Clear Channel engineers and my guys installed two 942.xxx MHz passive repeaters using 24 or 26 dB large grid antennas for STL when moving from one side of city to other over Franklin's. Used 1 1/2 inch heliax....2 miles to mountain on one side and under a mile at other side. I shared those pictures years ago and some even made fun of me for sharing them so much on different topics. We did allot of work for them. On Feb 17, 2016 11:32 AM, "Adam Moffett" <[email protected]> wrote:
> Exactly. Use an online freespace path loss calculator. > In real life, I've yet to encounter a scenario where the math actually > worked. > > Suppose the barn is 5 miles from the tower, and 100 yards from the > customer's office. > Using the calculator at https://www.pasternack.com/t-calculator-fspl.aspx: > 100 yards (customer to barn) = -87db FSPL > 5 miles (tower to barn) = -126db FSPL > sector antenna gain (tower) = +16dbi > 2' dish gain (barn1) = +28dbi > 2' dish gain (barn2) = +28dbi > 2' dish gain (customer office) +28dbi > tx power from tower = +26dbm > > That adds up to an RSSI of -87dbm assuming everything else is perfect. So > you've got a lot invested to get a signal they won't be happy with. > > If it were 900mhz > 100 yards = -71 db > 5 miles = -110 db > Let's say yagi antennas x 4 at +15dbi each for a total of +60 > Tx power at +21 (to be legal). > > That adds up to -100dbm. Doesn't work at all. > > So really, you need one path to be short and the other to be *extremely* > short. > > > > On 2/17/2016 1:11 PM, Ken Hohhof wrote: > > When this has been discussed before, it only works if one path is really > short. You add the antenna gains and the free space loss of both paths. > If both legs have FSL on the order of 100 dB, you are not going to make it > up with antenna gain. > > The huge billboard style passive reflectors are a different matter. > > > *From:* That One Guy /sarcasm <[email protected]> > *Sent:* Wednesday, February 17, 2016 11:40 AM > *To:* [email protected] > *Subject:* [AFMUG] passive relay > > We have a bunch of old 2' radiowaves dishes laying around. > > Im curious what the real world loss would be if we used them on a midpoint > with the feedhorns patched together. > > Like for a business buried in trees that has an old tall barn with no > power but line of site to our PoP. this is a really common occurrence. All > we would need to do is get the feedhorns replaced with dual pol horns. > > This is on my list of things I would like to set up here shooting around > the corner of our building out of curiosity, but I never have time to play > with it > > -- > If you only see yourself as part of the team but you don't see your team > as part of yourself you have already failed as part of the team. > > >
