From: firstname.lastname@example.org [mailto:email@example.com]
On Behalf Of N1BUG
Sent: Wednesday, December 22, 2010 8:03 AM
Subject: Re: Topband: Noise from 802.11 access point
This is a follow-up to my earlier post (included below for easy
The solution to this issue has been found. It was the switching
power supply in the POE injector, as many of you suspected. The
device is now running with a passive injector powered by a linear
power supply. All filters and common mode chokes have been removed.
Thanks to all who replied with suggestions. Special thanks to EA5EHS.
> My fellow topbanders,
> I have a new noise source this season. I don't seem to be making
> much progress, nor do I fully understand the issue, so I thought I
> would try asking for advice.
> I have a very unstable carrier wandering around between 1.820 -
> 1.830, plus broadband noise across all of 160m and 80m. Through
> process of elimination I found the source to be a wireless access
> device (Ubiquiti Bullet, see http://www.ubnt.com/bullet). Here is
> what has been tried so far and the results:
> There are two ethernet cables associated with this device. One runs
> from a switch to the POE injector (power supply); the other from the
> injector to the Bullet. I added two chokes to each cable. Each choke
> consists of 13 turns on a 2.4" OD #31 toroid core. Total of 4 of
> these chokes, two per cable. That reduced the noise approximately 10 dB.
> I wound 12 turns of the POE injector's AC power cord on another
> toroid, which reduced noise another 3 dB or so. Subsequently I added
> an Array Solutions AC-7B line filter, which provided no further
> noise reduction.
> I wound 10 turns (best I can do with "at hand" materials) of small
> diameter coax on another toroid and put that in the Bullet coax
> line. This reduced noise another 2 to 3 dB. Subsequently a good
> quality high pass filter has been added, which did not help at all.
> The coax (20 feet of LMR-600UF and 170 feet of LDF5-50A) feeds an
> enclosed 2.4 GHz yagi atop one of my towers.
> Some other interesting? relevant? facts:
> Disconnecting the coax from the offending device completely
> eliminates the noise. Reconnecting ONLY the coax shield (no center
> conductor connection) the noise comes back.
> Adding a 3 dB attenuator to the coax had no affect. 6 dB attenuator,
> no affect. 10 dB, still no affect.
> IF and ONLY IF my toroid common-mode choke is installed in the coax
> line, touching a finger to the N connector on the device silences
> the noise! Touching the N connector on the outboard (antenna) side
> of my choke does NOT have any affect. I have no idea what this
> means! Grounding the connector/device has no affect.
> The 2.4G yagi is directly off the end of one Beverage at a distance
> of some 150 feet, however that Beverage does not pick up the noise.
> Other Beverages which are further away and not pointing toward the
> antenna or the device itself are affected by this noise. I still
> need at least another 15 dB of noise reduction to get rid of it. I
> cannot figure out the method of noise coupling to only certain
> The device is located at my home, but it is not mine. I have
> physical access and can add filtering, etc. but I do not have access
> to device configuration.
> Does anyone have any ideas? Has anyone experienced anything similar?
> I guess I can work DX standing up, so I can reach to keep a finger
> on that connector! :-)
> Paul N1BUG
Aurora Sentry: http://www.aurorasentry.com
Piscataquis ARC: http://www.k1pq.org
UR RST IS ... ... ..9 QSB QSB - hw? BK
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