Yep, its amazing how loud some of those laptop supplies can be. had a guest
op bring one here one weekend, it was a replacement unit bought on-line
somewhere. It spewed across quite a few bands.
David Robbins K1TTT
e-mail: mailto:k1ttt@arrl.net
web: http://wiki.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://k1ttt.net
-----Original Message-----
From: RFI [mailto:rfi-bounces@contesting.com] On Behalf Of David Cole
Sent: Sunday, February 08, 2015 05:38
To: RFI@contesting.com
Subject: [RFI] Successful RFI hunt
Hi,
Just thought I'd pass on a quick story about a successful RFI hunt today...
A fellow ham who is also a teacher, asked me to assist in locating very bad
RFI problem in the new ham station for a local Middle School.
The teacher had installed the station about two weeks ago, only to find a 20
over S9 noise level on all bands, he has spent the past 2 weeks looking for
it. The antenna is perhaps 50 feet away from the station, on the roof and
is an R6 vertical.
Being a school I expected the hunt to take a few hours or more, the school
sits on an acre or so.
So I brought in my trusty FT-817, and the small hand held loop. Almost
instantly upon powering the FT-817, the RFI was present, and loud! I DFed
it using the small loop, and drew an imaginary line on the null in my head,
then walked into the hallway, maybe 50 feet away from the first point, and
did the same thing... There was a huge difference in bearing. I did a
mental triangulate on it, and was the Ham Station!
I went to the station, and unplugged everything but the radio, and the RFI
ended... Did the unplug each device one at a time process, and found it to
be the switching supply for the laptop intended for Digital work.
The power supply was 50 feet from the antenna, and generating 20 over S9. I
finally killed the radio, and you can hear it with your ear! It was
buzzing, in the audio spectrum as well as spraying RFI everywhere...
The teacher had an O-Scope there, so I put it on the power line to look at
what was happening... What a mess! signals all the way up to around
50 MHz.
Suffice to say, the RFI is gone now, and the Middle School students will get
their first exposure to Ham Radio Monday, when the ham/teacher, shows them
JT65-X in action!
I have the Power Supply, and will use it for presentations...
Some RFI stories turn out good, just thought I'd share a good story!
--
Thanks and 73's,
For equipment, and software setups and reviews see:
www.nk7z.net
for MixW support see;
http://groups.yahoo.com/neo/groups/mixw/info
for Dopplergram information see:
http://groups.yahoo.com/neo/groups/dopplergram/info
for MM-SSTV see:
http://groups.yahoo.com/neo/groups/MM-SSTV/info
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