Aerial grounding and QRM pick-up: theory & practice
 

art wrote:

...
I'm gone for a month or so and will not be using this newsgroup during
that time.
Will be back in the fall

Art

Have a safe journey.

Somehow, I almost suspect we will coast into boredom here, without you!

"You won't have Nixon to kick around anymore, because, gentlemen, this
is my last press conference."--Richard M. Nixon (well, until fall ;-) )

Regards,
JS

Aerial grounding and QRM pick-up: theory & practice
 

Hi All,

Since Artifice has left us with his errors intact, they can be
resolved quite simply before he returns later with more interesting
dismissals of his previous incarnations of "the truth."

On Tue, 25 Sep 2007 17:34:22 -0700, art wrote:

If you look at the field of a antenna that isr radiating an equal
amount in all direction
the volume of the radiation consists of usefull energy in the form of
radiation.

This volume, then, contains a fixed energy. Fairly simple stuff as it
happens 365.25... days of the year with the sun. Within the arc of
any orbit, there is so much energy from that same sun [hearing the
scrabbling of little feet in the cellar insisting stars and such fill
the void, I will simply bait the traps with better cheese].

If another antenna with the same energy input provides a radiation
field in all
directions that is equal but at a larger radius than the prior antenna
field

It doesn't need to be another sun, but if our "creater" insists, I
will return to that heresy.

Anyway [gad this is abysmally distant from SWLing and QRM - Dirk, you
can't possibly still be with us can you?], we have the same energy
within the volume of a larger orbit. Naturally, any inhabitant at the
original orbit must be wondering about this state of affairs.

Well, this latter Sun provides the same energy (unless more energy is
added, courtesy of our Great Decider bombing it with hydregen bombs in
the chance of killing Osama Bin Forgotten).

Um, sorry for the parenthetics, but Arty has never exhibited a very
good command of English - I suppose this means I will have to examine
both pair o' doxes.

the the latter antenna has gain over the prior antenna.

In fact, this is true in the classic engineering sense - to the degree
of negative gain. Given the obscurity of this missive of his, we must
judge this fact escaped him entirely.

To illustrate, same sun, same energy, different orbits, we return to
the original orbit to find less sunlight at noon (it has been
squandered to fill more volume). Any gain predictions are found in
the debit column of the account books.

----------- Part Deux -------------

OK, so somehow we nuked the sun to achieve this new golden age of
illuminating the expanded cosmos with the "same" energy (see how myths
are born?).

The inhabitant at the original orbit now sees a brighter city on the
hill. His sunburn is manifest in a cancer several years later (blame
technology). The inhabitants at the outer orbit now enjoy the
prospects of a future temperate climate (once the global ice shell
melts).

As we don't know the particulars of the orbit (Arty is never very
useful about providing facts that matter), they could be orthogonal -
or at least the traditional scientist (providing he has copies of
those books burnt by devotees of this "church of gain") would have to
allow for any point on the surface of a sphere.

However, if anyone is still reading this, what have been described
were TWO Isotropic antennas. As such, the only gain achieved is by
nuking the sun (cost $1 trillion per election cycle). In any
interpretation, no gain can be assigned to any antenna.

Of course, we all know that.

------------ Section C -------------

If you compare any fractional ground mounted antenna with a full wave
antenna the radius of the field
willhave a difference of aprox 3 db

As I've cautioned Arty in the past, we know what you don't mean - and
the light at the end of this tunnel ... we will skip the remainder of
doubling cliches here.

Arty is going to disappointed to discover that once again (always) the
facts he showers upon us are diametrically opposed to the fundamentals
of his proposition. Yes, there is a 3dB difference, but it certainly
doesn't favor the full wave (sic) antenna.

and the resistive impedance will
have a ratio of two to one.

Fractional/Full-wave? Not even close - unless this is expressed in
non-linear, 18 dimensional, gaussian string mathematics. It isn't
given that the full mathematical treatments of the total output from
Art wouldn't fill the back of a business card.

