I don't know. It was a Sprint phone. I remember the old Nextel iDEN phones
would actually operate in the ISM band for their Directalk local area
walkie-talkie feature, but I assume this was a Sprint network phone. iDEN
is kaput, right?
-----Original Message-----
From: Jay Weekley
Sent: Friday, December 18, 2015 5:05 PM
To: [email protected]
Subject: Re: [AFMUG] 900 MHz 450i update - details
Is that common for a cell phone to do that?
Ken Hohhof wrote:
The guy installing the AP who was right next to the sector.
-----Original Message----- From: Jay Weekley Sent: Friday, December 18,
2015 1:44 PM To: [email protected] Subject: Re: [AFMUG] 900 MHz 450i update -
details
The tower guys cell phone?
Ken Hohhof wrote:
At this tower with FSK, we knew there was another WISP (let's call them
ABC) with an AP 9 miles away LOS on 915 MHz. And we always got the best
results if we also went on 915 MHz and matched their timing parameters,
rather than trying to avoid them.
After experimenting with the 450i equipment, I am convinced that another
WISP (let's call them XYZ) is operating 900 FSK APs in our area with AP
Eval Data turned off. I know we have a competitor who thinks it's cute
to do that. I think that's a douchebag thing to do.
Anyway, I'm also convinced that while ABC and us have our APs pointed at
each other, we may be seeing XYZ's SMs as much as their APs. Coexistence
in 900 MHz is tough because free space loss is low so LOS signal carries
a long distance, plus NLOS signal gets through trees and even scatters
off them, plus even the highest gain antennas don't have narrow beams.
You can't count on SMs using narrow beam antennas pointed only at their
own tower.
So while smartgrid and RTK are certainly contributors to the noise level,
I think we have XYZ using the bottom and top of the band but in stealth
mode. Probably they see ABC on 915 and avoid them. So we are able to
coordinate timing parameters with ABC and coexist in the traditional
manner on the same channel.
It is possible that we are seeing SMs on other ABC sectors pointed away
from us, but we are only 135 feet AGL, and I don't think their subs would
be high enough that we would see them 10 miles away, given earth
curvature.
So the next hurdle was setting the timing parameters on the 450i to match
ABC's PMP100. For some reason there are checkboxes for what firmware
revision the PMP100 is running, and whether it uses timing port or power
port sync. We did not previously have to know this much detail, I wonder
why. Anyway, I finally hit on a combination that worked: 5 ms frame,
numbers from the Cambium compatibility tool, and Legacy Framing Mode off.
At this point, I was able to get the SMs to register at 915 MHz and run
MIMO-B in a 7 MHz channel. Actually, I started by putting the FSK timing
parameters into the compatibility tool (75%, 10 miles, 3 slots) and it
said OK without any futzing around.
Some other observations:
1) You can power the AP with power port sync off a CTM-2 in 56V OFDM
mode using an adapter cable with pins 5 and 7 swapped, as described in
the manual for a CMM4. I assume the same is true for a 430 SyncInjector.
2) According to the CTM-2, the AP is drawing 10 watts (we are not using
the AUX port to power anything), so don't get scared by the 30 watt
number.
3) The AP and SM are capable of up to 25 dBm xmt power, but with 12 and
13 dBi antennas it will be slightly less due to regulatory limits. Check
the AP config to make sure it is set to the max you are allowed, I think
mine started out set to 22 dBm. Many WISPs no doubt are using ~17 dBi
yagis or grids without turning down the EIRP to 36 dBm, if so, a legal
450i system will be at a disadvantage by comparison although antenna gain
doesn't always help through foliage.
4) If you leave all the channels and widths enabled, expect it to take
forever for an SM to register. You need to uncheck some of the boxes.
5) If you do an SA when you first install the AP and see -35 at 900 MHz,
it may be your tower guy's cellphone.
6) The AP has no internal GPS.
7) 16 inch coax jumpers will be a little tight, 18 inches or longer will
be better (assuming LMR240).
8) The AP comes with one gland which looks like the LPU grounding gland
but it has a rubber insert which is already slit and you can get a
pre-terminated cable through it. It doesn't come with a second gland for
the AUX port.
9) The sector requires lots of different wrench sizes, I think the list
is 10, 12 and 14 mm.
10) Cambium has made installing the CPE equipment a piece of cake.
Basically take the pre-assembled antenna out of the box, snap on the SM,
attach the SMA connectors and slide the boots down, the only assembly is
the U-bolts. It's very nice.
