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[aprssig] Why is my AvMap G6 flaky?

Andrew P. andrewemt at hotmail.com
Fri Jan 4 15:58:59 UTC 2013


Followup to all:

My problem with the AvMap G6 isn't GPS reception; when it starts up, it seems to get a good GPS lock pretty quickly and track accurately (although it appears to be inconsistent in using Snap-to-Road when I go into parking lots). My problem was getting the thing to start at all.

I did try Lawrence's suggestion; I had two deep-cycle batteries behind a battery isolator from the vehicle's regular power system (these batteries are primarily there to run my Engel DC-powered portable refrigerator without flattening the main vehicle low-voltage battery), so I plugged the AvMap's DC power cord into the DC outlets connected to the auxiliary batteries, and it seemed to start up much more reliably (although still slowly).

But that still didn't affect the AvMap's inability to calculate more than one trip routing per power-up. If I tried to change my destination, it would always fail with "Error calculating the path" until I power-cycled the AvMap. Oddly enough, when I deviated from the AvMap's chosen course (several times I tried switching to "shortest route" instead of "fastest time", and that routing always wanted to get my onto dinky side-streets), it was able to successfully re-calculate to account for my disobedience. It just couldn't deal with a new destination without a power cycle.

Much weirdness, and significant disappointment. If the touchscreen wasn't dying on my old Magellan GPS, I would go back to it, because it was more reliable and faster than the AvMap (and significantly cheaper, too). Good thing I knew where I was going, and was only using the AvMap as a GPS source for the Kenwood and for arrival time estimates.

Andrew Pavlin, KA2DDO
------Original Message------
From: Dave B
To: aprssig at tapr.org
Sent: Jan 4, 2013 5:23 AM
Subject: Re: [aprssig] Why is my AvMap G6 flaky?


On 2 Jan 2013 at 20:00, Ron Stordahl, AE5E wrote:

> 
> Wouldn't this electrical noise make the AM broadcast band 
> nearly useless? And if so how would this get by the 
> designers. 
> 
> Ron, AE5E
> 
> 

< big snip >

The EMC emission tests, are only designed to protect intended (local 
area) broadcast signals, who's levels are several 10's of dB greater than 
anything we might be interested in.

It's relatively easy too, to selectivly filter something, so it scrapes 
through a test.

Then, there is the "Technical Construction File" route to passing a test.

Vehicle system susceptability/immunity (call it whatever, but EMC the 
other way round) is rigerously designed for and tested, to *Very* high 
levels (100's of V/m across the spectrum) so it is unlikely even a modern 
Hybrid would falter or ever twitch at the sort of "normal" level RF we 
might genereate in a vehicle with regular Off the Shelf commercial Ham 
kit.

Much of this I've seen first hand, visiting Automotive EMC facilities, 
commisioning and supporting their EMC test equipment, especialy the multi 
kW amps they use.   Unless you have a free 3-phase feed (63A/phase at 
least) in the shack, you won't want one, as they tend to be under 20% 
efficent, on a good day!.

The emissions test receivers/analyzers also are not as sensitive as a 
"communications" grade RX, but they are stable accurate and calibrated.  
That, and knowing the feder cable losses vs frequency, plus the measuring 
antenna performance (from indipendant calibration) also how the chamber 
or OATS behaves (Open Area Test Site) gives them a good confidence level 
when measuring emission levels.

However, the nature of some emissions, beeing very wide band and very 
short duration (narrow pulse trains) can "fool" the RX's into recording a 
lower level, than is actualy being radiated.  There are test procedures 
to detect such phenominon, but they take time, and time is $ etc.

However, all that pales into insignificance, once a local mechanic has 
had their hands on it, as there are as yet, no requirements to re-test a 
vehicle after any service (or street modification) works are done.  Yet?

It's dificult enough for Trafic Cops to measure tail pipe noise levels if 
they suspect something is "too" loud, imagine them carting arround RF 
analyzers/receivers and test antenna's?   (plus exhaust gas analyzers and 
so on...)

Happy New Year All.

Dave G0WBX.


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