"Tobin Fricke" wrote in message
F.Berkeley.EDU
As a project to learn more about building radio receivers, I'd like to
build a WWV receiver (or maybe a receiver for the Canadian station
CHU, since it's nearby and the format sounds easier to decode). I'm
looking for suggestions for how to design such a radio, reading
material, etc.

I was thinking it might be easier to design a fixed-frequency receiver
(rather than a tunable one) because I could just select the L and C
in the resonant circuit to give the right frequency. Or, since WWV
is at such "round number" frequencies, maybe I could somehow use a
crystal oscillator?

thank you,
Tobin

You might try and find a user manual for the old Heathkit GC-1000 Most
Accurate Clock.
It synchonizes the clock and local oscillator to the WWV transmissions
at 5, 10 or 15 MHz. The kit came with a preassembled and prealigned RF
board but you still had to assemble the data recovery and other parts of
the unit. The manual includes full schematics (including RF board) and
a good theory of operation section. The only thing missing are
instructions on aligning the RF board. The silly thing works pretty but
I had to build an antenna and install it in by attic to get it to
sychronize reliably.

--
James T. White

CHU Time Station : Western Canada Coverage Proposal

The CHU time station is Canada's domestic shortwave time signal station.
CHU existed long before the Internet and sattilite navigation systems like
(GPS, GLONASS, Gallaeo).
CHU provides most of the functionality of the US WWV & WWVB (Bolder,
Colorado) and WWVH (Kauai, Hawaii).

Problems with CHU's configuation that this proposal addresses

The 3.3µs per km of path that makes CHU's signals problamatic for users in
Western Canada. Even the NRC realizes this: "for all distant users of CHU,
the dominant source of time error comes from the radio wave path reflecting
off the ionosphere as the radio signal travels from the transmitter".
The poor quality of CHU reception in Western Canada and the Artic, North of
55º Latitude.
It is suggested that the 7335 kHz frequecny be reused, but it may be
advisable to find alternate frequences.
The CHU signal fomat may need to be tweaked so as to take into consideration
2 transmitter sites.
A new set of atomic clocks will be needed, as well as equipement to sync
them to NRC's atomic clocks. It may be possible to obtain secondhand atomic
clocks from UBC (Vancouver) or other universities in Western Canada.
This proposal could be replicated in Newfoundland using another existing CHU
frequency, as Eastern Canada has CHU coverage problems as well.
Universally upgrading CHU's Ottawa transmitters to 10 kw may not fix CHU
coverage problems in Western or Eastern Canada.
[...]

http://cbc.am/CHU.htm


As a project to learn more about building radio receivers, I'd like to
build a WWV receiver (or maybe a receiver for the Canadian station CHU,
since it's nearby and the format sounds easier to decode). I'm looking
for suggestions for how to design such a radio, reading material, etc.

I was thinking it might be easier to design a fixed-frequency receiver
(rather than a tunable one) because I could just select the L and C in the
resonant circuit to give the right frequency. Or, since WWV is at such
"round number" frequencies, maybe I could somehow use a crystal
oscillator?
--
http://web.pas.rochester.edu/~tobin/

you HAVE to use a crystal oscillator. due to the nature of the tuned
resonant circuits, mistuning can change the propagation delay of the
signal through the receiver by incredible amounts. soooo, you have to
be on frequency. i think I still have some where a schematic of such a
receiver from Popular Elactronics but it may take a while for me to
find it.
Saandy 4Z5KS


Tobin Fricke wrote:
As a project to learn more about building radio receivers, I'd like to
build a WWV receiver (or maybe a receiver for the Canadian station CHU,
since it's nearby and the format sounds easier to decode). I'm looking
for suggestions for how to design such a radio, reading material, etc.

I was thinking it might be easier to design a fixed-frequency receiver
(rather than a tunable one) because I could just select the L and C in the
resonant circuit to give the right frequency. Or, since WWV is at such
"round number" frequencies, maybe I could somehow use a crystal
oscillator?

thank you,
Tobin
--
http://web.pas.rochester.edu/~tobin/

From: Tobin Fricke on Jan 24, 7:41 pm

On Tue, 24 Jan 2006, xpyttl wrote:

Well, I suppose it depends on where OP is. Here in the middle, 10 MHz isn't
much of a problem but 15 is.

I am in Rochester, NY.

There should be no real problem in receiving WWV in NY state unless
you want to do it with a few feet of hook-up wire dangling inside
the room. For just WWV on HF, use whatever is handy for a long-
wire OUTSIDE...some #26 or #28 coil wire would work and be near-
invisible on the outside.

The sensitivity needed by your receiver depends ENTIRELY on how
much signal arrives in your area and how much of that the antenna
intercepts.


*HOWEVER*, 10 has one huge advantage -- there are very low cost uP crystals
for 10 MHz, so building even a simple reciever with a brick wall front end
isn't such a big deal, if the only frequency you care about is 10 MHz.

Yes, that is what I was thinking. Is there a simple way to do frequency
multiplication (or division) to get 2.5, 5, 15, and 20 MHz additionally,
and thus be able to switch between all of the WWV frequencies?

