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ZL3AI > APRDIG 30.11.03 22:42l 238 Lines 9162 Bytes #999 (0) @ WW
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Subj: TAPR Digest, Nov 26, 1/3
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From: ZL3AI@ZL3VML.#80.NZL.OC
To : APRDIG@WW
TAPR APRS Special Interest Group Digest for Wednesday, November 26, 2003.
1. Best GPS for city work
2. Re: Slightly OT: Good source for *lots* of Gel-Cells?
3. Re: Slightly OT: Good source for *lots* of Gel-Cells?
4. Re: Slightly OT: Good source for *lots* of Gel-Cells?
5. Digitraveler altitude limit?
6. Fusing the ground lead...
7. Re: Fusing the ground lead...
8. Re: Slightly OT: Good source for *lots* of Gel-Cells?
9. ICOM IC-2AT info?
10. Re: ICOM IC-2AT info?
11. Re: ICOM IC-2AT info?
12. Re: ICOM IC-2AT info?
13. Re: ICOM IC-2AT info?
14. Re: ICOM IC-2AT info?
15. RE: ICOM IC-2AT info?
16. Re: ICOM IC-2AT info?
17. Re: ICOM IC-2AT info?
18. Re: Fusing the ground lead...
19. Re: Digitraveler altitude limit?
20. Re: Fusing the ground lead...
21. Re: Fusing the ground lead...
22. Re: ICOM IC-2AT info?
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Subject: Best GPS for city work
From: "Darryl Smith" <Darryl@radio-active.net.au>
Date: Wed, 26 Nov 2003 16:19:41 +1100
X-Message-Number: 1
People
I was wondering if anyone had done any trials of a GPS for city urban
canyons. I have tried a M12 from Motorola, but it is not working too well.
I am using an amplified antenna with a 10cm diameter plate.
My problem is that it must be mounted on a pushbike...
Any suggestions?
Darryl
---------
Darryl Smith, VK2TDS POBox 169 Ingleburn NSW 2565 Australia
Mobile Number 0412 929 634 [+61 4 12 929 634 International]
www.radio-active.net.au - www.radio-active.net.au\tracking
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Subject: Re: Slightly OT: Good source for *lots* of Gel-Cells?
From: David VanHorn <dvanhorn@cedar.net>
Date: Wed, 26 Nov 2003 00:46:07 -0500
X-Message-Number: 2
At 11:22 PM 11/25/2003 -0500, Wes Johnston wrote:
>Not to start another debate.... but our local "batteries plus" store
>collects old power wheels batteries for disposal. The newer power wheels
>toy cars come with - you guessed it - power poles. Granted they are black
>and white but they have a molded in fuse holder. Its easy enough to swap
>the housings for red and black. Two of those pairs of leads gives you two
>nice fuse holders for fusing positive and negative leads on your car for
>powering you ham gear... we all fuse both leads don't we? grin.
>Wes
Unless you also fuse your coax, I can't really see where the one in the
ground lead is accomplishing anything. Kirchoff's second law?
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Subject: Re: Slightly OT: Good source for *lots* of Gel-Cells?
From: Reid Crowe <kc0idi@yahoo.com>
Date: Tue, 25 Nov 2003 22:36:07 -0800 (PST)
X-Message-Number: 3
The second one is a safety, If your first fuse is bad then hopefully your
second isn't. Most modern rigs come with three fuses, two on the positive
and one on the negative.
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Subject: Re: Slightly OT: Good source for *lots* of Gel-Cells?
From: David VanHorn <dvanhorn@cedar.net>
Date: Wed, 26 Nov 2003 01:45:45 -0500
X-Message-Number: 4
At 10:36 PM 11/25/2003 -0800, Reid Crowe wrote:
>The second one is a safety, If your first fuse is bad then hopefully your
>second isn't. Most modern rigs come with three fuses, two on the positive
>and one on the negative.
That assumes that the only point connected to vehicle ground, is the
negative lead. Normally, the shield on the coax is grounded at the antenna
mount.
I've never heard of a fuse failing to blow (properly rated of course)
Failing to conduct, yes.
I certainly fuse my battery tap at the point where it comes off the
battery, but that's a much larger "aw !@#%" fuse, in case the wiring is
mangled and shorts to the frame.
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Subject: Digitraveler altitude limit?
