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Re: gpsd never updates ntpd shm due device->fixcnt == 0

From: Gary E. Miller
Subject: Re: gpsd never updates ntpd shm due device->fixcnt == 0
Date: Thu, 12 Jan 2023 13:07:04 -0800

Yo Tom!

Replying on list, so all can hear and participate.

On Thu, 12 Jan 2023 12:23:29 -0800
Tom Van Baak <> wrote:

> I subscribed to the list a month or two ago. All was well until this 
> posting. Is there something wrong with the Garmin 18 (or 18x) that I 
> need to know about?

Dunno if you need to know, but:

Many consider the WKRO bug immediately disqualifying.  No way to
update the firmware.

The default 4,800 is way too slow to move the NMEA data.

The base GPS-18 only supports 4 standard NMEA sentences.

By default it only sends NMEA 2.0!  You can configure to get 2.3.
An over 20 year old obsolete standard.  The Garmin Binary improves on

It is GPS only, although for time keeping that is good.

They claim -165 dbW sensitivity, but it only works outdoors with a very
good sky view.  (Thus the need to be waterproof).  Newer receivers
work fine indoors.

They claim cold start of 5 minutes, but 15 to 30 minutes is more common.
Newer receviers cold start in under 10 seconds.

Much less accurate than a modern GPS.  They claim CEP(95) of better than
15 m, or 3 m with WAAS.  But I've never seen that.

No modern multipath or spoofing protection.

Only 12 channels. Just 11 when using PPS.  Modern receivers have almost
180 channels.

PPS specified to +/- 1 us.  almost 100 times worse than a modern receiver.

No "sawtooth" correction.

> Lots of people I know use them

They should not.

> -- they are 
> well-known and always in stock, inexpensive and weather-proof, and
> run from a single integrated cable.

I see they have cut the list price of the GPS-18lvc to $80.  $63 on
amazon, but you need to add a power supply and conenctors and it is not

That is still way too much for their (lack of) performance.

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703  Tel:+1 541 382 8588

            Veritas liberabit vos. -- Quid est veritas?
    "If you can't measure it, you can't improve it." - Lord Kelvin

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