Eric,
In many cases, the problem being dealt with is the currents flowing
through the "grounds" and complicated by what K9YC refers to as the "pin
1 problem" in that the connectors for audio and RF paths are grounded to
the circuit boards, but not to the enclosure (the enclosure *should*
shield the boards and inter-connects, but it does not in modern gear).
While a single point star grounding system may be best from an EMC point
of view, it is not the best for noise reduction and 'sneak paths' in the
gear we deal with in a ham station. In fact the multiple paths to that
single point ground can create currents in the grounding system giving
rise to noise in the gear that we are trying to reduce the noise.
Review Jim's presentation on grounding in entirety. Jim does speak from
many years of experience dealing with noise and sneak paths in
professional audio installations, and I respect his opinions based on
his years of experience dealing with these issues.
If you have no ground current induced noise and are only striving for a
lightning protection grounding scheme, then yes, the single point
grounding system is the way to go, but that is not the situation in the
modern ham station where we have to deal with audio and digital paths
to/from computers, interface devices, ancillary gear and "who knows
what" to the transceiver. Bonding all equipment together (with a mind
to the path for the audio and RF) will minimize the extraneous noise
currents on the shields between the boxes in the shack which will reduce
the noise level in the receiver.
I too have years of experience with design and testing for EMC
considerations, and as I have indicated, each method of grounding has
its place, but we are not dealing with EMC considerations alone.
73,
Don W3FPR
On 11/25/2014 5:46 PM, Eric Buggee wrote:
Hi all,
One additional comment regarding grounding for RF interference,
extraneous noise & elecrical safety considerations is that the
preferred method for grounding should be:
Single point grounding, ie all rig & amplifier ground connections
should be taken from a single point, (shack grounding buss).
Relying on "daisy chain" grounding for example: through coax
cable(s) & their connectors; Rig > Amp > tuner > tground point can be
the source of intermittent RFI & distortion
problems that can be difficult to nail. This approach to
grounding should NOT be used for the foregoing stated reasons.
Eric, VK3AX. Retired EMC engineer.
On 11/26/2014 4:21 AM, Jim Brown wrote:
On Tue,11/25/2014 8:08 AM, Don Wilhelm wrote:
Bonding the station equipment together and to a station ground point
is to keep all the gear at the same potential and can assist with
such things as extraneous noise pickup, stray RF and other
electrical annoyances.
Excellent advice. And there are other good reasons.
Here's a talk I did this fall at Pacificon on the topic of grounding
and bonding.
http://k9yc.com/GroundingAndAudio.pdf
73, Jim K9YC
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