source for 60 kHz loopstick antenna

I'm trying to get a radio clock to sync up with WWVB (60 kHz out of
Colorado). In the place that I want to place the clock, I can not get
it to sync, even at night when the signal is stronger.

Inside the clock is a small ferrite-core loopstick antenna. I figured
out which way the gain pattern pointed on the thing (i.e. not along
the axis of the ferrite rod) and tried positioning the clock for
maximum signal, but no luck.

So now I'd like to try a better antenna. I won't have the time to
make one myself, and I'd probably do it badly anyway. It seems that I
should be able to buy an antenna for this fairly cheaply (thank you to
my capitalist exploiter overlords!), but I can't find one. Ideally,
one designed for WWVB's 60 kHz would be great, but I'll settle for
anything really, as long as it claims to have some decent gain at 60
kHz.

This clock is going inside a building, inside two layers of cinder
block / concrete walls, so it's possible that I just won't be able to
get a signal in there no matter what I use. The
external-antenna-and-a-wire-run concept is the next step, but I'd
rather not to that unless I have to. We're moving out of that
facility in a few months so that would be wasted labor.

What are some sources for loopstick antennas?

On another note, in searching this forum, someone said:

An LF loopstick antenna wound on a 1/2 inch diameter rod is *much*
less efficient than a 1-meter square air loop

Assuming I have the space, am I better off trying this with a few big
loops of wire instead of a small ferrite loopstick? What are the
rules of thumb for comparing the two types of loop antennas?

Thanks!

 

Hi Chris,
try to make a rectangular coil, about 1 ft x 1 ft, some 30 turns wound
by a fairly thin magnet wire (#25 to #30). Bring it into resonance at
60 kHz by a capacitor, some 8000 - 10000 pF. Place the coil
vertically, aiming to the transmitter, and place the clock to its
center. You do not need any mods of the clock. The signal should be
significantly stronger.

BR from Ivan

 

To design small, VLF to HF, multi-turn loop antennas, download program
RJELOOP3 in a few seconds and run immediately.

Sides of square, number of turns, spacing between turns, value of tuning
capacitor, and other data.

 

Where are you? I'm in Illinois and just got one of the clocks. I know it
helps you not not a bit for me to say mine sync'ed up quickly, but everybody
says that kinda' stuff -)..

Don't think there is anything to buy... Make is the only way.

The instructions for mine say that it only listens at certain times and can
take a few _DAYS_ to sync up. That seems strange to me...oh well.

Ivan's passive loop is a VERY good idea - easy.

I don't think cinder block walls will matter.

Search for "lowfer". I wanted to actually hear WWVB and do a little SWLing
for NDBs (300-500KHz) w/ my new IC 706 and did some snooping. A good loop
takes a little bit of work.

 

All you will hear is nothing, unless your detector and audio amp goes
down to DC. The modulation rate is one bit per second, by reducing the
carrier level by 10 dB. There is no audio modulation, because the signal
is also a frequency standard. The only way you would hear it would be to
mix a signal to beat against WWVB to produce a heterodyne in the radio's
pass band.

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Take a look at this little cutie! ;-)
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Michael A. Terrell
Central Florida

 

I hear it fine with several different receivers provided I use either CW
or SSB. But! I CANNOT hear it on my IC-706; it does not seem to come
alive until somewhere between 200 and 300kHz.

Dave

 

Try using a HP312 series Frequency Selective Voltmeter for the
receiver.

Build a 60 KHz tuned loop and look at it with a scope. You can see
the modulation, because it is so slow. It is a CW signal with a 10 dB
gain reduction modulation with a maximum level change of twice per
second. (Normal and -10 dB) I built a three foot square copper loop with
an insulator where it was mounted on a cast aluminum electrical box, and
wound 20 turns of wire inside the 3/4" copper pipe after it was soldered
together. I used an op amp to give some gain,. and I could watch the
modulation. The big problem was a neighbor about a half mile away left a
TV set on 24/7 and the horizontal oscillator drifted after the station
went off, and the harmonics would drift right through 60 KHz. I wanted
to use it for a frequency standard, but I couldn't do it there. I will
try it again, some day, now that I have a couple miles of woods between
me and Colorado. I have enough gain to get around 12V P-P at the power
inserter. I used 75 ohm cable and "F" fittings because they were handy,
but I would use Mini Circuits MMICs and 50 Ohm cable if I built another
outdoor 60 KHz antenna.

--
We now return you to our normally scheduled programming.

Take a look at this little cutie! ;-)
http://home.earthlink.net/~mike.terrell/photos.html

Michael A. Terrell
Central Florida

 

I have no problem receiving it on a number of different Ham and General
Coverage receivers using random wires or simple vertical whips. I also
hear it well with an active antenna. I have not noticed any real QRM
problems on 60kHz although there are some really strong noise sources at
other frequencies nearby.

