"clvrmnky" wrote
On 15/03/2005 8:33 PM, Richard Clark wrote:
As for the Neutral connection of the mains NO THAT IS NOT GROUND!

Absolutely. I actually have home wiring experience (I don't have my
electrician's ticket, but I could wire my own home, and it would pass
inspection.) I'm surmising that the ground my receiver is seeing (at
least the DC components within it) is the neutral wire. My comment was
more of a rhetorical comment, not a threat to use the white wire on my
AC outlet as ground!

Hi OM, it's clear you understand that wal-warts have only two connectors to
AC (hot and neutral), and neutral is bonded to ground at the mains.

My question to Richard (and group) is whether there is any RF or DC link to
ground via a radio's DC-power connection to a wal-wart? I have never
examined the internal components of a sealed wal-wart, only seen the results
of surge voltages from lightning that exploded them and damaged radios they
were connected to. Nothwithstanding the forces of lightning that made that
connection, isn't there isolation from ground when a DC converter is used?

Cheap DC converters can add noise to an electrical system and affect radio
reception, but I didn't think there was any DC coulping across the
transformer wiring, and probably limited if any rf-coupling there either.
Can anyone comment on this?


This goes again to the common misunderstanding. You won't suffer a
ground loop until it occurs. Solving it will be one of life's
greatest struggles, and the solution, if stumbled upon, will appear to
be one of life's greatest mysteries. Again, battery operation creates
its own bubble of isolation from these issues - however, adding a
charger brings the prospects back into the equation.

It's my understanding that ground loops are most common from having serial
v. parallel connections to ground from various equipments. Daisy-chaining a
series of radios to the common ground would thus allow radios to exhibit
feedback through each other instead of only to ground. When a properly
bonded system is connected (each unit indivdually connected to the single
point ground) there is no ground loop. Others often ask what about multiple
bonding-points of the external ground system and it's connection to the AC
mains? Answer: These are not ground loops and are not the cause of equipment
interference from the series-connections of equipments described above.


I get a bit of a boost in signal running off the wall-wart, but it is
actually more convenient for me to run off batteries. I end up moving
the receiver around quite a bit. I can pick the big blowtorches and the
relays from Sackville quite nicely off the whip, so I often listen to
them in the kitchen or when doing chores around the house. For "DXing"
I settle in near the door where I've got my antenna experiments going.


That's interesting OM, as it implies you are seeing a counterpoise effect of
rf-coupling across the windings of the dc transformer, or perhaps just the
secondary side? If a wal-wart helps complete an antenna, it would seem
there may be a design component missing from the antenna somewhere ;-)

Best regards,

Jack
(fmr navy instructor of strategic weapons systems electronics, now a
plug-n-play operator for the uscg)

On 16/03/2005 12:02 PM, Jack Painter wrote:
"clvrmnky" wrote

[...]

I get a bit of a boost in signal running off the wall-wart, but it is
actually more convenient for me to run off batteries. I end up moving
the receiver around quite a bit. I can pick the big blowtorches and the
relays from Sackville quite nicely off the whip, so I often listen to
them in the kitchen or when doing chores around the house. For "DXing"
I settle in near the door where I've got my antenna experiments going.

That's interesting OM, as it implies you are seeing a counterpoise effect of
rf-coupling across the windings of the dc transformer, or perhaps just the
secondary side? If a wal-wart helps complete an antenna, it would seem
there may be a design component missing from the antenna somewhere ;-)

I realized that my nomenclature was wrong. I should have said "bit of a
boost in amplitude" because this is what I'm /really/ hearing. I'm
guessing here that when running of the wall-wart we just have more
available current to draw on for RF and AF amplification, heterodyning
&etc. I have no proof that the signal coming into the set is any
better/stronger or that my antenna is more sensitive or selective.

That is, I don't recall the signal meter changing much when I switch
back and forth between battery and wall-wart. Although, quieter signals
will be uniformly attenuated (along with the noise) slightly when I
switch to battery.

Currently (with a random-wire antenna) the radio seems to not care what
is on the "ground" side. This is hardly scientific, but when I attach a
good number of feet (i.e., more than the length of the antenna) of
copper wire to the ground side of the antenna input (or touch it with my
hand) I get no noticeable change to tuned stations or between-station
noise. I may hear the slightest bit "tick" of noise when my finger
makes first contact with the case of the plug that goes to chassis
ground. Nothing obvious, however.