Note that gain is a measure of one radiator
level against another and is no way a distorted field of radiation
that has been manipulated by an additional near by radiator.

I can only wonder if this fractional ground mounted antenna is on some
crystalline planet circling a faint red dwarf.

A ground plane does nothing more than balancing the circuit provided

Ground mounted and ground plane(d) is not the same thing. If we are
to divorce this analysis from the distortions of ground (as in the
ground of earth) by mounting it in a ground plane (hung in free
space); then this 3 dB gain is going to evaporate like the White House
promises of a green card to migrant workers.

If you cannot follow the science of antennas then you are doomed to
be a follower, never a leader.

I suppose this admission will inform all future announcements.

Will be back in the fall

A dollar short and an equinox late informs us now.

My bets are follow ups in a very few moments ;-)

73's
Richard Clark, KB7QHC

Aerial grounding and QRM pick-up: theory & practice
 

On 2007-09-26, Richard Clark (67.168.144.41) wrote in
message


Anyway [gad this is abysmally distant from SWLing and QRM - Dirk, you
can't possibly still be with us can you?],

Sure Richard, I'm still listening in on this thread; I'm now thinking
about a 518KHz Gaussian antenna... :0)

BTW, it has been raining over here for 2 days, and the QRM levels are
still fine!

I have also done the following experiment: Instead of the commercial
"magnetic balun" I was using, I have now rolled my own 1:9 unun. The
main difference with the MLB is that the unun has isolated windings.
The primary is grounded to the earth rods, the secondary is grounded
via the receiver. I thought this was a better solution with regard to
ground loops.

73's - Dirk

Aerial grounding and QRM pick-up: theory & practice
 

Richard Clark wrote:
However, if anyone is still reading this, what have been described
were TWO Isotropic antennas. As such, the only gain achieved is by
nuking the sun (cost $1 trillion per election cycle). In any
interpretation, no gain can be assigned to any antenna.

Maybe it's the same kind of gain that causes
reflections from non-reflective glass to be
brighter than the surface of the sun. :-)
--
73, Cecil http://www.w5dxp.com

Aerial grounding and QRM pick-up: theory & practice
 

"art" wrote in message
ups.com...
If you compare any fractional ground mounted antenna with a
full wave antenna the radius of the field will have a difference
of aprox 3 db and the resistive impedance will have a ratio of two
to one. Note that gain is a measure of one radiator level against
another and is no way a distorted field of radiation that has been
manipulated by an additional near by radiator.
__________

art -- the difference in the gains of ground-mounted monopole radiators of
different heights is related to the height of the monopole, and the effect
that has on its r-f current distribution; therefore its radiation pattern.

The link below leads to a pattern and gain comparison of several monopole
heights commonly used in commercial AM broadcasting, over a perfect ground
plane.

Note that a 1/2-wave, ground-mounted monopole for these conditions has a
pattern and gain identical to that of a 1-wave, center-fed dipole in free
space. Also note that there are three radiator heights taller than
1/2-wave, whose gains are higher than the 1/2-wave (or a full wave in free
space).

In all cases, the area under the curve is the same for each radiator plotted
(mind the dB scale), showing that for a given input power each monopole
radiates the same total power into space regardless of the shape of its
pattern.

No nearby radiator was needed or used in the generation of these patterns.

So there's something for you to consider while you're gone for a month.

http://i62.photobucket.com/albums/h8...Comparison.jpg

RF

Aerial grounding and QRM pick-up: theory & practice
 

On Wed, 26 Sep 2007 09:14:16 GMT, Navtex-Fan wrote:

BTW, it has been raining over here for 2 days, and the QRM levels are
still fine!

Hi Dirk,

Great. We've been fog bound.

I recently bought a $40 SWL radio, and its noise comes from the
display with about 3 MHz bandwidth around the 49M band. I will soon
pop it open for some corrective surgery.