Dave
45N 75W

 

Look at the design of the front end. If it is capacitor coupled, the
capacitive reactance is so high that it blocks anything below 200 KHz.
In this case you can add another cap in parallel to improve the lower
frequencies. Multiply the original by 100 or higher, and add it in
parallel to reduce the capacitive reactance, and the attenuation. I
built a broadband DC block for my bench at Microdyne that had five caps
in parallel. It was flat to less that a half dB from 50 KHz to 450 MHz,
and had a VSWR of less than 1.05 across the entire range. It was built
to maintain a 50 ohm impedance end to end.

If it has a transformer, the losses are too high at low frequencies. In
that case I would build a low pass filter and pre amp, and couple it to
the input of the mixer to see how it performs. You would have to shut it
off to use other bands, though.

They only signals I saw were WWVB, and that damned TV's harmonics
drifting through 60 KHz after the station went off the air. The guy was
only there a couple days a month, and left the TV on to make people
think he was home.

--
We now return you to our normally scheduled programming.


Michael A. Terrell
Central Florida

 

Now, just so I understand you correctly, you're saying I don't
actually connect this loop antenna to the clock? I just place the
clock in the center of it, and the loop antenna (I guess) induces a
stronger signal in the clock's internal antenna? Wow, I'd love that.
As for the loop ends, I just connect them together across the cap?

And when you say "vertically, aiming to the transmitter", you mean
that the plane of the loop intersects with the transmitting station,
right? That is, I don't point the *face* of the loop at the
transmitter, I point the edge towards it. Right?


So, anyway, I'm making an antenna. Alright I downloaded and
played with Reg's program and have a configuration that might work
well.

Can I stack wire turns, and if not, why not? It seems that all the
designs have the wire turns lined up next to each other like:

*****

and never

*****
*****
*****

Is there something about keeping each loop *exactly* the same
circumferential length (not even 0.2% difference) that dramatically
affects loop antenna performance? Or some other affect?

I'd like to fill a 5mm x 5mm cross section with wire turns, which
means stacking them.

 

You got it.

"Towards" is a relative direction. You may have to experiment.

Hi Chris,

The ultimate explanation is that if you read the instructions
carefully, you may find they state to try on one wall, or move to
another and try again (pretty much the same advice as that above, less
all the wire and capacitors).

The "synchronization" does not always happen all at once (again, this
is undoubtedly discussed in the instructions - or used to be). You
may spend up to a week discovering the sweet spot where the receiver
responds. We have fielded many such questions as yours in the past,
and I cannot recall anyone coming back after having given up (and I
don't recall one needing an external antenna).

73's
Richard Clark, KB7QHC

 

Oh, I'm sure lots of folks ask questions here about these clocks

Believe me, I tried and I was very patient. I tried the clock set up
in five different locations, which included several orthogonal
directions, and I left it in each position for at least 24 hours, and
probably a lot longer. I spent a month on this and I'm not
exaggerating. It was months ago (I *did* give up and my memory is
fuzzy but I know I left it up at least overnight in each position, and
for a week or more in some locations (i.e. on the bench, pointing in
different directions). I never got a sync indoors.

It's just that now I'm trying again, after having given up. Thanks
for your help and I'll try the surrounding-loop solution. Makes me
wish I'd taken that antenna design course in EE school.

 

You, must have some phenomenal hearing......60KHz!!

 

(60 kHz out of Colorado). ...

From experience there are also differences in the performance
of WWVB clock receivers of the same brand and model
from opening the box and later from differences in aging.

Several years ago I ordered a wristwatch and two travel clocks
from one of then and still prominent "atomic" clock outfits.
One of the travel clocks locked up soon (overnight? - brain cells
fade) and the second shortly afterwards. The wristwatch
just would not lock up - very small antenna, so I wasn't
surprised that it would take longer. I tried leaving
it overnight in parts of the away from PC, TV, radio, ...
and orienting it in various ways to point it to Colorado.
After about two weeks, when I had given up and was ready
and call the company, I went on a trip from northern NJ
to California. Somewhere, sometime during the trip
it locked up. Then after returning home... nothing.
Making a very long story short, the company _finally_
sent me a replacement wristwatch. The new one
locked up nearly every night for the next 2 years
and then, after any guarantee was gone, it quit.
It still runs, just has long since drifted off time.
Nothing since in the last 3 years, despite the deal
of trying to find a 60-kHz quiet place, reorienting it...

