In article , "Victor Lick"
writes:

Thanks for the numbers, Gregg. I managed to find the program as a ZIP file
all over the Internet but everyone I downloaded wouldn't install.

The antenna you calculated is big, way too big to go in the attic. It was a
cool idea though. Imagine giving people of a tour of my house. "...And up
here we have the WWVB reradiating magnetic loop antenna with a resonant
frequency of 60 KHz and a bandwidth of 56.2 Hz." I can hear them now,
"Geez, Vic, you are a major geek."

Anyway, a 2M wide antenna is a bit big so I need to find another way.
Active antennas won't do either. One clock sits on my desk in my office and
the other one hangs on the wall. Antennas on those will have a very low
wife acceptance factor.

Can I build a repeater? The receiving antenna in these clocks is small.
Maybe a small low power transimitter with the same size antenna? Can I buy
a repeater? Can I buy a transmitter?

Some suggestions -

A two-meter loop antenna isn't needed. You could try one the
size that I made to receive WWVB in southern California from
Fort Collins. That one is 58 1/2 turns of #14 solid electrical wire
wound over a wooden former to a maximum diameter of 33 inches
(83.8 cm). That size was dictated by a trap door to the small
attic in my house. An electrostatic shield made from aluminum
foil went over that, the whole bound together by jute twine which
was varnished several times to hold it together. A single piece
of 1" diameter PVC plumbing pipe provides support for hanging
from a beam and maintain circularity.

Measured loop inductance is about 5.7 mHy so the 60 KHz
resonating capacity should be about 1230 pFd. But, with
high distributed capacity (measured by two-frequency method)
of about 395 pFd, the required parallel capacity would be
about 840 pFd. Q, measured as delta-f between -3 db
points around resonance is about 44. That results in a
bandwidth of 1.3 KHz but that can be narrowed by tuned
amplifiers.

Note: Those are actual measurements, not textbook data.
Ordinary THHN type insulated solid electrical wire was used
to reduce cost (in a 500 foot roll that is cheaper than buying
enameled solid magnet wire).

Signal strength in volts is proportional to the number of turns
in the loop. At this location, roughly a kilomile from Fort Collins,
the induced voltage was about 400 uV. That is less than WWVB
reports of higher field levels at San Diego, a slight increase in
distance from Colorado. My location is hampered, perhaps, by
a mile-plus of 100-foot higher hills in the direction of WWVB.
Two manufactured radio clocks have been working just fine here
for four years. My attic is about at the same height as my
uphill neighbor's ground level.

I've got a differential input first-stage amplifier, J310 FETs as
source followers into an MC1350P differential video amplifier.
The loop connections are brought in by RG-59 TV cable with
about 210 pFd per cable. A two-gang variable at the WWVB
receiver tunes for peak. Differential input helps reduce some
common-mode noise pickup (such as from "high efficiency"
switcher power supply lamps).

My use is just to extract the 60 KHz WWVB carrier. That is
done by additional MC1350P stages, that IC effectively working
as a limiter at high input levels. Tuned amplifiers without
limiting will work fine to preserve the two-level AM time code.

It is very difficult to arrange a 60 KHz "repeater" without inducing
feedback. I would suggest using one or two lengths of cheap
75 Ohm TV cable from an attic location to the basement level.
Normal 20.5 pFd per foot RG-59 will hold fairly stable despite
temperature variations. A long length of coax, even 500 feet,
wouldn't matter much relative to the long wavelength of 60 KHz.
Two lengths into a differential input amplifier to reduce stray
pickup from appliances and lamps over a long run.

A wired amplified 60 KHz signal can be coupled inductively to
a radio clock with a turn or two (perhaps) around the case or
even capacitively. That would depend on the internals of the
radio clocks.

Trying to make an on-frequency wireless repeater is a setup for
feedback and oscillation unless there's lots of space between
pickup antenna and the repeater transmit antenna. Not
recommended but it might work if the pickup is in the attic and
repeater transmitter is in the basement with low power output.

There's no such thing as a passive amplifier. One might narrow
the effective beamwidth of an internal radio clock loopstick with
an external loopstick but, in all probability, just orienting the radio
clock itself would help.



retired (from regular hours) electronic engineer person