Jawad, There are numerous factors to consider when selecting antenna.
First- legality and certification... If desiring to be legal regarding FCC certified, you must use an antenna type or equivellent that has been certified by the manufacturer. It allows for substitutions of lesser gain of same class. So if certified with dish use same seris dish. If panel line certified use a panel within that line. Second- Cosmetics and windload and mounting and space requirements... Some antennas have mounts for wide diameter masts and some dont. Almost always the DISH mounts can accommodate larger diameter poles. But then the dishes are almost always uglier. Panels often requrie less depth behind antenna. Sometimes PAnels have less pivots ability without banging into wall behind it or pole if mounted to a horizontal mast. Third- Cost. Ubiquiti 30DB PArabolics are cheaper than most Panels of similar gain. Its usually my first chocie antenna. Panels- Usually panels are nice antennas, so nothing wrong with using a panel over a parabolic, if the panel gets you the gain you were looking for. I'll use panels alot for urban areas, where I'm just shooting less than a mile or half mile. If space and cosmetics is not an issue, I almost always use a Prabolic on both ends. This gives me flexibilty to use 5.3/4 or 5.8. In high noise environments, and high modulations, 2ft dishes are sometimes minimum spec for 5.3/4G even if only 2 miles or so. If I'm definately using 5.8Ghz, then its more flexible to use a lower gain panel by default. On my towers with limited space, I'd rather use a small panel to conserve space. More so when considering that you dont want one antenna to block the beamwidth of another. My point here is that ther are many factors influencing antenna selection, before we even talk about RF characteristics and performance. Most of those factors are more important than the performance factor. Beamwidth may be a factor dependant on how you plan to use it. For example if it is a near-LOS or Non-LOS install, it should be noted that a wider beamwidth antenna will pickup more reflections from more places and may result in a higher gain received because of it. (or I should say less fade from the NLOS). A 21db panel can be perfect for NLOS. A 21-23 panel will ahve a bout a 11deg beam si it can be used for PTMP, where the few CPE with all be straight in front of you. Parabolics would be closer to 6deg and sometimes to little to operate in a PTMP fassion. In some cases, higher gain of the PArabolic helped NLOS more, because it blasted through the obstacles better, apposed to helpful reflections. As far as Port to Port isolation...... That is a good question.... Using two radios such as a Full Duplex link with two cards, or using 802.11a cards, large port to port isolation is super super important. Want 35-40db if possible. However, when we did sometests with Ubiquiti MIMO we found that the Port to Port isolations was much less relevent. Lets look at the example of having a link, and swapping the AP antenna out with three antennas.... Ubiquit large sector 20db(2.5ft), Ubiquiti small sector 19db (1ft+), Nano 16db (< foot). In a noise free invironment, I found the link to perform near identical with each of the antenna choices, all operating on full modulation. Ubiquiti claimed the Port isolation to be like 28db, 22db, and 16db, for each of the antennas, or something near that range. Something about the MIMO chipset, it does not care as much. It blew my mind that a NANO antenna worked as well. I'd still suggest selecting antennas with large port to port isolation, just because I'm old school, and it is a measure of antenna quality, and in theory it makes sense to have isolation. But it may not matter as much as we think with some MIMO gear like Ubiquiti. I have a 14 mile link running on a ARC Wireless Panel on each side paired with ROckets, which is passing 80mbps flawlessly. (no noise on the path though). The ARQ antenna spec almost 40db port to port isolation. I've got similar results with the ubiquiti integrated panel bridge. I just dont like to use the panel because it only supports less than 2" dia pipe. I've been using the 26db Ubiquiti integrated parabolics with great success, and they are super cheap, usually less than the panel antenna alone of another brand. But the mounts are flemsy. If I have something important, I'd probably spent the extra dolars on the panel, jsut so I had a nice solid mount. I often prefer parabolics because they are less susceptable to wierd interference issues at the antenna. I can give an example of one cheap panel I used... If I toughed the back of it, the link improved. If I stood close behind it the link approved. If I didn;t link got packet loss. What ever the interference was, the panel backplate was intercepting it. I never had that type problem with a parabolic, because the parabolic dish is just a reflector and positioned farther away from the feed receive element, apposed to the panel backplain that might interfact with the RF field because of proximity. With OFDM MIMO the bigger concern is going to be colocation self interference with other antennas. So if mounting several antennas at a sight, you'll want an antenna with good Front to back and sharp cut-off on edges, with minimal side lobes as possible. To compare a [arabolic to PAnel, you'd need to look at the antenna patterns, not sure which is better fif the two are the same gain. (for example 26db parabolic versus 26db panel). Tom DeReggi RapidDSL & Wireless, Inc IntAirNet- Fixed Wireless Broadband ----- Original Message ----- From: Jawad A Hai To: WISPA General List Sent: Wednesday, July 13, 2011 3:24 PM Subject: Re: [WISPA] PtP Flat Panel and MiMo Dish Antennas Hello Josh, What antennas did you use? Flate Panel or Dish (MIMO), ? What is your Radio that goes with ARC ?? did you get a chance to use other brands beside ARC ? http://en.jirous.com/antenna-5ghz/jrc-29-dx-pr http://www.lanbowan.com/products/en_vpro.asp?id=707 From: Josh Luthman Sent: Wednesday, July 13, 2011 10:20 PM To: WISPA General List Subject: Re: [WISPA] PtP Flat Panel and MiMo Dish Antennas I like ARC Wireless, been happy with them. Never heard of Lanbowan or Jirous. Josh Luthman Office: 937-552-2340 Direct: 937-552-2343 1100 Wayne St Suite 1337 Troy, OH 45373 On Wed, Jul 13, 2011 at 3:15 PM, Jawad A Hai <ahja...@hotmail.com> wrote: Hello, I have posted below in several forums without success, I will appreciate if you some body can advise me. Hi, This is my first post in the forum.( have posted in mikrotik and ddwrt without any luck ) I wanted to know what antennas users/Pros use for PtP needs.(Apart from UBNT) Both Flat Panel and MiMO dish as well as Panel. i was looking at different companies like Lanbowan, Jirous, ARCWireless. Lanbowan has 27 dbi Flat Panel, which others are not offering. ARC has got good reviews on mikrotik forum but jirous has got best port to port isolation(MIMO). Can you all please share your thoughts on antennas. Cuz a good Radio is nothing without a good antenna. My requirement is to have a good PtP links distance from 10-50 KMs range in very crowded environments. I have been trying different brands with different results and its difficult to test the brands in live environments, just thinking to take an advise here on the forum and buy the same and test it. Its not about just one link or two, i needed some permanent vendor. Thank YOu -------------------------------------------------------------------------------- WISPA Wants You! 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/ ------------------------------------------------------------------------------ -------------------------------------------------------------------------------- WISPA Wants You! 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