Re: SiRF receivers


Ralph Wallio, W0RPK <wallio@...>
 

Bill,

Use of SiRFStar chipsets above 60kft is being discussed because AXIOM
Sandpiper receivers are appearing on the inexpensive surplus market. I have
evaluated a pair of these receivers for terrestrial applications, e.g.,
APRS, and find documentation and PC software to be readily available.

Michael Castle has further contributed his knowledge that SiRF code will
allow receivers based on SiRFStar-II chipsets to work above 60kft when
velocity is <1000kts. However, the AXIOM Sandpiper receiver uses the
SiRFStar-I chipset which Michael had not yet completely investigated. Your
empirical evidence appears to definitively tell us that code in the
SiRFStar-I chipset limits performance to altitudes below 60kt regardless of
vehicle velocity and acceleration.

All models of AXIOM Swift receivers use SiRFStar-II chipsets so Michael's
contribution is valuable.

Please compile and forward detailed information required for an AXIOM
Sandpiper entry to http://users.crosspaths.net/~wallio/gps60kft.html and I
will add it to the RED list.

For comparison, this what I see when my Sandpiper receivers come up:

SiRF Baseline Version: 1.3.1DKIT144 Axiom Variant: k201AX
$
Build date: Nov 12 1999
$Build time: 14:42:07

TNX es 73 de Ralph Wallio, W0RPK
wallio@crosspaths.net
http://members.crosspaths.net/wallio
Results may not be reproducible

----- Original Message -----
From: <wb8elk@aol.com>
To: <GPSL@yahoogroups.com>
Sent: Friday, June 07, 2002 0:19 AM
Subject: Re: [GPSL] Re: SiRF receivers


Ralph,

I flew an Axiom Sandpiper model receiver using the SiRF chipset on a
mission in the Gulf of Mexico on our last Rockoon mission...it flew on the
launch platform gondola. Their engineer claimed it would work over 60k
feet
just like the Motorola VP Oncore would...i.e. as long as you didn't exceed
the speed limit (somewhere over 600 knots or so), the altitude limit of
60k
would not be a problem. Some receivers will lock up at 60k feet regardless
of
the speed travelled, it depends on the manufacturer. I know that the VP
Oncore works great, the Garmin 35 and (if specially modified, the Trimble
See
Vee 6).

My experience was that although we were only travelling about 20 knots
groundspeed, the Axiom Sandpiper receiver completely locked up at 60k feet
and never came back up again during the rest of the flight. I haven't
tried
any more flights with the Axiom units, although I may try an experiment
using
the very tiny Swift model Axiom receiver that I have as a backup GPS to
see
if it works above 60k.

73s de Bill WB8ELK

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