WWVB Loopstick Antenna & C-Max Receiver
2003 - 2010
| 2.5" rod
K5JHF Clock Kit for the CMMR-6P-60
Better Antenna for the CMMR-6P-60
Video of stock CMMR-6P-60
Table of Cap Value & Impedance
Thermal Time Constant
La Crosse WT-3102 WWVB Clock
I wanted to make a loop antenna for
receiving WWVB based on the Amidon R33-050-0750
Ferrite rod. This uses the type 33 material and is 1/2"
diameter by 7.5" long. After trying a number of different
windings I think the current version may be optimum for WWVB at 60
kHz. It's bank wound using 2 layers of 5x36x44 Litz wire.
The following explanation of "Bank Winding" is for a 4 layer coil.
"Bank Wound" means that you start the winding at the left end,
then make 4 turns then wind backwards for 3 turns then forward for
2 turns and then backward for one turn. Now there are 4
layers of wire all at the left end. This process is repeated
until the length of the rod is covered. The important fact
about this type of winding is that the electrical distance from
any one turn to it's immediate neighboring turn is is just a few
turns. If the coil was wound a layer at a time, then the
electrical distance between turns may be hundreds of turns.
The self capacity of the completed coil depends on both the
capacity between adjacent turns and also the voltage between the
If you look at the equivalent circuit for a single layer coil
where the turns are spaced about one wire diameter it can easily
be seen the the total coil voltage is divided so that 1/N of the
voltage is across each turn-to-turn capacitance. That's to
say the capactance is very closd to the capactance of the first to
the last turn. But if you added a second layer then the two
coil terminals are at the same end and the turn-to-turn
capacitance for the turns adjacent to the two terminals has 100%
of the coil voltage across it. The next turns away from the
terminals has (N-1)/N of the full coil voltage, etc. This
results in a huge self capacity.
There are a number of effects that cause the A.C. resistance of a
wire to be higher than the D.C. resistance.
Litzenhardt wire is made up of a number of independent conductors
that are insulated from each other. There are a large number
ways that the strands can be arranged.
In a straight wire, with no other wires near by, as
the frequency increases the electrons carrying the current
move away from each other and so end up more and more near the
surface of the wire and less and less along the centerline.
Is similar to Skin Effect, but is caused by the
interaction between wires that are near to each other.
The wire I used is made from AWG number 44 wires that are in
bundles of 36 wires and there are 5 of these bundles in the final
wire. If you needed a cable with 180 seperate wires you
could use this Litz wire that way. Since a single
44 wire has a diameter of 0.00198" the total area of the 180
wires is equivalent to a solid wire of diameter 0.02656", or
between AWG 21 and 22.
|The correct term may be
Litzendraht, meaning Litzen (braided) Draht (wire)
Thanks to John Portune W6NBC
The problem is the insulation takes up space that could be used
for copper. The result is that Litz wire typically only
works well below a few MHz. It's interesting that at mains
power frequencies (20, 50 or 60 Hz) the largest size single strand
wire you can buy is determined by skin effect. If a load
requires more square mills of copper area then you need to use
multiple insulated conductors.
MWS - Litz tool -
input the AWG size to get the cross sectional area and it tells
you the available strand count and wire sizes.
The following plots were made using the HP (Agilent) 4395A in the Network Analyzer mode and
using the Z Transform technique where the unknown device is placed
in series with the center conductor.
The problem with this winding is that it's very difficult to bring
it to reasonance because of the difficulty in finding fixed caps
of the exact value you need.
A much better approach is to make the coil on a sliding former so
tuning can be done simply by sliding the former. That's the
way the commercial WWVB antennas are made.
Imaginary Part of Impedance Plot
The marker shows 1.004 k Ohms at 32.960891 kHz. The
network analyzer has already separated the real and
imaginary parts so this is pure inductance.
L = X / (2 * PI * F) = 4.83 mH
Real Part of Impedance Plot
You can see that at 100 Hz the real part of the impedance
is about 1 Ohm. i.e. the DC copper resistance. The
marker shows the resistance has climbed to 29.325 Ohms at
Without making a plot of "Q" vs. frequency and analyzing
the slope it's hard to say what's causing the
resistance. It may be skin effect, proximity effect,
or dielectric losses or some combination of these.
