[aprssig] Why is my AvMap G6 flaky?

[Dave B]

As he asked, was the vehicle fully shutdown?

Some car stereo RX's can leak the 15th (I think) harmonic of the LO, and 
that can jam GPS reception when the FM RX is tuned to some particular 
frequencies.   One of the well known EMC "Banana Skins" of a few years 
back.

The vehicle beeing Off question, relates to noise on the internal 
electrics, even your auxilary battery system if it is still physically 
connected to one side, might still have enough broadband noise on the 12V 
to freak out the AvMap somehow.  (Though I'd have thought unless it's 
faulty, the AvMap should be fairly well immune to that sort of thing.)

If you have a portable osciloscope, that runs from its own internal 
batteries, it might be worth sniffing/poking about the 12V system with an 
AC coupled probe, just to see.   You'd need instantanious analogue scope 
bandwith to a couple of MHz, no more I suspect.

73.

Dave G0WBX.


On 4 Jan 2013 at 19:37, Andrew P. wrote:

> I had the AvMap running with the vehicle both "on" and "off"; it
> seemed to be a reliable start-up from the auxiliary batteries
> regardless of the engine status. Just an aggravatingly slow startup
> with no progress indicator (about 30 seconds or so).
> 
> The route calculation problem didn't seem to matter whether the
> vehicle was moving or not. Only the first calculation of a new route
> worked after power-up. To change the route, I had to enter the
> destination and route method (and let it fail), then power-cycle the
> AvMap, and it would then correctly calculate the route.
> 
> Sent from my Verizon Wireless BlackBerry
> 
> -----Original Message-----
> From: lawrence labranche <capdiamont at yahoo.com>
> Date: Fri, 4 Jan 2013 18:00:35 
> To: <aprssig at tapr.org>
> Subject: Re: [aprssig] Why is my AvMap G6 flaky?
> 
> 
> Was the vehicle parked and "off?"
> 
> 
> 
> 
> ----- Original Message -----
> From: Andrew P.  <andrewemt at hotmail.com>
> To: "aprssig at tapr.org " <aprssig at tapr.org>
> Cc: 
> Sent: Friday, January 4, 2013 7:58 AM
> Subject: Re: [aprssig] Why is my AvMap G6 flaky?
> 
> 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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> Sent from my Verizon Wireless BlackBerry
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