What is the highest radio frequency used for radio astronomy?

In article . com,
laura halliday wrote:

This happens with television too. VHF signals can reflect
off other things too, like auroras and patches of intense
ionization in the E layer ("E Layer Skip"). Sporadic E
signals can be extremely strong.

....except that VHF television is vanishing. In Sweden, the very last
VHF TV transmitters will close down this fall - most of them already
have closed down. After that, we only have digital UHF television.
Other European countries are expected to do the same within a few
years.

And UHF signals don't reflect as well off sporadic E layes.

--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/

(Paul Schlyter) writes:

...except that VHF television is vanishing. In Sweden, the very last
VHF TV transmitters will close down this fall - most of them already
have closed down. After that, we only have digital UHF television.
Other European countries are expected to do the same within a few
years.

More problematically: digital transmissions (TV or radio) have delays in
them that makes the time signal unreliable. Where to get reliable
time signals for time-critical observations (astrometry, occultation
timings, etc.) from now on?

pej
--
Per Erik Jorde

In article ,
Per Erik Jorde wrote:
(Paul Schlyter) writes:

...except that VHF television is vanishing. In Sweden, the very last
VHF TV transmitters will close down this fall - most of them already
have closed down. After that, we only have digital UHF television.
Other European countries are expected to do the same within a few
years.

More problematically: digital transmissions (TV or radio) have delays in
them that makes the time signal unreliable. Where to get reliable
time signals for time-critical observations (astrometry, occultation
timings, etc.) from now on?

pej
--
Per Erik Jorde

That was a change of subject, but OK.....

We still have shortwave radio time signals. Here in Europe, Moscow
transmits more or less continuously at 4996, 9996 and 14996 kHz - at
least one of these frequencies can be heard any time of the day or
night. This requires a shortwave receiver capable of reveicing CW
or SSB though.

And then you can get a radio controlled clock, which here in Europe
is controlled by the transmitter in Mainflingeln, Germany, which
transmits at (I believe) 77.5 kHz, i.e. in the LF band. I've
checked a few radio controlled clocks against time signals, and
they agree "exactly" as far as my eye and ear could determine
(which means any discrepancy is less than approx. 0.1 seconds).

Finally, if you want to be really "hi-tech", there are always the
GPS satellites, which transmit time information to a very high
accuracy. The typical GPS receiver units are pretty bad at displaying
this time info at the right time though - there's a typical delay of
some 1 to 2 seconds in the displayed time. There are probably other
GPS receivers which makes the GPS time available to a much higher
accuracy, but these units probably cost much more. The CW/SSB
shortwave radio receiver or the radio conrolle clock will be much
cheaper.

Personally I've never used TV transmissions as a time source with
high accuracy - I've always used radio controlled clocks, or shortwave
time signals.


People in North America can use shortwave time signals from WWV
in the US, or CHU in Canada. These transmitters use AM, not CW, for
their transmissions. The advantage for the user is that any shortwave
receiver can be used for these transmissions -- CW/SSB capability of
the receiver os not needed. The disadvantage for the user is that
AM transmissions don't reach quite as far as CW transmissions - if
the received signal is weak, a CW signal will "go through" more
clearly.

--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/

(Paul Schlyter) writes:

That was a change of subject, but OK.....

[snip]

Paul, many thanks for your detailed information.

pej
--
Per Erik Jorde

On Wed, 05 Sep 2007 09:40:11 +0200, Per Erik Jorde
wrote:

More problematically: digital transmissions (TV or radio) have delays in
them that makes the time signal unreliable. Where to get reliable
time signals for time-critical observations (astrometry, occultation
timings, etc.) from now on?

If you need to make time critical observations, you should be using GPS.
It's much more accurate than any of the radio time standards, and has a
much more widely accessible signal. GPS time receivers have become
fairly common and inexpensive (still a little more than a cheap radio
receiver, but not much).

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

On Sep 5, 10:12 am, (Paul Schlyter) wrote:
In article ,
Per Erik Jorde wrote:

(Paul Schlyter) writes:

...except that VHF television is vanishing. In Sweden, the very last
VHF TV transmitters will close down this fall - most of them already
have closed down. After that, we only have digital UHF television.
Other European countries are expected to do the same within a few
years.

UK still has TV on analogue UHF and digital UHF co-existing. The
delays are significant and annoying on the digital TV and the new
audio quality is dubious. Live Proms classical concerts that were very
dynamic and involving on FM radio were lifeless and dead sounding on
digital TV broadcast (although the noise floor was lower).

time signals for time-critical observations (astrometry, occultation
timings, etc.) from now on?

That was a change of subject, but OK.....

We still have shortwave radio time signals. Here in Europe, Moscow
transmits more or less continuously at 4996, 9996 and 14996 kHz - at
least one of these frequencies can be heard any time of the day or
night. This requires a shortwave receiver capable of reveicing CW
or SSB though.

And then you can get a radio controlled clock, which here in Europe
is controlled by the transmitter in Mainflingeln, Germany, which
transmits at (I believe) 77.5 kHz, i.e. in the LF band. I've

And Rugby MSF on 60 kHz in the UK. Although the German signal is
usable too.

checked a few radio controlled clocks against time signals, and
they agree "exactly" as far as my eye and ear could determine
(which means any discrepancy is less than approx. 0.1 seconds).

We used Rugby MSF together with a local phase locked Rubidium clock
for low frequency VLBI a long time ago. There was a slight systematic
delay error in their CW seconds pulse rise time in the early morning
if the ground was wet with dew. It showed as a few hundred microsecond
drift when the sun burnt it off (from memory). When asked about it
they were surprised. They were also astonished that it could be
measured at all.

