In some applications, the Featherweight GPS tracker won't fit with its standard antenna inside the avionics bay. Like this av-bay for example:
Shown above is an av-bay used in the sustainer of the StratoSpear rocket. Crammed into a 38mm av-bay that's about 2" long is a Blue Raven, GPS tracker, magnetic switch for the tracker, magnetic switch for the Blue Raven, and a battery charger. The Tracker antenna sticks out through a hole in the forward bulkhead and is taped down to the side of rocket's main chute deployment cannon.
I wanted to give this option to customers who don't want to have to remove the SMA antenna connector themselves and solder on their own, so now it's available. The antenna is AWG 22 polyurethane enameled copper wire (magnet wire) that I personally solder on, and then trim to the length that I have found provides the best performance. In short range tests, the link performance is pretty much the same as the standard antenna.