I have also done the following experiment: Instead of the commercial
"magnetic balun" I was using, I have now rolled my own 1:9 unun. The
main difference with the MLB is that the unun has isolated windings.
The primary is grounded to the earth rods, the secondary is grounded
via the receiver. I thought this was a better solution with regard to
ground loops.

Not really - it may cast the problem into a different coupling
mechanism. You still have capacitive coupling and you want to ground
the smallest signal end (the antenna), not the load end (the
receiver).

However, it sounds like it didn't make a substantial difference, or
any difference (seeing as you would have mentioned performance). This
suggests you have driven out as much noise as you can. Anything else
is coming in through the air from afar.

I've read (and tried) all the "expert" SWLing opinions of what pass
for BalUns (even professionals rarely get it right) and experience
still shows a tuner performs better - unless, of course, you really
have a sloppy installation (no choking, poor grounds, poor balance,
running lines past noise sources, the usual stuff).

73's
Richard Clark, KB7QHC

Aerial grounding and QRM pick-up: theory & practice
 

On 2007-09-26, Richard Clark (67.168.144.41) wrote in
message


I have also done the following experiment: Instead of the commercial
"magnetic balun" I was using, I have now rolled my own 1:9 unun. The
main difference with the MLB is that the unun has isolated windings.
The primary is grounded to the earth rods, the secondary is grounded
via the receiver. I thought this was a better solution with regard to
ground loops.

Not really - it may cast the problem into a different coupling
mechanism. You still have capacitive coupling and you want to ground
the smallest signal end (the antenna), not the load end (the
receiver).


Ehrm... that's exactly what I did. For a SWL, the antenna end is the
primary end :0)



However, it sounds like it didn't make a substantial difference, or
any difference (seeing as you would have mentioned performance).

QRM levels were the same, very low to totally absent. Signal quality/
performance seems to be the same.


I've read (and tried) all the "expert" SWLing opinions of what pass
for BalUns (even professionals rarely get it right) and experience
still shows a tuner performs better - unless, of course, you really
have a sloppy installation (no choking, poor grounds, poor balance,
running lines past noise sources, the usual stuff).

There is indeed a lot of confusing stuff about baluns circulating in
magazines and on the internet. Is thought it was only possible to use a
antenna tuner at the receiver end when the antenna wire is directly
connected to the tuner, ( that is: without using a coax line)
Right or wrong?

73's - Dirk

Aerial grounding and QRM pick-up: theory & practice
 

Navtex-Fan wrote:
There is indeed a lot of confusing stuff about baluns circulating in
magazines and on the internet. Is thought it was only possible to use a
antenna tuner at the receiver end when the antenna wire is directly
connected to the tuner, ( that is: without using a coax line)
Right or wrong?

What do you do when the antenna wire is not located
at the antenna tuner? Use a transmission line to
achieve maximum power transfer from the antenna to
the receiver (and vice versa for transmitting).
That's the basic function of transmission lines -
transfer the maximum amount of power from one point
to another with the least amount of losses.

Any reasonable transmission line impedance can be
brought to resonance through the use of stubs. An
antenna tuner performs that same maximum available
power transfer matching function.
--
73, Cecil http://www.w5dxp.com

Aerial grounding and QRM pick-up: theory & practice
 

On Wed, 26 Sep 2007 19:13:44 GMT, Navtex-Fan wrote:
Not really - it may cast the problem into a different coupling
mechanism. You still have capacitive coupling and you want to ground
the smallest signal end (the antenna), not the load end (the
receiver).


Ehrm... that's exactly what I did. For a SWL, the antenna end is the
primary end :0)

Hi Dirk,

But you lifted the secondary ground and use the ground at the receiver
end (if I understand your description). This creates a capacitive
link into the front end through that long path. By the designation of
UnUn, both sides (Pri/Sec) of the transformer go to ground. For low
noise, this grounding should be at the antenna end of the transmission
line (which re-introduces the possibility of ground loops if the
receiver is also grounded). You also lose choking action (an UnUn or
BalUn does not necessarily choke common mode currents).

