Monday, 9 April 2012

Garmin GPS 120 Antenna connection?

This is a call for help, someone out there has had to do this, so please tell me how!

This is an early (1995?) Garmin 120 stick antenna, the boat it was on sank but this bit was on a 3ft stainless pole and survived!

The idea is to install an outsdside antenna so I can check various GPS I have.
GPS signals can use a one wire feed, so how do I connect this eight (8) channel Garmin antenna? there is the center pin and the screen cover only.

So how do I power it and get a return signal via a BNC type plug?

we have the center pin/core and the braid outside, there is an alloy foil too
but thats under the braid, so connected to the braid.

The Garmin GPS 120

Any ideas?


Roy thinks this one out for himself, as the specialist he emails for assistance is yet to reply.

In this case the antenna I have from the Garmin 120 is passive, its an aerial only, it is not a transmiter back to a GPS plotter or computer! So if you have an old type GPS that accepts a BNC type plug as its receive signal, the Garmin 120 antenna should work?

Garmins web site tells me the following, I assume it needs the Garmin 120 connected to do most of those functions, its the eight satellites I am keen on.

Receiver: Differential-ready MultiTrac8™ continuously tracks and uses up to eight satellites to compute and update a position

Acquisition Times:

Warm: approx. 20 seconds
Cold: approx. 2 minutes
Autolocate™: approx. 7.5 minutes
Update Rate: 1/second, continuous


Position: 1-5 meters with DGPS
Velocity*: 0.1 knot RMS steady state
Dynamics: 3g's
Interfaces: NMEA 180, 182, 183 and RTCM 104 DGPS corrections
Antenna: Remote marine mount with 30' cable

This mail has just come in from John, thanks very much.

Hi Roy,

I don’t know if you have gotten any correct information regarding your external GPS antenna question

(I came across your OLD POST/question while researching something else – YES, I own & use the antenna pictured.!)

I currently use mine with my old Garmin 48 handheld GPS mounted on my pickup truck here in the USA. 

To answer your question, I believe it is an active antenna that gets the power from the GPS unit.  The connector on the end of mine is a BNC “thingy”.   (I’ll try to find my instruction manual and the proper antenna model number for you, if you wish.)


John S. Halsey, Jr.