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Author Topic:   GPS Receiver Antenna
SpongeBob posted 02-28-2008 05:16 PM ET (US)   Profile for SpongeBob   Send Email to SpongeBob  
Are different brands of GPS [receiver] and GPS antenna interchangable? For instance can a Garmin antenna be used with a Standard Horizon GPS [receiver]? Do they use the same frequency?


Chuck Tribolet posted 02-28-2008 08:23 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
In the general case, no. There may be a few exceptions.

1. "real" GPS antennas (see 2. below) usually have an RF amplifier
on board. That amp is powered by a DC voltage supplied by
the GPS unit. That voltage varies from manufacturer to
manufacturer, and even model to model from the same manufacturer.

2. A lot of current GPS "antennas" have the whole GPS receiver
inside. What goes over the cable is current position, over
and over and over again. This allows the elimiation of the
amplifier in 1. (zero cable length). It also allows one
RF design to be used across the product line (RF design is
REALLY HARD, digital design is easy (relatively)).

3. There's no standard connector.

What are the specific units you are interested in?


jimh posted 03-01-2008 09:11 AM ET (US)     Profile for jimh  Send Email to jimh     
"Do they all use the same frequency?"

Yes. The Global Positioning System is operated by the United States government, not by the private companies that make the receivers. The frequencies on which the satellites transmit are determined by the system designers, not by the brand of receiver being used. The usual frequency is designated L1, 1575.42 MHz

It is unlikely that you could interchange an antenna among different brands of receivers for various reasons. A state-of-the-art GPS receiver today costs about $30, so I don't see why there would be much concern about trying to reuse an existing antenna.

jimh posted 03-01-2008 01:59 PM ET (US)     Profile for jimh  Send Email to jimh     
To follow up on a point mentioned by Chuck, a current trend in GPS receiver design is to build the receiver into the antenna housing. The output of the "antenna" is not a radio frequency signal, but rather a NMEA-2000 serial data network node. You can attach this "antenna" to your vessel's NMEA-2000 vessel network, and any other device attached to the network will be able to make use of the data provided by the GPS receiver.

An example of such a design where the "antenna" is really the entire Global Position System receiver and a National Marine Electronics Association network node built into a small housing is the LOWRANCE LGC-2000 or LGC-3000. This is a complete GPS receiver and NMEA-2000 device built into what would normally be thought of as an antenna housing.

Another example is the Raymarine Raystar 125 GPS Sensor.

For non-marine applications, you can buy entire GPS receivers built into small assemblies which plug into a USB port.

jimh posted 03-01-2008 02:07 PM ET (US)     Profile for jimh  Send Email to jimh     
Here is a GPS receiver with Bluetooth interface for $35:

This is an amazing price point for a technology that just a few years ago was very expensive.

SpongeBob posted 03-02-2008 09:16 PM ET (US)     Profile for SpongeBob  Send Email to SpongeBob     
Sorry for not checking in on this thead sooner, I was out of town at a volleyball tournament with my daughter. Thanks for moving it Jim. I have a Standard Horizon CP 150 and need an antenna for it. I have a friend with an older Garmin antenna with the BNC style connector which is what I referred to as a "standard" connector. Before I have him go to the trouble of shipping it to me I wanted to know if it was compatable. I asked at West marine and they said they worked on different frequencies. This didnt make sence to me as they would be sending the information via a hard connection not through the ether. But what do I know.
Are the cheapo units that are sold on ebay (I think they are primarily used for cars)applicable for marine use?


SpongeBob posted 03-02-2008 09:28 PM ET (US)     Profile for SpongeBob  Send Email to SpongeBob     
The Garmin antenna in question is the mushroom type.


jimh posted 03-03-2008 05:51 PM ET (US)     Profile for jimh  Send Email to jimh     
I would not expect that a Garmin antenna would work with a Standard Horizon receiver.

The person who told you that they work on different frequencies perhaps was referring to a technique called down-conversion. It is common that the antenna contain a frequency convertor and that the L1 frequency is converted to an intermediate frequency (around 70-MHz, for example,) for conveyance along the antenna cable in order to avoid the very high attenuation of the signal which would otherwise result in the transmission line.

If you want a new antenna for your Standard Horizon CP150 I suggest you contact Standard Horizon. They have an excellent service department. They can check your unit and possible repair it at a modest cost. If you need a new antenna they can sell you one at a reasonable price.

You may find that reading this prior discussion will be helpful:

Standard-Horizon GPS/Chart Plotter: CP150

Here is the search string I used to find that article: CP150+antenna

SpongeBob posted 03-04-2008 09:39 PM ET (US)     Profile for SpongeBob  Send Email to SpongeBob     
That makes sense. I was trying to avoid buying a new antenna. I aquired this GPS without an antenna. Thanks Jim!


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