On Thu, 11 Oct 2007 06:23:44 -0700, Roy Lewallen wrote:
Frnak McKenney wrote:
. . .
Okay... ARRL Antennas, Chapter 8: Multielement Arrays. We've got
an (approximately, given skip) vertically-polarized 10MHz signal, so
the E-field is moving up and down and the wavefront is a circular
ripple (nearly a straight line by the time it gets to Richmond)
travelling roughly west-to-east, that is, it's hitting my house
end-on.
. . .
--snip--
While you're looking at the ARRL Antenna Book, look over the chapter on
propagation. You'll find that when receiving a signal by ionospheric
skip (as you are), the polarization will be randomly oriented. So
there's no point in choosing your antenna orientation on the basis of
some supposed wave polarization. Its orientation will, however, have a
striking impact on its pattern, so you should choose the orientation to
get the most favorable pattern.

Ah. So even if it starts out in vertically polarized in Fort
Collins 'way out thataway (he says, gesturing faintly west-ish)
WWV's signal might be polarized north-north-west by the time it gets
ro Richmond.

The fading in and out of the WWV signal you described in an earlier
posting is very likely due largely or at least partially to polarization
shift -- the signal fades when the polarization rotates to be crosswise
to your antenna, and gets loud when the polarization lines up with your
antenna's. I've seen tens of dB difference switching between a
vertically and horizontally polarized antenna, with the change going the
other way after a minute or so when the polarization rotates. If your
receiver needs a constantly strong signal, you're going to have a hard
time getting it what it needs.

Hm. Wonder if anyone has built an antenna whose polarization shifts
to "best match" the incoming signal? (No, not _this_ weekend!
grin!)

I haven't followed the thread closely, so please pardon me if I've
missed something. Your initial description of the problem sounded like
receiver overload. A sharp preselector would help a lot, although it
sounded like you were using a tuned loop which, if carefully balanced,
should provide that function.

A minor update: It seems that I was _mis_tuning my antenna,
adjusting it for the strongest signal (highest stack of LEDs lit).
Over the past two days either I've finally tuned it _correctly_ or
I've done that _and_ the signal has improved. Whatever the
cause(s), I can now -- at times, in fact for an hour at a time --
hear the tocks fairly clearly and even understand the voice. (Who
knew the announcer's phrase for UTC "Coordinated Universal Time"?).

How good? Well, I've unplugged the clock to reset it and it has
then received an "acceptable" WWV signal (it started showing digits)
eight times in the past two days. It might have been more times,
but I don't watch it constantly, and I've noticed that twiddling the
tuning knob tends to make sync-ing a little harder. ("Ack! It's
fading! See if I can tune the antenna _just_ a little better!"
grin!)

I _do_ know that the point of best reception is much narrower that I
thought it when I was tuning in that "other" signal. Turning the
tuning capacitor's knob a "minor wiggle" either way can decrease the
signal strength by an LED or 2, and I need to compensate for the
effect of moving my hand near the antenna to tune it. grin!.

Oh, and the MAC-II seems to be a lot pickier about what it will and
will not accept than my ears are. The microprocessor is driven by a
9.216MHz crystal and it's an 87C52 (an 8051-alike) which (as I
recall) means it only gets around 0.768 MIPS (clk/12) to do all its
work, so I doubt it's doing much "DSP" itself; its interrupt lines
are tied to a 567 tone decoder IC for WWV's "start of minute" and
BCD data subcarrier tones (1000Hz and 100Hz).

The MAC-II seems to be very "picky". Part -- but not all -- of its
requirement for starting the clock digits running is that it receive
a recognizable 100Hz signal for a full minute, that is, between one
1000Hz tone and the next. In other words, if WWV's signal is fading
on a 5- or 30-second cycle, odds are good that at one point the
signal will be come "bad". I've seen it recognize the start of a
"frame" by lighting its CAPTURE LED, but then turn it out ten or
forty seconds later when part of the frame has faded a bit; my ears
can still recognize the tones, but the're better designed and have a
better processor than the MAC-IIgrin!. This pickiness I suspect
is part of the reason it takes to long for the clock to start
running.

