I will start by saying that I am now coordinating the efforts of building the Mesh in Mississauga, Ontario. I am talking to people and reading the posts on this forum and elsewhere in the Internet. And from what I see is that out of ten people who had placed their Mesh antennas, nine would not connect to anyone so far. One out of ten is a pretty weak success rate. And the reason people tell for not being connected is the lack of line of sight.

It is pretty clear to me now that if you can literally see your counterpart and are using directional antennas to point there, even the stock power will be sufficient. Obstacles in the Fresnel zone might somewhat hurt you but in general you are good. My question is if it is at all possible to establish the link if you can not see the repeater, though the map shows your line of sight. I will give an example. Nowhere in our suburban area can I see our 70cm repeater antenna. I am always surrounded by a 1- or 2- storey buildings and 5-storey high trees. Yet the handy-talky works perfectly on 440 from inside the building not to mention the 2-nd floor or the roof.

Has anyone had a successful link on 2.4GHz where there was no visual, but the only obstacles were the trees and wooden houses, not the ground or concrete structures? With or without the amplifier.

Thank you,

Anthony va3idl

I think your characterization is correct.  Even with gain antennas, we're mostly line of sight. 

As for 2.4 GHz vs. 70 cm, we are 5 times shorter wavelength at 2.4, so we're a lot more line of sight.  I think water also absorbs a lot more signal at 2.4 GHz, so attenuation of trees and other obstacles is higher.

We're still basically wifi with a few advantages:

• Gain antennas are legal because we're hams.
• The mesh design lets us link multiple nodes automatically to fill gaps in RF coverage and daisy chain links.
  

Gain antennas help more than you might think because they not only give you a higher signal strength, they reduce the strength of interfering signals outside of the beam.  They still don't let you "blast" through houses or trees.  The attenuation is just too high.   You mostly have to get over or around the trees and houses.

Mesh also allows you to put one mesh node right at the actual elevated outdoor antenna location and not have to have a long coax run.  Coax loss per foot at 2.4 GHz are really high.  Put one node on the antenna, make long links to other nodes, and then you can put another mesh node inside if that helps. 

As hams, we CAN use amplifiers, but they don't help as much as you would think, and you should avoid amps except in special circumstances so you aren't unnecessarily interfering with other users.

You're not likely to blanket a city with enough mesh nodes that you can just set up a node with standard antennas and get a link.   You're going to have a limited number of fixed nodes prelocations with long range links and good antenna locations that serve as "hotspots."  You need to set up these locations ahead of time.

When an emergency arises, you either need these nodes at the places where you need service, or you need some deployable nodes with gain antennas that can connect to the fixed mesh node locations.  You'll also need people who can set these nodes up and places to put the antennas with a line of sight to the fixed nodes.

Even if you have no long range mesh connections, mesh is useful within an event site in several ways.

Thank you Mickey, That is exactly what we are doing now - looking at which elevated locations we can put the nodes. Part of my question was also trying to understand whether we should only count on tower-to-home links or the home-to-home links would also be possible? And I don't mean if they live next door, that would be obvious.

Also do you think using omni-s is possible in the mesh? I understand, that the high gain omni would be hard to target, as the vertical angle would be too low. However I could see a couple of cases where a node would have potential links in four different directions, so omni could have been a logical choice, but would it work? I mean is there a chance it will work reliably, or four directionals is the way to go?

And yes, I do mean the 3-5 mile links, not the event site mesh. I have been a part of the event site mesh and I know it works. Now we need to get the bigger stuff working. 73, Anthony va3idl

There IS a gain omni that is HORIZONTALLY polarized without the nasty downtilt of a standard omni (aka colinear, etc: more gain=more downtilt).

Its called a slotted waveguide.

I have a  borrowed one out in my shop, that used to be on the AMD site in SW Austin. It had excellent coverage when in use.

I have seen some DIY articles of people who made them out of gutter downspouts.....

You can buy one premade/tuned for around $400 (that stung, didnt it?)

73

KTF

Just found the following opinion on the web, would you think it is correct?