On Sat, 01 Dec 2012 07:02:26 -0500, Bob wrote:

Hi,

As apparently WWV doesn't transmit up that high in freq., what are some
good "freq. standard" signals to use for calibration in the vhf/uhf ranges ?

Thanks,
Bob

What could be used as frequency standard "plucked from VHF" is the TV line
frequency.
I'm not sure if like in Europe, all TV stations in the US would be equally
useful but if you enter this search string in Google
-----
"Calibration of high precision oscillators using the TV line frequency as a
frequency standard"
-----
you get several links that suggest it might be the case.

Jan

On Sunday, December 2, 2012 10:13:50 PM UTC-5, Arid ace wrote:
On Sat, 01 Dec 2012 07:02:26 -0500, Bob wrote:



Hi,



As apparently WWV doesn't transmit up that high in freq., what are some

good "freq. standard" signals to use for calibration in the vhf/uhf ranges ?



Thanks,

Bob



What could be used as frequency standard "plucked from VHF" is the TV line

frequency.

I'm not sure if like in Europe, all TV stations in the US would be equally

useful but if you enter this search string in Google

-----

"Calibration of high precision oscillators using the TV line frequency as a

frequency standard"

-----

you get several links that suggest it might be the case.



Jan

During the analog TV days maybe it was possible, but not now. I doubt if it could be done now at all...at least in the US. Best frequency standards are at low frequencies,such as 60KHz or even lower.

On Sun, 2 Dec 2012 23:07:55 -0800 (PST), wrote:

On Sunday, December 2, 2012 10:13:50 PM UTC-5, Arid ace wrote:
On Sat, 01 Dec 2012 07:02:26 -0500, Bob wrote:



Hi,



As apparently WWV doesn't transmit up that high in freq., what are some

good "freq. standard" signals to use for calibration in the vhf/uhf ranges ?



Thanks,

Bob



What could be used as frequency standard "plucked from VHF" is the TV line

frequency.

I'm not sure if like in Europe, all TV stations in the US would be equally

useful but if you enter this search string in Google

-----

"Calibration of high precision oscillators using the TV line frequency as a

frequency standard"

-----

you get several links that suggest it might be the case.



Jan

During the analog TV days maybe it was possible, but not now. I doubt if it could be done now at all...at least in the US. Best frequency standards are at low frequencies,such as 60KHz or even lower.

As far as I can remember, the time limit to end all analogue TV transmissions in
the US is somewhere in 2015 but if none are left already it's a pity.
However WWVB at 60 KHz now is modulated in phase just like happened with many
stations in Europe so you can forget to lock a 10MHz VCXO to the WWVB carrier,
to measure the drift of any XTO, even oven controlled ones. I looked up
available time & frequency stations and unless living close enough to Europe, no
luck: http://ac6v.com/standard.htm

On Monday, December 3, 2012 8:58:55 PM UTC-5, Arid ace wrote:
On Sun, 2 Dec 2012 23:07:55 -0800 (PST), wrote:



On Sunday, December 2, 2012 10:13:50 PM UTC-5, Arid ace wrote:

On Sat, 01 Dec 2012 07:02:26 -0500, Bob wrote:







Hi,







As apparently WWV doesn't transmit up that high in freq., what are some



good "freq. standard" signals to use for calibration in the vhf/uhf ranges ?







Thanks,



Bob







What could be used as frequency standard "plucked from VHF" is the TV line



frequency.



I'm not sure if like in Europe, all TV stations in the US would be equally



useful but if you enter this search string in Google



-----



"Calibration of high precision oscillators using the TV line frequency as a



frequency standard"



-----



you get several links that suggest it might be the case.







Jan



During the analog TV days maybe it was possible, but not now. I doubt if it could be done now at all...at least in the US. Best frequency standards are at low frequencies,such as 60KHz or even lower.



As far as I can remember, the time limit to end all analogue TV transmissions in

the US is somewhere in 2015 but if none are left already it's a pity.

