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 Garmin nüvi forums
 External antenna option for 1490
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LandNav

USA
362 Posts

Posted - 22 avr. 2012 :  07:58:46  Show Profile  Reply with Quote
I just bought a Range Rover Evoque and now I find my Garmin 1490 will NOT receive any GPS signals in the dashboard/windshield area because of the wires in the electrically heated windshield. UNBELIEVABLE!

I did a test and the 1490 runs fine by the back window behind the 2nd row of seats. I'm wondering if there is any external antenna option for the 1490 so that I can mount an antenna there and run the antenna wire up to the windshield area.

I also have a 760, but I would prefer to use the 1490 if there is an antenna option. I'm pretty sure there is for the 760.

Anyone know about the 1490 and this option.

I think I saw an antenna on eBay for the 760.

Any help would be appreciated. Yes, the Evoque does have factory GPS which IMHO doesn't come close to either of my Nuvis.

Current models : Garmin Nuvi 1490T- Garmin 192C (Marine) - Garmin Forerunner 101
Previous models: Garmin Quest - Garmin Quest II - Garmin 350 - Garmin360 - Garmin 650 - Garmin 760

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sussamb

United Kingdom
863 Posts

Posted - 22 avr. 2012 :  10:35:13  Show Profile  Reply with Quote
Sorry, but there is no external GPS option. Mine works fine through my heated screen though. If you haven't already, you might want to try positioning it nearer the corners of the screen?
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Captcaper

USA
376 Posts

Posted - 22 avr. 2012 :  14:37:44  Show Profile  Reply with Quote
There is an option for our 1490T. I've been using it for years and it works great. Costs around $40..
See link below..I velcro the repeater to behind the lower part of gps. This seems to give the best readings. One thing is you need to place the magnetic antenna were the repeater antenna can't see it directly. Easy enought to place it using the Nuvis' sat signal meter as it will show you signal strenght.
This works with my Nuvi 2460 and 1490T well.

http://www.semsons.com/gpsreran.html

Presently owned Dezl 760LMT Montana 600 2460lmt 1490T SP2610 SP2720 GPSMAP 276C GPSMAP 60CS NorthStar 951XD in the boat since 1996.
Previous owned Garmin 48,76cs,210. Nuvi 880,1490T.
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ST-Bob

USA
3684 Posts

Posted - 22 avr. 2012 :  14:46:08  Show Profile  Reply with Quote
Note that in the US, GPS re-radiators are illegal. See this statement of FCC policy http://gpsnetworking.com/pdf/FCCRegulatoryPolicy2007.pdf

The GPS bands are restricted and devices which intentionaly radiate in these restricted bands must have FCC approval. No such FCC approval exists or can exist. You risk considerable monetary forfeiture if you are caught using one.

Just because Semsons chooses to ignore the FCC rules does not make them legal to purchase and use. What's to stop Semsons from turning over your purchase records to the FCC allowing them to fine you directly. Be careful...

Bob Peloquin - Moderator-Lowrance iWay forum
Massachusetts, USA
Various Iways, nüvi 750

Edited by - ST-Bob on 22 avr. 2012 14:49:55
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Boyd

USA
1721 Posts

Posted - 22 avr. 2012 :  15:52:04  Show Profile  Reply with Quote
So, Captcaper is sort of like a one-man Lightsquared?
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Captcaper

USA
376 Posts

Posted - 22 avr. 2012 :  22:33:25  Show Profile  Reply with Quote
Some people are so Anal

Presently owned Dezl 760LMT Montana 600 2460lmt 1490T SP2610 SP2720 GPSMAP 276C GPSMAP 60CS NorthStar 951XD in the boat since 1996.
Previous owned Garmin 48,76cs,210. Nuvi 880,1490T.
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Landscaper2009

USA
27 Posts

Posted - 22 avr. 2012 :  23:40:28  Show Profile  Reply with Quote
It is possible but requires rework to the main board. Units that have both internal and external antenna capability have a switching circuit that detects when an external antenna is connected (by current draw) and flips a solid state RF (radio frequency) switch that switches out the internal antenna and connects the external antenna to the input of the GPS receiver.

Most external antennas have a built-in preamplifier that adds gain and helps to overcome cable losses. The preamp requires a voltage (~2.5VDC) and reaches the preamp/antenna through the coax cable. DC voltage goes up the cable to the preamp/antenna, while the RF (satellite signals) come down the cable to the GPS receiver.

Considering it would be quite a task to build a switching detector and add that to the main board, it would be simpler to just defeat the internal antenna all of the time and just go with the external antenna. Of course this would make the unit not receive reception without the external antenna.

The 7xx series already has an external antenna jack, while the 14xx series does not. So a jack would need to be added to the case with a small coax feeding the GPS receiver. There also needs to be isolation between the DC voltage and the GPS receiver but allowing both to coincide on the cable feeding the external antenna. A bias "T" circuit capacitively couples the RF signal coming down the cable, while blocking the DC to the GPS receiver and allowing the DC to go up the cable to the preamp/antenna.




