[time-nuts] Inexpensive modular gps with 1pps

[David]

On Thu, 15 Nov 2012 06:07:28 -0800, Jim Lux <jimlux at earthlink.net>
wrote:

>On 11/15/12 5:33 AM, David wrote:
>> On Thu, 15 Nov 2012 05:02:54 -0800, Jim Lux <jimlux at earthlink.net>
>> wrote:
>>
>>> On 11/15/12 4:30 AM, David J Taylor wrote:
>>>> i just used this to with a raspberry pi with good success.
>>>>
>>>> https://www.adafruit.com/products/746
>>>>
>>>> james
>>>> ===============================================
>>>>
>>>> It looks idea, James, but ... with the 15 mm square patch antenna it
>>>> seems deaf compared to similar devices with 25 mm antennas.  Perhaps
>>>> understandable, but I just bought one and it's been sitting for well
>>>> over an hour and not yet acquired lock.  The device I bought from China,
>>>> sitting next to it, has been happily locked for that whole period.  (As
>>>> I'm running a test I don't want to unlock the other device).  Just a
>>>> caveat for someone considering using these devices indoors - size matters!
>>>>
>>>> 25 mm antenna device:
>>>>    http://www.satsignal.eu/ntp/NEO-6M-under-initial-test.jpg
>>>>    http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html
>>>>
>>>> Cheers,
>>>> David
>>>
>>>
>>> ALl good ideas.. but I was looking more for something a bit more
>>> packaged.. like a hockey puck with wires coming out.
>>
>> I picked up a used Garmin GPS18-5Hz hockey puck to play with and after
>> updating the firmware, have gotten good results with the cable going
>> out a window and the unit sitting on the lower edge of the roof.  Its
>> 5 pulse per second output has 60ns of resolution according to the
>> Racal Dana 1992 I repaired implying about a 16.6 MHz timing clock.
>>
>
>That's the kind of thing I'm looking for.. or the Synergy TrakPuck  ... 
>or one of those pods that came with mapping software 5-10 years ago.
>I wonder if there's a new version of the GPS18, since I need something 
>that is available off the shelf (and likely to remain so for at least 
>2-3 years)..
>
>Is there a timing output on the GPS16x?  (or are the serial messages 
>synchronized in some way)

So the 16x manual says.  As far as I know, all of the Garmin LVC, HVC,
and 5Hz versions of their receivers have a timing pulse output.

The GPS18 series that I have was replaced by the GPS18x series.

Some of their receivers have "TIA-232-F (RS-232) Compatible Polarity"
which means exactly that.  They do not provide RS-232 voltage levels
so for my GPS18-5Hz, I had to hack together a little non-inverting
level shifter (two transistors, some resistors, and a dual power
supply) to convert the 0 to 5 volts into -12 and +12 volts.