... If a preselector isn't enough, the next
step is to add an attenuator -- I have to use one between my TV and its
antenna, in fact. You should consider the possibility that the 10 MHz
WWV signal itself is overloading the receiver, in which case an
attenuator is necessary, and the last thing you'd want to do is use a
better antenna. A directional antenna can be used to reduce the strength
of interfering signals if they're coming from directions different than
WWV. But making an antenna which has good rejection in the right
directions can be something of a project.

I do a lot of reading in comp.dsp (sometimes it's fun just watching
the phrases fly back and forth grin!), and one common topic there
is the difference between "noise" and "signal". For me, "signal" is
"what I want", "noise" is "everything else", and the fun(?) part is
figuring out how to get as much of the former as I can while
downplaying or being able to ignore the effects of the latter. My
next step is to add a "line out" jack to the MAC-II so I can capture
long stretches of the signal to disk; when reception goes bad again
I'll be able to use Scilab or Matlab or something to play "Beat the
Heathkit!" with my own algorithms.

And if I get tired of that, I can unsolder the 87C52 and wire in one
of Atmel's $20 Butterfly boards in its place, adding an LCD and my
own algorithms. And _then_ I can... and _then_ I can... grin!

Anyway, "It's feeling _much_ better now." grin!


Frank
--
The first Zen master in Japan to write extensively on good and
evil was Dogen Zenji... Dogen was one of the most adamant of
those who rejected the widespread use of Buddhism for social,
political, and material power; and he was driven out of the
capital area for his trouble.
-- Thomas Cleary / The Japanese Art of War
--
Frank McKenney, McKenney Associates
Richmond, Virginia / (804) 320-4887
Munged E-mail: frank uscore mckenney ayut minds pring dawt cahm (y'all)

Frnak McKenney wrote:

Ah. So even if it starts out in vertically polarized in Fort
Collins 'way out thataway (he says, gesturing faintly west-ish)
WWV's signal might be polarized north-north-west by the time it gets
ro Richmond.

Not exactly. The wave will still be nearly planar, that is, the
orientation of the E field will be in a plane which is perpendicular to
a line between you and the effective point in the ionosphere where the
wave is coming from. But the E field can be rotated in any direction
within that plane. So you want your antenna to have substantial gain in
the direction of Fort Collins and at the elevation angle of the arriving
signal (the latter will vary somewhat). But the polarization is a crap
shoot.


Hm. Wonder if anyone has built an antenna whose polarization shifts
to "best match" the incoming signal? (No, not _this_ weekend!
grin!)

Sure, many. Polarization diversity is an old idea. In a previous life I
worked on a phased array radar (cf.
http://www.globalsecurity.org/space/...an-fps-85.htm). The
transmitters have only horizontal dipole antennas so they transmit only
a horizontally polarized signal. But each of the 4660 receivers has two
dipole antennas, one vertical and one horizontal. This gives the
receiver information about whether an object is tumbling or rotating,
for example, by the way the polarization is shifted by the reflection.
Amateurs would have to use polarization diversity at both ends of a
contact, since there's no way to predict which polarization would be
best at a given moment for transmitting to a fixed polarization
receiving antenna.


A minor update: It seems that I was _mis_tuning my antenna,
adjusting it for the strongest signal (highest stack of LEDs lit).
Over the past two days either I've finally tuned it _correctly_ or
I've done that _and_ the signal has improved. Whatever the
cause(s), I can now -- at times, in fact for an hour at a time --
hear the tocks fairly clearly and even understand the voice. (Who
knew the announcer's phrase for UTC "Coordinated Universal Time"?).

How good? Well, I've unplugged the clock to reset it and it has
then received an "acceptable" WWV signal (it started showing digits)
eight times in the past two days. It might have been more times,
but I don't watch it constantly, and I've noticed that twiddling the
tuning knob tends to make sync-ing a little harder. ("Ack! It's
fading! See if I can tune the antenna _just_ a little better!"
grin!)

Be cautious in generalizing about your accomplishments. Day-to-day
propagation differences can be extreme. Unless you can do an immediate
A-B comparison or take many, many measurements over a very long period
of time, there's no way to distinguish between antenna and propagation
changes.