Resonated with Mica caps
Marker shows 94.308 dB at 62.485345 kHz.
Ohms = 10 ^ (dB/20) = 51, 927 Ohms.
The shunt capacitance is given by:
C = 1 / [ L * (2 * PI * F)^2] = 1.34 nF
The HP 4332 LCR meter measured
the caps at 1.35 nF.
The loading capacitance value was chosen so that when the
coil, caps and a small variable cap and the input
capacitance of an amplifier are connected the resonance
point can be brought right on 60.0 kHz.
The Q = XL / R = 51,927 / 32.96 = 1,575
A similar plot of just the coil shows that it's self
resonance frequency is very close to 500 kHz. That's
good in that you don't want to run a high Q coil near it's
self resonant frequency and here we are well away from it.
This appears to be an improved version of the Temic LF time
receiver chips. They specify the resistance at reasonance
[40k to 100k for the CME8000 = (1/Q) * SQRT( L/C) ] of the loop
for best signal to noise. They have an antenna design
to help. The Q should not be between 40 and 150 for the
CME8000 if higher temperature effects may tune the cirucit out of
reasonance. Note that they have a single IC that can be used
with a single loop antenna and by switching caps will tune to LF
time stations at 40, 60 or 77.5 kHz and knows how do decode them.
The above loop with the caps that are installed has a resistance at reasonance
(60 Hz) of about 52 k
The reasonating cap should not be an X7R type since they change
capactance up to 10% during soldering.
The desired loop would be 1.5 mH for WWVB and the cap would be 4.7
nF with a Q of 100.
To get the above coil down to 1.5 mH would require removing a lot
of turns which would reduce it's series resistance increasing the
Q, probably to way over 100. Then either a fixed resistor
can be added to control the Q or the reasonating capactance needs
to be designed to track with temperature.
C-MAX has an app note on the choice of resonating caps. In
order to get surface mount caps they have gone with multilayer
ceramic cape. But that makes for a big problem. If the
wrong type is used there will be large permanent changes in the
capacity because of the soldering operation (maybe measure cap
first then use silver epoxy for attach?). For the loop above
I used a combination of mica caps and a variable cap to tweak the
When the loaded Q is high there can be a problem with temperature
causing the center frequency to shift to the point the received
signal drops. For most commercial applications the Q is
limited to 120.
There is an upper limit on Q imposed by the signal
bandwidth. L.F. time code stations use a modulation that
changes once per second so a bandwidth of say 10 Hz would be
plenty. This implies that at a Q of 6,000 you will start
reducing the modulation.
But the C-max limitation of Q<=120 comes from temperature
In the photos above remember that my
loopstick is 7.5" long and the CME module is only 2.5" long.
It's interesting that both of the ICs on this module were made by
. The 3 station LF
time receiver is the Atmel CME8000 and the micro controller is the
(8051 based) driven by a 11.0592 MHz crystal.
They make a number of different versions of the LF time signal
board and all those that have an on board RS-232 chip, like the
MAX232, can NOT be used in real time because the switching noise
of the RS-232 chip for generating the negative voltage is many 10s
of dB higher than the received LF time signal. The model
shown here was chosen because it has only TTL/CMOS outputs, i.e.
does not have the RS-232 chip on the board.
is the 60 kHz version (they also offer 40 kHz and 77.5 kHz versions)
for WWVB. It's based on the C-MAX CME6005 which is the analog
front end without a CPU.
Digi-Key p/n: 561-1014-ND.
The C-Max data sheet has a table calling this the CME6005 w/o CPU
and that's the way Digi-Key has listed it. But it's really an
evaluation kit for the CME6005 and comes with an attached (and
tuned) 60mm x 10mm loop stick antenna. The C-max bag has a
sticker "Tested Sample". This is important because of the
difficulty in tuning the antenna to reasonance using surface mount
Notice that the wire between the antenna and PCB is twisted.
That is required to minimize interaction between the magnetic field
caused by any digital circuitry and the very low level input signal.
Note there is a through hole type cap on the loop stick and in
addition there are pads on the board for C4, C3 & C7 to
reasonate the antenna. Since those three have no cap installed
it's clear that the thru hole cap attached to the antenna is
resonating it at 60 kHz. A method to do that is described in
the CME6005 data sheet.
