Garmin Street Pilot III and Starcom problem?

[stewybear]

OK, So I have got my Starcom Advance wired up now with the Garmin as one of the audio inputs. I've got two problems though.

First is that there is a sound tone constantly in the background. I have spoken with Tecstar and they have given me some advice about cable routing that may cure that problem.

Second is I can't find a volume control on the Garmin unit. Its so loud that I have had to turn down the Starcom unit which means that I have had to turn everything else (MP3 player) up to compensate. This means that the MP3 is on nearly full volume all the time with no room to increase volume if needed at higher speeds.

Does anybody else have the same problem, or have you found a volume control on the Street Pilot III (I can't find one).

Any advice greatfully received.

[Cie]

Hold down the speak button on the GPS, a small sliding scale indicator will come up on the screen. Use the direction pad to raise/lower the volume, and press enter when you've done.

The whine on the intercom may be mulitple earth paths, if re-routing of cables doesn't help, let us know in here. I may have a solution.

[stewybear]

Thanks for that. I'll have to try it when I get home cos I'm at work now till 11:00pm :(

The multiple earth situation is what Tecstar suggested but when I told him that the engine was not running he couldn't offer an explanation apart from try and re-route the cable to stay clear of emitters like ignition, spark plugs, fuse box etc. He also mentioned that the isolating transformer (chunky bit in the cable) acts as an arial near those things.

He also mentioned that for the cable to work correctly, the GPS needed to be powered from the bike, rather than its own batteries so that an earth path was present for both ends of the cable. Didn't know that :oops:

Worst case scenario is that I take a trip to Tecstar. They are only 20 miles up the road from me. Trouble is I'm off on my trip on Thursday so rapidly running out of time to do anything.

I'll report back with whatever I find out, either way.

[Von Short Hausen]

He also mentioned that for the cable to work correctly, the GPS needed to be powered from the bike, rather than its own batteries so that an earth path was present for both ends of the cable. Didn't know that :oops:

Sounds a little bit like the tail wagging the dog there....You want the right cable to fit the way your system is configured, rather than reconfigure your system to suit the cable you've got :shock:

I'll (try to) explain. Theoretically, you only need an audio isolating cable when both the Starcom & the GPS are powered off the bike battery. This is because when they share the same voltage supply there is a possibilty that a voltage diiference may occur between between both units, and if this occurs a DC current will flow through the audio cable between them. To overcome this, the isolating cable contains a transformer which interrupts the conductors, and allows Alternating Current (the wanted audio) to pass, but blocks DC current (the unwanted offset current). If the offset current was to appear at the audio input of the Starcom, it might cause instability and distortion.

However since your GPS is running on internal batteries, and is not connected to the bike battery, you should theoretically be able to use a standard audio cable without a transformer in.

Anyaway that's the science bit.. The fact is that you need to fault find your system.....try unplugging one cable at time and seeing if the oscillation stops.

Is there any difference when the engine is running ?

Hope this helps :?

[ChrisH]

To overcome this, the isolating cable contains a transformer which interrupts the conductors, and allows Alternating Current (the wanted audio) to pass, but blocks DC current (the unwanted offset current).
Is it a capacitor or a transformer? I was considering making up the cable. On my Autocom system the phone plug is 2.5mm and I don't use the phone input so I was gonna use that with the relevant blocking component..... is that a runner? Any help/ideas gratefully recieved!

[Von Short Hausen]

Is it a capacitor or a transformer? I was considering making up the cable. On my Autocom system the phone plug is 2.5mm and I don't use the phone input so I was gonna use that with the relevant blocking component..... is that a runner? Any help/ideas gratefully recieved!

I don't own a Starcom, so I can't say. I referred to a transformer because Stewybear mentioned that the Tecstar bloke said there was a chunky lump, which was the transformer.

A capacitor in series would block DC, you can give it a try.

Maplin do Transformers, see...http://www.maplin.co.uk/Search.aspx?criteria=HX82D&DOY=26m6

And also a Ground Loop Isolator package....http://www.maplin.co.uk/module.aspx?TabID=1&criteria=audio%20isolating&ModuleNo=33172&doy=26m6

With your suggestion for using the phone input, there should be a handbook telling what you can plug into each input, but the idea sounds plausible. Are you powereing your GPS from the Bike battery ?

I've actually bought an Autocom system, because they had the appropriate interfaces for my Ham Radio gear and I was able to try my equipment out on their test rig at Whithouse M/Cs. Like several other people I'm in the middle of installing my own kit, so it'll be interesting to compare notes.

[Cie]

I bought my ground loop isolator on ebay (http://cgi.ebay.co.uk/GROUND-LOOP-ISOLATOR-NEW-CAR-AUDIO_W0QQitemZ9743439235QQihZ008QQcategoryZ14932Q QrdZ1QQcmdZViewItem)

Your GPS may be earthed through the mount perhaps? This would cause the same problem.

suggested but when I told him that the engine was not running he couldn't offer an explanation

It doesn't matter if the bike's running or not, but in having the same issue with the bike not running you've proved that it's not interference from the charging system.

the GPS needed to be powered from the bike

Nonsense... although I power mine from the bike, but can do either. It sounds to me like Tecstar will make money out of you, possibly through their ignorance.

