Richard Clark wrote in
:

On Sun, 03 Jan 2010 13:07:26 -0600, Lostgallifreyan
wrote:

If you look at that PDF you'll see the 15' whip antenna is directly
connected to ground through 80 turns of wire on a ferrite toroid. I
might add a spark gap in parallel as that wire is not a high current
path. So long as it is much more likely to go to ground rather than
along the line in to the house, I'll have done what I'm supposed to do.
The trouble would only exist (other than unpreventable natural excesses)
if it were evident that I had not done this.

Yes, it is a grounded design. The folded monopole is simpler, however
and you can deal with matching identically. 80 turns of wire on a
ferrite toroid is going to test the limits of self-resonance, poor Q,
and efficiency across so large a span of frequency.


Ok, I'll definitely extend reaserch to cover folded monopoles. (Another
curious term given that there has to be some kind of polarity there, but
never mind..) I'll be making by own transformers and housings so I don't mind
plenty of messing around with those.

Sounds like a lot of faith and work that will eventually require more
investment in faith and work. A shallow buried radial system would
puncture these superstitions.


The yard out there is partially covered by most of the trunk of a large
felled lime tree, along with lots of branch logs, as part of an effort to
retain nutrients on land that is part of a limited strategy to preserve
wildlife in an urban district. Burying anything out there is harder work than
sinking a ground rod. I think I'm going to have to take my chances.

Let's revisit one of your statements above:
balanced microphone cable with a screen grounded at one end
Which end? Any choice stands an equal chance of being the wrong
choice.


Well, I did think of that. And I didn't state it because I didn't
know for sure.

That's why I tossed that hand grenade into the mix.

As I imagine that local RF couplings from various digital devices might
place small currents on the local ground, I imagine that grounding a
shield at the remote ground makes sense.

It does, but that isn't the complete solution if you don't choke the
feedline. Again, ground is not found in the rod you drive into the
earth (which, by the way, will take years to "cure" to the ground
resistance you hope to achieve).


Even if I add a little salt water or dilute acid to accelerate that? This is
something I've been considering.. By choking the feedline, do you mean
placing ferrite slugs round it like those used on VDU cables? That's
something else that will be cheap and easy to test empirically.

Doesn't matter to me though. It's far
easier and faster to experiment than to try to predict because there are
only two ways to try.

This is about experience. You will find (and I have found) damn
little reference to grounding by connection to the earth. It has
taken me years to accumulate these rare references. They have been
topics of discussion here (use google to search the archives).


I'll do that. I gravited to Usenet for exactly this reason, I already
collected a few rare sources of info this way in other matters. A lot of the
best stuff is in web archives of usenet posts. (Although for audio I found a
single magazine called Sound On Sound to deal with it efficiently. Not RF,
but it's not exactly far removed technology). I think a lot of good
references just never reached the net, except via postings by people who have
read them. or if they have, they're in university archives I can't reach
anyway.

Dallas Lankford directly states that no shield is even
required, and I doubt he'd have said that if he couldn't demonstrate it,
and as that line is a two-wire loop that has no direct contact with
anything, it should reject any common mode noise that hits it.

Many people make direct statements (hard not to in this environment
that relies on textual postings). You need to find a better source of
study material as it relates to Common Mode. Twin line suffers it
equally. Again, all such discussion arrives through where the source
and load are, not in the line between.


There looks like one difference. Any signal hitting a coax screen if used in
this scheme will have a corresponding return current in the core wire, but if
there is any frequency dependent effect based on the nature of the coax
braid's dimensions or in the difference between that and those of the core
wire, then complexites beyond my ken might result (and maybe just as likely
be insignificant). The equality of nature in each half of a twin wire appeals
to me, so long as it actually works. Should be cheap and easy to test that
one...

Even in audio this matters
because the same method is used to reject RF pickup on audio lines. I
think some people persist in baluns instead of op-amp common mode
rejection specs for this reason, despite the chances of modest
distortion in audio bands from the transformers used. Not entirely
relevant but it illustrates how people can find themselves choosing
between two less-than-ideal circumstances for best effect.

You are confusing topics here. BalUns and what are properly chokes
are not always the same, although their discussion is often co-mingled
to considerable misunderstanding. BalUns are NOT transformers as you
might imagine from the point of view of AF. It is regrettable that
BalUns are called transformers, as their full nomenclature is
Transmission Line Transformer - meaning the transform of Z by
transmission lines that have their ends isolated through choking
action.


Very likely I am missing plenty. Thing is, I see an unbalanced antenna-to-
ground on one winding and an isolated and balanced line that loops back on
itself carrying induced current from the other. It seems to me that balun and
transformer are terms that apply equally there. In other words, it appears
that the distinctions are neatly avoided while I am directed to exploit the
common nature of the thing being used. Once I see if it works my interest
will grow and I'll explore it further.

Lest that sound too obtuse: The best BalUns do not operate through
magnetic flux linkage. You are not in Kansas anymore.

I understand that noise context matters for a real attempt to plan for
it, but that's far more difficult that presenting the basic antenna
scheme.

Hence the novelty of individual threads. Noise arrives in the same
manner as RF - it is indistinguishable until you put on your
headphones. Noise is what arrives between your ears.


That's actually the single best argument for empirical testing. Something
else that audio work has told me many times...

In regards to this last epithet, I noticed that Lankford wrote a piece
about quad detectors. I first designed one 40 years ago and the
critical component missing in Lankford's discussion (and probably from
many such discussions surrounding this method of detection) is that
the two channel output of a phase quadrature detector is meant to
drive STEREO headphones so that the last step of detection is found in
the brain's capacity to differentiate noise from signal.


That's interesting. I've considered exploiting that idea before now. Not in
much detail, just in principle because I've heard sounds that needed this to
resolve them.