[RFI] stealth RFI
N7QY at ARRL.net
Sun Jun 15 15:13:50 EDT 2003
My buddy has a RFI problem in the TV and home stereo. Here's the challenge.
(He has the Icom 756 Pro II, Icom linear and tuner, GAP Challenger)
THE SETUP TO DETERMINE EXTENT OF RFI PROBLEM-
"I turned on TV, sat the wife down, asked what channel was the worst,
and did a baseline test with Icom linear on (500w), voice and CW.
The TV screen does a little herringbone on key down full 500w and the
speakers mumble on SSB, worse with processor on."
"So I tear out my grounding harness made of 1.5 inch braid bus bar
and 0.5 inch braid straps going to each piece of equipment and
replace it with individual braid lines all going to the back of the
Icom tuner, and the tuner uses #8 ground wire on a 10' run to a 8'
ground rod just outside the shack. Then I installed a Radio Works
T-4G grounded Line Isolator at the Gap Challenger antenna hooking the
isolator ground strap to the 10' ground rod at the foot of the
Gap.Then back in the shack I put T-4 Isolators (The Radio Works:
http://www.radioworks.com/clitop.html) between the Icom 756 Pro II
and the Icom linear and another T-4 Isolator between the linear and
the tuner. So after much cussing, cutting of finger on who knows
what, writhing in dust behind the rigs and multiple contortions
working on the back of equipment from the front, I declare the
project done and RFI hereby gone."
"So I sit the wife down in front of the TV again and fire off the rig
to show her how OUR $100.00+ worth of Isolators and ground rods had
banished the RFI. So I lay on the key while we are both watching the
screen . . . . . and.....
BIG blankety blank 4 INCH WIDE DIAGONAL BARS GO MARCHING ACROSS THE
SCREEN . . . 5 X 9 !!!
much more blankety blank, blankety blank. . . It is easy 3 times
worse than before I installed the line isolators!!!
So do I still have RF in the shack? Darned if I know, how am I going
to tell? Do I still have RFI on the TV? Oh yeah, big time.
Maybe, just maybe the RF on the coax is now gone, and there is less
RF in shack, but the result was more power to the antenna or a
different pattern which is pumping more RF into the house wiring
which is really the way the RF was getting into the system in the
first place, thus more RFI at the TV. I still have 4 split ferrite
squares that I was going to put on the 110v power cords of the TV and
the Tuner box. I almost hate to do it cause I have this sinking
feeling it will make it even worse."
SO THERE WE HAVE THE CHALLENGE-
Can anyone make any suggestions for us?
Thanks and 73,
"What could possibly go wrong?" Laurel and Hardy
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