hobbyist frequency standard [Design]

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From: a7yvm109gf5d1 on 24 Oct 2009 10:38

Hi gang,
There seem to be a lot of surplus GPS discliplined 10MHz OCXOs on eBay
lately.
Anyone here have experience using a setup like that?
I'm still looking into getting my lab equipped, I'm looking into the
frequency thing.
Besides GPS, there's the national standards.
The Canadian equivalent to WWV is CHU, they broadcast time signals on
a few frequencies.
Has anyone tried disciplining an OCXO to the carrier of these signals?
The carrier is derived from an atomic clock, but atmospherics probably
mean I'd have to average over a few days to get ~10-11 accuracy.
I'm not finding a lot of information about CHU setups. I'm guessing a
dipole in the backyard, some gain, and that's it?

From: Phil Hobbs on 24 Oct 2009 14:56

From: a7yvm109gf5d1 on 24 Oct 2009 16:05

On Oct 24, 1:56 pm, Phil Hobbs
<pcdhSpamMeSensel...(a)electrooptical.net> wrote:
>
> The usual method is to use WWVB at 60 kHz, with a ferrite loopstick
> antenna, a crystal filter, and a PLL. You can get nice 2400 mu ferrite
> from Amidon. The ground wave delay is more stable than the sky wave
> from the 10 MHz stations.
>

I see, thanks.

From: Jon Kirwan on 24 Oct 2009 16:17

On Sat, 24 Oct 2009 14:56:36 -0400, Phil Hobbs
<pcdhSpamMeSenseless(a)electrooptical.net> wrote:

>a7yvm109gf5d1(a)netzero.com wrote:
>> Hi gang,
>> There seem to be a lot of surplus GPS discliplined 10MHz OCXOs on eBay
>> lately.
>> Anyone here have experience using a setup like that?
>> I'm still looking into getting my lab equipped, I'm looking into the
>> frequency thing.
>> Besides GPS, there's the national standards.
>> The Canadian equivalent to WWV is CHU, they broadcast time signals on
>> a few frequencies.
>> Has anyone tried disciplining an OCXO to the carrier of these signals?
>> The carrier is derived from an atomic clock, but atmospherics probably
>> mean I'd have to average over a few days to get ~10-11 accuracy.
>> I'm not finding a lot of information about CHU setups. I'm guessing a
>> dipole in the backyard, some gain, and that's it?
>
>The usual method is to use WWVB at 60 kHz, with a ferrite loopstick
>antenna, a crystal filter, and a PLL. You can get nice 2400 mu ferrite
>from Amidon. The ground wave delay is more stable than the sky wave
>from the 10 MHz stations.
>
>Cheers

Isn't that a once per minute thing? Perhaps combine the OCXO to
provide interim precision, tethered to and recalibrated for accuracy
periodically by WWVB? Could also make knowing when to wake up for
receiving WWVB precise, as well.

Odd thing is, I'm wearing a Casio WR50M that does close to this and I
paid a grand total of $14 for it, including the watch band, case,
display, etc. Too bad that isn't made into a nice, convenient
embedded module.

Jon

From: ChrisQ on 24 Oct 2009 17:02

a7yvm109gf5d1(a)netzero.com wrote:
> Hi gang,
> There seem to be a lot of surplus GPS discliplined 10MHz OCXOs on eBay
> lately.
> Anyone here have experience using a setup like that?
> I'm still looking into getting my lab equipped, I'm looking into the
> frequency thing.
> Besides GPS, there's the national standards.
> The Canadian equivalent to WWV is CHU, they broadcast time signals on
> a few frequencies.
> Has anyone tried disciplining an OCXO to the carrier of these signals?
> The carrier is derived from an atomic clock, but atmospherics probably
> mean I'd have to average over a few days to get ~10-11 accuracy.
> I'm not finding a lot of information about CHU setups. I'm guessing a
> dipole in the backyard, some gain, and that's it?

I'm in the uk, but bought one of the telco surplus HP Z3816A ones from
Ebay US around 5 years ago and been powered up ever since. The Hp active
antenna came from an Ebay vendor in Korea. They were very expensive in
the uk at the time. There's a similar unit (58114A ?) in a fancy box and
expensive, but these are the half rack width x ~4" high industrial
finish types with a single huge toggle power switch + leds on the front
panel and rf + serial interfaces on the rear panel. Mine is line input,
but they come in 48v dc input as well.

There's a utility that talks to the box, which you drive through a
serial line from a dos shell. This allows you to get status reports and
set up / compensate things like the nS delay from the antenna cable
length. It has a couple of 10Mhz sma outputs into 50r, (which drive all
the counters and synthesisers in the lab) and another odd ball frequency
which I don't remember.

Stability wise, they can be a bit noisy in the short term, depending on
the actual unit that you get. Long term of course, they are locked to
Caesium standards. Certainly good enough for any work done here.

I have the utility on the server if you can't find the download, though
it's been some time since I hooked a terminal to mine. It just works...

Regards,

Chris

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