60Khz transmitter/repeater
 

Hi folks,

I have several "radio controlled" clocks in the house and all but one won't
receive WWVB tranismissions. They work OK but they are below ground. I was
wondering if I can buy a repeater, build a repeater, or build a transmitter.
I'm thinking I could put a repeater where the signal is always strong and
rebroadcast the signal a little stronger so that the entire house is
covered.

Another thought I had was a transmitter. All the PC's in my house use
Internet time servers. I can easily build an interface to create the WWVB
time code from PC time. If I had a transmitter, I could broadcast
throughout the house.

Can anyone help? By the way, I've been working in electronics since the
mid-70's but my knowledge of RF is limited to tuning the radio in my car -
and that stuff is pre-programmed!

Thanks in advance.

Vic

Hey, something I can answer intelligently! :-)

In your attic, make a resonant loop of wire as big as possible (think
magnetic loop design without the feed coupler - lotsa programs out there
to design one). That will enhance the field throughout your house.

I've tested and used them for AM radio and cellular phones with success.

You'll need a radio receiver in your basement (or wherever "undergound"
is in your home and someone to confirm peak strength as you tune. FRS
talkies come in handy for this ;-)

--
Gregg "t3h g33k"
http://geek.scorpiorising.ca
*Ratings are for transistors, tubes have guidelines*

Thanks for the info, Gregg. In my original post I indicated that RF
knowledge is very limited (FM does not mean frequency modulation to me).
Your response was intelligent - my understanding is not.

I gather I can build a loop of wire that resonates at 60KHz, put it in my
attic, and it will reradiate the signal. Does that sound right? Won't it
have to be big - the wavelength at 60KHz is 5000 meters!

I did do a search on the Internet and found a lot of stuff about magnetic
loop design but most of it appears to be connected to transmitters. Do you
have good links I can review?

Thanks again for the reply!

Vic

Behold, Victor Lick scribed on tube chassis:

Thanks for the info, Gregg. In my original post I indicated that RF
knowledge is very limited (FM does not mean frequency modulation to me).
Your response was intelligent - my understanding is not.

Oh, OK ;-)

I gather I can build a loop of wire that resonates at 60KHz, put it in
my attic, and it will reradiate the signal. Does that sound right?
Won't it have to be big - the wavelength at 60KHz is 5000 meters!

It will create a resonant field and concentrate the 60KHz energy in your
house.

You can use a multi-turn loop. Square, 4-turns, maybe 2M per side and an
AM tuning capacitor.

I did do a search on the Internet and found a lot of stuff about
magnetic loop design but most of it appears to be connected to
transmitters. Do you have good links I can review?

The program you want is called MLOOP31.EXE (exact filename). That will
help you find it easier. All you need to know is the physical dimensions
of the antenna, like 2M/side, 1cm spacing, etc., physical dimensions of
the wire (alarm wire is 1mm in diameter for example) and so on. Just
ignore the dimensions for the feedloop.

Tell ya what - when I reboot into Windows, I'll use my copy to make some
calculations of some dimensions for you :-)

But you might want a copy for yourself, 'cause it's a real neat proggie!

Come to think of it, it's redistributable freeware - I can post it on
ABSE (alt.binaries.schematics.electronic) tonight.

--
Gregg "t3h g33k"
http://geek.scorpiorising.ca
*Ratings are for transistors, tubes have guidelines*

Some calcs for you Victor,

4-turn loop, 2M each side, seperated by 1cm. The following tuning
capacitance is required for 60 KHz:

1mm dia. wi 60,180p
1.5 and 2mm dia. wi 65,580p

That's an awful lot and the tuning will be only a few tens of Hz wide.

If you have the capacitors, go for it.

If not, maybe an active antenna for your underground receivers?

BTW - the program is posted to ABSE. It won't go down to 60KHz, but you
can scale 1MHz results accurately.

--
Gregg "t3h g33k"
http://geek.scorpiorising.ca
*Ratings are for transistors, tubes have guidelines*

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?

Thanks for all your help on this,

Vic

Victor Lick wrote:

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?

Thanks for all your help on this,

Vic

For a wall clock, I would try adding a field concentrator antenna all
around the back edge of the clock, to put most of the field that
passes through that area, mostly through the clock's antenna. For a
small table clock, this approach is not so tenable, unless you can
paste it on the under side of the table, and produce the concentration
where you normally sit the clock.
--
John Popelish

Behold, John Popelish scribed on tube chassis:

Victor Lick wrote:

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?

