Re: 10MHz Source - DAB ???


David <david.g6feo@...>
 

Hi Andy,

I've opened a can of worms I see.

From the previous mails I assume the Halcyon is only any use as a time
base for test equipment, which is it's only use here to date.

I looked at the 2 GPS modules in your email and I cannot see a 10kHz
output on them, unless I'm missing something.

Can you suggest a simple design for a GPS locked source that uses the
1pps signal?

73, David.

On Mon, 2013-06-24 at 09:19 +0100, Andy Talbot wrote:


How would DAB be used as an off air timing / frequency source? I
eralise that when passed though a decoder it may be possible to
extract timing information, but that is not going to be any more use
than a GPS 1PPS signal, surely.

Carrier may well be high stability GPS locked, but recovering the DAB
carrier from an OFDM stream is well - shan't claim impossible, but....

And on the subject of GPS...

I've just been looking at a new generation RF Solutions GPS module
(actually not so new; G8ACE recommended it 3 years ago. I bought one
but did not touch it until now) Google the term " DS-GPS1513R " for
details. Small postage stam sized and ideal for embedding into
stuff.

I'm very very impressed: rapid turn on from cold (freezing, even,
after 3 years in the box). Modern thrid generation weak signal
capability with lockup from an antenna on the window ledge. Low power
consumption, and proper NMEA data stream without any setting of
commands. Ie simple plug-and-play timing solution. The 1PPS
stability isn't brilliant for GPSDO applications, though, it is quoted
as 300ns, so OK for a 'ZAZ type based around a good OCXO to start
with, but not suited to locking lower spec. master oscillators. 3.3V
logic level signals, but within TTL voltage switching thresholds so
will directly drive a PIC run at 5V rail providing the standard I/O
lines are used; not the Schmitt input ones. On the majority of 16F
family PICs, this means PORTB is OK, PORTA is not. Cost these days
looks to be around £20 - or maybe less.

I also have on order, and recommended, by G4GUO, a Globaltop
FGPMMOPA6H GPS module (Google it) . Again a small module, but this
claims to have a high quality 1PPS signal with specified jitter of
just 10ns. Whick puts it on a par with the Palisades I think. High
sensitivity and NMEA output so should be a simple solution. It has a
built in patch antenna, or option for an external powered one with
automatic detection and antenna switching - a nice touch. Cost
aroud £30 total

Andy
G4JNT



On 24 June 2013 00:24, David GM6BIG <freevil@...> wrote:

Hi All,

the other off air source im thinking of is DAB.

All the DAB transmitters I work with are GPS locked.
The data is critically timed too.

The national services are all on the same frequency (SFN), and
are intended to have overlaping service areas.
They have to be accurate.

Example, BBC National DAB 12B 225.648 MHz


Must be a way of extracting a reference from it....

Cheers, DAvid GM6BIG

Cheers, David

PS--
Actually, there is another off air source, will have a
think about it....!






Join UKMicrowaves@groups.io to automatically receive all group messages.