...That's not a problem you seem to have to deal with based on a map of where your QTH is supposed to be. Very rural...
It used to be when we lived out in Yamhill County, with about 3 houses within a
quarter mile of the house. Now, however, we've moved to a suburban 90' square lot
where the neighbors (and their noisy devices) are much closer.
But the point of my post was that none of the hams I've known, even those
who run full legal limit (or more!), have needed such an extreme grounding
system to eliminate problems. It's not that I'm against hams grounding their
stations if they want to, or if it serves some specific purpose, but from an
engineering perspective I'd rather understand and fix the root cause of the
problem rather than apply folklore solutions and hoping that they work.
So let me pick a couple items you mentioned and see what clues they might
give use...
First step was to solidly ground every coax shield at the QTH entrance using Alpha Delta arrestor blocks and a cluster of 10 ft copper ground rods - due to relatively poor soil conductivity (and use an RF choke near the resonant antennas feed points)
Second step was to run a dedicated 4-gauge ground wire from the (nearby) house power entrance ground to the coax ground rod cluster.
These are both good practice (and the second is required by building code in
most places).
Third step was to run dedicated 120/240 VAC power and ground to QTH "shack" area, exactly parallel to 4-gauge ground wire.
Fourth step was to individually ground each piece of equipment to an inside copper grounding buss bar using heavy braid, and to the outside ground rod, which was very close by (about 3 feet).
Let's consider the overall situation. Ideally your antennas should be
the only source of RF radiation. If the neighbors devices are picking up
a signal
radiated from the antenna, then no amount of grounding
in your station should make any difference, unless it reduces the radiated
power, or
changes the current distribution on the radiating conductors.
The same, of course, goes for picking up noise from the neighbors' devices
on receive.
So the question then is, what is allowing the RF signal go transfer to the
neighbors if it isn't radiation from the antenna (because in theory that
hasn't changed)? It must be radiation from another part of the system, or
via conduction. And why would changing the power wiring make a difference,
unless that was somehow either radiating or conducting an RF signal?
You had mentioned "leakage from the coax" in a prior post: why would
grounding the station reduce that? Besides, I'm assuming you used
reasonable quality coax, and not the cheap stuff with only 60% braid coverage.
How much power might be radiated from such leakage? We can set an upper
limit by looking at the loss figures for the coax, since the leakage must be
considered as part of the cable loss. If we assume 50' of Belden RG-213 on
40m, the cable loss is about 0.23 dB. At 1 kW output, the total power loss
is about 30 watts, and that due to leakage likely is much less that that. To
get another estimate, consider using RG-214 instead, which has a double shield
that should reduce the leakage. Turns out that the loss in that case is 0.245 dB:
it actually went UP when we added more shielding. (That's probably because
the added shield forced a reduction in the inner conductor size to maintain the
impedance with the same outer diameter to fit a PL-259 plug.) But that would
tend to confirm that the actual "leakage" from the coax is a relatively small part
of the total rated loss - perhaps 0.01 dB, for a total leakage power of 1 watt
over a 50' run at 1 kW input. That hardly seems likely to account for the differences
you are describing.
Now, let's consider the need for separate power runs. Sure, one way that a transmitter
can interfere with nearby equipment is by RF getting on the power wiring through the
power cord, and getting distributed from there to the other devices. This actually isn't
that uncommon. Of course, you also could have voltage regulation problems on an
undersized supply line, especially trying to run an amp on a 15A or 20A circuit along
with other equipment: that can manifest itself as lights dimming when you key up,
and possibly could cause various symptoms in consumer equipment (especially on
SSB). But assuming your power drop was properly sized to start with (and size
doesn't appear to be the only problem if the layout of the cabling also made a
difference) then a more likely explanation is that RF was getting into the power
line somehow from the case of the rig, typically onto the AC ground wire. If that
was the source, then filtering the AC power cord should have fixed the problem.
Both of those symptoms sound to me as though there is RF on the outside of the
coax that not only can radiate (and conversely pick up signals) more than can be
accounted for by "leakage" from the coax, as well as passing from the rig/amp
chassis onto the AC wiring and affecting other equipment that way. Basically
the outside of the coax is acting like part of the antenna - our old friend,
common
mode current.
Now, I know you say your antennas are all resonant, and (at least some) have RF
chokes near the feedpoints. I don't question that, but
that doesn't say they
can't have common mode current. Resonance doesn't matter - in fact, I've
had antennas that had resonances
because of common mode current (there
was more current on the coax than on the other antenna wire).
How does this fit with the observed symptoms? If the common mode current is
from the antenna feedpoint down the coax shield, past the neighbor's house, into
the rig, then out through the ground wire into the AC wiring, it would cause all the
symptoms you are reporting: running new power wiring can change the current
distribution on the coax, as well as reducing the feedthrough into adjacent devices
on the same electrical circuit. And in my experience, most radiation from coax is
much stronger due to common mode current than actual leakage from the coax
(except in repeater installations where very high levels of isolation are required).
Oh, but you can't have common mode current because you have RF chokes at the
antenna feedpoints, right? No, not at all. Ever seen one of those VHF colinear
antennas that uses parallel tuned circuits between adjacent half wave sections
of radiator? That same circuit would look like a trap in a standard antenna, but
in that case, because it is added at a high impedance point, it simply provides
the phase shift between sections without impeding the current. (Well, that's the
theory anyway. In practice they don't actually work that well.) The point is that
adding an impedance
at a high impedance / low current point on a radiator
doesn't really provide any reduction in current. And where is the high impedance
point of an end-fed half-wave antenna? Right at the feedpoint, where folks
typically add chokes and expect them to be effective. They aren't.
So when I read your initial description of all the things that you did to eliminate
interference in and out of your system, they all just screamed COMMON MODE
CURRENT to me, even without looking at the antennas you are using, because
those are exactly the symptoms that it would cause.
So, yes, by now you've fussed around enough to where you appear to have it
under control, though that might just because you found a lucky length of
power cable that gave a high impedance at the antenna - similar to grounding
the coax 1/4 wave down from the feedpoint. And, of course, that doesn't mean
you might not still have some common mode current, only that the distribution
along the coax doesn't put maximum radiation at trouble spots.
But if you had solved the common problems
at the antenna in the first place,
it would have saved you a lot of work, and you might not have even needed a
ground system (except for lightning protection if that is an issue).
I have no problems with folks grounding their stations, though much of my operation
over the years has been without one (the ground pin of the AC power plug provides
my safety ground). But grounding isn't a magic cure when the problem is really
something elsewhere that should be fixed at the source instead.