EIRP is a TRANSMIT number. "Equivalent isotropic RADIATED power". This is the radiated power on transmit in dBm leaving the transmit antenna in the favored direction compared to the  power that would be radiated if 1 milliwatt (0 dBm) were fed into a theoretical isotropic antenna that had 0 dBi (no) gain in any direction.

EIRP = TX power (minus) transmission line loss (plus) antenna gain = EIRP

Further,

2.4 GHz allows more than 6 dBi antennas even with 1-watt radios under the "3:1" rule for point-to-point use. This is why CPE can run more than +36 dBm because the CPE are effectively point-to-point radios talking to only one access point. The AP is NOT a point-to-point radio therefore it is limited a maximum EIRP of +36 dBm.

5.8 GHz allows more than 6 dBi antennas with 1-watt radios for point-to-point use. That's how those long 5.8 GHz backhauls can be made to work reliably.

jack



Marlon K. Schafer wrote:
Yeah.

People all too often forget that eirp is a RECEIVE number not a TRANSMIT 
number.  All it takes is big, big ears and you can hear the other end from a 
very long ways away.  Makes for much less noise in the area too.

I hate the trend toward high power radios with low power antennas.

You guys do realize that 2.4, 900 and 5.8 gig bands limit you to a 6 (that's 
S-I-X) dB antenna if you use a 1 watt (30 dB) radio?  Base station 
especially.  For CPE you can use higher gain cpe antennas on 5 gig and still 
be OK within the rules.

But all of these stupid, noisy, wasteful, cpe systems with 1 watt radios and 
19dB panels make a mess of your networks.  (and mine)

marlon

----- Original Message ----- 
From: "Mike Hammett" <wispawirel...@ics-il.net>
To: "WISPA General List" <wireless@wispa.org>
Sent: Saturday, October 31, 2009 10:50 AM
Subject: Re: [WISPA] Backhaul Questions


  
30 dB EIRP with a 44 DBi antenna on each side over 73 miles produces -75 
signal.  I'll let him say what he did to make it work, but it's certainly 
possible.


-----
Mike Hammett
Intelligent Computing Solutions
http://www.ics-il.com




From: Bret Clark
Sent: Saturday, October 31, 2009 11:02 AM
To: WISPA General List
Subject: Re: [WISPA] Backhaul Questions


Man...what is the EIRP on these links that people are posting high bit 
rates? As someone else stated, gotta wonder if the FCC won't start getting 
suspicious at some point.

Travis Johnson wrote:
 73 miles... and I get 28Mbps total (14Mbps each direction) using a 20mhz 
channel.

 Travis


 Josh Luthman wrote:
Travis is getting 28 megs on a really long backhaul - like 58 miles?

You will not see >30.

On 10/31/09, Eric Rogers <ecrog...@precisionds.com> wrote:
 Ok guys...Looking for both Mikrotik experience and others.  We currently
have a Mikrotik backhaul between each of our towers using NStreme and we
have been extremely happy with the performance.  We recently upgraded a
tower because we were hitting 15M or so during peak times and was afraid
it couldn't handle much more.  We upgraded that backhaul to a Motorola
PTP for future capacity.



The questions:



MT Gurus:

Each backhaul ranges in distance, each ranges from 3 miles (3 backhauls)
and the rest are about 12 miles (5 backhauls).  Since we have been using
Mikrotik, I have reliably seen up to 10 Meg, and I am afraid 15 Meg is
pushing the envelope on a 20 MHz channel.



How much capacity can I reliably push on a 20 MHz channel using NStreme?



Other Gurus:

I understand the following are loaded questions, but budget is around
$1000-3000 range and the capacity needs to be around the 60Meg mark (30
each way or without a defined 1:1 guarantee, capability to flex and be
able to push 30M each way).



If I start upgrading to larger backhauls on busy links, what type of
equipment should I look at?

What can support VoIP?

Anything that GPS times for frequency reuse?

Anything work in the 5.4GHz range at a 12 mile distance?



Eric Rogers

Precision Data Solutions, LLC

(317) 831-3000 x200





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-- 
Jack Unger - President, Ask-Wi.Com, Inc.
Author - "Deploying License-Free Wireless WANs"
Serving the Broadband Wireless Industry Since 1993
www.ask-wi.com  818-227-4220  jun...@ask-wi.com

Sent from my Pizzicato PluckString...




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