. . .

I do a lot of reading in comp.dsp (sometimes it's fun just watching
the phrases fly back and forth grin!), and one common topic there
is the difference between "noise" and "signal". For me, "signal" is
"what I want", "noise" is "everything else", and the fun(?) part is
figuring out how to get as much of the former as I can while
downplaying or being able to ignore the effects of the latter. My
next step is to add a "line out" jack to the MAC-II so I can capture
long stretches of the signal to disk; when reception goes bad again
I'll be able to use Scilab or Matlab or something to play "Beat the
Heathkit!" with my own algorithms.

The whole objective to receiving system design is to maximize the
signal/noise ratio, where "noise" is "everything you don't want". Making
both larger by the same amount accomplishes nothing you can't do with a
simple amplifier.

. . .

Roy Lewallen, W7EL

On Sun, 14 Oct 2007 17:13:57 -0700, Roy Lewallen wrote:
Frnak McKenney wrote:

Ah. So even if it starts out in vertically polarized in Fort
Collins 'way out thataway (he says, gesturing faintly west-ish)
WWV's signal might be polarized north-north-west by the time it gets
ro Richmond.

Not exactly. The wave will still be nearly planar, that is, the
orientation of the E field will be in a plane which is perpendicular to
a line between you and the effective point in the ionosphere where the
wave is coming from. But the E field can be rotated in any direction
within that plane. So you want your antenna to have substantial gain in
the direction of Fort Collins and at the elevation angle of the arriving
signal (the latter will vary somewhat). But the polarization is a crap
shoot.

So... I'd need a really crappy antenna? I think I have one around
here... grin!

Seriously, thanks for the description.

Hm. Wonder if anyone has built an antenna whose polarization shifts
to "best match" the incoming signal? (No, not _this_ weekend!
grin!)

Sure, many. Polarization diversity is an old idea. In a previous life I
worked on a phased array radar (cf.
http://www.globalsecurity.org/space/...an-fps-85.htm). The
transmitters have only horizontal dipole antennas so they transmit only
a horizontally polarized signal. But each of the 4660 receivers has two
dipole antennas, one vertical and one horizontal. This gives the
receiver information about whether an object is tumbling or rotating,
for example, by the way the polarization is shifted by the reflection.

Sounds like a really neat setup... on the other hand, it may be a
bit much for my poor MAC-II clock. Grin!

--snip premature self-back-patting--
How good? Well, I've unplugged the clock to reset it and it has
then received an "acceptable" WWV signal (it started showing digits)
eight times in the past two days.
--snip--

Be cautious in generalizing about your accomplishments. Day-to-day
propagation differences can be extreme. Unless you can do an immediate
A-B comparison or take many, many measurements over a very long period
of time, there's no way to distinguish between antenna and propagation
changes.

Um. I just noticed.

Yesterday I powered the clock off and added a "line out" jack so I
could record the received audio. I got distracted here and there,
and when I put it all back together I couldn't get WWV to save my
life. I finally ripped out my wiring, assuming I'd inadvertently run
a wore too close to the RF stuff... but even _that_ didn't help.
I'm now concluding that I reacted too rapidly, that the WWV signal
had simply faded into the background noise.

Seems to be true today as well. I re-added my wiring, and the
signal was unchanged (still rotten: bits and pieces of WWV tones
fading and returning a random-appearing basis). I can now record
long segments of bits of WWV... plus much louder bits of other
shortwave activity and assorted noise sources.

Ah, well. It'll be back some day. grin!

I do a lot of reading in comp.dsp (sometimes it's fun just watching
the phrases fly back and forth grin!), and one common topic there
is the difference between "noise" and "signal". For me, "signal" is
"what I want", "noise" is "everything else", and the fun(?) part is
figuring out how to get as much of the former as I can while
downplaying or being able to ignore the effects of the latter.
--snip--
The whole objective to receiving system design is to maximize the
signal/noise ratio, where "noise" is "everything you don't want". Making
both larger by the same amount accomplishes nothing you can't do with a
simple amplifier.

Yup.

