GHz... where terrain matters

Earlier this week the Calvert Amateur Radio Association (CARA) hosted its monthly meeting with a program by a local guru of mesh networking. Keith KB3TCB gave a presentation on what mesh networking is and what it can be used for.  I've known about mesh networking for some years but never found enough people in my local area that also found the idea intriguing.  Since moving to Calvert County (MD) I've discovered a lot of people that are interested in experimenting with different things, mesh being one of them.

Many club members went out and purchased gear to use as a mesh node and brought their gear with them.  I brought a Ubiquiti M2HP Bullet with a 14dBi-gain antenna.  Using the firmware provided by Broadband-Hamnet everyone's systems almost immediately linked up with everyone else's and advertised services could easily be consumed.  I cranked up httpd and hosted my Fedora test page (I'll try to do better next time with some actual content).  It would seem that there are many people that would like to try experimenting with the technology.

Keith stressed that line-of-sight was very important to making contact with others.  I, personally, am used to Eastern North Carolina where a hill is something seldom seen.  Calvert County is not Eastern NC.  I figured that since I was about a mile and a half from the K3CAL clubhouse that I should be able to easily make a connection there (through the trees).  A quick check of the path finder yielded other results.

[caption id="attachment_533" align="aligncenter" width="640"]Microwave path between W4OTN and K3CAL Microwave path between W4OTN and K3CAL.[/caption]

Of course this assumes 30 feet of elevation on each end but you can see that there is clearly a plateau in the way of my line-of-sight and several geographic features in the way of my Fresnel path.  Wow, I was not expecting that.  Turns out, the K3CAL side would need to be up around 150 feet to make it over the hills (and we'd still have to deal with the trees) or we'd both have to raise our antennas up to around 50 feet (doable?).

I ran into similar surprising results when calculating paths to a couple of friends.  On friend, Jim K3UGA, seems impossible to reach without help of some infrastructure up high:

[caption id="attachment_535" align="aligncenter" width="640"]Microwave path between W4OTN and K3UGA. Microwave path between W4OTN and K3UGA.[/caption]

And so it seems I'll be learning what line-of-sight truly means here. I'm not waving the white flag on my experimentation but rather setting my sights (sites?) a little higher.