From: "K. Mark Caviezel" <kmcaviezel@yahoo.com>
Date: Wed, 26 Nov 2003 00:08:20 -0800 (PST)
X-Message-Number: 5
Scott:
try Ralph Wallio's website
http://users.crosspaths.net/~wallio/gps60kft.html
for the reported list of those that pass and fail the 60k foot limit. Be
sure to report the results of your findings to Ralph so he can include it
there. The failure of the Garmin GPS45 was classic- above 60 k feet, it
started spitting out zeros. On the way down, still zeros. It was a
clear blue sky day and we tracked it visually to landing. I don't
recommend this 'visual DFing' as a highly reliable way of getting balloon
payloads back, though.
- KMC kc0jhq Denver
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Subject: Fusing the ground lead...
From: "Mike Yetsko" <myetsko@insydesw.com>
Date: Wed, 26 Nov 2003 07:04:39 -0500
X-Message-Number: 6
I knew this would start up again once someone threw down the gauntlet!
People need to remember. BATTERY ground is NOT the same thing as CHASSIS
ground. In normal operation, it may only be a small fraction of a volt,
but when starting a vehicle, the HUNDREDS of amps through the circuit can
make chassis ground be whole volts from battery ground. Also, remember
most instruments under the dash (and wiring in general) will be closer to
engine ground then anything else.
Why does that affect a HAM?
Well, where do you have 'grounds'? If you have DC connections for ground,
then you have to be aware of any currents that could take place. With a
rig that has DC connection from the (-) lead to the chassis and then
hooking to the battery can cause SERIOUS problems if you have your chassis
to antenna ground at the attenna mount for current loops.
Some rigs, however not that many, actually isolate the (-) lead from
chassis with capacitive coupling. Although this is NOT near as common as
it used to be when rigs supported both positive and negative ground
designs.
While hooking the (-) to the battery sounds like a good idea, in modern
vehicles with modern equipment it can cause a LOT of other problems. IF you
choose to hook this way, then the best course of action in this
configuration is to fuse the (-) lead.
However, it is much more 'practical', in my opinion, to hook (-) to a
chassis ground NEAR the radio. In modern vehicles there are usually 'low
impedance' tap points you can use. Most vehicles have these near audio
equipment, the main computers (airbag, body, and engine), and don't rule
out truck taps. My Intrepid has a 'ground tap' in the trunk under the rear
deck for attachment by the Infinity sound system amp. I ran my (+)
directly from the battery to the trunk for my remote mounted dualband
Alinco, and I ground at the Infinity tap.
By the way, one 'common' failure of car power systems is failure of the
'engine ground strap'. Failure here can lead to sudden and HUGE ground
differentials in the vehicle during attempted engine starts, and can lead
to 'dash fires'. And realize that failure does NOT mean the strap goes
'open'. Just that it's resistance goes higher than optimum. Remember,
starting uses HUNDREDS of amps, close to a THOUSAND! Doesn't take much for
I2R to become a major player!
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Subject: Re: Fusing the ground lead...
From: "Mike Yetsko" <myetsko@insydesw.com>
Date: Wed, 26 Nov 2003 07:08:44 -0500
X-Message-Number: 7
One thing...
IF you connect ground to the battery, and you blow that fuse, your radio
may now be grounding at the chassis (your physical mount) and at your
antenna, and even at other points, like a speaker connector or a 'common'
between units like GPS or TNC. So, do you really want that? If one part
of your system happens to be attached to a point that is different from
another point, the current will flow through your rig connections. Heck,
you may even get POWER to the rig through the antenna ground, speaker
ground, mic ground, whatever, with a BLOWN FUSE IN THE BATTERY (-) LEAD!!
Like I said, I don't ground to the battery, and I DON'T fuse it.
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Subject: Re: Slightly OT: Good source for *lots* of Gel-Cells?
From: Bob Bruninga <bruninga@usna.edu>
Date: Wed, 26 Nov 2003 08:19:51 -0500 (EST)
X-Message-Number: 8
On Wed, 26 Nov 2003, David VanHorn wrote:
>Unless you also fuse your coax, I can't really see where the one in the
>ground lead is accomplishing anything. Kirchoff's second law?
No, it protects you if you wire the negative lead straight to the battery.
It protects your rig from 600 amps of starting currrent should the
battery-to-frame cable become intermittant.. it does happen...
Bob
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Subject: ICOM IC-2AT info?
From: Bob Bruninga <bruninga@usna.edu>
Date: Wed, 26 Nov 2003 12:31:55 -0500 (EST)
X-Message-Number: 9
Battery Pack BP-5A for ICOM 2AT. I need to understand internals?
I apply 13.8v regulated to the 13.8v DC port on it, and the voltage
delivered to the radio drops to 6 volts? I have 8 packs, all do the
same..
Bob
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