Antenna for receiving WWV/10MHz: am I asking too much?
 

On Thu, 11 Oct 2007 11:26:03 -0700, K7ITM wrote:
On Oct 11, 5:12 am, Frnak McKenney
wrote:
On Wed, 10 Oct 2007 10:19:49 -0700, Richard Clark wrote:
On Tue, 09 Oct 2007 02:16:37 -0000, Frnak McKenney
wrote:

Am I asking too much?

Hi Frnak,

Judging by the questions and responses, I would have to say "Yes."
--snip--

Gee, all this trouble you're having getting a good signal from WWV on
10MHz makes me wonder, "why??" I mean, why bother? It must be the
challenge! I'm a bit closer to Ft. Collins, but I wouldn't expect
things to be all that much different, and in any event, the same
antenna I've used for them has worked fine for signals from W1AW, for
frequency measuring tests. That antenna is just a short piece of
wire, maybe five feet long, connected to a signal analyzer's input
port. The signal analyzer's input doesn't even have a particularly
good noise figure. But with it, I get a good enough signal from WWV
to easily track the nocturnal/diurnal frequency shifts that happen as
the path length changes. (The analyzer may not have a great RF front
end, but it has a very stable frequency reference...) Similarly, I
have a portable short wave radio that has an awful front end, and with
just a 3 foot whip antenna, it gets WWV 10MHz fine most of the time.
Obviously, there are times of the day when propagation just doesn't do
it, but over the period of one day, and not during a geomagnetic
storm, the signal is usually available.

Hm. Sounds great.

All this makes me wonder if the receiver in your clock is OK. I'd
start by looking at that; or at very least, see if a known-working
radio receiver has as much trouble with the signal as the clock seems
to. Given that the clock has a single frequency receiver, even a
pretty simple receiver design should give decent performance.

The RF section is a one-transistor (J-FET) amplifier followed by a
TDA1072A "Integrated AM receiver" chip. I'm not sure how to go
about comparing that to your equipment.

It's also possible that you have some signal source on nominally 10MHz
nearby, and you hear than instead of WWV. There are soooo many
microprocessors around the average home these days that it's entirely
possible that the source of the trouble is very nearby--but could also
be in a neighbor's house (or car -- or garage -- or ??).

Highly possible, but the noise level "at the speaker" seems to have
fallen off appreciably in the past few days. Also, I think I'm
doing a better job of tuning the antenna; adjusting with no clearly
defined signal is a chicken-and-egg problem, but two days ago I
started hearing a deafening cackle. grin!

If you want an accurate clock and get tired of fooling with WWV-10MHz,
and don't want to use WWVB-60kHz, you might consider using a GPS. As
long as you can manage an antenna with a reasonably clear view of the
sky, you should be able to have a clock reliably set to within less
than a second accuracy practically all the time. Or, if you'd like to
be independent of external references, modify your MAC with an oven
oscillator. Oven stabilized crystal oscillators left on for a long
time will almost always settle out to very low drift rates---one part
in 10^8 over a year shouldn't be difficult, in my experience, and GPS
signals can be used to calibrate it occasionally. One part in 10^8 is
about 1/3 of a second per year.

Yup. GPS would eb the way to go for accuracy... or -- for the
billion-dollar-budget people -- your very own Cesium Clock. grin!


Frank
--
To learn is to change. Learning allows an animal child to
finish the long, slow process of evolution by changing in its
own lifetime. Tiger cubs, eaglets, or babies, nature brings
us all into existence with the ability to learn, and the rest
is up to us. -- Susan McCarthy / Becoming a Tiger
--
Frank McKenney, McKenney Associates
Richmond, Virginia / (804) 320-4887
Munged E-mail: frank uscore mckenney ayut minds pring dawt cahm (y'all)

Antenna for receiving WWV/10MHz: am I asking too much?
 

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

Antenna for receiving WWV/10MHz: am I asking too much?
 

