[HamWAN PSDR] Beacon Tower-Capital Park Backbone Link

Nigel Vander Houwen nigel at nigelvh.com
Thu Mar 29 17:26:09 PDT 2018

Hello All,

Currently HamWAN Puget Sound operates all of our backbone links in 5.9 GHz Part 15 space to keep the Part 97 space clear for the sectors. There’s only enough room for three channels in the Part 97 exclusive space (including guard bands). In many cases, this has worked well for us. In some cases like the current link between Capital Park and Queen Anne, there’s simply so much other noise an interference that despite very strong signals, the performance is abysmal.

We’ve found that co-channel and nearby channel interference is a significant problem for the modems, not to be underestimated. Even with shielding and the guard bands between sector channels we’ve seen some impact from busy sectors on it’s neighbors in some cases. We usually try to limit this additionally by putting sectors on different sides of buildings if possible for more isolation. I don’t think it’s a good idea to try to reuse sector frequencies for backbone links if it can at all be avoided, even with shielding.

In some cases, additional shielding may help, in some it won’t. I think there is a use case for other bands like 3.4GHz or 10-11Ghz. The keys will be finding what works from a cost and regulatory standpoint. I think it’s definitely something we need to at minimum research the options more. Ubiquiti and some other vendors certainly do have some appealingly priced gear on bands that would be more open.

There’s been some hesitation as 5.9GHz has worked for us, so we’ve had some inertia behind it, and it makes all the bits pretty cookie cutter to swap as needed. As bart has said, we’ve also seen convenience from emergency rerouting with everything being compatible, and from everything being the same type of gear so it’s more straightforward to manage.


> On Mar 29, 2018, at 16:45, Bryan Fields <Bryan at bryanfields.net> wrote:
> On 3/29/18 7:38 PM, Doug Kingston wrote:
>> For example... Can we reuse a PtoP 5GHz frequency with high isolation (shielding)?
> Why not use 3.4 GHz UBNT radios?  We have a link here in Tampa at 16.2 miles
> across Tampa Bay running at 130 Mbit/s.
> 3.37 to 3.5 GHz (the frequency range of the M3 radios) is totally unused for
> the most part.  A complete link is well under $1000 including antennas.
> -- 
> Bryan Fields
> 727-409-1194 - Voice
> http://bryanfields.net
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