Edited by - Landscaper2009 on 23 avr. 2012 22:04:26
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LandNav

USA
362 Posts

Posted - 19 juin 2012 :  20:17:24  Show Profile  Reply with Quote
quote:
Originally posted by Captcaper


http://www.semsons.com/gpsreran.html



I bought one of these and it works great although a bit messy with the wires. I placed the antenna inside my rear hatch door track and ran the long antenna wire back up to the power port between the front seats. When I hook it up, I just dangle the "powered" antenna from my inside rear view mirror. Picture below shows the antenna in the rear hatch door track.

Note: The round antenna end is magnetic and could be placed outside the vehicle as well. But since it works here, I don't have the lead-in "pinched" in a window or door.

I would highly recommend this solution to anyone having weak GPS signals. Should work with ANY GPS as there is no direct plug-in to the GPS.

http://i680.photobucket.com/albums/vv168/cgarrity/gps-1.jpg

Current models : Garmin Nuvi 1490T- Garmin 192C (Marine) - Garmin Forerunner 101
Previous models: Garmin Quest - Garmin Quest II - Garmin 350 - Garmin360 - Garmin 650 - Garmin 760
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ST-Bob

USA
3684 Posts

Posted - 19 juin 2012 :  20:26:49  Show Profile  Reply with Quote
And recommending something specifically prohibited by Federal law is not very wise. See my previous post.

If we continue to buy these things from Semsons they'll keep breaking the law with total disregard for FCC rules. All it takes is for one un-knowing person to install it incorrectly (as you've done here) and you've created a GPS jammer in the right circumstances.

GPS re-radiators MUST HAVE THE RECEIVING ANTENNA SHIELDED FROM THE TRANSMITTING ANTENNA BY A LARGE EXPANSE OF METAL; not that little lip in your rear hatch.

Even with this advice - you're still illegally using a restricted frequency in the US. I suggest you either get another GPS with an external antenna jack or get a vehicle which doesn't block the GPS signals to the interior of the dashboard.

Bob Peloquin - Moderator-Lowrance iWay forum
Massachusetts, USA
Various Iways, nüvi 750
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Captcaper

USA
376 Posts

Posted - 20 juin 2012 :  12:59:50  Show Profile  Reply with Quote
lannav
good for you. It's much better to have good gps signals if that's what you need ( I do in my work) and have safe navigating then worry about some law that's out of touch. It's against the law to have sex on sundays too in some states.

Presently owned Dezl 760LMT Montana 600 2460lmt 1490T SP2610 SP2720 GPSMAP 276C GPSMAP 60CS NorthStar 951XD in the boat since 1996.
Previous owned Garmin 48,76cs,210. Nuvi 880,1490T.
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ST-Bob

USA
3684 Posts

Posted - 20 juin 2012 :  18:26:38  Show Profile  Reply with Quote
No, Captcaper, you're wrong. Your comparison to antiquated laws has nothing to do with this case. GPS re-radiators are bad. They can and do cause interference to licenced and unlicensed radio communications. and should be banned. Just because you 'need' one doesn't make it legal. You could always buy a GPS that has an external antenna port on it.

The GPS system is owned and run by the US government. They say it's a vital national resource and needs to be protected. The FCC has authority over all radio emitting devices and they ruled that nothing, no-how, no-way, could be allowed to transmit on the GPS frequencies without a license. These damned GPS re-radiators are built as cheaply as possible and do not have anti-feedback circuitry in them which 'might' make them eligible for a license but no such license could be issued because the FCC says so.

When a cheaply made GPS re-radiator hears its own signal, it causes a feedback loop that blots out all GPS reception for quite a distance. Just because it seems to work most of the time does not mean it's not causing harmful and destructive interference to either the GPS signal or nearby PCS phones.

Get your act together. You don't like the law, break it at your own peril; but don't give out atta-boys for people who do break the laws. GPSPassion is a law-abiding group and I, personally, don't like people who scoff the laws. Use your voting power if you don't like a law but this is a democracy. The majority rules whether you like it or not.

Bob Peloquin - Moderator-Lowrance iWay forum
Massachusetts, USA
Various Iways, nüvi 750
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Captcaper

USA
376 Posts

Posted - 24 juin 2012 :  10:28:40  Show Profile  Reply with Quote
I emailed Garmin and complained about them taking away the external jack on these newer and future models and how it takes away safety for us who need good strong signals and can't get them in cities or with overhead cab's. Also mentioned how some are using re re radiators that are a hazard and illegal because they took the external jacks out.

Presently owned Dezl 760LMT Montana 600 2460lmt 1490T SP2610 SP2720 GPSMAP 276C GPSMAP 60CS NorthStar 951XD in the boat since 1996.
Previous owned Garmin 48,76cs,210. Nuvi 880,1490T.
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