However, it sounds like it didn't make a substantial difference, or
any difference (seeing as you would have mentioned performance).

QRM levels were the same, very low to totally absent. Signal quality/
performance seems to be the same.

Then, as the song from Oklahoma suggests, "you've gone about as far as
you can go."

A simple test is to tune off frequency to background noise (absolutely
no signals). Remove the antenna, what happened to the noise level?

There is indeed a lot of confusing stuff about baluns circulating in
magazines and on the internet. Is thought it was only possible to use a
antenna tuner at the receiver end when the antenna wire is directly
connected to the tuner, ( that is: without using a coax line)
Right or wrong?

Yes (for the simple answer).

Depends (for the complex answer).

It is far easier to try and see. The issue is one of mismatch and
fully coupling ALL of the available power in the signal into your
front end. You want a transmission line instead of a drop wire so
that you cut down on QRM from devices in the home near you. Hence the
choking of the line to cut down on nearby home noise that
conducts/inducts onto the exterior of the shield traveling down to the
antenna connection and coming back into the front-end. If you float
that far end at the antenna, the noise will simply leap the choke and
capacitively couple to the antenna and then travel back into the front
end with your desired signal (what a bitch).

The conventional usage of BalUns or UnUns for SWL is for matching, not
noise control. However, through careful selection of those BalUns and
UnUns by their construction methods, you can get both. Unfortunately,
most SWL BalUn UnUn designs are built backwards with the thought that
the typical home SWL antenna represents a Hi-Z transmission line with
respect to earth. By and large that is true, but as a signal source,
most home SWL antennas are Low-Res, Hi-Imp sources. Yes, a Hi-Z
results, but it is the R that counts and the step-down is discarding
power.

I am well aware that testimonials abound to "prove" nothing is lost. I
am equally aware that there are negative testimonials too. As such,
this contradiction gives the lie to the credited theory of "magnetic
baluns" (the term being a dead giveaway to a con job). I've also read
the apology that SWLers don't have time to tune up with every
frequency change - sounds like whining slackers to me. Tuners come
with knobs and numbered scales. It takes very little effort to log
settings once for a band, and use them forever after with slight
adjustments to pull in DX.

Power matching involves equalizing the source R to the load R and
eliminating the source/load I through conjugation. This requires a
tuner which supplies the necessary L for the excess C, or versa-vice
(it is, of course, more complex that this, but this convenient short
hand is sufficient to explore the topic).

Just to cover all bases, there will be problem tunes for certain
frequency/line-length/antenna-length combinations. There is no
universal fix. You can anticipate this by building a fan antenna, or
using cage construction techniques. Something tells me that this is
probably not an option or even within the scope of your interest.

73's
Richard Clark, KB7QHC

Aerial grounding and QRM pick-up: theory & practice
 

On 2007-09-27, Jimmie D (71.68.80.78) wrote in
message


"Navtex-Fan" wrote in message
...
On 2007-09-26, Richard Clark (67.168.144.41) wrote in
message


Anyway [gad this is abysmally distant from SWLing and QRM - Dirk, you
can't possibly still be with us can you?],

Sure Richard, I'm still listening in on this thread; I'm now thinking about
a 518KHz Gaussian antenna... :0)

[..]


Dirk I suspect the feed point impedance of your antenna is less than 1 ohm at
518Khz. This make a good ground imperative. With just a couple of ground rods
for a ground I suspect your ground impedance is probably around 20 ohms for
60hz and considerably higher for RF. Putting in 120 radials 1/4wl long would
be a tall order but perhaps you could add 20 or so as long as you can.


Jimmie

Thanks for the info, Jimmie, but installing radials of that size is
simply impossible in my garden.
I guess I'll have to accept it...

73's - Dirk