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ZL3AI > APRDIG 01.04.04 20:43l 243 Lines 9641 Bytes #999 (0) @ WW
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Subj: TAPR Digest, Mar 29, 3/7
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From: ZL3AI@ZL3VML.#80.NZL.OC
To : APRDIG@WW
Subject: Re: New tracker design suggestions
From: David VanHorn <dvanhorn@cedar.net>
Date: Mon, 29 Mar 2004 12:58:26 -0500
X-Message-Number: 15
At 09:47 AM 3/29/2004 -0800, Scott Miller wrote:
>>Twice the weight for same power, or half the power per unit volume though.
>
>Well, I've got samples of Li-Ion charger chips around here too. Not sure
>that I want to get into that, though.
Li-Polymer is interesting, but the flammable electrolyte in Li-Ion and
Li-Poly makes me nervous.
>>Radio power is interesting as well. Lowest possible current on receive,
>not very important what it draws on transmit.
>>
>>Maybe no receiver at all, though you pay for it in collisions.
>
>Makes a lousy digipeater, though. =]
Well.. :)
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Subject: Re: New tracker design suggestions
From: "Scott Miller" <scott@opentrac.org>
Date: Mon, 29 Mar 2004 10:14:33 -0800
X-Message-Number: 16
>Proper bypassing, and grounding the bypasses to the proper point solves
>most of it. Buck topology is pretty quiet too.
I think I've got a handle on this, but I'll probably have someone with more
experience take a look at my board layout later on. For now I'm building
the individual subsystems on small breakout boards for prototyping. The
modem board has separate analog and digital ground planes, connected to each
other and supply ground directly under the IC. Decoupling is done to
manufacturer's specs, with 100 nh inductors and .1 uf and 10 uf caps on both
analog and digital supplies.
I have yet to power up the modem and test it, though. I spent yesterday
working on processor setup. The chip's supposed to be sensitive down to -45
dBm, so it's certainly going to take some caution.
>5-3 isn't really LDO territory, you have 1.7V margin.
>An LDO wouldn't hurt.
1.7 volts is about the minimum some regulators can handle. I'd just feel a
lot safer with a LDO regulator that'll only need a margin of .3V or so.
>High efficiency LEDs, in series, and turn them off after a few seconds.
Haven't spec'd out a display yet. I'd like to go with something cheap. Or
at least let the end user buy a board and build their own enclosure with
display. Electronic Goldmine sells suitable LCD modules for about $1.50.
Only those have the backlight permanently on - you've got to desolder the
current limiting resistors to shut it off.
Scott
N1VG
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Subject: Re: New tracker design suggestions
From: David VanHorn <dvanhorn@cedar.net>
Date: Mon, 29 Mar 2004 13:22:57 -0500
X-Message-Number: 17
At 10:14 AM 3/29/2004 -0800, Scott Miller wrote:
>>Proper bypassing, and grounding the bypasses to the proper point solves
>most of it. Buck topology is pretty quiet too.
>
>I think I've got a handle on this, but I'll probably have someone with more
>experience take a look at my board layout later on. For now I'm building
>the individual subsystems on small breakout boards for prototyping. The
>modem board has separate analog and digital ground planes, connected to each
>other and supply ground directly under the IC. Decoupling is done to
>manufacturer's specs, with 100 nh inductors and .1 uf and 10 uf caps on both
>analog and digital supplies.
In the SMPS, don't even use planes. Take the return current to the point
where you want it delivered. In three-pad nodes, like in pi-filters, make
the connection as In-cap-inductor, and incuctor-cap-out, not interconnected
triangles. Another engineer challenged me on this, and I showed him that it
made a 2dB difference to bridge just one of my "V" connects into a
triangle.
>1.7 volts is about the minimum some regulators can handle. I'd just feel a
>lot safer with a LDO regulator that'll only need a margin of .3V or so.
I've seen 1.1, though I guess the LDO/regular line is just a bit fuzzy :)
>>High efficiency LEDs, in series, and turn them off after a few seconds.
>
>Haven't spec'd out a display yet. I'd like to go with something cheap.
>Or at least let the end user buy a board and build their own enclosure
>with display. Electronic Goldmine sells suitable LCD modules for about
>$1.50.dOnly those have the backlight permanently on - you've got to
>desolder the current limiting resistors to shut it off.
I'm using some amazingly bright SMD leds from Chicago miniature.
They are not expensive, which was rather a surprise.
They are bright enough that I lay paper over them when working on a printer
with the cover removed.