Frnak McKenney wrote:

If I'm following the ARRL handbook correctly, I want the elements
laid out _across_ the incoming wavefront. For Fort Collins to
Richmond, that is, going west to east, that would mean I'd want to
string the wires/elements north-south. Naturally (per Murphy, the
patron saint of Data Processing) my house is oriented E-W. Which
does still, as you point out, leave the possibility of building
something outdoors.

You're following it correctly only if you're using elements which are no
longer than about 5/4 wavelength. The direction of maximum gain isn't
longer perpendicular to the wire if the wire is longer. This is covered
very will in the _Antenna Book_.

Still, my current indoor loop seems to be picking up a nice strong
signal. It was upright when I first started testing, but it wound up
being laid flat at some point in the past few days -- about the time
I discovered that I had been mis-tuining it. Wonder which had more
effect: my changes, or atmospherics? grin!

As I mentioned in my other recent posting, there's no way for you to tell.

Anyway, thank you for your time and suggestions. I did some looking
around on the 'web for introductory material to help me understand
the ARRL Antenna Handbook and stumbled onto these:

Antenna Newcomers and the Language of Antennas
http://www.cebik.com/tales/nc.html

Antennas from the Ground Up
http://www.cebik.com/gup/groundup.html

Some really nice propagation plots. Now, if there were just some
simple way of figuring out which way the antenna is oriented
relative to the plots... "It's an imperfect universe" grin!

You can duplicate the plots for the kinds of simple antennas you're
dealing with, with the free demo version of EZNEC available from
http://eznec.com. In the View Antenna display, select View/Objects, then
check the "2D Display" box. Then you'll see a 2D plot superimposed on
the view of the antenna, to show how the two are related. When viewing a
3D plot, the View Antenna display rotates along with the 3D pattern, so
you can see how they're related if you keep both windows open.

Roy Lewallen, W7EL

Antenna for receiving WWV/10MHz: am I asking too much?
 

Jimmie D wrote:

Normally WWV rxceivers have there antennas tilted at 45 degrees in an
attempt at polarity diversity. Im not sure if the department store clocks do
anything like this. The only one I have ever seen used a loopstic antenna.
The professional grade rx I am familar with that was used to set the time on
a computer used a contuously loaded dipole on an outside mount with 45
degree polarization.

*Chuckle*

Tilting would work fine if an incoming wave couldn't have any
polarization except vertical or horizontal. But it can -- it can be at
any angle. So it doesn't matter how you tilt the antenna, the
probability of the incoming wave's polarization being aligned with it,
at right angles to it, or having any other relationship to it, is the
same as for any other tilt. (For simplicity, I'm ignoring the fact that
the probability of a wave arriving with a particular polarization angle
varies with the elevation angle when ground reflection is involved --
which it virtually always is with HF skip propagation.)

A 45 degree tilt might be useful if you were receiving a line-of-sight
signal which might come from either a horizontally or vertically
polarized antenna. But even then, if the transmitter's antenna was
tilted 45 degrees the other way, you'd be cross polarized and in the
same boat as if one were horizontal and the other vertical.

One solution is a circularly polarized antenna, which responds equally
well to linearly polarized waves at any polarization angle. However,
there are a few problems involved with that. First, it's difficult to
get circular polarization from an antenna when ground reflections are
involved. Second, most of the simpler circularly polarized antennas like
a turnstile are circularly polarized in only one or two directions. For
that antenna, for example, the polarization is elliptical at other
azimuths and elevation angles, and linear to the side. And finally, it
seems to me possible that ionospheric propagation can cause a received
signal to be elliptically polarized even though it's linear when it's
transmitted. I don't know if this is the case, but if it is, it
guarantees that even a circularly polarized antenna would experience
fading from polarization shift. Of course, even if you completely
eliminate fading from polarization shift, you still have to deal with
multipath.

Roy Lewallen, W7EL

Antenna for receiving WWV/10MHz: am I asking too much?
 

On 14 Oct, 19:41, Roy Lewallen wrote:
Jimmie D wrote:

Normally WWV rxceivers have there antennas tilted at 45 degrees in an
attempt at polarity diversity. Im not sure if the department store clocks do
anything like this. The only one I have ever seen used a loopstic antenna.
The professional grade rx I am familar with that was used to set the time on
a computer used a contuously loaded dipole on an outside mount with 45
degree polarization.