Consumer grade kit may have a small systematic delay in decoding the
signal and presenting it on the display. Likely to be at most 50ms or
so.

Finally, if you want to be really "hi-tech", there are always the
GPS satellites, which transmit time information to a very high
accuracy. The typical GPS receiver units are pretty bad at displaying
this time info at the right time though - there's a typical delay of
some 1 to 2 seconds in the displayed time.

Most people using GPS want to know where they are...

Regards,
Martin Brown

On Sep 5, 7:51 am, Martin Brown
wrote:

Finally, if you want to be really "hi-tech", there are always the
GPS satellites, which transmit time information to a very high
accuracy. The typical GPS receiver units are pretty bad at displaying
this time info at the right time though - there's a typical delay of
some 1 to 2 seconds in the displayed time.

Most people using GPS want to know where they are...

It's not difficult to pick up surplus timing GPS receivers, like
the ones cell towers use. They provide an accurate
1 PPS signal, plus other data. Depending on the model and
the circumstances, the 1 PPS accuracy will be microseconds
to nanoseconds. If that's not accurate enough for you, I'm
not sure what will be. :-)

My timing sources include a WWVB clock, shortwave
receivers, GPS, my cellphone, and, if needed, a phone
call to the WWV and WWVH audio feeds (+1 303 499 7111
and +1 808 335 4363, respectively).

From the west coast of Canada CHU is a tough signal,
but WWV and WWVH are fine most of the time. I used
to pick up VNG from Australia a lot, particularly in the
morning. One morning VNG was the strongest signal on
5 MHz, with WWVH in the background. I got two QSLs
for that one! VNG's other strong frequency was 8638 kHz,
right next to Korean station HLW on 8636 kHz.

Laura Halliday VE7LDH "Non sequitur. Your ACKS are
Grid: CN89mg uncoordinated."
ICBM: 49 16.05 N 122 56.92 W - Nomad the Network Engineer

In article . com,
Martin Brown wrote:
On Sep 5, 10:12 am, (Paul Schlyter) wrote:
In article ,
Per Erik Jorde wrote:

(Paul Schlyter) writes:

...except that VHF television is vanishing. In Sweden, the very last
VHF TV transmitters will close down this fall - most of them already
have closed down. After that, we only have digital UHF television.
Other European countries are expected to do the same within a few
years.

UK still has TV on analogue UHF and digital UHF co-existing. The
delays are significant and annoying on the digital TV and the new
audio quality is dubious. Live Proms classical concerts that were very
dynamic and involving on FM radio were lifeless and dead sounding on
digital TV broadcast (although the noise floor was lower).

Is UHF TV (either analog or digital) useable for detecting meteor
showers?


time signals for time-critical observations (astrometry, occultation
timings, etc.) from now on?

That was a change of subject, but OK.....

We still have shortwave radio time signals. Here in Europe, Moscow
transmits more or less continuously at 4996, 9996 and 14996 kHz - at
least one of these frequencies can be heard any time of the day or
night. This requires a shortwave receiver capable of reveicing CW
or SSB though.

And then you can get a radio controlled clock, which here in Europe
is controlled by the transmitter in Mainflingeln, Germany, which
transmits at (I believe) 77.5 kHz, i.e. in the LF band. I've

And Rugby MSF on 60 kHz in the UK. Although the German signal is
usable too.

checked a few radio controlled clocks against time signals, and
they agree "exactly" as far as my eye and ear could determine
(which means any discrepancy is less than approx. 0.1 seconds).

We used Rugby MSF together with a local phase locked Rubidium clock
for low frequency VLBI a long time ago. There was a slight systematic
delay error in their CW seconds pulse rise time in the early morning
if the ground was wet with dew. It showed as a few hundred microsecond
drift when the sun burnt it off (from memory). When asked about it
they were surprised. They were also astonished that it could be
measured at all.

Consumer grade kit may have a small systematic delay in decoding the
signal and presenting it on the display. Likely to be at most 50ms or
so.

Finally, if you want to be really "hi-tech", there are always the
GPS satellites, which transmit time information to a very high
accuracy. The typical GPS receiver units are pretty bad at displaying
this time info at the right time though - there's a typical delay of
some 1 to 2 seconds in the displayed time.

Most people using GPS want to know where they are...

True - however, accurate time is available through GPS - worldwide,
even if most users haven't discovered that yet.

Regards,
Martin Brown


--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/

In article ,
Chris L Peterson wrote:
On Wed, 05 Sep 2007 09:40:11 +0200, Per Erik Jorde
wrote:

More problematically: digital transmissions (TV or radio) have delays in
them that makes the time signal unreliable. Where to get reliable
time signals for time-critical observations (astrometry, occultation
timings, etc.) from now on?

If you need to make time critical observations, you should be using GPS.
It's much more accurate than any of the radio time standards, and has a
much more widely accessible signal. GPS time receivers have become
fairly common and inexpensive (still a little more than a cheap radio
receiver, but not much).

Can you give some examples of available and not that expensive
GPS time receivers?

_______________________________________________ __

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com


--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/

On Wed, 05 Sep 2007 15:42:51 GMT, (Paul Schlyter) wrote:

Can you give some examples of available and not that expensive
GPS time receivers?

I regularly see used GPS time bases (crystal oscillators with GPS
training) on sites that sell surplus equipment. Common prices are on the
order of US$200.

For my work, I use Garmin GPS18 modules, which run about $US80. But
there are a number of modular GPS units with 1pps outputs in that price
range.

To make use of the output, you can use a number of free or cheap
computer programs, use the 1pps signal directly on an audio track, or
use an OSD generator for video. A Kiwi OSD, for example, is just US$165.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com