The way I look at this (and fixed my GPS/Phone/Autocom problem) is that everything must have power, and multiple power earths are fine. But the audio earths need isolating. This is with a transformer, and known by some as a ground loop isolator.

Now, the one I bought from ebay has two leads going through it, that's two pieces of co-axial cable. If you break those out, you have 4 posibilities of isolation.

So, you just remove the plugs from the isolator and make some connections up that'll enable you to isolate upto 4 audio paths.

There's the beginnings of a wiki page on this subject here (http://wiki.xrv.org.uk/index.php/Ground_Loop) Feel free to add/amend it with your experinces/opinions

[ChrisH]

I don't own a Starcom

Neither do I :?
I think I understand the transformer idea now - It passes AC by induction, but blocks the DC part. Isn't a blocking capacitor a cheaper alternative though? Haven't tried the GPS yet as it hasn't arrived :wink: but my MP3 player is powered by its' own battery. Trouble is I don't know quite enough about electrickery and will probably end up paying £20 for something that's worth a few pence which will piss me off with Autocom even more :? Didn't think much of them not supplying the connection lead with the second headset for the intercom..... that'll be another £10, sir...
Apart from that I'm happy with the Autocom unit.

[Von Short Hausen]

I don't own a Starcom

Neither do I :?

Yessss, sorry about that. :oops: That's what happens when you're trying to answer 2 questions at once.....well it does with me anyway :roll:

Isn't a blocking capacitor a cheaper alternative though?

It is..... but it runs the risk of affecting the audio, depending of course on what values you use and how you do it. Whereas if Rupert Neve is happy to have transformers on the inputs to his (incredibly expensive and fantastic sounding) mixing desks, I can live with them on my intercom :lol:

As it happens I've just ordered a couple of Audio Isolating Transformers from Maplins for £1.94 each. I'm hoping that the one with a 20K ohm input impedance and 1K ohm output impedance will do the trick. The Autocom should be happy with those values, but I have a sneaky feeling that it may step down the signal level by 20x, which is no good !

That reminds me...One thing that I particularly like about the Autocom is that its 3.5mm input jacks are bog standard stereo (ie, 3-pole) leads which can be bought almost anywhere. If I understand correctly the Starcom leads are 4-Pole, which is a PITA !

Getting back onto Stewybear's original topic......I've just tried a standard stereo lead to hook up my Steetpilot 3 to the Autocom with them both on a (highly regulated) 12V supply - IT WAS HORRIBLE ! There's a steady 3Kilohertz tone, and when I press the speak button I get an earful of what sounds like digital hash. I shall definitely be isolating it, one way or another !

The adventure will continue, just as soon as I get the Maplin delivery (and if their transformers don't do it, I'll be following Cie's suggestion of the Ground Loop Eliminator thang).

[stewybear]

I finally took all the batteries out the streetpilot and connected via the bike supply. I reduced the volume from the streetpilot (it was only just over half way anyway, but hey, whatever works) which effectively did away with the steady tone I was getting. Well it didn't really get rid of it, merely reduced the volume so that the tone could not be heard. Then I increased the volume of the Starcom and hey presto. Crystal clear GPS info piped directly to my ear :D

Then I started up the bike and was quite impressed by how low the volume of the RF interferance from the bike was. You can just hear it in the background but it can easily be ignored. Just like tuning the missus out when she is going into one. Just stick your fingers in your ears and go lalalalalalalalala :lol: . This noise is a very different noise that came from the Garmin though. The garmin noise was steady and clear whilst the RF noise changes with engine revs and is classic 'alternator on radio' type noise.

The key seems to have been lowering the volume of the streetpilot to a similar level as the MP3 player at mid volume, then using the Starcom amp do the work instead of the indiviual amplifiers on the seperate devices.

I have to say that I am one happy chappy now. I'm off to Romania tomorrow morning so won't get a chance to re-route the cables before I go. I will do it when I get back though just to see if it can get any better. I don't really expect it too though.

Thanks for everybodies help.

Regards
Stewart

[FOAMER]

I don't own a Starcom

Neither do I :?

Getting back onto Stewybear's original topic......I've just tried a standard stereo lead to hook up my Steetpilot 3 to the Autocom with them both on a (highly regulated) 12V supply - IT WAS HORRIBLE ! There's a steady 3Kilohertz tone, and when I press the speak button I get an earful of what sounds like digital hash. I shall definitely be isolating it, one way or another !

Hi guys,i bought my shielded Autocom leads from a guy Piers on Ebay & they are 1st class with no interference.Im running an Ipod,an Fm radio(handy for traffic info) & have my mobile phone plugged in as well & everything is crystal clear(All items are bike powered).He will make up the leads in any size up to 2m long & at £15 each,its much better than the £30 Autocom are charging for basically the same thing!He also does leads for Starcoms.Try the following link & ask seller a question directly:
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=8066852864&sspagename=ADME:L:AAQ:UK:1

[DaveS]

Useful link Foamer thanks for that.