Any number of things could be causing the interference you recorded. I
presume this occurs continuously. If so, it should be fairly easy to locate.
Grab the battery-operated receiver with a signal strength indicator. It's
time to go for a walk or a drive around the neighborhood. If this source is
fairly new, one of your neighbors probably just took delivery of a
Wobbulator Deluxe 5000 with a switching power supply and/or a
microprocessor. But ASSUME NOTHING. Trust your gear.
When you find it, let us know what it is. The device will be added to the
list of millions of other (unintentional) transmitters being imported into
the US and adding to the noise floor.
If you don't know the homeowner and don't want to go knocking on the door
unannounced, you can try to learn more about the resident or address using
various online resources. You can mail or drop off a letter asking to visit.
Be ready for an unexpected reaction from the device owner. The device owner
will likely not want to shut off/unplug the device and may become indignant,
even belligerent, at the realization that their investment may need to be
returned or repaired to stop the interference problem. Worse, they may tell
you, "It's YOUR problem! Deal with it!"
This points out one of the forgotten components of Interference
Investigation: Human Relations. Diplomats have nothing on skilled
interference investigators who must confront owners (especially lay owners)
of interfering equipment. Choosing one's words carefully is vital...equally
vital to the ability to locate the source. If you lack tact, get ready for a
If an offending device is owned by a neighbor and the neighbor is
uncooperative, this is one area where the pitiful assistance of the FCC can
actually be helpful. That letter from the Feds usually gets their attention
and suddenly they are more willing to contact the manufacturer, importer
Of course, all three of those parties usually won't give the matter any
attention. An overwhelming majority of manufacturers, importers and vendors
either have no idea how to resolve the interference caused by their products
or simply don't care. Either way, the customer is left to fend for himself.
Most manufacturers ignore the problem and hope it will go away. At best,
they may give the issue lip service. Anonymity and large faceless
corporations with web-like bureaucracies help filter and bury complaints.
Because the total number of complaints about interference is so small most
manufacturers don't see any reason to devote any resources to the issue.
These unfortunate circumstances has already begun to produce an ever
increasing interference problem for ham and all others who cherish the HF
spectrum. I don't believe our federal government will ever do anything to
stop the tsunami of poorly designed consumer electronic devices/transmitters
flooding our shores. There are so many millions of these devices already
entrenched in our communities that even if something were done, it would
take a decade or more for most of them to wear out or fail and take up
residence in the landfill.
So... along with learning how to locate interference sources, hams will also
need to learn a new set of human relations skills for dealing with neighbors
who believe that if they paid good money for the device, they have a right
to use it, no matter who gets bothered in the process.
Good luck with the hunt.
Frank N. Haas KB4T
Professional Interference Investigator
Date: Fri, 12 Feb 2010 12:38:01 -0600
From: K4RO Kirk Pickering <email@example.com>
Subject: [RFI] 12 meter QRM - please help identify
I have a new source of QRM that is audible on 12 meters only. It
appears to cover 24 to 25MHZ. The audio frequency of the signal
changes as I go lower in frequency. Both of the following recordings
were made with a 6kHz filter in AM mode.
At 24.890MHz it sounds like this:
At 24.820MHz it sounds like this:
The signal has QSB and, my ham neighbor and I both locate it as coming
from due west. Is anybody else hearing this signal? Any ideas as to
what the source might be? Thanks for any ideas.
73 Kirk K4RO
RFI mailing list