On 14/03/2005 5:51 PM, Richard Clark wrote:
On Mon, 14 Mar 2005 16:07:50 -0500, clvrmnky
wrote:

Right now I'm running battery only because I have perfectly useful
rechargeables. Anyway, it is giving me a chance to see if the PS adds
any noise. It doesn't appear to.


Hi OM,

That is fortunate. Try not to introduce any grounds such as you
discuss below.


It would seem this is another place where various holy wars have waged
over the years. My survey of the literature indicates that a great many
people don't even consider a dipole of any stripe fed to an unbalance
RX/TX as a "dipole."


Dipole has only one meaning of value: Two Poles. Each pole acts as
the electromotive opposite of the other. Without opposites, no
current flows (and in a sense, a monopole finds its dipolar opposite
in ground).

I've had an epiphany of sorts, and I think you may be partially to
blame! Well, that and "Basic Electronics" published by the US Navy.

The reason I'm so doggedly trying to get all this is that I'm also
working on getting my amateur radio license. One problem with this is
that I may be conflating "best practises" I'm reading about for TX with
RX purposes. This is the danger of just enough knowledge. I'm
determined to learn how these devices work, and how to best use them.

However, last night I realized that I can think about a RX antenna as an
HF AC current /generator/ running with a small voltage potential (i.e.,
~1 uV), and that my receiver completes this AC circuit.

Then it follows that a longwire needs an RF ground (of some nature) to
"complete" the circuit. Hence, the use of a counterpoise in some
situations. My receiver is one part of an AC circuit that wants some
kind of RF ground to see the voltage potential being generated by the
antenna. Crystal radio sets seem less like magic now.

Of course, grounds for lightning, static or noise attenuation is
related, but not specifically part of the antenna as an AC generator.

So, my "folded dipole" (or, likewise, any doublet) does not rely on
ground to complete this AC circuit, and works relatively well as an AC
generator with a small voltage potential it presents at the receiver
front-end. It follows that all the ground I should need (for good
operation) is a good chassis ground, even if that is only the neutral
side of the wall-wart (is that where it is?). Other issues like ground
loops, reduction of common-mode noise &etc. is a separate issue; these
can *sometimes* be solved by different devices on the antenna system,
but I see now how they could also add problems.

So, when people complain about balance/unbalanced situations, they often
talk about the radiation lobes of a TX antenna being uneven in some
manner they would like to minimize. Perhaps there are gain issues, as
well. I have no idea how my analogy works in this regard with RX
antennas (perhaps my dipole will be slightly "deaf" on a particular axis
if I do not balance/tune it before plugging it into my receiver), but I
can take a baby step and suggest that the various things we can put
between the antenna and the receiver are often RLC circuits meant to
lengthen or shorten the electrical length of the wire. The main intent
is to manipulate the resonance of the antenna for whatever purpose.

I know my explanation has a certain amount of hand-waving and holes, but
it is really helping me understand how the antenna fits into the
receiver as a total system.

The rest of your comments make a lot more sense to me when I think of
things in this manner.

Thanks to everyone in this thread for coaching me in what I hope is the
right direction.

-- cm