To make a simple superheterodyne receiver, even if just single-
conversion using a legacy 455 KHz IF, capitalize on some simple
tuning arrangements using an RF Amp, Mixer, 1 or 2 stages of IF:

1. A single set of front-end inductors, tune RF and LO with Cap.

2. Capacitor tuning using fixed+trimmers. Frequency range of
5, 10, 15 MHz selected by rotary switch has a total frequency
range of 3:1 high to low. The capacitance change ratio for
this is the square of the frequency change ratio or 9:1.

Note: In the old "communications receiver" designs, it was
typical to cover a 3:1 frequency change ratio with a "365 pFd"
variable capacitor (typically 40 to 360 pFd min. to max.).

3. If there are temperature-drift problems in the LO, just make
use of a small front-panel control to a parallel trimmer cap
on the LO tuning (added to the cap. of the LO resonant ckts).

4. In most cases, the temperature drift is negligible and one
can make do with behind-the-front-panel trimmer cap. settings
for three switch-selected frequencies. Some simple experiments
with an oven termometer and a frequency counter would let you
check out the drift versus temperature and compensate. Begin
with mostly NPO caps fixed for the LO tuning, expect a towards-
low-frequency drift, compensate with negative-temp coefficient
fixed capacitors for the NPOs. Temperature drift is highly
dependent on WHAT you build and HOW you build it.

"Brick wall front end"?

No need. WWV time-frequency service frequency allocations have a
protected 10 KHz bandwidth, protected from other modes in other
radio services. Given a typical Q of about 40 and two tuned
stages (ant to RF amp, RF amp to Mixer), the bandwidth would be
about 80 KHz (5 MHz) to 250 KHz (15 MHz) in the front-end. With
an IF of 455 KHz, the image frequency would be 910 KHz away.

WWV is AM, not SSB, and most probably will be used to zero-beat
external CW frequency sources that are going to be calibrated.

For those who want "extreme accuracy" in time, just compare the
time-ticks to a 1 Hz (divided down from standard to be checked)
local tick. That was the way things were done with the old
General Radio primary standards equipment circa 1950-1960, good
to 1 part per million accuracy without sweat.


Personally, I'd go with a DC rather than a regen - a lot simpler and these
days, a simple SA612 will give you way more sensitivity than you can
possibly use on 10 MHz for a couple bucks.
Heck, if the local QRM isn't too strong, I bet a 10 MHz uP crystal, a
612 and an audio amp (like a 386 or so) is all you would need.

That sounds great.

If all that is wanted is SIMPLICITY, just use any old SW BC or
wide-tuning-range HF receiver. [suggested by another]

You can convert an old "All-American-Five" AM BC receiver to
receive 5 to 15 MHz just by substituting the "coils" (inductors
is the proper word now). Substitute an inductor for the old
loop or loopstick...with a primary link for an external antenna.
[I did this many, many years ago...it works] It won't be "top
of the line" in performance, but then a regen isn't that either.
The IF can be aligned easily and the new front-end alignment
is fairly easy.

The old Hallicrafters S-38 four-band "starter" receiver that
many used was really a simple "All-American-Five" Mixer-Single IF-
AM detector-Audio Output arrangement with an added BFO. A BFO
isn't needed to beat a local frequency standard with WWV.

Assuming an original 45 pFd, 101 pFd, 405 pFd capacitance (which
includes the stray circuit capacity) to tune 15, 10, 5 MHz, a
2.5 uHy inductance will do the job. A trimmable inductor would
be best there. The first task is to check the inductor
substitutions with the existing variable capacitor. If that works,
the variable can be substituted by a switched trimmable capacitor
to avoid the knob-twisting for three HF selections...or two, or
none at all assuming fixed tuning to 10 MHz.

An old tube AM BC receiver relegated to the basement/garage
junkpile is a good candidate for this kind of thing. Tube type
radios are a bit easier to work with if you aren't acquainted
with newer solid-state circuitry. Those are certainly cheap. :-)

A converted "All-American-Five" will NOT have great sensitivity.
But, since tubes' stage gains are essentially transconductance x
load impedance, the individual gain stages can be optimized by
going for minimum-C in resonant circuits. Not that easy with
old transistor radios having individual transistor stages...those
needing fussing about with matching input-output impedances.

A friend of mine did an article on a simple WWV reciever for QRP Homebrewer
recently, issue #5 I think. He was more interested in the frequency
standard than hearing the sounds, so his contribution was recognizing the
zero beat, but still an interesting article if you can find a copy.

I don't see any articles on WWV receivers there... Does anything look
familiar: http://www.njqrp.org/data/qrp_homebrewer.html

Depends on WHAT EXACTLY you are striving for and your own
experience-knowledge. If you are a relative beginner (we all
were once), then I'd suggest converting an old tube type BC
receiver. That avoids the construction hassle and concentrates
on individual theory areas during conversion. It's the least
expensive route if using an old BC junker receiver. Individual-
area concentration can teach more about those areas than building
a pre-designed kit or magazine article project.

