always overwhelm the wireless power?

I think the access points and cards operating in the milliwatt range? I

3 REPLIES
New Member

Re: interference from cordless phone - i think - can different a

The 2.4GHz phones that I have seen are 100mW, so even if they are Frequency Hoppers they have the potential to interfere. You can see an example of that here: http://www.bluemodal.com/siemens.jpg

The simplest solution is to increase gain at your AP with a different antenna (there are hundreds of models available) - the phones should be more tolerant than the WiFi devices.

The alternatives are:

1. Replace the phones with 900MHz units

2. Migrate the Wireless LAN to 5.2GHz (802.11a)

3. Use Wireless VoIP phones (handsets or PocketPC devices) with the Access Points and get rid of the cordless phones, because 'they're just so 90s'.

Call if you need help with parts.

Matthew Wheeler

Chief Wireless Architect

www.BlueModal.com

New Member

Re: interference from cordless phone - i think - can different a

clarifications:

1. the link is a example of the output of a cordless phone? Is it showing that the strength is such that it would knock off a wireless connection?

2. are you saying that with the 'best' antenna we could avoid the disruption by the phones or is the power from the phones (100mW) still more than a wireless card?

what is the power of a wireless card?

New Member

Re: interference from cordless phone - i think - can different a

The link I posted shows the signal strength and frequency range used by a Siemens 2.4GHz phone in operation right next to a 2.4GHz scanner.

Placed in close proximity, the phone would likely kill a WiFi connection for a data device in Channel 4 (2432MHz center frequency). Idealy, you would check the exact frequency of your phones (they probably span some portion of 2400-2484, but not all of it), then set your AP to the least conflicting channel. You may be able to restrict the channels that the phones use, but it's not likely unless you can tell them they are in another country (different regulations, different channels).

Since the phones use frequency hopping, they would be fairly tolerant of a strong WiFi signal (but don't put the AP in the center of a hallway where they'll walk under it while using the phones).

Even though Cisco 350 series PCMCIA cards have the same signal strength as the phones (100mW), using a high-gain antenna on the AP will help the users 'hear it' and help the AP 'hear' them over the phones. I would suggest a 9dBi or better patch placed inside an outside wall for up to 200 meters of range. They're less than $50, so it's a quick fix to get 500mW effective power.

Matthew Wheeler

Chief Wireless Architect

www.BlueModal.com

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