You do.
On 11/21/19 12:27 PM, Adam Moffett wrote:
There might be something I don't understand, but I thought you had flat
EIRP limit of +30dbm whether it's an SM or an AP.
On 11/21/2019 12:11 PM, castarritt . wrote:
6 dBm loss for the AP transmit isn't the end of the world. It's the up
to 23 dBm loss on the SM transmit power that destroys the
usefulness of DFS for PTMP past a couple miles. The ~16 dBi gain 90°
sectors 2-300' up in the air just can't hear those SMs over all the
noise they are picking up. What we need is the ability to run
downlink on DFS and uplink on 5.2 or 5.8.
On Thu, Nov 21, 2019 at 10:56 AM Adam Moffett <dmmoff...@gmail.com
<mailto:dmmoff...@gmail.com>> wrote:
Yeah I think on most equipment you can set alternate channels that
are just shifted over 5mhz from where you were. And yeah I think
the channel needs to be clear for a few minutes before you can go
back to it.
Assuming you don't really have a TDWR near you, I don't think DFS
events are that big of a deal. My understanding is that DFS
events are more likely if you lie to the software about antenna
gain to cheat the EIRP limit. False detects happen, but I don't
think it's a daily event. Disclaimer: I've mostly used it on
Point to point with dishes. I'm not sure if you'd pick up more
anomolies on a sector antenna.
The biggest bummer is the EIRP limit. When you're trying to get
that 32 SNR for the 256QAM then losing 6db kind of hurts. Or when
you've already got someone hooked up 10 miles away and lowering
the power ruins them.
Where you really want to use DFS (In my opinion) is at a site
where you have a bunch of customers within 1-2 miles.
Unfortunately I don't have sites like that.
-Adam
On 11/21/2019 11:31 AM, Ken Hohhof wrote:
We mostly avoid DFS frequencies on APs because of the impact if
we get false radar detects. Also we are mostly a Cambium shop.
So I’m a bit confused about DFS on other vendor equipment like
Ubiquiti as well as home routers.
Question 1 – what happens when there’s a DFS detection? On the
Cambium gear, we have to select 1 or 2 alternate frequencies.
But on other gear, I don’t see this. When there’s a DFS hit,
does it jump to another random frequency? Does it rescan the
current frequency until it tests clear and only then resume
transmission? Is the answer right in front of me and I’m being
stupid? Maybe in the case of routers they are exempt because of
low EIRP?
Question 2 – what about 40/80/160 MHz channels? We have a
competitor using Ubiquiti gear and advertising residential
subscriber speed plans up to 100x100. Clearly they must be using
at least 40 MHz channels if not 80 MHz, or else their marketing
people have burning pants and long noses. And I don’t see how a
WISP, especially one surrounded by other WISPs, could use wide
channels other than in DFS bands. We have some PTP links using
40 MHz but only 10 and 20 MHz channels on our APs. So assuming
you are using 40 or 80 MHz in DFS, what happens when there’s a
DFS detect? Does the whole 40 or 80 MHz have to find a new
home? Can it slide over 2.5 or 5 MHz and substantially overlap
the previous occupied spectrum? DFS bands come with enough
spectrum to use wide channels, but is there enough to jump around
when you take a DFS hit?
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