The cylindrical package is a 60 kHz series resonant crystal acting
as a filter. It's possible to connect two crystals in parallel
(and two of the three frequencies and this board would then output
the time code for whichever station was within reception
range. But C1 and C2 may need to be different values for
This circuit operates on 1.2 to 5.5 volts aned draws about 100
uA. That means all inputs and outputs are very high impedance.
13 Jan 2009 - have a receiver module powred at 3 V and a DMM
watching the output (1 second per bit should be visable) but so far
the output is between 2.9 and 3 V. Maybe later tonight it will
start working. Looking with a scope shows pulses about 4 us
wide at random times. The outputis mostly at +3 V and the
pulses go to 0 V. Using a GPS receiver to supply a trigger
pulse once per second confirms that the narrow pulses from the
CMMR-6P are not correlated with the time.
4:30 pm it's starting to work. See the scope photo below:
The gaps in the bottom part of the trace correspond
to the time code. But they are not solid.
by 7:23 about the same, dots, not solid at the bottom.
This is connected to TCO and not working very well. Maybe
there was a wiring probllem?
Changed from powr supply to battery operation and added LED and
resistor to monitor.
First connected LED to the TCO output, but that means the LED
is normally on all the time draining the batteries and it
didn't seem to work very well.
Connecting the LED to the logic inverted output TCON works better
and saves the batteries.
This is a very handy gadget in that you can take it to different
places to see how well it works.
Put in the bedroom at night you can see that the data is more solid,
but far from noise free.
Next to put a scope on TCON.
|A couple of wires were
soldered to the board so that other antennas can be
The unit shown at left did not have solid blinking
of the LED but the unit built in Octobeer 2010 does
have solid LED blinking 24/7. See video below.
|2 AA Batteries
|3 AA Batteries
|direct LED connection (1 & 7)
|Resistor & LED (1 & 7)
|PCB (5) ground
|PCB (5) ground
This is a kit to make a clock based on the CMMR-6P-60. Shown below
Graphic displays, both CRT and LCD, emit radiation because of the
scanning and modulation signals. When testing the CMMR-6P-60
using the Rigol scope
receiver gets too close to the screen the data is totally garbled.
|When the scope is close to
the receiver the data is corrupted.
|Moving the receiver away
from the scope solves the problem.
In a real application if the receiver is near electronic
equipment there may be a similar problem.
A Nikon D300s camera when close
also corrupts the data, discovered when making the video below.
My first testing with a LED
directly connected to the CMMR-6P-60 showed noise during the
daytime, but around local midnight the flashing was a solid one
pulse per second. In Oct 2010 with a different CMMR-6P-60
I'm seeing no noise 24/7. There are two differences, now
there's a resistor in series with the LED to limit current (make
the battery last longer) and I'm using three AA cells (make the
battery last longer).
I notice that the K5JHF clock, just below, did not sync up as
soon as it was powered up at 3 pm but did sync around
midnight. It uses two AA batteries and the receiver output
drives a micro controller input pin that's very high
impedance. That seems to say the receiver wants to run
from about 5 VDC and not from two AA batteries.
Note: This clock DOES NOT make the DST/ST switch
automatically, i.e. there's a software bug.
This kit makes use of some surface mount parts but is straight
forward to hand assemble with a soldering iron. But there's
one gotcha. The2x5 header for the LCD is located inside the
2x8 DIP socket for the micorcotroller so you have to install the 2x5
first then the 2x8.
|Kit Assembled Running Without
|The clock comes up in
hh-mm-ss mode and with
CW ID active. The LED
flashes along with the CW.
[Another way is to solder in the 2x5 pin header upside down and then
press the plastic block down to the PCB.]
Also be sure that pin 1 on the LCD matches pin 1 on the kit
PCB. The piezo has seperate "Tic" and "Toc" sounds that are
Now, where did I put the CMMR-6P-60?
Got another CMMR-6P-60 from the maker of this clock kit.
When first powered on around 3 pm local time the clock did not sync,
but did sync around midnight, but ever since it has not displayed
any starting letter when I've checked.