Tobin Fricke wrote:

As a project to learn more about building radio receivers, I'd like to
build a WWV receiver (or maybe a receiver for the Canadian station CHU,
since it's nearby and the format sounds easier to decode). I'm looking
for suggestions for how to design such a radio, reading material, etc.

I was thinking it might be easier to design a fixed-frequency receiver
(rather than a tunable one) because I could just select the L and C in the
resonant circuit to give the right frequency. Or, since WWV is at such
"round number" frequencies, maybe I could somehow use a crystal
oscillator?

Tobin-

A couple other ideas:

1. Try your hand at building a crystal set! Just an antenna, a tuned
circuit, a diode and earphones. There could be more sophistication such
as using an amplified speaker and higher-Q tuned circuits.

2. Try a direct-conversion receiver. It may be just a more sophisticated
crystal set with RF preamplifier and on-frequency crystal filter. A
product detector could be included to convert to audio, but a diode
detector should work and wouldn't change the audio tone frequencies.

I considered using this direct-conversion approach to obtain an accurate
10 MHz signal. I wanted to use it to synchronize my oscilloscope so I
could adjust a counter's timebase (or vice-versa). However, I never built
it after finding a Rubidium controlled oscillator on eBay.

Fred

Fred McKenzie wrote:

Tobin Fricke wrote:

As a project to learn more about building radio receivers, I'd like to
build a WWV receiver (or maybe a receiver for the Canadian station CHU,
since it's nearby and the format sounds easier to decode). I'm looking
for suggestions for how to design such a radio, reading material, etc.

I was thinking it might be easier to design a fixed-frequency receiver
(rather than a tunable one) because I could just select the L and C in the
resonant circuit to give the right frequency. Or, since WWV is at such
"round number" frequencies, maybe I could somehow use a crystal
oscillator?

Tobin-

A couple other ideas:

1. Try your hand at building a crystal set! Just an antenna, a tuned
circuit, a diode and earphones. There could be more sophistication such
as using an amplified speaker and higher-Q tuned circuits.

2. Try a direct-conversion receiver. It may be just a more sophisticated
crystal set with RF preamplifier and on-frequency crystal filter. A
product detector could be included to convert to audio, but a diode
detector should work and wouldn't change the audio tone frequencies.

I considered using this direct-conversion approach to obtain an accurate
10 MHz signal. I wanted to use it to synchronize my oscilloscope so I
could adjust a counter's timebase (or vice-versa). However, I never built
it after finding a Rubidium controlled oscillator on eBay.

Fred

I know that there are several plans on the internet for building a radio
controlled clock. These involve building a fixed frequency rx and then
hooking it up to a clock. How feasible would it be to hook the same
circuit up to an amp and speaker instead of a clock? I suspect that the
clock radios listen in on 60khz, but it should be simple to insert a
crystal or change it to get 10Mhz. Also, you could build a radio with
three frequencies-5Mhz, 10Mhz, and 15Mhz in order to take advantage of
day vs night propagation.

On Sat, 04 Feb 2006 19:12:18 -0800, running dogg wrote:



I know that there are several plans on the internet for building a radio
controlled clock. These involve building a fixed frequency rx and then
hooking it up to a clock. How feasible would it be to hook the same
circuit up to an amp and speaker instead of a clock?

I haven't looked at any of these circuits, but I'd expect it to be
quire easy to connect and audio amplifier and speaker to the output of
the detector.

I suspect that the
clock radios listen in on 60khz, but it should be simple to insert a
crystal or change it to get 10Mhz. Also, you could build a radio with
three frequencies-5Mhz, 10Mhz, and 15Mhz in order to take advantage of
day vs night propagation.

Converting a 60 KHz receiver to 10 MHz is likely impossible -
construction techniques and tuned circuits will be quite different -
you can almost use audio techniques and iron-core coils at 60 KHz, but
are well into RF territory at 10 MHz, and will likely have to use
air-core coils in the tuned circuits.


--
Peter Bennett, VE7CEI
peterbb4 (at) interchange.ubc.ca
new newsgroup users info : http://vancouver-webpages.com/nnq
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca

Hello Peter,


Converting a 60 KHz receiver to 10 MHz is likely impossible -
construction techniques and tuned circuits will be quite different -
you can almost use audio techniques and iron-core coils at 60 KHz, but
are well into RF territory at 10 MHz, and will likely have to use
air-core coils in the tuned circuits.


Not just that. The transmitted code is also different.

Regards, Joerg

http://www.analogconsultants.com

"Peter Bennett" wrote in message

are well into RF territory at 10 MHz, and will likely have to use
air-core coils in the tuned circuits.

Huh? Yes, he is well into RF and construction techniques will be different.
But while there are advantages to air-coil cores, their use in recievers
went out with hollow state detectors. Even in transmitters they tend to be
only used in the KW neighborhood anymore. I can't imagine that even in the
wilds of BC people are winding air coils and building on heavy steel
chassis.

...

"Joerg" wrote in message
news:TwmFf.27179

Not just that. The transmitted code is also different.

He wants to listen, and at least at 10 MHz there's something to listen TO.
The 60Khz signal is pretty strange.

...