In the meantime, the travel clocks were doing fine,
no matter where they were left or what part of the
country I was in. Then about 2 years ago,
one of them quit. Again - try finding that sweet, magic spot,
leaving it side by side with its brother, oriented
in the same direction. Always the same result -
one fine, one deaf.

I have thought about building a loop antenna
like as has been disussed here to see if I could
get at least the deaf travel clock locking.
Tek makes tunable AM Loop antennas where the AM radio
sits next to the loop and they do work
out here in rural New Jersey.
This discussion may yet spur me
to physical wire and solder,
not just typing, action.

Somewhere I did have the URL of web page
where a fellow built a shielded loop
with an amplifier and all. The passive design,
using Reg's program as a start, is simpler.

I have several of the Sam's Club US$23 atomic wall clocks
that lock up just fine, mounted on walls facing
every which way. The outside temperature reading
433MHz receiver seems to be a flaky, marginal design,
but that's a different story.

Cheers, 73

Ron McConnell



N 40º 46' 57.9" W 74º 41' 21.9"

FN20ps77GV75 per w2iol
or FN20ps77GU46 per K2RIW

http://home.earthlink.net/~rcmcc

 

Hi Chris,

Some years ago in my Cal Lab, the antenna that I used to receive WWVL
was a 16 foot whip. I had it connected to a specialized receiver that
separated out the Naval Observatory's TOC which was a specifically
shaped pulse that occurred every 17 minutes. I used this to
synchronize my Atomic Clock to within 100nS of UTC. It was never a
simple feat, and missing that pulse meant a delay of at least 17
minutes (which was about how long the entire process took).

One question that I have failed to ask the various posters that came
here was "how do you know it hasn't synchronized?" I can imagine
there being a gross error of seconds if not minutes (which may
contribute their/your problem), but under one second variation is
difficult to confirm.

73's
Richard Clark, KB7QHC

 

I built a Sheilded, amplified loop for my tests, and got a decent
signal a few miles north of Orlando, years before they built the new
towers, and transmitter.

As far as the oudoor thermometer, Some cordless phones on the same
band search for an open frequency, and wipe out the sync between the
sensor and the clock. I need a cordless phone, more than the outdoor
temperature, so I don't worry about it.

 

Steve and group:

I tuned my IC706 down there, and apparently the front end filters block
anything that low. My Kenwood R-5000 hears the signal fine with a 100'
random wire. The radio I would really like to try, the RCA AR-88LF, only
goes down to 74 KHz, and I sold the old RAK? RAL? Navy monster which covers
that range, so I have to believe the R-5000 on this one. The signal is a
little weak mid-day, but strong the remainder of the time.

I bought one of the cheap "atomic" wristwatches last month, and have been
experimenting with orientation for sync. It has an indicator which shows if
it has locked up in the last 24 hours, and the manual says it tries at 3 AM
in whatever time zone it is set to. The wall clocks also have a lock
indicator, and their manual says they try several times in the wee hours if
the first try doesn't result in synchronization. But BEWARE, I have now
observed two different instances, once each with two different clocks, that
while indicating that resynchronization had occurred the previous evening,
the clock indicated the time which was exactly 1 minute off, apparently due
to a thunderstorm during the night.

The orientation where the wristwatch synchronizes reliably is face down,
BTW.

 

[I asked this a couple days ago but it was at the tail end of a longer
message so maybe that's why nobody replied.]

Can I stack wire turns, and if not, why not? It seems that all the
designs have the wire turns lined up next to each other like:

*****

and never

*****
*****
*****

Is there something about keeping each loop *exactly* the same
circumferential length (not even 0.2% difference) that dramatically
affects loop antenna performance? Or some other affect?

I'd like to fill a 5mm x 5mm cross section around the perimeter of the
clock with wire turns, which means stacking them.

 

Chris:

I thought someone else would answer, but here it is: For highest Q you want
the minimum capacitance between start and end, so what you suggest will
work, but try to actually make the layers carefully so the outside layers
don't collapse down to the first.

--
Crazy George
Remove N O and S P A M imbedded in return address

 

My cordless phones work on 2.4GHz and the remote thermometers
are on 433MHz - a frequency which is shared among many types
of gadgets.

I should add that there seemed to have been a redesign
of the Sam's Club clock about a year ago. The remote
temperature receiver seems better in new ones.
I have 3 different brands of atomic-clocks-with-remote-thermometers
working from one remote Sam's Club remote thermometer transmitter.

Back to ham antennas...

Cheers, 73

Ron McConnell



N 40º 46' 57.9" W 74º 41' 21.9"

FN20ps77GV75 per w2iol
FN20ps77GU46 per K2RIW

Magnetic declination 13ºW in early 2004

http://home.earthlink.net/~rcmcc