I'll be checking closer to noon to see how it's doing.
|yy mm dd hh mm ss
|19 Feb 2010 about 11:51 (Day
of Year = 50) UTC = 19:50
|10 02 19 05 01 59
|19 Feb 2010 about 12:01
||10 02 19 05 01 59
means that the clock lost lock at 5:02 am this morning, but
no first letter has appeared since so am confused how they
|20 Feb 10 am
|10 02 20 01 01 59
|23 Feb 9:32 am
|10 02 20 01 01 59
menas the clock has NOT synced for a few days. The
time show is 12 seconds slow.
photo of the clock running a little before noon shows no prefix
letter. Note I have assembled the kit so that the setting
buttons are facing the same direction as the LCD face to make it
easy to operate the buttons.
Top button is "Up/Increase/On"
Center button is "Down/Decrease/Off"
Bottom button is Mode,
First Letter of Display
|Loss of detectable signal
|detected a signal
but has not detected a 200ms sync (Un Locked)
|received noise and is
starting the sync detect again
|detected a 200ms Sync and needs a
second sync before it sets the clock
|two consecutive syncs
detected and the clock is set/synced
14 March 2010 DST Problem
|The WWVB wall clock is
displaying the correct time
of 14:34:16, but . . .
The K5JHF clock is displaying 13:34:19, i.e. there's a 1
The Heathkit GC-1000 WWV clock has a similar problem in
that it makes the DST/STD time swtich when the station in
Colorado changes, not in your time zone.
The last sync word is:
yy mm dd hh mm ss
10 03 14 05 03 59,
so it was in sync early this morning and so the problem is
a software bug, not a lack of sync.
25 Oct 2010 - Since the Rigol scope
was being used to investigate the CMMR-6P-60 antenna a quick look
at the K5JHF clock confirmed that the Pon pin was grounded and to
check for digital interference. If the loop is brought close
to the micro controller PCB the data gets garbled. But when
the loop is as far away as the short wires that come with the loop
stick antenna the noise is gone. For most applications
seperating the loop stick from any digital electronics by say 6"
or more might be a good idea if you don't have a scope to check
Better Antenna for the CMMR-6P-60
I have some Russian Ferrite rods on
the way. The eBay ad says:
"Large Balun Ferrite Rods 10x200mm"
They are very similar to the 7.5" rod above, but this time I'll
make provision to tweak the resonant frequency in a simple manner.
After cutting the tape each rod needs to be cleaned of tape
Rods measure: 9.75 mm (0.383") dia x 199..2mm 7.846" long.
Making coil former from 67 # paper. Wrapped a little more
than one turn then glued and tapped. Rod slides easily in
and out of former now. The hope is that it will also slide
on the rod after the coil is wound on it. Note that if
ordinary 20 # copy paper was used the wire tension would lock it
to the rod.
This is about 750 turns of 32 AWG wire. The former works,
i.e. the rod easily slides in and out of the former (O.D. about
Luh = (N*N*R*R)/(9*R + 10*H)
N = 750
R = 0.2205"
H = 6.78"
L = 392 uh = 0.392 mh without the ferrite rod inserted.
relative permeability = 25.62 mh / 0.392 mh = 65.4.
Using the HP 4275A LCR meter
to measure L and Q while pushing the ferrite rod using vernier
calipers gives the following data:
Measured at 40 kHz with 1 ma current in coil.
Note: a Q of 150 is a single count from a Q of 150.
The inductance is very close (R² = 0.9998)
Lmh = -0.0169x4 + 0.3405x3 - 1.8206x2 - 1.742x + 25.705
C(resonance) = 1/[L*(2*PI*f)^2] = 1/[25.0*(2*PI*60E3)^2] =
2.81E-13 = 0.281E-12 = 0.281 pf
R(resonance) = (1/Q) * SQRT( L/C) = (1/150) *
SQRT(25.62E-3/.281E-12) = 2013 Ohms
Shown below are the 750, 60 and 120 turn coils.
The 120 T coil has been adjusted to reasonate at 60 kHz with the
It would work a little better if turns were removed so it was
closer to the center.
This( 750 turns) is way too much inductance. It
should be more like 1.5 mh (see above
First cut would be 1.5 mh/ 65.4 = 22.9 uh.
Luh = (N*N*R*R)/(9*R + 10*H)
L = 22.9
R = 0.2205"
H = since L is proportional to N^2 reducing the inductance
from 25 mh to 22.9 uh requires a change in turns of 33.
