| |
ZL3AI > APRDIG 05.08.03 19:41l 250 Lines 9820 Bytes #999 (0) @ WW
BID : 1729-ZL3AI
Read: GUEST
Subj: TAPR Digest, Aug 01, 2/3
Path: DB0FHN<DB0RGB<DB0MRW<DB0ERF<DB0FBB<DB0GOS<DB0EEO<DB0RES<ON0AR<ZL2TZE<
ZL3VML
Sent: 030803/1154Z @:ZL3VML.#80.NZL.OC #:5845 [Chch-NZ] FBB7.00i $:1729-ZL3AI
From: ZL3AI@ZL3VML.#80.NZL.OC
To : APRDIG@WW
Subject: D700 and digitraveler update
From: "Sean \\The RIMBoy\\" <sean@rimboy.com>
Date: Fri, 1 Aug 2003 11:31:57 -0500 (CDT)
X-Message-Number: 9
Ok, it's what I get for reading too much into the instructions (or so I
think).
I confirmed with Bruce KQ4TV that the digitraveler will work RJ-11 to
mini-stereo without any additional mods or hoopes to jump thru. An
archived post in a yahoo group confirmed it too.
So, at least using a terminal block for testing I flipped the silver satin
cord coming into it and of course, it starts working.
Sync took place in about a minute which is very good.
I'll be heading to 9-land again running KG4NRC-8, the destination Swansea
Il (although I'll be in Mascoutah most of the time).
Thanks again to all for the heads up on the bargain. My Rand McNally will
soon be retired to reserve status.
Cheers,
Sean...
--
Believing I had supernatural powers, I slammed into a brick wall.
--Paul Simon
_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
KG4NRC http://www.rimboy.com Your source for the crap you know you need.
----------------------------------------------------------------------
Subject: RE: Kantronics' latest offering...
From: "Mark Fellhauer" <sparkfel@qwest.net>
Date: Fri, 01 Aug 2003 13:04:40 -0500
X-Message-Number: 10
At 12:35 PM 8/1/2003, Curt Mills, WE7U wrote:
>Hopefully you're not talking about the "8" channel Garmin units
>versus the 12-channel ones. The "8" channel Garmin units were
>really 1-channel units that time-multiplexed one receiver across up
>to 8 satellites. Trimble and Magellan used to have 2 or 3 channels
>that they'd multiplex across multiple satellites.
I don't know why this appears to be such a hard concept to understand. I
understood Mr. Sadowski's comments perfectly. It's not the number of
received channels per se, but of the AGE of the technology involved. The
point is that Kantonics is trying to sell a new whiz-bang product with an
embedded GPS engine that was considered '"state-of-the-art" EIGHT years
ago, and was superceeded on the street seven years ago. His other point
is that the newer OEM engines not only have better GPS characteristics, but
have lower unit prices today than the less advanced receivers did just a
few years ago.
My guess is that Kantronics was stuck with a surplus bunch of older OEM GPS
engines and just chose to use them, rather than buy something newer. I
don't think anybody here needs a primer on GPS technology. It can be
summed up with the axiom that newer = better.
Mark
KC7BXS
----------------------------------------------------------------------
Subject: RE: Kantronics' latest offering...
From: "Curt Mills, WE7U" <hacker@tc.fluke.com>
Date: Fri, 1 Aug 2003 11:16:00 -0700 (PDT)
X-Message-Number: 11
On Fri, 1 Aug 2003, Mark Fellhauer wrote:
>I don't know why this appears to be such a hard concept to understand.
It's not.
>It's not the number of
>received channels per se, but of the AGE of the technology involved.
My comments were basically meant to say that the technology they're using
is good-enough. Once you go with parallel receivers, other gains due to
newer technology/better algorithms are small in comparison.
>My guess is that Kantronics was stuck with a surplus bunch of older OEM GPS
>engines and just chose to use them, rather than buy something newer.
Likely.
--
Curt Mills, WE7U hacker_NO_SPAM_@tc.fluke.com
Senior Methods Engineer/SysAdmin
"Lotto: A tax on people who are bad at math!"
"Windows: Microsoft's tax on computer illiterates!" -- WE7U
"The world DOES revolve around me: I picked the coordinate system!"
----------------------------------------------------------------------
Subject: TNCless 1-wire weather?
From: "Scott Miller" <scott@opentrac.org>
Date: Fri, 1 Aug 2003 11:32:23 -0700
X-Message-Number: 12
What's out there for running the Dallas 1-wire weather station on APRS
without a TNC? TAPR says the T-238 board is out of production. Are the
source code and PCB patterns available for it? I've got an HC908GP32
sitting on my desk doing nothing and it'd be easy enough to build a board
myself. Or is there something else readily available that'll do the job?
The station's going to be located on a winsock mast at the local paraglider
training hill, with more to follow at other sites in the area if it works
out well. There's a half-sized intermodal cargo container there that'll
provide plenty of room to house batteries and hardware, with the solar panel
safely out of sight on the roof. The other sites will be a bit less
accommodating.
