Ok, here's another dumb question: If I only have spatial diversity on
the tower side and not on the client side, does that actually help both
directions, or only the uplink? I was told in the past that it only
helps on the uplink.
On 8/26/2015 9:16 PM, David Milholen wrote:
Spatial Diversity is mainly used to over come multipath issues or a
link that will stretch the curvature of the earth.
It is really interesting what link planner does when you configure for
spatial diversity on a link. There are a ton of
factors that go into getting reliability,throughput or both.
The longest link I ever did was 71mile using 4x 4ft HP dishes on
either end of the link with ptp600 radios.
We had connection and enough reliable bandwidth to do what we needed.
I dont think I ever saw much loss with rain fade either. That is what
sold me on the product.
When the link was configured it had to have the H and the V swapped
at opposite ends of the length and the spatial distance
was slightly different at each end
On 8/26/2015 12:03 PM, Rory Conaway wrote:
Part of the idea between spatial diversity is creating a second path that won't
have the same obstructions. Take this out of the idea of the MIMO technology
and simply go with the idea that possibly one path will have different or less
tree blockage/absorption or possibly that reflections are more advantageous
than a single path. I did this in an RV park but didn’t have anything to
compare it to so did it work better, I'm not sure.
Rory
-----Original Message-----
From: Af [mailto:[email protected]] On Behalf Of Adam Moffett
Sent: Wednesday, August 26, 2015 8:20 AM
To:[email protected]
Subject: [AFMUG] Spacial Diversity - helps how much?
There are a couple of products out there selling 4x4 MIMO (Telrad is one, but
there are others).
In Telrad's case, two of the chains have a time offset from the other two, so
you get two chains on each of two polarities. Their default antenna is a
single sector antenna with 4 N-connectors on it, so there's no significant
spacial diversity. In the past it's been suggested that we use two dual pol
sector antennas and space them 3 feet apart to get spacial diversity.
When I asked why they do the single antenna, a source at Telrad told me that spacial
diversity "only helps a little". The party selling us the two panels considers
it to add 6db when they run coverage projections.
I suspect any gain from spacial diversity is going to depend on a lot of
circumstances and I doubt it could be as simple as adding 6db.
I'm wondering if anyone here has any opinions on the topic? Maybe even facts :)
(I'm sort of eyeballing a certain guy in Utah who designs antennas and isn't
trying to sell me anything.)
--
