Correction, under the 3 for one rule you can go UP 3 dB in antenna gain for every 1 dB of radio transmit power that you go down, but only for client side or ptp installations. It STARTS at 30 dB radio and 6dB antenna.
So if you have a 30dB radio, it's a 6dB antenna. 29dB radio you can use a 9dB antenna. 28-12 27-15 26-18 25-21 24-24 This is the one that excited me years ago. This meant I could use a quarter watt amp, 24dB with a 24dB grid for a ptp link! That'll give you a -72dB rssi (54 meg speeds!) at 100 miles! Get this one, -78dB rssi at 200 (not a typo, two HUNDRED MILES)! I love big antennas! grin Again, this is only for 2.4 client side installs (radio only talks to ONE other radio). There is a bit of an exception to this rule based on smart antenna technology. One that no one has successfully used (as far as I know). Vivato and Nivini tried. We (WISPA) did get the FCC to issue a written interpretation of the rules allowing us to use routed AP's as a substitute for active beam steering systems (in the end it has the same effect). In theory we COULD ring a building with 24dB grid antennas with 24dB radios for a 42 WATT system and still be within the power level rules. In reality though, antennas are too "leaky" and you'd be hard pressed to avoid massive self inflicted interference. I always wanted to try building a system like this though! grin. (disclaimer, it's been a while since I studied that part of the rules, the max output power could be lower than 42 watts.....) laters, marlon ----- Original Message ----- From: Jack Unger To: WISPA General List Sent: Sunday, November 01, 2009 12:17 PM Subject: Re: [WISPA] Backhaul Questions 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 -------------------------------------------------------------------------------- WISPA Wants You! 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Join today! http://signup.wispa.org/ -------------------------------------------------------------------------------- WISPA Wireless List: wireless@wispa.org Subscribe/Unsubscribe: http://lists.wispa.org/mailman/listinfo/wireless Archives: http://lists.wispa.org/pipermail/wireless/ -- 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... ------------------------------------------------------------------------------ -------------------------------------------------------------------------------- WISPA Wants You! 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