Yeah, the beads are amazing!  We're starting to use them on almost all tower 
installs.

Supposed to help with lightning too.  Though we've not had enough of that 
around here for a couple of years to really be able to see any difference.

The worst part about the beads is getting the right ones!  I'm still not 
sure we're using the right stuff.  sigh  Ours are big enough that we can 
(and do) wrap the cat 5 through them 3 turns.  More turns is supposed to be 
better.  Whatever it is, they've REALLY cleaned things up at my FM radio 
station site!  Our customer compliant calls have dropped by 80 to 90% out 
there!  Wish I'd have really understood what was happening out there 4 or 5 
years ago when the new station went online.  I always thought I was ONLY 
fighting the massive amounts of 2.4 gig interference in the area.  That's 
still a problem, but much more easily dealt with than I'd ever have 
imagined.

marlon

----- Original Message ----- 
From: "Eje Gustafsson" <e...@wisp-router.com>
To: "'WISPA General List'" <wireless@wispa.org>
Sent: Wednesday, April 29, 2009 8:10 AM
Subject: Re: [WISPA] Noise by me on a tower


> Ethernet crystal harmonics. The crystal on Ethernet is 25MHz. So your
> hitting them with the 9th harmonics. This bleeding is worst with PoE 
> powered
> devices because it couples into the DC power over the cat5 cabling and if
> the power supply is not nice and clean it will couple into the AC system 
> as
> well. I have been involved in certifying 4 radios in a FCC certification
> lab. Each time we ran into this problem especially when powered by PoE. A
> different power supply could make a huge difference but also installing
> ferried beads on the cat5 cabling (close to the radio port, directly after
> the poe device out port and directly on the poe data in port) cleaned up
> this emission. Using shielded cable will help on equipment that is picking
> up this radiated signal directly from the cat5 cabling but if it's bad
> enough and the powersupply isn't good enough the harmonics signal will go
> out into the AC source unless ferried beads been installed properly.
>
> On one of these devices I helped getting certified we had to make it
> mandatory to have these beads installed to be able to pass (product never
> made it to market).
>
> / Eje
> CTO
> WISP-Router, Inc.
>
> -----Original Message-----
> From: wireless-boun...@wispa.org [mailto:wireless-boun...@wispa.org] On
> Behalf Of Steve Barnes
> Sent: Wednesday, April 29, 2009 10:02 AM
> To: WISPA General List
> Subject: [WISPA] Noise by me on a tower
>
> I have an odd situation, I have 2-2.4 180* sectors MT RB411 and 5-5.8 
> StarOS
> War1 backhaul radios and a RB600 router at the top of a 265ft old AT&T
> microwave tower. The top has a grounded NEMA metal box and POE powered by 
> an
> Allen Bradley converter. I have an AC and an Ethernet run to the base 
> where
> I have a APC UPS.
>
> The owner just leased space to another client 20 Feet away on same level
> from me.  It is a local REMC doing meter reading on 221Mhz.  They were
> having problems with receiving they brought in a spectrum analyzer and 
> there
> was a noise floor of -71 at 220Mhz.  The tower owner being an radio guy 
> not
> a wireless guy just killed power on the ups. (taking down all my stuff and
> locking up 1 one of the radios for an hour GRRR)  When our equipment was 
> off
> the noise floor went to -108.  As soon as he powered me back up the noise
> returned.  They actually said that there was noise from around 150Mhz to
> 240Mhz.
>
> Everything is grounded and cased in metal except the LMR that goes to the
> Antennas, the AC wire is in flex and the shielded Ethernet down the tower.
>
> Ideas? there might be a little noise off the oscillators of the War-1 
> boards
> but that's 175Mhz.  The Ethernet is 100Mhz, RB411 300Mhz and RB600 266 MHz
>
> Steve Barnes
> RCWiFi Wireless Internet Service
>
>
>
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