Re: PPS USB GPS recommendation

[Gary E. Miller]

Yo USNR!

On Sun, 29 Mar 2020 16:47:28 -0400
"IT1 Stuart Blake Tener, USNR" <address@hidden> wrote:

> 1. It is my understanding that PPS via USB GPS devices have come way  
> down in price (sub $10 range) on eBay for US customers. Can anyone  
> suggest a reasonably decent and inexpensive unit to order?

Good, and bad, choice abound.  Except for the obvious supply chain
problems from China.  The thing to watch out for is that most GPS do not
put PPS on the USB.  No real technical reason not to, but vendors are
worried about confusing their customers.

> 2. If one were to compare using the NTP servers provided by the NIST  
> vs using a PPS via USB GPS device, which would seem the better choice
> and why?

Well, if you doing PPS over USB, then with luck you'll almost get to 1
millisec jitter.  So most any GPS that gets a signal will be far better
then the USB transport.

To check that just add a NIST chimer to your NTPD.

> I am intending to place into my router (I currently use Gargoyle  
> firmware but am contemplating to switch to DD-WRT or OpenWRT soon) on
> such device, so that my router can provision local NTP services.

Is your router near a window?  Only the newest GPS, like a u-blox 9
work OK indoors.  So you probably need a USB GPS with an SMA antenna
connector.  You still need the antenna in a window, with a fair sky
view.

RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        address@hidden  Tel:+1 541 382 8588

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    "If you can't measure it, you can't improve it." - Lord Kelvin

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