On 8/13/2021 11:04 AM, David Eckhardt wrote:
But, I have a rather monstrous common mode choke on the new
refrigerator/freezer power cord.
Remember that effective common mode chokes work by exhibiting a low Q
(broadband) resonance, so should be tuned (wound) to the range where
suppression is needed.
At least that was accessible unlike
the clothes washer/dryer and dish washer, and a few additional SMPS's in
other appliances.
And.....if I get serious about a specific radio astronomy associated
project, only the computer serving that project is on. All others are
off and the internet is OFF, including the wireless router. Not just
OFF, but denied AC power!
A lot of our network infrastructure can be suppressed by choking
connecting wiring, including, but not limited to, their power, coax from
CATV internet and CAT5 between modem and router. DSL is a more difficult
kettle of fish, as the service cable can radiate. Noise from their SMPSs
can be eliminated by replacing them with suitably rated linear supplies.
I go a step further by using the linear supplies to float-charge sealed
lead-acid batteries. I do the same with outboard video monitors. Mine
were purchased about five years ago when Samsung and several other
vendors were using 14VDC, and work fine in the 12-14 range.
I've used nothing but Thinkpads since about 2005. They're pretty good
for RFI, although I recall one vintage that was nasty on 2M. Running
with only their built-in screen and a wireless mouse eliminates more
wiring that could radiate. I always choke PSU wiring and cables to
external monitors.
73, Jim K9YC
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