18 inches is what I used back I first tested the M900 many years ago....Chuck actually recommend it. On Feb 17, 2016 7:43 AM, "Chuck McCown" <[email protected]> wrote:
> Somewhere, in one of my 50 or so antenna books, there is a graph showing > mutual coupling of yagi antennas mounted on the same mast with respect to > separation. Right now, I am 50 miles away from those books. > > As I recall, if they are cross polarized, there is very little coupling at > close distances. > > I think there is theoretically zero coupling of the far field. But you > get strong reactive nearfield effects at 900 MHz around the 7 inch range or > less. That just means that the two antennas will start throwing off the > impedance and resonant frequency of the other one the closer they get. > > However there is the Radiating Nearfield Distance too. If you are inside > that limit the two will mess with each others patterns pretty bad. That is > on the order of 22 inches. However due to being cross polarized the > effects should not be strong. > > So, yeah... 2 feet is good if cross pol. I don’t think I would not go > under 1 foot. > If you have some time, experiment a bit. > > *From:* Brandon Yuchasz <[email protected]> > *Sent:* Tuesday, February 16, 2016 9:09 PM > *To:* [email protected] > *Subject:* [AFMUG] 450i 900 using existing yagi > > > Since we are now deploying some 450 900 gear we are pulling down lots of > old FSK with M2 Yagi antennas. In general I really like the Cambium yagi > they are well thought out and the SM being mounted on it is really clean. > Swaps are a breeze. That said I am still thinking about using the M2 in > specific situations like tripods. I did some retrofitting today to convert > two to slant and we went and tested and got good results. There were > separated from each other vertically about 8 inches at the mounting > brackets and I didn’t see any issues . We got 8x8x line of site. > > > > So my question to the group is, in general is there a rule of thumb to use > for vertical separation on dual polarity antennas being mounted like this? > Could they be stacked tight near each other? > > > > Best regards, > > Brandon Yuchasz > > GogebicRange.net > > www.gogebicrange.net > > >
