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View Full Version : 2 Q's : reradiating antenna and compasses



tc67
6th December 2007, 09:10 AM
Folks,
two questions that I'd like help with:

1. I assume the Rx part of a reradiating antenna sits outside a vehicle, but some references on the web seem to indicate it can mount on the interior of the windscreen. What are the options and what is best? How does the mount of the Rx attach?
Also, it seems that the rerad ant needs the cig lighter socket, so running the GPS via cig lighter becomes a conflict....need two lighter points, perhaps?

2. Is it OK to store a magnetic compass with the GPS unit, or are there magnetic components in the GPS that will, in the long run, affect magnetic compass accuracy?

Thanks in advance,
TC67

Nicko
6th December 2007, 11:09 AM
Did you watch rge re-radiating antenna video? Have a look at hat and you will see the setup.

We have the double adapter for the cig lighter socket in stock.


Magenetic compass and GPS do not interfere with each other

tc67
6th December 2007, 01:52 PM
Did you watch rge re-radiating antenna video? Have a look at hat and you will see the setup.


Thanks Nicko. Not sure where to find this video. My web link is slow (ISDN) so might not be able, but will try if you provide details of where to view it.

Re the cig lighter 'double adaptor', I will look at it on shop site if there. Depending on design, I may have to choose between the ability to change gear in the ute versus power from cig lighter.

TC67

Another Q: can you use the GPS to convert from AMG to MGA UTM grid references. That is, put in a waypoint in AMG and then alter the grid system displayed to show the same location accurately in MGA?

Nicko
6th December 2007, 02:08 PM
http://www.gpsaustralia.net/forums/forumdisplay.php?f=89

As to the conversion, well all GPS read satellite data in WGS 84 and then depending upon what you have chosen as your datum and datum format it will automatically display the "grid" in that dataum and format. If you already have waypoints stored on the GPS you can change it to whatever dataum or datum format you like and it will display it accordingly. RAW data is always WGS84, for your specific datum it will display your datum for you assuming you have gone into the GPS setup and chosen a particular datum.


When you buy the re-radiating antenna I will throw in the double adapter for free :)

tc67
7th December 2007, 02:42 PM
When you buy the re-radiating antenna I will throw in the double adapter for free :)

Thanks for the offer Nicko. I will try to swing my next purchase your way. Is the cig lighter double adapter bulky or slim, as it will be an issue possible with location near my gear stick?

A couple more q's:

1. I wonder how the rerad antenna works in ensuring that the GPSr only recieves signal via the antenna and not from the sat direct in the case where is could pick it up direct but weaker. That is, is there some mechanism as used in UHF radio duplex repeaters?

2. What are the comparitive signal losses of a rerad ant versus a direct fixed external antenna?

3. What external ant options are there for the GPS60 series? From the info I see, the Garmin and Garmin compatible antennas on you shop site and on GME site are both BNC terminated, and 60 series not listed. Is it a matter of a different fitting/adapter or am I not seeing all that is available.

I guess if the rerad antenna has good specs, it is the more versatile option, and especially as it can quickly be moved from vehicle to vehicle (a point not made in the video).

Cheers,
TC67

Nicko
7th December 2007, 05:00 PM
1. I wonder how the rerad antenna works in ensuring that the GPSr only recieves signal via the antenna and not from the sat direct in the case where is could pick it up direct but weaker. That is, is there some mechanism as used in UHF radio duplex repeaters?

Not impotrtant, the GPSr performance is not affected in anyway if it receives the signal direct or indirect from the sats.


2. What are the comparitive signal losses of a rerad ant versus a direct fixed external antenna?

There are no signal loss on either as both have similar length cables from the external antenna to the end connector, whether it be end connector directly to the GPSr or end connector to the re-rad.



3. What external ant options are there for the GPS60 series? From the info I see, the Garmin and Garmin compatible antennas on you shop site and on GME site are both BNC terminated, and 60 series not listed. Is it a matter of a different fitting/adapter or am I not seeing all that is available.

BNC is for the marine tpe GPS such as the Garmin Chart Plotters or even the old GPSII/II+ and V. in the instance with the GPS 60 series, 76 series they use the MCX which is available from us.



I guess if the rerad antenna has good specs, it is the more versatile option, and especially as it can quickly be moved from vehicle to vehicle (a point not made in the video).

The fact it is a portable device makes me feel I don't need to give people the impression I am making them out to be dumb, but valid point all the same :)

tc67
11th December 2007, 10:10 AM
Not impotrtant, the GPSr performance is not affected in anyway if it receives the signal direct or indirect from the sats.


Thanks Nicko
I just wondered if there was a problem re getting two signals (direct and indirect) at the same time.

Cheers TC67