Guess N= 750/33 = 23 then
H = 0.0095 * 23 = 0.216"
Now Luh = (23*23*0.2205*0.2205) / (9*0.2205 + 10* 0.216) = 6.2uh
SQRT(22.9 uh / 6.2 uh) = 1.92 times more turns or 44 turns
N = 44 turns
H = 0.42"
Luh=(44*44 * 0.2205*0.2205) / (9*0.2205 + 10* 0.42) = 15.22 uh
SQRT(22.9 uh / 15.22 uh)* 44 = 54 turns
N = 54
H = 0.513"
Luh = 19.9 uh
N = 60
H = 0.570" (former 1" long)
Lwire = 60*PI*0.441 + 12" = about 8 feet
L = 422 uh & Q = 63 with coil at center of core.
L = 20.356 uh with air core (a little lower than the target of
22.9 uh) so the target needs to be higher by about 4 times or
abut twice the number of turns, so:
120 Turns close spaced
H = 1.14" (former about 2.5 " long)
Lwire = about 16 feet
Self resonant frequency with ferrite core is about 2.3
Mhz. i.e. well above 60 kHz.
|HP 4274A LCR Meter
measuring 160 turn Loop antenna.
It looks like a few turns can be removed to improve the Q at 1.5
mh, but the next step will be to sweep the inductance on the HP 4395A
After sliding the former/coil to peak at 60 kHz:
|Loop 120T close spaced
Imaginary no cap
|Something may be wrong
with this plot
|WWVB Loop 120T on Russian
|A 4n7 cap has an
impedance of 564 Ohms at 60 kHz. If the real
resistance of the tank at 60 kHz is 37.3 k Ohms then the
Q is 66 which is about half the Q from the 4274A LCR
meter at 40 kHz.
|WWVB Loop 160T on Russian
|1 Hz RBW
Noise is about -146 dBm
detection method is sample (i.e I&Q true noise, not
Tank circuit connected directly to 50 Ohm input.
When a Galleon 60 x 10 mm 60 kHz resonant loop-stick was
connected to the exact same setup, after 32 averages
there is no signal at 60 kHz so the 200x10 mm Russian
ferrites make better antennas.
I think the antenna performance metric should be G/T, i.e. the
ratio of the Gain to the noise.
C-Max says that too high a Q leads to temperature instability.
The other factor is the impedance at reasonance, i.e. related to
the value of the resonating cap. The cap needs to be
larger than the coil's self capacitance in order to get a high Q
value, so miniumzing the self capacity of the coil seems like a
120 Turns spaced one wire diameter
Maybe try a coil that resonates with the same 4n7 cap but haS
120 spaced turns.
turns over 2.27" spaced apart. aprox 100 turns.
Measured on 4275A at 40 kHz shows 0.952 mH and Q of 92.
Self resonant frequency with ferrite core is about 4.8 MHz.
|Something may be wrong
with this plot
131 Turns Spaced
Loop WWVB 60 kHz
The photo is named as a 125 Turn loop ( Loop125STcaps.jpg)
because the turns had not been counted. It was in
Photoshop that it was determined to be really a 131 Turn
An extension wire was soldered to
the above 120T loop
antenna and about 30 more
turns were wound (to the end of the former. Then it was
measured on the HP 4275A LCR
meter showing about 2.4 mH. Turns were removed until it
measured about 1.5 mH with a Q of 235 at 100 kHz. Then put
onto the HP 4395A
in Z:Trans mode (RF
OUT & A input) with the same 4n7 cap as before and the former
moved until resonance was at 60 kHz. This turns out to be
very difficult at this high a Q so a fine tune can be made be
tuning a little high then winding on a fractional turn. Then
one wire was opened between the loop and the cap to make a series
circuit and that was connected to the 4395A in spectrum analyzer
mode (R input).
This is about the same real impedance as the above close
spaced 120Turn loop. Which is consistent with using
the identical 4n7 resonating capacitor and the same 32 AWG
21 Oct 2010 - When soaked in the freezer (zip lock bag)
overnight and tested next morning the peak was at 62.5
kHz. The cap was out of the bag and quickly came to
room temp. Much better to use the C-Max method of
using shrink tube to hold the cap next to the
ferrite. Have a bunch of caps of different chemistry
on order to see what tempcos are available.
|The same setup as above
("C?" means not calibrated) with the parallel combination
of the loop and cap fed from 50 Ohms and driving a 50 Ohm
load. The Q is about:
Q = Fcenter / (Fhi - Flow) = 65
where Fhi and Flow are down 3 dB from the peak.
