TRI-M Big Brother Remote Active Re-radiating Antenna Review
Review by Joe Mehaffey and Jack Yeazel
Additional material provided by Dave Martindale
(Revision 31 January 1999)
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The purpose of this specialized Remote Active Re-Radiating Antenna (RARA) GPS antenna is to provide GPS reception in areas where no reliable signals exist  for receivers without a normal external amplified antenna connection.  The cable is such that the GPS can be located about 10 feet (3m) from the small (2-inch square x 1/2 inch) antenna.  The greatest utility would seem to be with the Lowrance GPS receivers or the Garmin G-12(not XL) or the Magellan M-2000 that do not provide for an active remote antenna.  The procedure is to place the re-radiating 3-inch long probe near (or actually touching the GPS case) to the GPS's antenna.  Power for the RARA is obtained through a 12vdc cigarette-lighter plug.  For the tests, it was provided by a cell phone power supply.

Tests were made with the GPS under a 6-inch thick built-up roof with the antenna on a platform outside the house.  Tests in a more severe environment where the GPS would not lock on at ALL weren't available...  (Current GPS are so sensitive, they will lock on most ANYWHERE).  However, this doesn't mean the GPSs are USABLE under these conditions.  Most experience gross errors no one could use for any useful purpose.

For our own purposes, often times it is unhandy to evaluate a GPS under 'ideal' conditions.  This antenna makes the GPS perform almost as it would under normal conditions.  Other uses can well be imagined.  In the screen shots below, you can see that the GM-100 would not retain lock without the Big Brother antenna, and the G-III+ experienced a sever loss of signal with a higher DOP.  Both receivers showed fewer satellites locked on without the boost.

                                                  Lowrance GM-100

  Antenna: ON                         OFF                               ON                              OFF

                                                              Garmin G-III+

We were especially interested to see if the remote antenna could improve the excessive excursions of a Lowrance receiver under adverse conditions which has been documented previously.  The first screen shot below is one hour with the remote antenna OFF, and the second is an hour with the antenna ON.  The second plot looks more like a normal Selective Availability excursion.  (Note:  This test was not done during the same time,  so the actual position of the SVs may have had an effect.)                      TRI-M Antenna


Note: there is both a "Big Brother" antenna alone, which plugs into GPSes that have powered antenna jacks, and the Big Brother re-radiating unit which combines the BB antenna, power supply, and little re-radiating antenna all in one.   Contact TRI-M for this special configuration amplified antenna.

There has been some discussion recently about Wolfe's "Global Link" antenna which, from the picture, looks like exactly the same thing imported by someone else.  So all of the discussion for the Global Link applies to the Big Brother re-radiator too. The BB RR/Global Link is designed for use in a car, where 12 V power is plentiful, and it works well there. These antennas are less suitable for use hiking, because of their higher power consumption (0.15-0.20W) compared to something like the Mighty Mouse  (.05 W)