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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