Something with the ability to vary its transmit rate would be great.
Frequent updates are only needed from maybe 8 am to 4 pm.
Suggestions?
Scott
N1VG
----------------------------------------------------------------------
Subject: RE: Kantronics' latest offering...
From: "Mark Fellhauer" <sparkfel@qwest.net>
Date: Fri, 01 Aug 2003 13:55:13 -0500
X-Message-Number: 13
At 01:16 PM 8/1/2003, Curt Mills, WE7U wrote:
>My comments were basically meant to say that the technology they're
>using is good-enough. Once you go with parallel receivers, other
>gains due to newer technology/better algorithms are small in
>comparison.
But's it's not good enough. Part of selling a product is CSAT - Customer
Satisfaction. And I can guarantee you most AVL consumers these days will
not tolerate technology that regularly fails in urban environments. In
1996 people accepted those problems. In 2003 they don't.
Mark
KC7BXS
----------------------------------------------------------------------
Subject: Re: Kantronics' latest offering...
From: Gerry Creager N5JXS <gerry.creager@tamu.edu>
Date: Fri, 01 Aug 2003 14:06:41 -0500
X-Message-Number: 14
Between my headache and the schedule I'm keeping, I don't have time to
debate this on the list.
The methodologies for determination are simple. For a 3d autonomous fix,
you require 4 satellites. Geometry matters. If all you have is 4, then
you're stuck with whatever geometry you have.
If you have 6 stellites (97% or so of the time) you have 2^6 theoretical
combinations and more like 6 real combinations of geometry to achieve a
best solution. For 12 satellites <2% of the time, the number of real
combinations is, if memory serves, 20.
When you have more than 2 real combinations of solutions you can start
doing a least-squares comparison of the various position determinations,
providing more weight to the solutions with lower GDOP. Not HDOP, not
PDOP, not TDOP. You usually arrive at 2 or so solutions that have a low
GDOP and a best-fit least squares solution. These are your best answers
for autonomous positioning using code-phase data. The differences are
small.
The differences in receiver technology that have allowed better processing
include newer and faster processors, better DSPs and additional channels.
I *NEVER* said there was no benefit from the newer receivers, but I did
imply and now I'll say, that given the normal distribution of satellites, 6
channels will generally provide as good a positional resolution as 12
channels. 18 channels is just one-ups-manship.
In point of fact, the 12 channel consumer grade receivers were generated,
pretty much, because they could get a 12-channel DSP and front-end on the
wafer without any real extra work or loss of yield. Didn't cost anything
and made the marketing types happy.
Are there any questions? There's a quiz next class period.
--
Gerry Creager -- gerry.creager@tamu.edu
Network Engineering -- AATLT, Texas A&M University
Cell: 979.229.5301 Office: 979.458.4020 FAX: 979.847.8578
Page: 979.228.0173
Office: 903A Eller Bldg, TAMU, College Station, TX 77843
----------------------------------------------------------------------
Subject: RE: Kantronics' latest offering...
From: Gerry Creager N5JXS <gerry.creager@tamu.edu>
Date: Fri, 01 Aug 2003 14:12:48 -0500
X-Message-Number: 15
Curt Mills, WE7U wrote:
>On Fri, 1 Aug 2003, Mark Fellhauer wrote:
>
>
>>So you're saying that underlying technology doesn't make a difference? And
>>that newer hardware doesn't work better than the older 8 channel
>>units? That seems to fly in the face of at least my anecdotal experiences
>>with 8 channel GPS receivers vs 12+ channel (parallel) receivers.
>
....
>FWIW: I _have_ had a lock on 12 satellites at once, with the NMEA
>data showing data from all 12 satellites being used in the position.
>Was very cool to see! The nicest thing about it was that a buddy of
>mine told me it couldn't be done. That means I had to get proof.
I've seen 14 satellites in the sky once, for a brief period, of about 6
minutes. It happens periodically. We typically have 8-9 in the sky. Spare
channels, when you're outta birds doesn't help much.
But, yes, it's possible. And, I've been doing satellite geodesy, with a
variety of Trimble and Ashtech geodetic receivers since before we HAD 24
birds in the constellation. You don't know how happy I was when we had
enough satellites up to get 8 birds routinely in the visible sky.
Oh... I *have* locked up to 18 or 19 satellites at one time on L2 using a
Javad system. Another time, I locked up 24 channels (Javad again) but
because of their accounting system, when you got through winnowing it all
down, that was 12 on L1 and the same 12 on L2; different DSP channels were
used, hence the better marketting numbers.
gerry
--
Gerry Creager -- gerry.creager@tamu.edu
Network Engineering -- AATLT, Texas A&M University
Cell: 979.229.5301 Office: 979.458.4020 FAX: 979.847.8578
Page: 979.228.0173
Office: 903A Eller Bldg, TAMU, College Station, TX 77843
----------------------------------------------------------------------
Read previous mail | Read next mail
| |