Thanks for all your help on this,

Vic

For a wall clock, I would try adding a field concentrator antenna all
around the back edge of the clock, to put most of the field that passes
through that area, mostly through the clock's antenna.

Oh, yes!

This reminds me of an old PopComm article, where someone re-wound a
ferrite loop antenna and tuned it as a concentrator. They are only 6"
long!

--
Gregg "t3h g33k"
http://geek.scorpiorising.ca
*Ratings are for transistors, tubes have guidelines*

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

I gather I can build a loop of wire that resonates at 60KHz, put it in
my attic, and it will reradiate the signal. Does that sound right?
Won't it have to be big - the wavelength at 60KHz is 5000 meters!

It will create a resonant field and concentrate the 60KHz energy in your
house.

You can use a multi-turn loop. Square, 4-turns, maybe 2M per side and an
AM tuning capacitor.
=============================
Just a construction hint. For a neat multi-turn rx loop you could consider
ribbon cable as used in computing gear .
Some time ago ,at a fleamarket I bought a roll of 100 ft (30.5 metres) of 15
leads wide ribbon cable.

Example : To make a 4 turns loop as above you would need 2*4 equals 8 metres
of 8 lead ribbon cable using end of lead 1 and 8 as ends of the loop , join
ends of lead 2 and 3 , 4 and 5 , 6 and 7.
Although the ribbon leads multi-strand overall diameter is only 0.2 - 0.3 mm
,it should be OK for rx purposes.

Frank GM0CSZ / KN6WH

On Mon, 31 Jan 2005 21:49:21 GMT, "Highland Ham"
wrote:

Example : To make a 4 turns loop as above you would need 2*4 equals 8 metres
of 8 lead ribbon cable using end of lead 1 and 8 as ends of the loop , join
ends of lead 2 and 3 , 4 and 5 , 6 and 7.

Loops made of multi conductor cables in this way tend to have a very
large capacitance between turns and in the worst case the loop will
have a self resonance frequency below the desired frequency band. Even
if the self resonance is above the desired band, the amount of
external tuning capacitance is greatly reduced.

When a wide ribbon cable is available, it can be a good idea to use
only every other lead and let the intermediate leads floating to
reduce the capacitance between turns.

Paul OH3LWR

Example : To make a 4 turns loop as above you would need 2*4 equals 8
metres
of 8 lead ribbon cable using end of lead 1 and 8 as ends of the loop ,
join
ends of lead 2 and 3 , 4 and 5 , 6 and 7.

Loops made of multi conductor cables in this way tend to have a very
large capacitance between turns and in the worst case the loop will
have a self resonance frequency below the desired frequency band. Even
if the self resonance is above the desired band, the amount of
external tuning capacitance is greatly reduced.

When a wide ribbon cable is available, it can be a good idea to use
only every other lead and let the intermediate leads floating to
reduce the capacitance between turns.

Paul OH3LWR
=============================
Paul , Tnx for the above advice ,although for a loop made with flat multi
ribbon to be tuned to 60 kHz , the self-resonance freq will highly likely be
higher than 60 kHz . The ribbon I have is 15 leads wide ,hence for higher
freqs I could leave out every other lead .
Tnx again , this is good education .

Frank GM0CSZ / KN6WH

Beyond 3 or 4 turns on a single-layer coil, the coil's resonant
self-capacitance is not very much related to capacitance between adjacent
turns.

This is because the individual between-turn capacitances are all in series
with each other and the resultant rapidly decreaes.

For a 10 turn coil the end-to-end capacitance due to adjacent turns is only
1/10th of the individual turn-to-turn capacitance.

Coil self-capacitance soon becomes a linear function only of coil diameter
and length of the coil former.

It's rather complicated but the resulting self capacitance is much smaller
and the resonant frequency is higher than what you think it might be just by
considering the individual turn-to-turn capacitances.
----
Reg, G4FGQ

Well, Mr. Anderson, thank you very much for your detailed reply. This all
sounds very interesting but I think it's going to have a low benefit-to-work
ratio, especially with the long project list I already have. I was hoping I
could down to the passive re-radiator store and pick up something that you
would work. Oh well.

Thanks again,

Vic