I have a handy flow chart for location of RFI at:
https://www.nk7z.net/i-have-rfi-now-what-locating-it/
Plus a few hints on location of RFI at the same URL.
73, and thanks,
Dave (NK7Z)
https://www.nk7z.net
ARRL Volunteer Examiner
ARRL Technical Specialist, RFI
ARRL Asst. Director, NW Division, Technical Resources
On 12/22/20 1:53 PM, donovanf@erols.com wrote:
Hi Gary,
The process for identifying this type of RFI is the same as for any other RFI,
except you need to use your transmitter to excite the RFI generating source.
First verify that the RFI is not coming from your own home
- kill all of the circuit breakers in your home and power up ONLY
your transmitter. All accessories should be DISCONNECTED from
AC power. You may need to use your amplifier to produce
enough RF to trigger raspy harmonics from RFI generating source.
- Put your transmitter on the air, keying it from a memory keyer
is a good approach
- if the raspy harmonics have gone away, start turning on the
circuit breakers in your home, one by one, until the raspy harmonics
reappear.
If you determine that the RFI is not being generated in your own home,
turn your directive antenna in the direction that produces the strongest
raspy harmonics. A sensitive spectrum display such as the Elecraft P3
helps immensely.
Then use a portable receiver to hunt for the RFI source along the line
of bearing identified by the previous step.
Good luck
73
Frank
W3LPL
----- Original Message -----
From: "Gary Johnson" <gwj@wb9jps.com>
To: rfi@contesting.com
Sent: Tuesday, December 22, 2020 12:48:16 AM
Subject: [RFI] QUESTION
That’s easy. RF is picked up on the AC lines then enters any nonlinear device plugged
into those lines, such as a walk wart. There, RF is rectified, harmonics are generated, and
that’s mixed with all the garbage on the power line, then re-radiated via conducted
emissions. Many harmonics are normally expected. This is the classic problem for any SO2R or
M/M station.
Case study: At 8P5A, Tom has very little ancillary stuff plugged in and yet he
had your problem. He traced it to a single LED light. Once removed, the
harmonic garbage disappeared.
Gary Johnson NA6O
gwj@wb9jps.com
On Dec 21, 2020, at 4:06 PM, rfi-request@contesting.com wrote:
From: David Eckhardt <davearea51a@gmail.com>
Subject: [RFI] QUESTION
I'm out of ideas on this one! Where does the raspy modulation come from
on the harmonics which changes with position in my radio room on a battery
operated receiver?
Situation:
transmit on 7.010 MHz
receive on second harmonic, 14.020
transmitter: IC-7300
receiver: IC-7610
and reversed
Demod: CW or SSB (or AM, for that matter)
Fundamental sounds clean. Second harmonic sounds modulated by 120-Hz (and
a few harmonics of the line) and quite raspy - pretty awful.
Receiver: portable battery operated receiver (Grundig G3) with same
transmitters: I can walk around the room tuned to the second harmonic and
find places in the room where things are clean and other positions where
the second harmonic (and third) sound awful with 120 Hz raspy
'modulation'. Any idea how I can account for this localized behavior? I'm
out of theories.
Dave - W?LEV
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