On Wed, 13 Feb 2008 03:41:49 -0000, Dave Hachadorian wrote:
>Maybe you could just try some alternative hookups:
You may be right, but I doubt it.
In other words, it's far more likely to be common mode current
lighting up a pin 1 problem.
If the transmit frequency is 28 MHz or 50 MHz (unlikely nowadays),
changing between Ch 3 and 4 is more likely to do something. FWIW,
in all of this correspondence, I have not seen transmit
frequencies mentioned.
BUT:I have seen individual clamp-on ferrite beads mentioned. A
string of individual beads, even a dozen of them, provides FAR TOO
LITTLE IMPEDANCE below 50 MHz to make a dent in RFI, even if the
RF is being coupled on the cable that they are on (remember, we
must add enough impedance to reduce the current), and the lower
the frequency, the less they will do. We must use multiple turns
around a #43 (at least six) to begin to make a dent in RFI at
upper HP (20, 15, 10M) twice that number for 40 and 75 (and you'd
better be using a #31 toroid on 75/80 or 160).
Again, I remind everyone to study the part in my tutorial about
what I call "threshold effect" and then study the measured data
for various chokes.
73,
Jim Brown K9YC
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