Mounting a Big Red Bee GPS Tracker
Among the more popular GPS trackers for rocket tracking, at least among those with a ham radio license, is the 70cm Beeline Transmitter. This is a completely integrated GPS transmitter, which only needs to be mounted in the rocket and have an antenna attached.
I opted for a coaxial dipole antenna, which is very compact on 70cm and provides very good omni-directional coverage. I used RG-223, 50 ohm, coax since the double layer shield makes this antenna easy to build. You simply strip off the jacket, reverse the outer shield to form one half of the dipole, removed the inner shield from the center insulator, and use the center conductor as the other half of the dipole. So the dipole winds up in line with the remaining feedline and about the same diameter, and in these photos is covered with orange heat shrink tubing. The feedline can be any length up to the beginning of the dipole. The antenna and feedline can then be fed through a ¼” hole in your electronics bay bulkhead. Having the radiating portion of the antenna outside the EBay helps keep the RF energy from interfering with the altimeter. I have had issues with transmitting too close to other electronics in other installations.
The Beeline unit has three mounting holes that fit #4-40 machine screws. The fourth corner is where the antenna connector is, so there is no mounting hole. The two ounce Beeline unit can easily be held by three screws. I use plastic stand-offs to hold the Beeline a half-inch or so off the mounting plate. The Beeline has the GPS module, connectors, and other components on one side, and the battery attached to the other side. It is not a good to squish the battery against the mounting plate, so the stand-offs are needed. In the four inch diameter electronics bay shown in the photos I decided to have the altimeter mounted on the other side of the mounting plate, which is slightly off-center in the bay to allow the hole for the antenna coax to be centered. I simply ran the coaxial dipole and feedline out the hole, but you could easily use an SMA bulkhead connector. In fact, after these photos I changed to a short coax jumper with a bulkhead connector on one end rather than run the antenna coax through the bulkhead.
When the connections are all made from the electronics to the bulkheads, the electronics bay is ready to go. I used binding posts on each end for the recovery charges, a plywood mounting plate, and two ¼”-20 all-thread bolts to hold everything together. This is a Wildman EBay, so the two holes in each bulkhead for the all-thread were already drilled, and a hole was started in the center. I just had to drill out the center hole in one bulkhead for the coax, and two holes in each for the recovery binding posts. Speaker wire runs from the altimeter to the binding posts.
This installation was tested on the ground at my house and in the air at BALLS-27, with good results. It is really nothing unique or fancy, just a straightforward way of putting a tracker in your rocket. The Beeline GPS is only 1.25” wide, so it should be small enough to mount in a 1.6” payload section or EBay. The circuit board is 3” long, plus antenna connector on one corner.
Later versions of the BRB tracker have different mounting holes, but it is still mounted about the same way.
Any receiving system that decodes APRS packets can be used to receive the data from a Beeline GPS transmitter. I use several, including a simple interface between a FM receiver and an Android smartphone. I also have a Yaesu FTM-100D mobile radio and a Kenwood hand-held (shown with glare, above) available for APRS use, including rocket tracking. I have a write-up on this site about the Android phone interface.
To order a Beeline GPS tracker: