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[jamsat-bb:4758] Re: decoding GPS signal


藤本さん、

TAPRにtacgpsと称するGPSに関するメーリングリストがあります。
最近この分野に詳しいTom W3IWIの投稿メールを添付しました
のでURL等を参考にして下さい。

先ず、GPSユニット(受信機)を入手しなければなりませんが
Garmin等は可成り安く市販されていますがTomによれば最も
良いのがMotolora製でONCOREと言うブランドが良かったのですが
このブランドが最近になって製造中止になり代わってM12が
これから出るようです。TomのWebに写真入りで載っていますが
大変小さく魅力的です。

次に、TAPRから入手可能なTAC-2と言うPCインターフェースを
入手されるのをお勧めします。
キットになっており1PPS出力・RS232Cインターフェースなど
至れり尽くせりです。これはTom以下Lyle達が開発した物。

もう一つ、TAC-32と言うソフトが面白く必要でしょう。
余談ですが僕のPCは53nSecで管理されています。

これらに関しては;
http://www.tapr.org/tapr/html/Ftac2.html
をご覧になって下さい。

Tom達は間もなく(?)GPSを使ってTOCと言う開発名で
基準発信をGPSで管理するプロジェクトも存在します。

山田 - JR1EDE

-------------------------------------------------------
Date: Mon, 27 Sep 1999 02:18:46 +0000
From: "Dr Thomas A Clark (W3IWI)" <tac@clark.net>
Reply-To: "TAPR Special Interest Group" <tacgps@lists.tapr.org>
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Subject: [tacgps] M12 Receiver photos
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There has been some interest here in the new Motorola M12 receiver,
which we hope will inherit all the ONCORE capabilities. As I noted
last week, Rick has a "beta" M12 OEM board, plus a Axiom MCORE
development kit on loan to support software development. I was
at Rick's today and had my camera with me, so I took some High-Res
photos.

So you can see what the hardware looks like, I just posted three 
photos on my ISP's web site at URL

          http://www.clark.net/pub/tac/m12.htm

[When you connect to this URL, you see some compressed thumbnail
pictures. The real photos download when you click on the smaller
thumbnails and are 300-400 kbytes in size. The photos can be
downloaded from URL ftp.clark.net/pub/tac -- the other pictures
on this site are of AMSAT's P3D satellite in July and can be seen 
at http://www.clark.net/pub/tac ]


The top two pictures are of the M12 board front & back. The big
white areas are paper labels that cover some of the chips. The MMCX
RF connector is to the right in both photos. The think that looks like
a small wrist watch in the lower right corner of the top is a socketed
backup battery. The small dual-row power+I/O connector is seen on the
top-side photo, in the upper left-hand corner above the big chip.
The coin provides a reference scale. Yes, the board is really
small!

At Rick's, I did see the M12 board running with TAC32Plus, 
tracking satellites and producing a 1PPS signal. Rick had
it driving a TAC-2 equipped with his IRIG time-code generator
add-on board.

  - - - - - - - - - - - - - - - - - - - - - - - -

The third photo is of Axiom's MCORE development system, which is
described in some detail on Motorola's MCORE M2003 web site. Near
the center of this board is a stack of smaller boards, topped off
by the RF & correlator deck (see the words "PowerStrike"). The
M2003 CPU is on one of the middle layers. The two EPROMS in the
lower-left corner are the M2003 debugger, and above them (also
occupying two 32-pin sockets) is a flash EPROM. I didn't put a
scale on this photo, but the EPROMs are 28-pin parts and hence
~1.5 inches in size. The overall board is about 8" x 6" in size.

The MCORE development board is obviously intended for the
development of M12 code, and it appears that the intention is that
the serious (ab)user will be able to provide some customization of
the firmware -- but the detail of hooks & interfaces only exist
on the MCORE web site in the guise of a big (~120 page) PDF file,
which describes both the hardware and some of the software
details. (Yes, that was a vague statement -- but it reflects
the vagueness of my understanding of the details of the M12/
MCORE!).

73, Tom



FYI -- the camera that was used for these photos is a Nikon
CoolPix 950 with 1200x1600 pixels. The ~400 kbyte JPEG pictures
are ~10:1 compressed from their original raw ~6 megabyte size.
The macro pictures were illuminated with a desk flourescent lamp --
the ones I did with a flash had too much glare.