Again, interesting post/idea. The thing about 5.8G omnis (compared to 900 and such) is they are short. Would be easy to have the vert space to stack one on top of the other.
Tom DeReggi RapidDSL & Wireless, Inc IntAirNet- Fixed Wireless Broadband ----- Original Message ----- From: "Chuck McCown - 2" <[EMAIL PROTECTED]> To: "WISPA General List" <wireless@wispa.org> Sent: Sunday, January 13, 2008 6:46 PM Subject: Re: [WISPA] 5.8 vertical antenna w downtilt > You can slightly adjust the lengths of the coax between the antennas and > the > splitter. You will have to have a quarter wave matching segment too. > There > are telescoping transmission lines for this. Line stretchers, phase > shifters, phase adjustable SMA connectors... they go by many names. Some > of > them have threaded portions that allow a very fine adjustment. > > http://www.atmmicrowave.com/coax-Line-stretcher.html > http://www.microwavedistributors.com/pdfs/midisco/21-30/pg_25.pdf > > The distance apart will affect the pattern and will influence the amount > of > phase difference you have to add. Pretty much it is all trig that you > have > to work out on a case by case basis. If I was doing it for myself, I > would > work out the trig and then put them on my outdoor test range and rotate > them > and obtain some cuts for verification. > > In the real world, you could have a beacon transmitter in the center > region > of your coverage area and adjust the phasing section to maximize received > signal from the beacon. A bit tricky as your body will foul up the works. > So, adjust-get out of the way-test, rinse and repeat. Get some of those N > or SMA phase shifting connectors. At 5.8 you only have to have about a > quarter inch of adjustment or less. If the antennas are close enough to > each other, you will eliminate the multiple lobed pattern called a grating > pattern. Again, it is all trig. I suppose you could work out an excel > spreadsheet to calculate the antenna spacing and phasing vs downtilt > angle. > The minor and unintended length difference in the combining harness are > going to foul up a good pattern at this frequency in any event so having a > way to adjust phase would be good even when you are not trying to add > downtilt. > > Perhaps a new product in the making here. Adjustable downtilt omnis. I > think the 2 way industry has had them for years. > > ----- Original Message ----- > From: "Tom DeReggi" <[EMAIL PROTECTED]> > To: "WISPA General List" <wireless@wispa.org> > Sent: Sunday, January 13, 2008 3:22 PM > Subject: Re: [WISPA] 5.8 vertical antenna w downtilt > > >> Interesting. How do you get them slightly out of phase? Is the difference >> in >> length of the LMR, enough? And is the distance apart the mechanism to >> increase downtilt, or the amount out of phase? I'm assuming distance >> apart? >> >> Tom DeReggi >> RapidDSL & Wireless, Inc >> IntAirNet- Fixed Wireless Broadband >> >> >> ----- Original Message ----- >> From: "Chuck McCown - 2" <[EMAIL PROTECTED]> >> To: "WISPA General List" <wireless@wispa.org> >> Sent: Sunday, January 13, 2008 4:47 PM >> Subject: Re: [WISPA] 5.8 vertical antenna w downtilt >> >> >>> Two vertical collinear antennas. One mounted above the other. Fed >>> slightly >>> out of phase. You can have as much downtilt (or uptilt) as you want. >>> >>> ----- Original Message ----- >>> From: "rwf" <[EMAIL PROTECTED]> >>> To: "'WISPA General List'" <wireless@wispa.org> >>> Sent: Sunday, January 13, 2008 1:41 PM >>> Subject: Re: [WISPA] 5.8 vertical antenna w downtilt >>> >>> >>>> Thanks for the suggestion. >>>> >>>> I am not a fan of any omnis, really, but this needs to be an omni >>>> because >>>> this is a mesh AP. Not only that, it is a gateway or root (place where >>>> bandwidth is injected). I don't have the option of different RF >>>> hardware. >>>> An array would work, but I don't really want the (RX) loss from a power >>>> divider and an omni