But this may not mean much considering the source and load
|The loop and cap are series
connected for this spectrum plot.
Taken at 9:30 am 19 Oct 2010 in my office, i.e. near a
working computer and during the day. The signal is
WWVB 20 dB above the noise!!!
Note the "Smp" means the 4395A is in "Noise" mode, i.e.
instead of peak detecting it's actually measuring power by
squaring the I signal and squaring the Q signal then
adding them and taking the square root
To make the noise easier to see the video bandwidth has be
lowered to 0.1 Hz rather than use averaging.
The improvement may be because of the series LC
connection, the spaced turns covering more of the ferrite
or reducing the self capacitance, or something else?
Oct 22, 2010: Some more of the CMMR-6P-60 WWVB
receivers have been received so that a number of receivers can be
tested in parallel with different loops.
The first test will be to compare the stock receivers to see how
similar they are with the stock loop antennas.
Then replace one of the stock antennas with the 131T antenna and
see what difference it makes on the output at different times of
the day. So far the first stock receiver is producing strong
output all the time.
Video of stock CMMR-6P-60
The CMMR-6P-60 WWVB Receiver is shown for just over one minute, a
full digital data frame and in the background you can hear sharp
ticks that are coming from another WWVB receiver. In another
room is a Self Winding Clock Co. "Western Union" pendulum clock
that can also be heard. The red LED is fed through a 4k7
resistor and the receiver is being powered by three Alkaline AA
batteries (about 4.5 Volts).
There was a problem making this video in that when the Nikon D300s
was close(4" or so) to the
CMMR-6P-60 the receiver quit working. In order to make the
video I used a 2X tele extender so that the camera could be about
a foot from the receiver.
The data format is at:
Recorded 25 Oct 2010 at about 0913 to 0914 Pacific Daylight Time
(1613 to 1614 UTC).
Table of Cap Value & Impedance
* 4.7 nF is the cap that C-Max uses on their antennas.
The above improved WWVB loop has
been tested using a 4n7 cap which has an Xc of 564 Ohms. The
loop is measuring about 37 k Ohms when parallel resonated with
that cap. That means that the Q is about 66. This is
using 32 AWG for the wire. (Wiki: Skin Depth
Terman's formula for a wire diameter
that's 10% higher in resistance when operating at some frequency f
(Hz) compared to operating at DC is:
Dwire = 7.874" /SQRT(f) = 0.032" which is 20 AWG. So
using a larger wire diameter in solid copper should improve the Q
and lower the resistance of the coil.
The skin depth in copper is about 10 mills.
32 AWG is 0.00795" diameter (Wiki AWG
Note 32 AWG is about the wire size C-Max uses.
Temic (now C-Max)
10/999,339 Radio-controlled clock and method for acquiring time
information from a (C-Max), application - ignores non data bits
US 2005/0122952 A1Radio-controlled clock and method for
automatically receiving and evaluating ...(C-Max), application -
multi frequency receiver
Horst Haefner et al
7369628 Method for gaining time information and receiver for
implementing the Method, (C-Max), May 6, 2008, 375/324 -
discriminates based on width of
7317905 Radio-controlled clock and method for gaining time
information (C-Max), Jan 8, 2008, 455/265 ; 368/47; 375/354
Calls: same as 7317905 below except for the last one
5818851 Method for detecting the time messages in the faulty signal
of a time-signal Transmitter (Temic), Oct 6 1998, 714/746 ;
368/47; 968/907; 968/922
AGC control in the front end rather
than by the uC
of automatic adjustment of self-contained radio-clock by
means of time mark
|Apr 3, 1984
precision radio signal controlled continuously updated
|Aug 30, 1988
signal controlled digital clock
|Apr 18, 1989
|Apr 14, 1992
operation of a radio-controlled clock and radio-controlled
clock for use in an environment subject to interference
||Sep 20, 1994
of a broadcast time-signal for correcting a time error
|Jun 18, 1996
improving the signal-to-noise ratio in a transmission
system by the formation of area equivalents
||Mar 10, 1998
for detecting the beginning of time messages
||Sep 8, 1998
detecting the time messages in the faulty signal of a
||Oct 6, 1998
time activated phase locked controller in a selective call
|Sep 24, 2002
5727022 Method for improving the signal-to-noise ratio in a
transmission system by the Formation of Area Equivalents (Temic),
Mar 10, 1998, 375/238 ; 375/285; 375/346 - radio controlled
4768178 High precision radio signal controlled continuously
updated digital clock, (Precision Standard Time, Inc.) Aug 30,
1988 - see PST1020
4823328 Radio signal controlled digital clock, (not assigned, same
names as on 4768178), Apr 18, 1989
5528560 Timepiece receptive of a broadcast time-signal for
correcting a time error, (Seiko) Jun 18, 1996 - time
receition only when watch error needs correcting based on past
history to save battery
Width Modulation Representation of Paired Binary Digits,
Device In Use In Particular in a Transmission Link with a
for extracting zero and one bits from a coded message of
Thermal Time Constant
If a free running 32 kHz oscillator
was enclosed in a combination of thermal mass and insulation where
the time constant was much longer than a day then the daily
temperature variations would not be such an influence. To
get a feel for how big a mass and what insulation that represents
some experiments follow.
