Hi Stan,
One thing we have learned in supplying thousands of Kx33s to hams is the
importance of minimizing or eliminating common-mode currents in the
antenna system. The transverse mode RFI output of the Kx33 is extremely
low and has never been the cause of noise to our customers, but if the
antenna system has significant common-mode potential, it will always
seek a current path through whatever is attached to the rig...through
the power supply, your body, as well as grounds. The outside of the
coax shield, the rig, the power supply and AC mains are all in a series
path for common-mode currents.
The most direct cure is to place a high common-mode impedance in the
antenna feedline. The DC power lead on the Kx33 is smaller in diameter
than most RF coax lines, so it may be easier to form a choke on that
cable. You mentioned "YES, I HAD CHOKES ON ALL SUPPLIES, CABLES,
WIRE." The exact core material used and number of turns is important in
constructing common-mode chokes. Jim Brown, K9YC has excellent
tutorials on this subject: http://audiosystemsgroup.com/RFI-Ham.pdf
Another measure which will shunt common mode currents away from other
paths is a low impedance ground on the rig.
Something else I want to mention, as it is an issue which has cropped up
recently: There are several sellers on both eBay and Amazon stating "Pro
Audio Engineering Kx33 power supply" in their ads, but no supplies
other than those sold directly from us are the actual Kx33. We know
this because we worked with one such customer to resolve noise issues
and it turned out the unit he had was not a Kx33. eBay and Amazon both
state they can not do anything, since the other vendors are claiming
they use our part number and name only to state an equivalency, which
they most assuredly are not. Our Kx33 has less than 70 pF of input to
output coupling vs. 1000 pF or more for most other supplies, making it
far easier to choke common-mode currents. This was the most difficult
spec of the supply to arrive at, but considering we knew it could be
used with temporary antenna systems with common-mode potential it was
important to achieve.
As we unconditionally guarantee everything we sell, please contact us at
i...@proaudioeng.com and I am sure we can help you eliminate this noise
or refund your purchase price.
Cheers & 73,
Howard Hoyt - WA4PSC
www.proaudioeng.com
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