Heath's algorithm, or at least my interpretation of it based on its
behavior, is to require clear reception -- from start to end -- of
complete TOD "frames", and to only statr the display running when
they're reallyREALLYsure they're locked in.

I have a feeling that one could do a more "statistical" approach and
get better results on poor signals. For example, it appears that
the MAC-II requires that, to be acceptable, a BCD TOD "bit" has to
have its start and end within certain time boundaries. On the other
hand, one could capture whatever bits of 100Hz tone were around and
attempt, over time, to fit them into a pattern and see if it matched
a valid WWV frame. You'd have to take into account that the
contentsof the frame (the TOD) would be changing during your
accumulation, but I think it makes more sense to strip and squeeze
every useful bit of information one can get out of what one _does_
receive rather than waiting for life (or propagation) to be nearly
perfect.

But that's for _next_ month. grin!


Frank
--
"We are taught you must blame your father, your sisters, your
brothers, the school, the teachers -- you can blame anyone but
never blame yourself. It's never your fault. But it's always
your fault, because if you wanted to change, you're the one
who has got to change. It's as simple as that, isn't it?"
--Katherine Hepburn
--
Frank McKenney, McKenney Associates
Richmond, Virginia / (804) 320-4887
Munged E-mail: frank uscore mckenney ayut minds pring dawt cahm (y'all)

Frnak McKenney wrote:


Hm. Wonder if anyone has built an antenna whose polarization shifts
to "best match" the incoming signal? (No, not _this_ weekend!
grin!)


Yes, such things have been built. There are some French researchers who
built an adaptive combiner that combined multiple polarizations, and
also did the processing to allow using both the ordinary and
extraordinary ray, and substantially improved link reliability on 1000km
skywave paths.



A minor update: It seems that I was _mis_tuning my antenna,
adjusting it for the strongest signal (highest stack of LEDs lit).
Over the past two days either I've finally tuned it _correctly_ or
I've done that _and_ the signal has improved. Whatever the
cause(s), I can now -- at times, in fact for an hour at a time --
hear the tocks fairly clearly and even understand the voice. (Who
knew the announcer's phrase for UTC "Coordinated Universal Time"?).

UTC is not an acronym. It's a madeup identifier that matches neither
the English (Coordinated Universal Time) or the French (T U C.. I won't
even attempt to figure out what it is..).

These sorts of international metrology things have all sorts of such
negotiated compromises in them, stemming all the way back to the Prime
Meridian being in Greenwich, but measuring in meters.

On Mon, 15 Oct 2007 09:06:49 -0700, Jim Lux
wrote:

hear the tocks fairly clearly and even understand the voice. (Who
knew the announcer's phrase for UTC "Coordinated Universal Time"?).

UTC is not an acronym. It's a madeup identifier that matches neither
the English (Coordinated Universal Time) or the French (T U C.. I won't
even attempt to figure out what it is..).

Hi All,

In fact, UTC is an acronym (already anticipated by Frnak and
explicitly stated every minute). It is but one of several, this one
being rather genericized (because any longer would force a lot of
talking, and minute passes by pretty quickly). The others would
include: UTC(NIST), UT1; and the academic UT0, and UT2.

The reason for the initials order is that there is an hidden comma.
Universal Time, Coordinated. Wikipedia reports this as an erroneous
expansion, but Wikipedia wasn't there in my Metrology classes (a
couple dozen miles from NBS) where we worked with these NBS standards.
It wasn't there when (1974) I performed the second leap second on my
Cesium Beam Standard which was calibrated through WWVB (taking about
half an hour, part of which was waiting during the roughly 15 minute
intervals between TOCs). My antenna was so far away (on the fantail
of the ship in another "time zone"), that I had to slip the time by
100nS.

Knowing that Arthur only reads his own threads, I won't have to
anticipate his rejection of the following efficiency reports for a
non-gaussian antenna. From NIST (the people who know efficiency)
about their 60KHz antenna system:

"Each antenna is a top loaded monopole consisting of
four 122-m towers arranged in a diamond shape.
A system of cables, often called a capacitance hat or
top hat, is suspended between the four towers.
This top hat is electrically isolated from the towers,
and is electrically connected to a downlead suspended
from the center of the top hat. The downlead serves
as the radiating element.

