The RFI snip hunt
I may have mentioned my quest to find and stomp RFI.
I found a very handy tool. The dual purpose pill bottles,
the ones with a single top that can be child proof, or
non child proof by simply turning the cap over are great
for a variety of RF uses. I have used them for coil forms
and by mounting tow pill bottles end to end, you can
lift it away from the metal case wall.
I wound about 24 turns of solid #26 insulated hook up wire
on one pill bottle. I drilled ~.1" holes to carry the wire to
the inside of the bottle and mounted a BNC female connecter
in the lid. By drilling a hole in the bottom of another
pill bottle I can feed coax and have a nice holder keeping
my fingers away from the coil.
I use RG-174 to connect the probe to my DX398. With a
4' piece of coax I am set to check every device in our
home for RFI.
I built a similar unit with only 2 turns for hunting higher
frequencies. And I built a probe in a larger sharpy with
a 300uH radial inductor to sniff inside of equipment to
find the exact noise source.
While I used BNC connectors, there is no reason why a
dedicated probe with RG174 terminating in the approbriate
connector couldn't be used for cast savings. Since I had
the BNC connectors in my junk box, and because I
wanted to be able to use a double male BNC to mount
it on my HT or scanner I decided to go to the additional
trouble and "expense".
I found an allusive "pop" RF source in one of the battery
operated smoke detectors.
Every time I find another noise source and clean it up, I can
receive ever weaker signals. Of course I don't have any such
success with my neighbors.
These little probes added to my 400MHz mini yagi with a
PRO34 allow my to farily quicky find internal and external
RF noise sources.
And while I use a DX398, there is no reason why any portable
couldn't be used. A desktop receiver will also work, but a portable
is so much more convinient.
Be sure to check the incoming telephone line, CATV etc.
While a few odd sources only emit RF on one frequency, most
are broadband jammers.
Terry
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