[RFI] New RFI source for me...
Frank N. Haas KB4T
utility.rfi.pro at gmail.com
Tue Jul 26 13:43:21 EDT 2016
I have no desire or interest in debating the speculation point. Experience
is the best teacher here. Every investigator I've ever met has a different
idea about how the job should be done. Results are what count.
For me, time is money. I don't want to waste my time. For me guessing,
speculating, wondering about what a source might be is a waste of time.
When I find it my curiosity will be satisfied. When I find it quickly and
accurately, my boss and the complainant are happy.
Our motivation may be different just as our preferences and circumstances
are different. If your method produces the desired result quickly and
accurately or at least fast enough to satisfy you, then by all means use
Many people who read these notes are not professionals our engineers. They
want to know how to solve an annoying problem.
When I am consulted I try to keep my advice simple. Focus on finding the
source using proven techniques and equipment. Avoid cluttering your mind
with stuff that won't help find the source.
When one searches with eyes and guesses, failure is guaranteed. Sources are
found fastest with an open mind, proper equipment and techniques.
If you find it informative, entertaining or whatever to try to guess what a
source might be, enjoy! As long as you understand that it does little to
actually locate the source.
Signature analysis is a good technique and is often helpful. However,
signatures are not like fingerprints. Many devices have very similar
signatures. Effort is wasted when the search focusses on devices rather
than the actual source signal.
Results are what count. Whatever method produces results is a good method.
Frank N Haas KB4T
Utility Interference Investigator
On Jul 24, 2016 11:05 PM, "Roger (K8RI)" <k8ri at rogerhalstead.com> wrote:
> "To me", knowing the signature of different devices, and speculating on
> the type of device is important. Based on the device signature, you can
> often simplify and shorten the search and fix.
> With no idea as to the type of device the search become a systematic
> search, eliminating devices, one at a time, particularly if the noise is
> local (in your own house) can make for a very tedious search.. Knowing
> device type and any recent changes leads one to a much narrower and faster
> search. OTOH a guess based on "I think maybe it's such and such a device"
> can add a great deal of time.
> Knowing as much as possible about devices and their noise signatures gives
> the ham a "leg up" before starting the search and make educated speculation
> worth while.
> I have a very expensive line conditioner that originally was quiet, but
> recently a horrendous noise turned up (20 over), with no new devices
> added. It had the signature of a switching supply. Disconnecting the
> antenna showed the noise was local, really close as there was no change in
> the signal strength. Speculation told me that being that loud made the line
> conditioner a prime candidate. I powered down the line conditioner and
> plugged the FTDX5000MP into a dedicated 120 VAC line to the shack. The line
> conditioner is on its own 30 A circuit. Turning the line conditioner on and
> off told me the "majority of noise was from the line conditioner, but there
> is still substantial noise (S6) with the same signature. There are 3 so
> called, "wall warts" in here when the line conditioner is off. One is the
> telephone. The other two are the modem and network. Any one could be the
> culprit, or not. Any one could also be triggering the hash multiplied by
> the line conditioner (or not). So the next steps are clear.
> Roger (K8RI)
> On 7/24/2016 Sunday 11:36 AM, Frank N. Haas KB4T wrote:
>> I will not speculate as to what the source might be. As I have said in
>> forum many times, I consider such attempts to be a complete waste of time.
>> However, I will say that the periodic character of the source should make
>> it easier to find. If the highest frequency at which this source can be
>> detected at your location is 4.0 MHz, options are limited. The first tool
>> would use is a battery operated receiver and the National RF HFDF Vector
>> Gun active loop antenna kit.
>> You don't describe the antenna or radio equipment being used to hear the
>> source. You also don't describe the relative signal strength though from
>> the audio recording it would seem that the source is fairly strong. It may
>> be difficult to hear the source on any portable receiving system. If so,
>> you may have to perform an expanding circle or square search to find a
>> location where you can hear the source well enough to begin pinpointing
>> I have been faced with this kind of source many times over my RFI
>> investigation career. Patience, good record keeping, more patience and an
>> open mind are essential.
>> Don't waste time trying to guess what this source might be. Find it. Then
>> report your findings.
>> Each time one is involved in a search of this sort, the experience is
>> valuable, educational and, when successful, very satisfying.
>> Good luck and good hunting.
>> Frank N. Haas KB4T
>> Utility RFI Investigator
>> On Sunday, July 24, 2016, Dave Cole <dave at nk7z.net> wrote:
>>> I have had a new RFI source pop up here in the past few days... It
>>> appears to be on a timer, running at night, but does not sound like a
>>> lighting system I am familiar with. It starts about 8:30 PM, and ends
>>> at about 8 AM the next morning. It is quite odd from my prespective, in
>>> that I have never heard one like this before...
>>> Audio is here:
>>> Anyone ever hear something like this?
>>> It appears to cover 1.7 MHz., to about 4.00 Mhz, and I swear, it rolls
>>> off to protect the AM band. It reminds me of one of the Ethernet over
>>> power line devices when I look at it with a Spectrum Analyzer. The
>>> signal looks to be rolled off starting at 1.7 MHz., and gone by 1.6 MHz.
>>> Anyway, any suggestions as to what it might be would be helpful to me in
>>> locating it. My mobile antenna is under repair at this time, so I am
>>> doing my homework prior to a locate run.
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