"Ideally, an efficient antenna system requires a
radiating element that is at least one-quarter wavelength
long. At 60 kHz, this becomes difficult. The wavelength is
5000 m, so a one-quarter wavelength antenna would be
1250 m tall, or about 10 times the height of the WWVB
antenna towers. As a compromise, some of the missing
length was added horizontally to the top hats of this
vertical dipole, and the downlead of each antenna is
terminated at its own helix house under the top hats.
Each helix house contains a large inductor to cancel
the capacitance of the short antenna and a
variometer (variable inductor) to tune the antenna
system.

"Using two transmitters and two antennas allows the
station to be more efficient. As mentioned earlier, the
WWVB antennas are physically much smaller than
one quarter wavelength. As the length of a vertical
radiator becomes shorter compared to wavelength,
the efficiency of the antenna goes down. In other words,
it requires more and more transmitter power to increase
the effective radiated power. The north antenna system
at WWVB has an efficiency of about 50.6%, and the
south antenna has an efficiency of about 57.5%.
However, the combined efficiency of the two antennas
is about 65%. As a result, each transmitter only has to
produce a forward power of about 38 kW for WWVB to
produce its effective radiated power of 50 kW."

73's
Richard Clark, KB7QHC

Richard Clark wrote:


Knowing that Arthur only reads his own threads, I won't have to
anticipate his rejection of the following efficiency reports for a
non-gaussian antenna. From NIST (the people who know efficiency)
about their 60KHz antenna system:

"Each antenna is a top loaded monopole consisting of
four 122-m towers arranged in a diamond shape.
A system of cables, often called a capacitance hat or
top hat, is suspended between the four towers.
This top hat is electrically isolated from the towers,
and is electrically connected to a downlead suspended
from the center of the top hat. The downlead serves
as the radiating element.

"Ideally, an efficient antenna system requires a
radiating element that is at least one-quarter wavelength
long. At 60 kHz, this becomes difficult. The wavelength is
5000 m, so a one-quarter wavelength antenna would be
1250 m tall, or about 10 times the height of the WWVB
antenna towers. As a compromise, some of the missing
length was added horizontally to the top hats of this
vertical dipole, and the downlead of each antenna is
terminated at its own helix house under the top hats.
Each helix house contains a large inductor to cancel
the capacitance of the short antenna and a
variometer (variable inductor) to tune the antenna
system.

"Using two transmitters and two antennas allows the
station to be more efficient. As mentioned earlier, the
WWVB antennas are physically much smaller than
one quarter wavelength. As the length of a vertical
radiator becomes shorter compared to wavelength,
the efficiency of the antenna goes down. In other words,
it requires more and more transmitter power to increase
the effective radiated power. The north antenna system
at WWVB has an efficiency of about 50.6%, and the
south antenna has an efficiency of about 57.5%.
However, the combined efficiency of the two antennas
is about 65%. As a result, each transmitter only has to
produce a forward power of about 38 kW for WWVB to
produce its effective radiated power of 50 kW."

73's
Richard Clark, KB7QHC

The NIST folks could probably increase the efficiency to greater than
90% if they dug a large pit to temporarily store the decaying electrons.
All of those dying electrons lying on the ground tend to discourage the
active electrons from working as hard as they could.

The efficiency could be raised to nearly 100% if the two helices were
wound in opposite directions. That would provide the best shot at
equilibrium.

73,
Gene
W4SZ

On Mon, 15 Oct 2007 19:48:48 GMT, Gene Fuller
wrote:

However, the combined efficiency of the two antennas
is about 65%. As a result, each transmitter only has to
produce a forward power of about 38 kW for WWVB to
produce its effective radiated power of 50 kW."

The NIST folks could probably increase the efficiency to greater than
90% if they dug a large pit to temporarily store the decaying electrons.
All of those dying electrons lying on the ground tend to discourage the
active electrons from working as hard as they could.

The efficiency could be raised to nearly 100% if the two helices were
wound in opposite directions. That would provide the best shot at
equilibrium.

