I'm not at all an expert on propagation. So are you saying that
propagation of 60 kHz signals is via ionospheric skip? E or F layer? I
didn't think the LUF ever got anywhere near 60 kHz at any time.

Roy Lewallen, W7EL

Paul Keinanen wrote:
On Sat, 04 Oct 2003 18:06:23 -0700, Roy Lewallen
wrote:


At 60 kHz, there shouldn't be any difference between daytime and
nighttime propagation. Certainly the ionosphere isn't involved.

Roy Lewallen, W7EL


Don't forget the daytime LF/MF attenuation in the D-layer, by
preventing it from reaching the E-layer, which sets the LUF (Lowest
Usable Frequency). At night, the D-layer disappears, thus, the signal
can reflect from the E or F layer.

At least the 77,5 kHz Maiflingen standard time transmitter in Germany
is usable to about 2000 .. 2500 km from the transmitter during the
night at least in the winter. However, during the summer nights, the D
layer is in constant sunlight all night nearly 1000 km south of the
arctic circle, which may explain the worse conditions during summer
night, but of course the number of lightnings is also higher during
the summer, increasing the band noise.

Paul OH3LWR

Roy Lewallen ) writes:
At 60 kHz, there shouldn't be any difference between daytime and
nighttime propagation. Certainly the ionosphere isn't involved.

Roy Lewallen, W7EL


Roy,

I believe that even at 60 kHz, propagation is within an earth-ionosphere
waveguide, the height of which is controlled by the sun (60 km during
daylight and 90 km during night).

Precise RF phase comparison is easy at these freqs because the phase
stability of the path is excellent during all daylight conditions, but
there is some random variation at night. It is best to avoid making
measurements (of phase) while the path is only partly in daylight because
of the diurnal shifts in phase as the sunrise-sunset terminator passes
over the radio path (due to the changing height of the waveguide).

The U.S. VLF OMEGA navigation system, the old WWVL (now SK) on 20 kHz, MSF
on 60 kHz, and WWVB on 60 kHz all suffer from these effects.

73,
.... Martin VE3OAT

Roy Lewallen ) writes:
At 60 kHz, there shouldn't be any difference between daytime and
nighttime propagation. Certainly the ionosphere isn't involved.

Roy Lewallen, W7EL


Roy,

I believe that even at 60 kHz, propagation is within an earth-ionosphere
waveguide, the height of which is controlled by the sun (60 km during
daylight and 90 km during night).

Precise RF phase comparison is easy at these freqs because the phase
stability of the path is excellent during all daylight conditions, but
there is some random variation at night. It is best to avoid making
measurements (of phase) while the path is only partly in daylight because
of the diurnal shifts in phase as the sunrise-sunset terminator passes
over the radio path (due to the changing height of the waveguide).

The U.S. VLF OMEGA navigation system, the old WWVL (now SK) on 20 kHz, MSF
on 60 kHz, and WWVB on 60 kHz all suffer from these effects.

73,
.... Martin VE3OAT

For those interested in getting full and complete details of WWVB, go to:

http://www.boulder.nist.gov/timefreq/stations/wwvb.htm

That is the home page for the NIST radio stations and there is a link to
NIST's radio coverage every two hours or so during a 24 hour period
using small hemispere map projections of North and South America.

---

What I am personally interested in is a source for the direct conversion
of WWVB field strength from or to Volts per Meter to confirm the 60 KHz
loop antenna constructed a year ago here. I have a particular reason
since there is some shading effects of nearby-to-residence San Gabriel
Mountain range. Reception is fine, I'm just trying to tie others' numbers
of field strength into the equations for a magnetic loop.

Len Anderson
retired (from regular hours) electronic engineer person

For those interested in getting full and complete details of WWVB, go to:

http://www.boulder.nist.gov/timefreq/stations/wwvb.htm

That is the home page for the NIST radio stations and there is a link to
NIST's radio coverage every two hours or so during a 24 hour period
using small hemispere map projections of North and South America.

---

What I am personally interested in is a source for the direct conversion
of WWVB field strength from or to Volts per Meter to confirm the 60 KHz
loop antenna constructed a year ago here. I have a particular reason
since there is some shading effects of nearby-to-residence San Gabriel
Mountain range. Reception is fine, I'm just trying to tie others' numbers
of field strength into the equations for a magnetic loop.

Len Anderson
retired (from regular hours) electronic engineer person

Bill Janssen wrote:
I would suggest using a shielded loop antenna to help with the local
noise problem.
The loop is directional so it could be oriented to reduce at least one
source of noise.

I was planning to use a coil wound on a ferrite bar core to reduce the
overall size of the antenna, but the web does show people successfully using
large 'air core' loops, as you've suggested. I was thinking of shielding
the ferrite bar antenna by placing it in something along the lines of a
copper pipe with the edge slitted, but apparently it might be bet to enclose
the antenna in a U-shaped piece of metal, such that, oh, say, 1/4 of the
broadside of the antenna is still exposed? I'm not sure why this should
matter, though?

---Joel

Bill Janssen wrote:
I would suggest using a shielded loop antenna to help with the local
noise problem.
The loop is directional so it could be oriented to reduce at least one
source of noise.