1# Brass Rod
A brass rod 1/2" dia by 3 3/4"
long weighing 102 grams is heated in the oven, removed and
lightly wrapped in a towel. The time and temperature are
recorded. The time for the temp to drop by 1/e is 6 min 35
seconds. So to get a multi-day time constant would take
much more mass and much better insulation.
Thermal Conductivity of some
materials (Wiki: List
of thermal conductivities
||Thermal conductivity (W·m−1·K−1)
((PS Only) 0.1-0.13)
Specific Heat (Wiki: Table of
specific heat capacities)
(Sea level, dry, 0 °C)
|Air (typical room conditionsA)
#2 Aluminum Block &
Block is 6061 3.362" x 2.500" x
2.000" (16.81 cu in or 275.5 cc) and weighs 1 # 12.4 oz (805
grams); 2.92 g/cc or 1.68 oz/cu in.
Styrofoam Insulation is sold by Michael's Arts & Crafts
store. Branded as "Make It: Fun!" for floral
B10125WS 1-3/16 x 9-7/8 x 11-7/8 inch (3 x 25 x 30.1 cm
Styrofoam Block weight: 2.6 oz (73.7 g) 0.0325 g/cc or 0.0187
B181WS 15/16 x 11-15/16 x 17-15/16
inch (2.4 x 30.3 x 45.6 cm) Styrofoam Block weight: 4.2 oz
(119 g) or 0.0359 g/cc
Styro Cutter Model No. 601+ nominal hot Rod ( a hot wire is
supported at both ends so can not cut trenches, but a rod can)
kerf is 1/16"
The wall wart is rated at 6 VAC
& 500 ma for a power of 3 Watts. This means that it
cuts very slowly, not recommended. The Hot Wire
Styrofoam cutters on You-tube are using much more power and
cut at a more reasonable rate. Also it's easy to bend
the rod over if you try to cut too fast.
#1510 StyroGlue 4 oz
Looks like Elmer's wood
glue. After one hour still not starting to set. No
info on the bottle about set time. Some faster way would
make doing an assembly much easier.
Notice that the denisty of the Styrofoam is about 90 times lower
La Crosse WT-3102 WWVB Clock
This is a newer generation WWVB
clock compared to the earlier ones. It syncs much faster and
it rotates the hands very fast for the daylight savings time
signal receiver and decoder, (Microchip), Jan 29, 2008,
375/343; 455/181.1 -
Q-quenching super-regenerative receiver, (Microchip), Aug 28,
2007, 375/316; 331/16; 455/258; 455/259 -
Time signal peripheral, (Microchip), Filing date
: Dec 24,
2003, 375/340 -
Portable weather detector and alert system, Feb 5, 2008, 340/601;
324/72; 340/525; 340/539.28; 340/600; 340/602; 340/690; 700/21;
- an I&Q type LF time receiver - the builder,
Kasper, suggests that a direct to DSP approach would be better,
Poul-Henning Kamp - an improvement would be to band limit the loop
antenna, but not high Q since sferics will cause ringing.
- the MSF signal suffers the same problems as
the WWVB signal.
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