RFI: At the Receiver or in the "shack".

In spite of my comments in "What is a good RF ground", grounding
considerations are extremely
important at the receiver. There are so many different configurations
used by SWLs that it is hard
to offer specific advice.

Receiving setups range from a single receiver and a single antenna to
multi-receiver multi-antenna
coupled with audio processing and data decoders.

In systems more complex the most simple it is vital to bond all of the
equipment to either a single
"star" grounding point, or to a ground buss. My ground buss is a 1/2"
X 1/4" X 8' copper buss with
taped (threaded) mounting holes every 4". I use 1/4", 1/2" and 1"
tinned braid to bond every device
to this bar.

I have the bar bonded to the house NEC ground with 6AWG and 1" tinned
braid. The 6AWG is for
NEC compliance, and the braid is for the lowest impedance I can
achieve.

I use audio isolation transformers with an internal electrostatic
shield to prevent audio ground loops
to interconnect all of the devices.

A good electrical bond will reduce the risk of lightning transients
damaging equipment. It will also
prevent, or reduce, RFI produced in one device from sneaking into
another device.

While this is probably over kill, I have a Topaz Ultra-isolation
transformer that has 0.005pF
coupling between the primary and secondary on the AC mains. Since my
entire "shack',
with everything powered up, draws less then 200W, a 250VA unit works
fine. I have multiple
Curtis 2 stage RFI filters between the AC mains and the Topaz and
another on the output of
the Topaz. The power supply(ies) all have Curtis 2 stage RFI filters
on the AC input. I also
have Curtis 2 stage RFI filters on the AC mains for the lap top power
supplies. The lap top
power supplies all use IEC C7 (http://www.accesscomms.com.au/
reference/IEC320.htm)
so one IEC C13 cable connects the RFI filter to the Topaz AC output,
and a Triad 553-N68X,
50VA, AC isolation filter followed by another Curtis 2 stage RFI
filter services all of my laptops.

As a friend said in 1985, mulit-tasking means multi computers.

Ideally I would like to place a solid metal ground plate under either
tempered glass or Lexan,
or a conductive rubber anti static mat, on my radio desk and the two
shelves. The metal would
be bonded to the ground bus. I would love to use 1/8" copper, but I
would settle for 20G galvanized
sheet metal. Sadly due to my injured arm, I lack the ability at this
time to build such a ground mat.

All of my incoming lines, AC mains, telephone, and antennas all come
through a 1/8" X 4' X 4'
aluminum entry bulk head. The ground bus is bonded to the bulkhead and
the bulkhead is bonded
to the NEC ground. I use bulkhead RF connectors to pass RF from
outside to inside. The telphone
line enter via a barrier strip on the rear (outside) and pass through
1000pF feed through capacitors
to a bud box that is mounted to the bulk head with 6 #8 stainless
hardware with star washers to
insure good electrical contact. The telephone line passes through a
RFI filter (balanced 500uH with
500pF 2 stage filter) and scavenged gas discharge OVP clamp.

The Topaz is mounted on the inside of the bulk head, and the AC enters
via a Curtis RFI filter on
the rear and passes through 1500pF feed through capacitors (protected
by 2 small lexan boxes
on both sides) to the Topaz. A high quality,laboratory grade, power
strip is mounted on the bulkhead
and all of the AC cables run there. I hope to mount my new AC-ONE DC
power supply on the bulkhead.

In the past I used a RF patch panel, but at the present I have some
Pasternak coaxial relays that allow
me to route my RF through or around my Kiwa MW reject filters, one low
pass on high pass, and
through or around my Mini Circuits hybrid power divider/combiners.

I have found it is much more important to apply proper bonding to the
devices at the receiver
and to apply proper RFI control at the noise sources then to spend the
extreme energy needed
to achieve a super ground. A whole house ground ring is really
overkill.

One advantage of my current setup is that from the outside our home no
longer screams radio
equipment inside. Not that my wife ever complained about the wide
variety of antennas I have
experimented with, but she mentioned it is nice to not live in Dr.
Frankenstein castle anymore.
It is funny that the only RFI complaint I ever received for my ham
activities occurred at a time
when I had no ham equipment in my radio room. A new neighbor saw my
75' wire antenna and
just knew I was the source of the noise that was wiping out his TV
reception. When in fact it
was an idiot who was doing some welding at home to earn extra money.
The welding stopped
when he set his garage on fire.

Our roof line has 4 ~30" Air Terminals, lightning rods, bonded to the
ground ring with 4AWG.
It also has a version of Dallas Lankford's latest antenna near one end
that has a 6" element.
I have a 2M 19" 1/4Wave ground plane and a 3" 800-1100MHz NMO mount
antenna. From the
ground it is not at all obvious that a real radio nut lives here.

I have the Win Radio Dual Transformer mounted in a small weather proof
box under the eves in case
I decide I simply have to have a wire antenna. I doubt if it will
every get used again.

Terry