However WWVB at 60 KHz now is modulated in phase just like happened with many

stations in Europe so you can forget to lock a 10MHz VCXO to the WWVB carrier,

to measure the drift of any XTO, even oven controlled ones. I looked up

available time & frequency stations and unless living close enough to Europe, no

luck: http://ac6v.com/standard.htm

We don't have any analog tv broadcasting since 2009 over here,in NYC. If WWV and its sisters like WWVB or WWVH cannot be used due to the phase modulation- I think the Canadian CHU still uses simple AM modulation or something very close to it.

On Mon, 3 Dec 2012, wrote:


We don't have any analog tv broadcasting since 2009 over here,in NYC. If
WWV and its sisters like WWVB or WWVH cannot be used due to the phase
modulation- I think the Canadian CHU still uses simple AM modulation or
something very close to it.

The problem with CHU is that it's not on an exact MHz frequency, so you
won't be able to adjust your 100KHz calibrator to that

I suppose it matters less now since you can easily divide 10MHz or 100KHz
down to 10KHz that will have a harmonic on CHU's frequencies, but it used
to be a big issue, and people who rely on 100KHz calibrators are likely
those unwilling to mod the receiver to get 10KHz.

But of course, if you're using a 100KHz calibrator, some phase modulation
isn't likely to be a problem.

Wait a minute. I WWV and WWVH have phase modulation (excrpt
whatever comes from propagation), it's WWVB that was mentioned. For a lot
of purposes, WWV is good enough, and on exact multiples of 1 MHz. The
issue is that due to propagation, it comes and goes, and can pick up
distortion along the way. But for those who were beating their 100KHz or
such calibrators against the carrier, it was good enough. The ability to
beat absolutely was hindered by the frequecy response of the receiver
(which made it harder to hear the really low beats) and once the beat is
really slow, it takes time to figure out whether you are too fast or too
slow.

Which is why WWVB was seen as the frequency standard ifyou needed
something better. If you could receiver the signal, you'd have a reliable
frequency standard, since it was groundwave (not bouncing off the
ionosphere where other issues come in). For a long time, WWVB was only a
frequency standard, initially that's all it was, then of course the
decoders to get the time took up so much circuitry that you wouldn't see
clocks that sync'ed up except in the lab. It's only the last ten or so
years where you could cheaply get "atomic clocks" and the time became
important. (And despite the low frequencies, WWVB was used because the
signal was always there, unlike WWV where the signal would fade. The
"World's Most Accurate Clock" from Heathkit used WWV, but apparently
adjusted the internal clock so it even kept good accuracy when WWV was not
receivable.)

Technically with the right receiver, you could get a 60KHz frequency out
of a WWVB receiver that was really accurate, while trying that with WWV
would fail due to fading and such. No transfer oscillator need, that
100KHz calibrator, though 60KHz isn't too useful a frequency reference in
itself.

The phase modulation on WWVB is recent, like sometime this fall. It
reflects the demand for all those "atomic clocks" since it's a secondary
method of sending the time on the carrier. Just like FM is noise-free
because you can put limiters in, the same with phase modulation, and in
plces that are at the farther edges of WWVB's pattern, phase modulation
would be more distinct since it won't be confused by interference from
other things like switching supplies that are generating "am noise".

I guess they've decided that "atomic clocks" in every household are more
important than a frequency standard, and at least nowadays there are other
methods to get accurate frequency, though less so for the hobbyist.

Let's not forget all those ads in the magazines for Hammarlund recievers
where crystal manufacturers and broadcast station engineers would plug the
receivers for profeesional use. Up until a certain time, WWV and WWVB was
used by a lot more people as a frequency standard (and WWVB for those who
needed something more), and they'd use off the shelf shortwave receivers
for that.

Then it become possible to get an expensive but still within reach Cesium
standard. Who can forget that wave of articles in the seventies about
getting a frequency standard from the color subcarrier frequency in color
tv? It wa accurate because it was set by the cesium standard at the
network. ANd then it soon faded because local stations started getting
their own cesium standards, and they weren't necessarily calibrated to the
extent of the ones at the network. They stopped using the network
standard. I may have garbled this, but there wa a point when it became
possible to get some standard that was better than a crystal oscillator
but wasn't as absolute as the atomic clock at the time stations.

