Re: [44net] ON7LR Contest Cam

On Thu, Oct 24, 2013 at 3:04 PM, Robbie De Lise <robbie.delise(a)gmail.com> wrote: Robbie, Thanks for the photos. I am intrigued. We have started deploying a similar network here in western Washington (see hamwan.org). One of the problems we have encountered is crosstalk/IMD between our 5 GHz modems. We typically have 5-6 modems on a tower (three sectors and 2-3 PtP dishes). We're using 10 MHz guard band between channels. With all the modems running, we see significant increase in noise floor across the band. Throughput is degraded. By turning off all but one modem, we get the throughput back. We've employed spatial diversity where possible, but never have enough space to completely escape the noise. We're experimenting on other fronts--testing with cavities, isolators, and antenna shielding (for improved front-to-back ratio). I notice you have many 5 GHz antennas in very close proximity on some towers and I'm curious what that does to your noise floor. How are you mitigating it? It looks like you mix GPS-sync gear with non-sync gear, so that cannot be the whole solution. Tom KD7LXL