*Chuckle*

Tilting would work fine if an incoming wave couldn't have any
polarization except vertical or horizontal. But it can -- it can be at
any angle. So it doesn't matter how you tilt the antenna, the
probability of the incoming wave's polarization being aligned with it,
at right angles to it, or having any other relationship to it, is the
same as for any other tilt. (For simplicity, I'm ignoring the fact that
the probability of a wave arriving with a particular polarization angle
varies with the elevation angle when ground reflection is involved --
which it virtually always is with HF skip propagation.)

A 45 degree tilt might be useful if you were receiving a line-of-sight
signal which might come from either a horizontally or vertically
polarized antenna. But even then, if the transmitter's antenna was
tilted 45 degrees the other way, you'd be cross polarized and in the
same boat as if one were horizontal and the other vertical.

One solution is a circularly polarized antenna, which responds equally
well to linearly polarized waves at any polarization angle.

snip
Doesn't a circular polarized antenna lose 3 db when responding to
linearly polarised waves?
IF that is the case it doesn't "respond equally as well"
As far as 45 degrees goes that is not correct for maximum response,
more likely a 45 +- 11 degrees would supply the most gain.
Kraus refers to this empirical tilt action in his chaptor on helix
antennas
which I now see as the summation of all radiator vectors when
expanding Gauss.
Art

Antenna for receiving WWV/10MHz: am I asking too much?
 

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.

Antenna for receiving WWV/10MHz: am I asking too much?
 

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

Antenna for receiving WWV/10MHz: am I asking too much?
 

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

Antenna for receiving WWV/10MHz: am I asking too much?
 

On Oct 14, 12:34 pm, Frnak McKenney
wrote:
Tim,

Thanks for joining in.







On Sat, 13 Oct 2007 17:27:01 -0700, Tim Shoppa wrote:
Frnak McKenney wrote:
I'm in Richmond, Virginia and I'm trying to noticeably improve my
reception of WWV's 10MHz signal from Fort Collins, Colorado. It all
seemed so simple, two weeks ago: wind some wire, solder a
connector, and Hey...presto! a clean WWV signal. grin!
--snip--

Frank -
I am up in Maryland, not too far from you.

WWV on 10MHz is only usable for about a third or less of the day for
locking an electronic clock. Generally the late afternoons and
evenings are great, early afternoons and mornings are a little more
variable.

Overnight 5MHz works best. During the mid-day 15MHz or when
propogation permits 20MHz rules for WWV. I don't think your Heath has
any frequency diversity capability, right? Well, 10MHz is a pretty
good choice if you only have a choice of one, it is usually coming in
strong in the evenings there. Over wintertime 5MHz gets pretty good at
night.

My current box, the MAC-II, only monitors 10MHz; its predecessor,
the GC-1000 MAC, monitored (IIRC) 5/10/15MHz and chose the
strongest.

You will, especially in the early morning, occasionally hear WWVH on
10MHz or 5MHz or 15MHz. Sometimes I hear both WWV and WWVH at the same
time. You can recognize WWVH by the woman's voice reading the time.

My best antenna for 10MHz WWV is my 40-meter dipole strung between
two trees. Mine mostly points broadside to the NE/SW but if you could
arrange it, it would be slightly preferable to have it broadside to be
sensitive to the W.

A dipole optimized for 10MHz would be even shorter - the formulas
put a half wave dipole at 47 feet long.

Thanks for your signal report and the antenna suggestion. I'll keep
it in mind.

On the other hand, my tuned (and currently horizontal) loop is
suddenly picking up WWV/10MHz remarkably reliably, and I didn't even
have to "sacrifice a goat at midnight"! grin

Has your reception improved lately as well (last few days)?

Don't know about WWV in particular, but this past weekend on the ham
bands there was an obvious uptick in propogation conditions. The MUF
was up enough that I heard several pileups on 15 meters and 40 and 30
Meters were more hopping than usual in mid-day/early evening.

Tim.

Antenna for receiving WWV/10MHz: am I asking too much?
 

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