The point is that the time stations became less important with time. Yes,
they are still fun and useful for the hobbyist, and WWVB is certainly
getting much more use via all those home "atomic clocks" than when it was
"merely' a frequency standard, but professional needs are being met
other ways (an indeed, professional needs often need something better
now).

Wikipedia says that there will be no phase modulation of WWVB for a
period each day, at 7 and 1900 UTC, it says for 30 minutes but it's not
clear if that's each time or 15 minutes each time. So you have some time
with an accurate frequency source, but not something that can be locked
too constantly.


Michael

On Tuesday, December 4, 2012 4:22:53 PM UTC-5, Michael Black wrote:
On Mon, 3 Dec 2012, wrote:





We don't have any analog tv broadcasting since 2009 over here,in NYC. If

WWV and its sisters like WWVB or WWVH cannot be used due to the phase

modulation- I think the Canadian CHU still uses simple AM modulation or

something very close to it.



The problem with CHU is that it's not on an exact MHz frequency, so you

won't be able to adjust your 100KHz calibrator to that



I suppose it matters less now since you can easily divide 10MHz or 100KHz

down to 10KHz that will have a harmonic on CHU's frequencies, but it used

to be a big issue, and people who rely on 100KHz calibrators are likely

those unwilling to mod the receiver to get 10KHz.



But of course, if you're using a 100KHz calibrator, some phase modulation

isn't likely to be a problem.



Wait a minute. I WWV and WWVH have phase modulation (excrpt

whatever comes from propagation), it's WWVB that was mentioned. For a lot

of purposes, WWV is good enough, and on exact multiples of 1 MHz. The

issue is that due to propagation, it comes and goes, and can pick up

distortion along the way. But for those who were beating their 100KHz or

such calibrators against the carrier, it was good enough. The ability to

beat absolutely was hindered by the frequecy response of the receiver

(which made it harder to hear the really low beats) and once the beat is

really slow, it takes time to figure out whether you are too fast or too

slow.



Which is why WWVB was seen as the frequency standard ifyou needed

something better. If you could receiver the signal, you'd have a reliable

frequency standard, since it was groundwave (not bouncing off the

ionosphere where other issues come in). For a long time, WWVB was only a

frequency standard, initially that's all it was, then of course the

decoders to get the time took up so much circuitry that you wouldn't see

clocks that sync'ed up except in the lab. It's only the last ten or so

years where you could cheaply get "atomic clocks" and the time became

important. (And despite the low frequencies, WWVB was used because the

signal was always there, unlike WWV where the signal would fade. The

"World's Most Accurate Clock" from Heathkit used WWV, but apparently

adjusted the internal clock so it even kept good accuracy when WWV was not

receivable.)



Technically with the right receiver, you could get a 60KHz frequency out

of a WWVB receiver that was really accurate, while trying that with WWV

would fail due to fading and such. No transfer oscillator need, that

100KHz calibrator, though 60KHz isn't too useful a frequency reference in

itself.



The phase modulation on WWVB is recent, like sometime this fall. It

reflects the demand for all those "atomic clocks" since it's a secondary

method of sending the time on the carrier. Just like FM is noise-free

because you can put limiters in, the same with phase modulation, and in

plces that are at the farther edges of WWVB's pattern, phase modulation

would be more distinct since it won't be confused by interference from

other things like switching supplies that are generating "am noise".



I guess they've decided that "atomic clocks" in every household are more

important than a frequency standard, and at least nowadays there are other

methods to get accurate frequency, though less so for the hobbyist.



Let's not forget all those ads in the magazines for Hammarlund recievers

where crystal manufacturers and broadcast station engineers would plug the

receivers for profeesional use. Up until a certain time, WWV and WWVB was

used by a lot more people as a frequency standard (and WWVB for those who

needed something more), and they'd use off the shelf shortwave receivers

for that.



