Bob, I hear what you're saying and have been through the figures a few times
and even tried turning the power of the radio cards down to 1dB output
(still unable to run both links simultaneously) but this doesn't explain why
others are able to use the same radio cards with similar antennas with
little to no problems.

Charles, unfortunately Canopy isn't a financially viable solution at
present. I have a rough idea of these 2 terms but I'll research them a
little deeper to see if they shed some light. Anything else that may help on
my quest?

-----Original Message-----
Behalf Of Bob Moldashel
Sent: 18 January 2006 00:25
To: WISPA General List
Subject: Re: [WISPA] Multiple Radios on Single antenna

Ahhhhh......Lets do some math.......

Lets say the radio has a +20 dB output.  For this example there is no 
line loss.  The antenna is rated at 30dB x-pole isolation.  Here we go...

+20 dB
-30dB xpole
-10 dB receive level. 

In my book that is high enough to kill any link of the same freq on the 
opposite polarity....No???

Add to that a radio that needs to Rx and Tx on and off and you should 
have receiver blocking....... 


Matt Liotta wrote:

> Depending on various factors, you should see at least 15db of 
> attenuation between polarizations on a dual-pol antenna. 
> Theoretically, you should see 20db. In any case, 15db is enough 
> attenuation even on the same channel to operate two links reliably.
> -Matt
> Jason Wallace wrote:
>> List,
>> When antennas are separated by normal distances, they can only "see" 
>> each other electromagnetically (ie, radio waves).  However, when they 
>> are close they will experience capacitive and inductive coupling.  
>> Dual pol antennas work fine when only receiving (as in those large 
>> satellite dishes from the 80's that used 90° pol changes between 
>> adjacent channels).  I think you will always have trouble overloading 
>> the receiver when transmitting with this setup.

Bob Moldashel
Lakeland Communications, Inc.
Broadband Deployment Group
1350 Lincoln Avenue
Holbrook, New York 11741 USA
800-479-9195 Toll Free US & Canada
631-585-5558 Fax
516-551-1131 Cell

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