Yep, this works.
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I've been applying the same principle with an external ferrite rod
to squash QRM and QRN for many years now.
On 23/09/2020 12:38, Gary DeBock via
After many dual FSL antenna experiments I've finally determined
how to effectively cancel out QRM from a local pest that is off to
the side (90 degrees different) from a weak DX station, although
I'm not quite sure of the theory behind this discovery.
This experiment was an attempt to cancel out QRM from a local
pest, 950-KJR in Seattle, WA (35 miles/ 56 km to the north) and
chase 950-KKSE in Parker, CO (1005 miles/ 1617 km to the
southeast) during the early morning hours. The receiver was a
basic (non-SSB) C.Crane Skywave, and two identical 5 inch ferrite
rod FSL antennas were used. Please refer to the attached photo to
follow this description.
Step 1) Null out the pest station with the portable radio's
loopstick (away from the FSL antennas). Set the radio down in this
nulled position, so that the pest station is as weak as possible,
while ensuring that there is space to set up the FSL antennas to
the back and side (see photo).
Step 2) Take the "Reception FSL" and use it to peak the pest
station's frequency, setting it up parallel to the portable radio
as shown, at the position providing the maximum inductive coupling
gain. This will temporarily boost up the pest station, which
previously was nulled.
Step 3) Take the "Nulling FSL" and pretune the frequency to that
of the pest station. You can do this either by adjusting the
variable cap plates to match those of the "Reception FSL," or by
temporarily peaking the pest station's signal in a position in
front of the portable radio. After setting this frequency, set the
"Nulling FSL" off to the side of the portable radio as shown, with
the spacing identical to the spacing between the radio and the
Step 4) Slowly and carefully tune the "Nulling FSL" until you
hear the pest station's signal take a sharp drop. This setting
will be very sharp, but once you find this position you will have
nulled out the pest very effectively, and if another station is on
the frequency, it may suddenly become dominant, even if it is far
away (like 950-KKSE in Denver).
Some MP3's from this morning's experiments:
950-KJR in nulled position with the portable only https://dreamcrafts.box.com/s/c2hkjl979oz12m3dcbcr9uz73ziid2y3
950-KKSE generally dominant over the local pest KJR when the
"Nulling FSL" is peaked https://dreamcrafts.box.com/s/5ctshbrf5tk9duwyruimgq85ml7ngn8c
More experiments will be conducted with identical FSL antennas in
an attempt to provide a front-to-back ratio for the nulling of
domestic splatter, and front to side nulling of the same splatter.
If successful, this would dramatically increase the effectiveness
of FSL antennas on flat ocean beaches, where domestic splatter
from both the back and side is routine.
Gary DeBock (in Puyallup, WA, USA)