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)