I know at least one thing for a fact. The FCC does not require RF immunity
testing to be sold in the US, however just because it has a CE mark doesn't
mean its perfect either. Look through the installation manual. According to
the new EMC directive the manufacturer must disclose the intended
installation procedure which will contain grounding instructions, etc.
The ferrites on the power cable should help. If you wanted to, you
can get a power conditioner for further filtering. That is the largest
receiver of low frequency transmission in the 10 kHz to 30 MHz range.
Shield grounding inside the TV set can be a problem around 200 MHz range,
also the HVdc on the tube connection. Hope this helps.
Ted Bohrer
<N7QY@arrl.net> To: rfi@contesting.com
Sent by: cc:
rfi-bounces@conte Subject: [RFI] stealth RFI
sting.com
06/15/2003 04:13
PM
Well, All
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."
INTENTED SOLUTION-
"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."
THE TEST-
"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,
Ted N7QY
--
"What could possibly go wrong?" Laurel and Hardy
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