Howdy,
I am testing a totally new setup for DFing... An untuned, small,
shielded loop, and a Icom IC-705.
I want a fast setup and tear down process, and I want to be able to
distinguish between multiple RFI sources. The 705 has a waterfall
display, so I can see different RFI signals. This allows me to null
just the one I am interested in. It is odd to see one pattern null
while the other pattern does not null... But it works like a champ!
I have two strong sources close to me, one is a current pain in the
rear, (I am getting ready to report it), the other was a pain in the
rear, and has been dealt with, (thank you Steve at the ARRL), and is no
longer a problem. This pair sources makes a perfect test bed for this
sort of thing... So using the above setup I headed out in the field...
I was able to easily distinguish each source of RFI from the other,
using the spectrum analyzer style display of the 705. This enabled me
to null the RFI source I wanted. Then using the nulls I found via the
loop, I was able to take a few bearings, and add them into SigTrax. See
attached image.
I have three more images, each closer to the source than the ones
attached. Each image show greater and greater detail, as to the
location of the RFI source.
I am completely satisfied with the loop, and the directionality of the
nulls, even though it was just hand held and loose... Next step is to
get the loop mounted in a way I can just yank out of the back of the
car, take a bearing, and move on...
I will build a small cross like you see in church, then pivot the
horizontal section so it is parallel to the vertical section for
storage, and perpendicular to the vertical section for usage.
I'll add some sort of loop hangers, so the loop can be hung in a hurry,
(in a repeatable fashion), then permanently mount the feedline and
ferrites, (must keep the pattern symmetrical for best nulls), on the
vertical part of the mounting frame for the loop.
That will give me a loop, I can coil up and put in a small bag, and a
stick...
I can take the stick out, open up the cross piece, hang the loop on it,
connect it to the feedline, plug it into the 705, and start DFing...
This should allow for a very fast stop, take a heading, and move on,
sort of approach to DFing...
Happy Thanksgiving to all of you!!!
--
73, and thanks,
Dave (NK7Z)
https://www.nk7z.net
ARRL Volunteer Examiner
ARRL Technical Specialist, RFI
ARRL Asst. Director, NW Division, Technical Resources
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