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Subject: Re: New tracker design suggestions
From: David VanHorn <dvanhorn@cedar.net>
Date: Mon, 29 Mar 2004 13:24:18 -0500
X-Message-Number: 18
>I have yet to power up the modem and test it, though. I spent yesterday
>working on processor setup. The chip's supposed to be sensitive down to
>-45 dBm, so it's certainly going to take some caution.
Assuming perfect power, would you ever get that low on an FM rig, without
the SNR going to hell first?
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Subject: Re: New tracker design suggestions
From: "Curt, WE7U" <archer@eskimo.com>
Date: Mon, 29 Mar 2004 10:24:10 -0800 (PST)
X-Message-Number: 19
On Mon, 29 Mar 2004, Scott Miller wrote:
>Haven't spec'd out a display yet. I'd like to go with something cheap. Or
>at least let the end user buy a board and build their own enclosure with
>display. Electronic Goldmine sells suitable LCD modules for about $1.50.
>Only those have the backlight permanently on - you've got to desolder the
>current limiting resistors to shut it off.
For my uses a headlamp or flashlight will suffice. I don't need the
backlight. For a mobile situation though I suppose you couldn't get by
without it.
--
Curt, WE7U archer at eskimo dot com
Arlington, WA, USA http://www.eskimo.com/~archer
"Lotto: A tax on people who are bad at math." -- unknown
"Windows: Microsoft's tax on computer illiterates." -- WE7U
"The world DOES revolve around me: I picked the coordinate system!"
----------------------------------------------------------------------
Subject: Re: New tracker design suggestions (fwd)
From: "Curt, WE7U" <archer@eskimo.com>
Date: Mon, 29 Mar 2004 10:26:26 -0800 (PST)
X-Message-Number: 20
---------- Forwarded message ----------
Date: Mon, 29 Mar 2004 12:08:01 -0600
From: John-Thomas Beadles <beadles@nortelnetworks.com>
To: "Curt, WE7U" <archer@eskimo.com>
Subject: RE: [aprssig] Re: New tracker design suggestions
Curt,
The primary email is down, and so can't send mail to the list. See comments
below:
>-----Original Message-----
>From: Curt, WE7U [mailto:archer@eskimo.com]
>Sent: Monday, March 29, 2004 11:49 AM
>To: TAPR APRS Special Interest Group
>Cc: TAPR APRS Special Interest Group
>Subject: [aprssig] Re: New tracker design suggestions
>
>The same setup (ammo-can with TX/RX radio/TNC) can be used as
>aquick-to-setup mobile rig for SAR, so we can move it to
>whatever vehicle we're using at the time. There it's better
>to use a gel-cell, a cigarette-lighter plug, and a mobile rig though.
>
>I'd like to see TX/RX for portable trackers as well, so that
>the positions of nearby teams can be displayed on the Garmin
>map screen. Yes, this involves more complexity in the TNC and
>radio, and higher current consumption hence extra battery
>weight, but I think it's worth it.
This would be good, but I want a tracker that has a separate port for
connection to a $50 Palm V or VII unit. I don't necessarily want the
tracker to see locations, but definitely want the tracker to be able to send
a message from a list of preprepared feature messages.
Also want the cabling and connections to be ruggedized. DB-9s and power
connections that can't be screwed down are just asking for trouble in the
field.
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Subject: Re: New tracker design suggestions
From: "Scott Miller" <scott@opentrac.org>
Date: Mon, 29 Mar 2004 10:35:41 -0800
X-Message-Number: 21
>Assuming perfect power, would you ever get that low on an FM rig, without
the SNR going to hell first?
I suppose not, but then the chip wasn't designed for FM radio. While I
don't see any reason it shouldn't work, I don't know of anyone that's used
this particular chip (CML CMX860) for packet before. Probably because it's
not available in a DIP package, and it doesn't have a raw FSK output like
the MX614 or TCM3105 - all host communication is through a programmed serial
interface.
It's also more expensive than the MX614, but it includes a DTMF decoder.
Since I was planning to add a DTMF decoder anyway, this saves money, power,
and board space. It's also got some programmable tone detector and
generator features, but I'm not sure yet what I'll do with those.
Scott
N1VG
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Subject: Re: New tracker design suggestions
From: "Scott Miller" <scott@opentrac.org>
Date: Mon, 29 Mar 2004 10:38:50 -0800
X-Message-Number: 22
>For my uses a headlamp or flashlight will suffice. I don't need the
>backlight. For a mobile situation though I suppose you couldn't get
>by without it.
I think I'll just provide a standard 16-pin header and leave LCD selection
up to the user. It'd be nice to have the backlight power under software
control - that'll require a FET or something since I don't think any of the
LED drive pins on the CPU can sink enough current for a backlight.
Scott
N1VG
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