[TowerTalk] Mains Filter for 80M
jim at audiosystemsgroup.com
Fri Jun 8 09:07:43 PDT 2012
On 6/8/2012 8:41 AM, Jim Hargrave wrote:
> I use an ISOBAR IB-4 dual stage line filter.
> It is a combination noise and surge protector.
Remember that shunt mode surge protectors (MOVs) are safe ONLY at the
building service entrance (so-called "whole house" suppressors). When
installed on branch circuits at at outlets, they are as likely to CAUSE
equipment failure as to prevent it.
I've put several RF line filters that "look good on paper" into
enclosures and wired to connectors for use on Field Day and Califorrnia
QSO Party county expeditions to clean up noisy generators. They have
been totally ineffective for common mode noise, and the noise most
likely to cause us trouble is common mode noise. What DOES work for
common mode noise is to wind turns of the power cord through a suitable
ferrite core. 12-14 turns through a #31 toroid would be just about
optimum for 160-40M. 6-8 turns would be about right for the higher HF
bands. A #43 core needs at least 14 turns for 80M, and works as well as
#31 for the higher bands.
What is equally important is proper bonding of all grounds and systems
in your home and shack. That means bonding the power system ground to
your shack ground, cable TV, satellite, telephone, etc. AND it can also
help to use ferrite chokes on the Beverage coax, and any nearby wiring
that can radiate noise into your antennas, including the Beverage.
73, Jim Brown K9YC
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