Beats the hell out of me....

speighty58 · Occasional Visitor Joined: Apr 14, 2005 Posts: 8

as to why the following happens.

Setup:

I have a motorbike, running 2 cigarette lighter power sockets, which run my Dell Axim X3 running TomTom on....this gets a GPS signal from my old Garmin Emap thorugh a combined power and signal lead. The Dell connects to my intercom system for voice guidance. This worked fine and dandy.

However, I've been getting a feed back loop when i have the dell attached to the intercom. Talking to the intercom people, seems that the intercom ground itself through the aerial as well as the earth lead. So i severed the earth lead. All fine and dandy....all have power etc.

Sticks it all on the bike on sunday...switches it on...puts in the destination....signal to TomTom and route plotted. Hops on bike, starts her up and starts down the road....TomTom shows i've got no GPS signal.... hmmmm i thinks.....loose lead. Stops switches off bike, plays with leads.....bingo....signal comes back. Starts bike starts off again.....no gps signal...

Anyways....whats happening is....i can get a gps signal to pda just fine.....but if i connect the headset (headpone) lead.....i stop getting a gps signal....either way the emap works fine...

Anyone got any ideas?

Chris

mikealder · Posted: Mon Sep 26, 2005 8:16 pm Post subject:

The key to this has to be the Bike On or Off when off the PDA will revert back to power from its battery (unless you have it connected direct to the bikes battery). And the severed lead to avoid the comms problems, try re-connecting the severed lead as this might have been supplying the GPS from the lead with the ground it needs - the book might say otherwise but its worth a try (it could quite easily use the ground that is still connected when de-powered and therefore work when not running on bike power to the PDA, earth loops are problematic at the best of times). The noise needs cancelling at source try backing the volume down if it is feedback - Ihope this gives you a pointer to start with - Mike

speighty58 · Occasional Visitor Joined: Apr 14, 2005 Posts: 8

I'll try with changing the leads around, however, the wierd thing is the PDA doesnt power down, the GPS signal is just 'lost'. Although from your response i wonder if it is providing a 'ground' when connected which somehow creates the same problem.

I'll let you know how i go on.

Chris

SharpEye · Posted: Wed Sep 28, 2005 1:19 pm Post subject:

If you don't connect the headphone lead and then start the bike do you still lose GPS signal?

I am thinking that perhaps electrical interference is swamping the gps receiver.

SharpEye

jimbo_hippo · Frequent Visitor Joined: May 18, 2005 Posts: 444

speighty58
This is interesting because I have a similar problem and have chased it for months with no avail. You'll see my setup in the sig below. In essence, your setup is like mine, i.e. hardwired GPS, PDA and wired headphones. I discussed it here:
http://www.pocketgpsworld.com/modules.php?name=Forums&file=viewtopic&t=27348&highlight=headset

I had never considered an earthing issues. For what its worth I've used TTNavigator5, Navman and Destinator, all with the same problem. However, the degree of the problem has varied with different software. And with Navman I could navigate but lost the GPS whenever a wav file was loaded for voice instruction. But this ONLY happened with the headphones in. Otherwise its absolutely fine.

I haven't nailed it yet but i will endevour to share anything I find from the other threads here. But I think it would be worth taking your setup away from the bike, i.e. into a car and see if the problem still occurs as this would eliminate the interference issue.

I have toyed with the idea that with all the 'Naving' and data from GPS going on, the wavfile loading forces it to run out of memory but I haven't proved this yet.

If you leave the headset in and wait does the signal come back? Mine would occasionally do that.

A colleague has just begun using the same setup as me but with a ThinkNavi cradle instad of the Holux CR100. Hes away at the moment but I intend to narrow the problem down using his cradle which will help.
_________________
Tom Tom GO 720
Orange M3100, Orange SPV M5000
TomTom Navigator 6, Destinator 6
Holux GPSslim

mikealder · Posted: Wed Sep 28, 2005 9:35 pm Post subject:

jimbo_hippo · Frequent Visitor Joined: May 18, 2005 Posts: 444

Chris. Promised I'd report anything. For what its worth see here: http://www.pocketgpsworld.com/modules.php?name=Forums&file=viewtopic&t=28701
_________________
Tom Tom GO 720
Orange M3100, Orange SPV M5000
TomTom Navigator 6, Destinator 6
Holux GPSslim

speighty58 · Occasional Visitor Joined: Apr 14, 2005 Posts: 8

Sorry for the slow response....work and all that.

Mike,
Yes the PDA does show charging...the GPS (emap) doesnt lose a signal at all, its satellite status shows a good spread all the time.

to answer further questions, i've left the gps and pda 30mins without the signal coming back.

Sharpeye,

If i dont connect the headphone lead and start the bike the GPS signal is nice and strong.

I've reconnected the severed lead in the mean time and as expected everything is fine and dandy. Tho i have 'charging cycle' interference back through the headphones.

I've spoken to a technical bod at the 'intercom' manufacturer who confirmed that earth loops are a royal pain in the butt to resolve as modern technology has a real tendency to be overly sensitive with earthing itself all over the place, not necessarily to its dedicated earth lead ! !

I've ordered a isolated lead for the GPS (headphone) socket which 'should' hopefully resolve the problem...if not i'll have to figure out a way of isolating the power for each input. Not an easy task on a motorbikes as its a very basic electronically...

speighty58 · Occasional Visitor Joined: Apr 14, 2005 Posts: 8

Jimbo,

I've just read your post and interestly enough i was wondering if it was driver related.
However, this will be a problem for me to resolve on the PDA as windows is ROM based and i'm not sure that i can remove drivers for it. There are options pre-loaded with TomTom, so i'll have a try with that 1st and see if it makes any difference

Chris

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