Hi Jose,
You had no problem hearing my 5W signal in the "Summer Stew" and you were
the farthest contact made during my limited operating time. Some loud signals
could
not hear me at all so I figured you probably had an excellent receive system.
I enjoyed reading the description of your interference filters.
Thanks and Best Regards,
Jim / W1FMR
--- On Sun, 6/24/12, N4IS <n4is@comcast.net> wrote:
From: N4IS <n4is@comcast.net>
Subject: Re: Topband: Reducing Noise in the Shack
To: "'Guy Olinger K2AV'" <olinger@bellsouth.net>, "'DAVID CUTHBERT'"
<telegrapher9@gmail.com>
Cc: Topband@contesting.com, "'Wayne Willenberg'" <wewill747@gmail.com>
Date: Sunday, June 24, 2012, 11:43 AM
Hi guys
Let me share what I've done about reducing noise in the Shack, not all
station has this kind of configuration, you may not need it.
1- Tom is 100% right about common mode noise. I killed all common mode noise
outside the Shack. My desk is in the corner of the house and I'm using two
steel galvanized box, one for AC with a huge common mode filters made with
wire #10 and FT270-31. The second 24x24x8 for the RX and TX cables, all
grounded inside. The RX cables have also FT240-31 chokes with RG142 cables.
2- The 220Vac enters the wall and is connect to another filter with very
large surge protectors and feed my amplifier. After the filter connected to
a large aluminum bar 8"x 1/4"x 72 " followed by an 1 KW isolation steep
down transformer to 110Vac. It is important to avoid ground loop using only
one point of grounding.
3- EMI/RFI has two components, electrical and magnetic field must be
blocked. My RX antennas has low gain and they work near RX noise floor ,that
requires a high gain preamp, my preamp has >40 db gain. Aluminum boxes are
not enough to kill the magnetic field noise from the PC and from my 2 LDC
screen monitors, the solution was steel tinplated 24"x36"galvanized steel
plate bellow the desk and to build a large box 20" x 30" x 3" to install
all preamps and the RX switches inside.
4- Also there is a long ground #00 cable around the corner of the house with
ground rods each 10 FT, one leg is 40Ft log and the other is 60 FT long and
connected to the house power meter ground rod. at the end, like NEC
requires. That builds a huge low impedance ground protecting the house and
the shack. It is a good ground but for protection it is never good enough.
If my station has a big secret it is the ground system for sure, one for RF
and another for lightening connected together in one point by a large
galvanized 4"steel pipe between the box in the house and the box in ta the
base of the TX tower 70 FT apart. All my cable runs inside a galvanized
steel pipes to cut the magnetic field.
I know it is overkill the problem but I'm glad I did it that way.
Regards
Jose Carlos
N4IS
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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