I first tried grounding each end but found the diagram in
http://www.members.aol.com/WA1ION/nrants.pdf to
be much more effective in reducing QRM in my location.
Putting the coax 18" underground helped a lot also.

I tried the choke presented in
http://www.dxing.info/equipment/coax_leadin_bryant.pdf
to be nearly as effective with each end of my coax grounded.

With both ends isolated from ground and the adition of the
inductance in/on/with the coax it completely removed all the
noise from our home. This is before I connect an antenna.

I had wondered about the QRN versus signal I was receiving
on the 20' run of wire from the ground mounted 9:1 transformer.
I wanted to mount the transformer 20' up where the horizontal
wire ended. I tried coax first and while it was better then having
the 9:1 on the ground, it wasn't "perfect". Since I had the triax I
decided to try it. I tried this once before but got rushed due to rain
movng in. This time I made sure to connect both ends as discribed.
I suspect the "magic" is the 1:1 isolation transformer that connects
the inner conductors of the triax to the coax that carries the signal
to
the house.

IF I could arrange for for my ~70' wire antenna to be a perfect 1:1
match to my 50 Ohm coax across the 100KHz through `30MHz I
suspect I would have less noise. The way cobbled this mess is the
result of trial and error. I am not offering it as the best, or even a
preferable setup. But for me, in this location it gives me the quitest,

as in reducing man made noise, conditions I have yet managed to
achieve. It was more then a bit of a hasssle to get permission from
the electrical instector and our insurance homeoffice to allow a "non
conforming" isnstallation. A strict following of the NEC would require
all grounds to be bonded. I didn't go to all this trouble just for the
fun of
being odd.

Several years ago someone in this group made the suggestion of
using a cathode follower at the wire to coax interface to force a 50
Ohm match. One of these days I plan on trying that now that I have
a usefull supply of Nuvistors and a diagram that I suspect will work.

I would prefer to live in a quiter (RF) location. But I can't retire
yet,
so I must live reasonably close to where I work. I am half afraid that
by the time I retire "broadband over powerline" will have made HF
useless.

For very weak signal HF reception, designers go to great lengths
to prevent any current flowing on the outside of the braid. It will be
coupled via inductance. Our astronomy friend's lab had 1:1 low loss
RF isolation transformers at the antenna, before the grounding bulk
head, and at the receiver. She demonstrated the increase in noise
when any of these where removed by just jumpering across from the
incoming braid to the outgoing braid. She also demonstrated that
audio isolation transformers were also a "must have". She used
balanced antennae so had to use a transformer to match the balanced
antenna to coax. She experimented with twinax but found it to produce
more complications then it was worth.

I was concerned about the loss and Ms C pointed out that HF reception
is almost always limited by the backgroudn RF noise. And that if you
get an increase in noise when you connect the antenna, you are almost
certain to have enough RF. Most "decent" radios have at least a ~30dB
lower noise floor then the atmospheric/comsic noise. So a few DB loss
is well worth the 10dB to 20dB reduction in interference a "proper"
installation can achieve.

(This is why a single passive transformer "power divider/coupler/
hybrid" will not impact 99% of our reception. Even with the additional
~3.25dB loss, the real world noise still dominates reception.)

Most of us don't need anywhere near this level of complexity.
The standard "Doty" "L" antenna is likely to be all that 90%
of us would need. The "nrants.pdf" will help 90% of the rest.
Few of us will have coax long enough for the issues addressed
in the "coax_leadin_bryant.pdf" to be a major concern. My system
may be viewed as overly complex, and of "flawed design", but it
is the best I can do right here and right now.

Terry