I was planning to use a coil wound on a ferrite bar core to reduce the
overall size of the antenna, but the web does show people successfully using
large 'air core' loops, as you've suggested. I was thinking of shielding
the ferrite bar antenna by placing it in something along the lines of a
copper pipe with the edge slitted, but apparently it might be bet to enclose
the antenna in a U-shaped piece of metal, such that, oh, say, 1/4 of the
broadside of the antenna is still exposed? I'm not sure why this should
matter, though?

---Joel

Thanks for the link. That picture brought back vivid memories of times
outdoors in the Rockies in some really attention-getting weather. Whoa,
mama, time to be lookin' for some cover!

Roy Lewallen, W7EL

Avery Fineman wrote:
For those interested in getting full and complete details of WWVB, go to:

http://www.boulder.nist.gov/timefreq/stations/wwvb.htm

That is the home page for the NIST radio stations and there is a link to
NIST's radio coverage every two hours or so during a 24 hour period
using small hemispere map projections of North and South America.
. . .

Thanks for the link. That picture brought back vivid memories of times
outdoors in the Rockies in some really attention-getting weather. Whoa,
mama, time to be lookin' for some cover!

Roy Lewallen, W7EL

Avery Fineman wrote:
For those interested in getting full and complete details of WWVB, go to:

http://www.boulder.nist.gov/timefreq/stations/wwvb.htm

That is the home page for the NIST radio stations and there is a link to
NIST's radio coverage every two hours or so during a 24 hour period
using small hemispere map projections of North and South America.
. . .

In article , Roy Lewallen
writes:

Thanks for the link. That picture brought back vivid memories of times
outdoors in the Rockies in some really attention-getting weather. Whoa,
mama, time to be lookin' for some cover!

Roy Lewallen, W7EL

Avery Fineman wrote:
For those interested in getting full and complete details of WWVB, go
to:

http://www.boulder.nist.gov/timefreq/stations/wwvb.htm

I'm sure the photographer for NIST was counting on that attention-getting
weather for the WWVB page's photogenic qualities. :-)

A link on the WWVB page has some typical field strengths given for
various locations in the USA along with a tabulation of daily changes
in that field strength level. There's also a log of outages of WWVB for
those who want to check if they are on when you want them to be.

Almost any Internet search engine will turn up a surprising number of
links to 60 KHz loop antennas built by all sorts of electronic hobbyists.
I did that search a year ago when preparing to build my WWVB loop
receiver and phase-locker for the frequency counter timebase standard.

One of the most innovative in my estimation was the loop built on an
unused bicycle wheel rim (spokes removed). A couple of cuts of a
hacksaw put the gap in the wheel rim to prevent the "shorted turn
effect" from happening. The wheel rim should be a very sturdy former
for winding heavy coil wire around it. A strip of plastic provided
mechanical support for the gap in the wheel. If memory serves, it was
done in San Diego, CA, area and mounted outside under a patio cover.

My own loop is 58 1/2 turns of #14 AWG THHN electrical wire self-
supporting with a mean diameter of 2 feet, 8 inches, then bound with
cheap twine that was well varnished with McCloskey's "Gym-Seal"
floor varnish. The electrostatic shielding was provided by heavy-grade
kitchen aluminum foil (with a gap, of course) that was bound with a
second application of twine, then varnished. Q at resonance is about
44, good enough for about 1.4 KHz BW by itself. With 58 1/2 turns,
inductance is 5.6 to 5.7 milliHenry. Distributed capacity is about 390
pFd, not too bad considering that winding took all but 9 feet of a 500
foot spool (purchased at Home Depot for $14).

The loop is mounted in the attic space above the center room of the
house with half of that room as the workshop. That attic space is
closed off from the rest of the attic by recent roof remodeling so it has
become essentially waterproof now...construction was originally done
to work in direct rain, tested only with liberal garden hose sprinkling
and measuring of characteristics. The loop connections are balanced
above ground with the electrostatic shield at ground potential and two
12 foot RG-59 TV cables are used something like Twinax to a
balanced input FET differential amplifier stage below in the workshop.
Resonating at 60 KHz is done with a sacrificed dual variable capacitor
in the differential FET amplifier. Worked out well and I can't observe any
funny spikes from appliances or other non-WWVB signal things after
the FET stage. 60 KHz signal voltage across the loop at resonance is
estimated at about 90 to 120 microVolts. Location here is northern
Los Angeles in the Verdugo Hills (a mile of hills between here and
Boulder, CO)..

There are two Oregon Scientific radio clocks in the house, a small
one about 4 years old that indicates it has solid automatic updating.
Has a small "loopstick" like gizmo inside as the antenna. A large
one in the office room, very visible from 12 feet, 1 year old, misses
a midnight update about once every two weeks. The small one is
"solid copy" all the time. Don't know what the large one uses for a
loopstick antenna...wife won't let me open it up to look. :-)

Ferrite/powdered-iron core "antennas" used in consumer market
radio clocks seem to work very well. Neither is very directional.
The little radio clock was $20 retail and the big one about $25.
Battery life is over a year, closer to two years. Both have built-
in calendars (leap year is probably derived directly from WWVB
data coding).

Len Anderson
retired (from regular hours) electronic engineer person