will do the job. It is a historic bell tower, used >>>> in >>>> many popular movies and the array would also be a lot harder to >>>> stealth. >>>> >>>> The reason I want severe downtilt is that in a mesh, you need to make >>>> sure >>>> that you don't make yourself heard by radios that are too far away >>>> because >>>> CSMA will keep both them and you from being able to transmit and will >>>> seriously harm the rest of the mesh. If I could get the antenna lower, >>>> I >>>> would. Unfortunately this is only mounting location choice to achieve >>>> LOS >>>> for this area. >>>> >>>> I am familiar with the 2 degree downtilt antennas, but for this case, I >>>> need >>>> much more that that I believe for this short of a range. >>>> >>>> >>>> >>>> -----Original Message----- >>>> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On >>>> Behalf Of Tom DeReggi >>>> Sent: Sunday, January 13, 2008 2:27 PM >>>> To: WISPA General List >>>> Subject: Re: [WISPA] 5.8 vertical antenna w downtilt >>>> >>>> Yes, to not use an Omni, but to use an Array. >>>> >>>> Max Rad made some of the first ones for 2.4G. >>>> Hyperlinktech makes some 4 sector arrays for 5.8Ghz. >>>> If needing only Verticle polarity, this is easy. Thats the >>>> configuration >>>> they sell them in. >>>> Will probably cost you around $600, for the kit with all antennas and >>>> the >>>> combiner. >>>> You could always make your own. >>>> >>>> With a mount hieght of only 50 ft though, not sure why this is a >>>> problem, >>>> if >>>> >>>> you are only needing to extend 1/10th of a mile coverage. >>>> A nice 10dbi Omni with 2 deg elect downtilt, Proxim makes one, or >>>> Tessco's >>>> terrawave Omni, would probably work just fine for that application. >>>> >>>> For such short range, even a 7-9db antenna would be fine, giving you a >>>> plenty large enough verticle beamwidth and high enough power. >>>> If its not good enough because of NLOS foliage or Noise, I'd argue you >>>> shouldn't be using an Omni in the first place. >>>> >>>> If a low bandwdith applications, as perfect application for a StarOS >>>> system, >>>> >>>> using 4 radios (or 3 radio in this app), each on their own 5 Mhz >>>> channel, >>>> using directional antennas using the Front to back ratio advantage, >>>> buying >>>> verticle pol 120 deg sector antennas for under $150 each. Its >>>> sometimes >>>> easier to do that, than get 1 channel to survive the noise in all >>>> directions. >>>> >>>> Tom DeReggi >>>> RapidDSL & Wireless, Inc >>>> IntAirNet- Fixed Wireless Broadband >>>> >>>> >>>> ----- Original Message ----- >>>> From: "rwf" <[EMAIL PROTECTED]> >>>> To: <wireless@wispa.org> >>>> Sent: Sunday, January 13, 2008 11:14 AM >>>> Subject: [WISPA] 5.8 vertical antenna w downtilt >>>> >>>> >>>>>I have an application where I need a 5.8 omni antenna with downtilt. >>>>> The coverage diameter of the area is only about 1/10th of a mile >>>>> total, >>>>> and >>>>> my HAAT is about 50 ft so I will need some pretty severe downtilt. >>>>> Gain doesn't really matter, but a higher gain antenna is going to give >>>>> me >>>>> a >>>>> flatter pattern- I just need it to be tilted down. >>>>> >>>>> This is to keep an access point from interfering with a mesh >>>>> deployment >>>>> further out that I want to protect as much as possible. >>>>> >>>>> Anyone got a suggestion for such an antenna.. >>>>> >>>>> Oh yeah- this has to be vertically polarized >>>>> >>>>> >>>>> >>>>> >>>> ---------------------------------------------------------------------------- >>>> ---- >>>>> 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! 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! 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! 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! 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! 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! 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/