Hi Gene,

You shave points too close. They could achieve 130% efficiency if
they simply tapped into the current return on the inside of the wire.

Arthur's 3dB here and 3dB there, if you use enough wire, then you are
beginning to talk about GAIN!

Also, Fort Collins is a higher altitude than Podunk Illinois, so
impedance is less than 377 Ohms too! High gain, maybe 129% efficient.

***** irony mode off ********

Load resistance seen by the transmitters is roughly 0.85 Ohm
transformed to 50 Ohms.

73's
Richard Clark, KB7QHC

Richard Clark wrote:
On Mon, 15 Oct 2007 09:06:49 -0700, Jim Lux
wrote:


hear the tocks fairly clearly and even understand the voice. (Who
knew the announcer's phrase for UTC "Coordinated Universal Time"?).

UTC is not an acronym. It's a madeup identifier that matches neither
the English (Coordinated Universal Time) or the French (T U C.. I won't
even attempt to figure out what it is..).


Hi All,

In fact, UTC is an acronym (already anticipated by Frnak and
explicitly stated every minute). It is but one of several, this one
being rather genericized (because any longer would force a lot of
talking, and minute passes by pretty quickly). The others would
include: UTC(NIST), UT1; and the academic UT0, and UT2.

Au contraire...
while UT1, UT0, and UT2 are, in fact, acronyms of a sort, primarily
based on astronomical time, this is not the case for UTC..

the coordination has to do with matching up UT and TAI (atomic) time..
all those leap seconds, etc.

As one online source puts it:
The (Bureau Internationale de l'Heure) BIH was charged with the task of
monitoring and maintaining the program and introduced the term Temps
Universel Coordinné or Coordinated Universal Time for the coordinated
time scale in 1964.

BIH is the predecessor of the current BIPM (who seem to have a problem
with the standard kilo losing mass) http://www.bipm.org/


or, for more information:
http://syrte.obspm.fr/journees2004/PDF/Arias2.pdf

which says: The name of Coordinated Universal Time UTC appeared in CCIR
documents in the early 60s.

One might also seek a paper from 1964, by Guinot. (who was a time guy at
the BIH back then)

A paper by Dennis McCarthy at USNO on "Evolution of Time Scales"
mentions in Section 6 that: the term "Coordinated Universal Time" was
introduced in the 1950s to designate a time scale in which the
adjustments to quartz crystal clocks were coordinated among
participating laboratories in the US and UK.


A more recent paper by Guinot says:
"Until 1965, the more or less common scale for emission of signals,
which had received spontaneously the name of Coordinated Universal Time
(UTC), had not been strictly defined."



The reason for the initials order is that there is an hidden comma.
Universal Time, Coordinated.

Funny, thing, though, that if one searches the literature of the time
for that particular sequence of words, it never occurs..

Given that Coordinated Universal Time existed well before UTC, I suspect
that the comma thing is a post hoc creation.


Wikipedia reports this as an erroneous
expansion, but Wikipedia wasn't there in my Metrology classes (a
couple dozen miles from NBS) where we worked with these NBS standards.
It wasn't there when (1974) I performed the second leap second on my
Cesium Beam Standard which was calibrated through WWVB (taking about
half an hour, part of which was waiting during the roughly 15 minute
intervals between TOCs). My antenna was so far away (on the fantail
of the ship in another "time zone"), that I had to slip the time by
100nS.

Jim Lux wrote:
Richard Clark wrote:

The reason for the initials order is that there is an hidden comma.
Universal Time, Coordinated.

Funny, thing, though, that if one searches the literature of the time
for that particular sequence of words, it never occurs..

Given that Coordinated Universal Time existed well before UTC, I suspect
that the comma thing is a post hoc creation.

Not everything is English, folks. UTC is for Universale Temps
Coordinaire. No comma is implied or needed because in French, an
adjective follows the word it modifies, with very few exceptions.

Roy Lewallen, W7EL

Roy Lewallen wrote in
:

Not everything is English, folks. UTC is for Universale Temps
Coordinaire. No comma is implied or needed because in French, an
adjective follows the word it modifies, with very few exceptions.

Then wouldn't it be Temps Universale Coordinaire?

Owen