Jack,

The classic ground loop can occur even when individual components are
perfectly bonded to a single point ground. The "loop" is formed when a
signal cable connects the bonded components together along an alternate
path. There are many proper fixes for this problem, but one popular
quick and dirty fix is to disconnect the bonding by removing the third
pin on the power plugs. Not a good idea, but it happens a lot.

If correcting ground loops was simply a matter of properly bonding the
components to a single point then nobody would ever bother mentioning
ground loops.

73,
Gene
W4SZ

Jack Painter wrote:

[snip]


It's my understanding that ground loops are most common from having serial
v. parallel connections to ground from various equipments. Daisy-chaining a
series of radios to the common ground would thus allow radios to exhibit
feedback through each other instead of only to ground. When a properly
bonded system is connected (each unit indivdually connected to the single
point ground) there is no ground loop. Others often ask what about multiple
bonding-points of the external ground system and it's connection to the AC
mains? Answer: These are not ground loops and are not the cause of equipment
interference from the series-connections of equipments described above.

"clvrmnky" wrote
Currently (with a random-wire antenna) the radio seems to not care what
is on the "ground" side. This is hardly scientific, but when I attach a
good number of feet (i.e., more than the length of the antenna) of
copper wire to the ground side of the antenna input (or touch it with my
hand) I get no noticeable change to tuned stations or between-station
noise. I may hear the slightest bit "tick" of noise when my finger
makes first contact with the case of the plug that goes to chassis
ground. Nothing obvious, however.

that's normal - wait until you discover "the paper clip principle"...

Or, "when a paper clip attached to the back of the radio receives as much as
your just erected antenna", LOL. Stranger things happen, and it helps if you
record in a log what your antenna experiments have yielded. If you use the
S-meter to help relate signal strength (including noise levels), remember to
measure it against at least three frequencies in your intended listening
range (lowest, mid-range, and highest). No antenna treats the whole hf
spectrum the same and you may develop favorite arrangements for particular
listening desires.

Good luck,

Jack Painter
Virginia Beach, Virginia

On Wed, 16 Mar 2005 12:02:48 -0500, "Jack Painter"
wrote:

My question to Richard (and group) is whether there is any RF or DC link to
ground via a radio's DC-power connection to a wal-wart?

Hi Jack,

The simple boding of neutral to ground, as you offered elsewhere,
suits the RF ground path. If there's an isolation transformer, such
as may be found in the common wall wart, you may be assured that the
interwinding capacitance is suitably high enough to overcome any
notion of being isolated at RF. Precision and low noise applications
that demand higher quality isolation between primary and secondary
mandate a faraday shield between them. This shield only insures an RF
path to ground that is optimized for tight coupling - it has no other
purpose.

73's
Richard Clark, KB7QHC

Good points Gene, and thanks for your reply. The AC connections could
certainly be responsible for a ground loop. But it has been my experience
that so few stations actually bond properly that the preponderance of
possibilities would occur foremost with the direct connection from improper
bonding, not the indirect connection from electrical wiring, which usually
has distance and other connections before circling back to the
offending/receiving equipment. All things need to be considered, and is a
good reason for Richard's comment that "Solving it will be one of life's
greatest struggles, and the solution, if stumbled upon, will appear to
be one of life's greatest mysteries." ;-)

I once had a ground loop from a yagi-rotor that resisted all manners of
alternative grounding, wiring, routing, rf-chokes, etc. You either put up
with it or remove it in that case!

If removing the third plug from the power cord isolated a ground loop
problem, then safer alternatives could be accomplished such as an isolated
ground and separate neutral for a particular power supply, as is common in
sensitive computer systems.

Best regards,

Jack

"Gene Fuller" wrote
Jack,

The classic ground loop can occur even when individual components are
perfectly bonded to a single point ground. The "loop" is formed when a
signal cable connects the bonded components together along an alternate
path. There are many proper fixes for this problem, but one popular
quick and dirty fix is to disconnect the bonding by removing the third
pin on the power plugs. Not a good idea, but it happens a lot.

If correcting ground loops was simply a matter of properly bonding the
components to a single point then nobody would ever bother mentioning
ground loops.

73,
Gene
W4SZ

Jack Painter wrote:

[snip]


It's my understanding that ground loops are most common from having
serial
v. parallel connections to ground from various equipments.
Daisy-chaining a
series of radios to the common ground would thus allow radios to exhibit
feedback through each other instead of only to ground. When a properly
bonded system is connected (each unit indivdually connected to the
single
point ground) there is no ground loop. Others often ask what about
multiple
bonding-points of the external ground system and it's connection to the
AC
mains? Answer: These are not ground loops and are not the cause of
equipment
interference from the series-connections of equipments described above.