Then it become possible to get an expensive but still within reach Cesium

standard. Who can forget that wave of articles in the seventies about

getting a frequency standard from the color subcarrier frequency in color

tv? It wa accurate because it was set by the cesium standard at the

network. ANd then it soon faded because local stations started getting

their own cesium standards, and they weren't necessarily calibrated to the

extent of the ones at the network. They stopped using the network

standard. I may have garbled this, but there wa a point when it became

possible to get some standard that was better than a crystal oscillator

but wasn't as absolute as the atomic clock at the time stations.



The point is that the time stations became less important with time. Yes,

they are still fun and useful for the hobbyist, and WWVB is certainly

getting much more use via all those home "atomic clocks" than when it was

"merely' a frequency standard, but professional needs are being met

other ways (an indeed, professional needs often need something better

now).



Wikipedia says that there will be no phase modulation of WWVB for a

period each day, at 7 and 1900 UTC, it says for 30 minutes but it's not

clear if that's each time or 15 minutes each time. So you have some time

with an accurate frequency source, but not something that can be locked

too constantly.





Michael

Very much so. WWV +CHU+ several others are still broadcasting around the clock. What about GPS signals? They must be extremely accurate,considering how many uses this service provides worlwide.

On Tue, 4 Dec 2012, wrote:


Very much so. WWV +CHU+ several others are still broadcasting around the
clock. What about GPS signals? They must be extremely
accurate,considering how many uses this service provides worlwide.

I think that's where a lot of it in non-hobby circles (and for peole who
wnat accuracy for its own sake, like those participating in the ARRL
Frequency Measuring Tests, if they still have those) has gone.

After I posted, I got curious, and the phase modulation on WWVB, while in
testing for a while, only became standard at the end of the October. But
in doing a search, I found one company that made frequency standards that
locked to WWVB, and it posted a warning, yet admits that since they
haven't made any of those in some time, GPS-based frequency standards
being the new route, the issue is less relevant.

Someone else, who had a home made WWVB receiver and crystal oscillator
locked to it, he mentions adding a modification where he doubles the
frequency of the amplified WWVB signal and then compares that with the old
reference now doubled, and it works fine. I can see that, it's
reminiscenet of a wave of DSB adapters in the ham magazines in the
seventies, where they fed the incoming signal into a 2X multiplier and
then divided that down by 2, which took out any problems, and the signal
divided by 2 was the "bfo".

Michael

On Mon, 3 Dec 2012 21:49:28 -0800 (PST), wrote:

[...]

We don't have any analog tv broadcasting since 2009 over here,in NYC. If WWV and its sisters like WWVB or WWVH cannot be used due to the phase modulation- I think the Canadian CHU still uses simple AM modulation or something very close to it.

The phase modulation used by WWVB is a bit messy. The value of 180 deg for all
data would be OK because multiplying the signal with itself would remove the
modulation. Unfortunately, the station ID uses 45 deg, see
http://en.wikipedia.org/wiki/WWVB
CHU might be the better alternative then, that the frequencies in use aren't a
multiple of 100 KHz or 1 MHz isn't a problem. With some creative calculation I
managed to lock both 153 KHz and 77.5 KHz to a 10 MHz VCXO so this case is
unlikely to be much different. 14670 and 7335 KHz would have my preference as
the first is twice the second so one receiver could easily use both signals.

Jan

On 12/05/2012 03:28 AM, Bob Dobbs wrote:


CHU no longer uses the 7335 slot but has moved to 7850,
has been for over three years now.


If anyone is still looking for a traceable frequency reference:
http://www.jrmiller.demon.co.uk/proj...std/frqstd.htm

On Wednesday, December 5, 2012 10:52:25 AM UTC-5, dave wrote:
On 12/05/2012 03:28 AM, Bob Dobbs wrote:





CHU no longer uses the 7335 slot but has moved to 7850,

has been for over three years now.





If anyone is still looking for a traceable frequency reference:

http://www.jrmiller.demon.co.uk/proj...std/frqstd.htm

Nice unit.Stable at 10E-11 part.That is MUCH better than HF transmissions and their inherent delays and fading/dropouts !