I do standoffs on all towers for a couple of reasons. Mainly it is to keep the tower clear for climbing. We have also had towers where we started on the tower itself and ran out of room and then had to build standoffs. So the other reason is for capacity. You can fit big sectors on standoffs better. There is also the alignment and mounting issue. Many of the manufacturers clamps hit the cross bracing in the tower so you have to mount them at a certain height or turn them to a certain angle because the cross braces are in the way. Two ten foot sticks of conduit and one ten foot stick of unistrut with a couple strut straps and it solves all of these problems. Plus it looks really cool, like a cell tower.
On Thu, Sep 25, 2014 at 7:35 PM, Josh Reynolds via Af <[email protected]> wrote: > Wait, you're NOT supposed to step on the top of the sectors and dishes? > Well how do you know if the guy before you mounted things securely or not? > !? > > Josh Reynolds, Chief Information Officer > SPITwSPOTS, www.spitwspots.com > On 09/25/2014 05:26 PM, Ken Hohhof via Af wrote: > > I thought the standoffs were so tower climbers could climb past your > equipment without using them as footpegs. > > *From:* Paul McCall via Af <[email protected]> > *Sent:* Thursday, September 25, 2014 7:51 PM > *To:* [email protected] > *Subject:* [AFMUG] Standoff question, rule of thumb, etc. > > > Over the years we have employed different philosophies on mounting sectors > to towers. Our reference point was the Moto 100 series connectorized > radios with sectors. We started out with 18” standoffs on a Rohn 25G > tower, because some “smart guy” suggested that was what we needed. Another > smart guy suggested 24”, so some of them were done like that. Then, > someone else suggested that we really didn’t need standoffs at all, that > they could be mounted each on a leg of the tower and we would be fine. (we > always ran 3 120 sector/AP configuration per tower in 2.4 Ghz). As far > as difference that we could measure, we found no difference in AP to SM > performance when we measured at any distance of connection. Maybe we were > missing something, but anyway, we settled on mounting them directly on the > tower leg. > > > > Moving forward to today. We have been installing the ePMP 2.4 series > instead of 100 series 2.4s. The installation techs mounted them back to > back, with North/South on one frequency (Front/Back Frequency Reuse > configuration) and East/West on the other frequency. One of the 4 sectors > had to have a custom mounting bar made to replace the short stubby one that > comes with the sector, thus allowing the 2 sectors (North and East at 90 > degree offset) to be put on one leg right near each other. Again, this is > Frequency Re-use a bit of a different scenario. > > > > Anyway, today in working with Cambium, they told us we need to have at > least 3 ft of vertical separation between each radio on the same frequency, > so North and East could be at one level (dif. Frequencies) and South and > West would be vertically separated. Alrighty then J ….. so we have 6 > towers to go move things around on. We are going to some test tomorrow on > the first tower to see exactly how much separation yields us how much F/B > isolation. Using ePMP eDetect feature, that should be pretty easy to > see. > > > > OK….so here is where I want opinions. Really I’d like “expert advice”, > but I will settle for opinions J > > > > How far “should” these sectors be “stood off” from the tower, if at all? > I am not expecting to be able to measure any difference with the F/B ratio > data, so its back to this is “all theory”. Is the standoff question a > front to back issue at all, or a “we want the metal” sector away from the > metal tower a little bit? > > > > Paul > > > > > > > > > > > > Paul McCall, Pres. > > PDMNet / Florida Broadband > > 658 Old Dixie Highway > > Vero Beach, FL 32962 > > 772-564-6800 office > > 772-473-0352 cell > > www.pdmnet.com > > [email protected] > > > > >
