Eggtimer Rocketry
Tips and Tricks
Tips and Tricks

 Eggfinder Tips and Tricks

Here's a few tidbits that we've found to be helpful...


o  Get a cheap 10x jeweler's loupe or head magnifier to inspect the solder joints on the GPS module.  Trust us, it's VERY helpful...

o  Make sure that the half-moom pads on the GPS module are centered on the PC board pads.  There's a little room for misalignment, but not much.

o  When you solder the GPS pads, make sure that the solder fills up the half-moon pads on the GPS module.  It's VERY easy to solder the PC board's pads and actually miss the GPS module's pads themselves...

o  Use some extra cut-off resistor leads to line up the holes in the Hope RF module with the holes on the PC board's pads before you tape the module down.  This will ensure that you have good alignment.  There's a lot of space between the pads, so it will tolerate a little misalignment, but it's always better to get it right.

o  We state this several times, but we'll state it again... TAKE YOUR TIME.  Believe us, it takes a whole lot longer to try to go back and fix a boo boo than to take the time to get it right the first time.

o  DO NOT use ANY extra flux or cleaners on the board.  Just about anything you buy over the counter is going to be incompatible with the special solder that we supply, and it's either going to just make a mess, or (worse) prevent the solder from flowing and possibly causing you to overheat the parts while boiling off the extra flux.

o After you've tested your TX transmitter, run a bead of non-conductive epoxy like RocketPoxy between the base of the GPS antenna and the metal shield (avoid getting it on the pads, though, in case you have to resolder them).  this will keep the GPS antenna from jarring loose in the event of a hard landing or a a drop.  (Don't ask us how we know...)  Don't use JB Weld or any other metal-bearing epoxy... they will detune the GPS antenna and attenuate your signal making it harder to get a good fix.

You can also take a 1" long piece of 1 1/2" clear heat-shrink tubing, slide it over the GPS module, and shrink it in place using low heat. It's easier, but it's not as effective as the epoxy.


o  KEEP THE ANTENNA AWAY FROM METAL, OR OTHER CONDUCTIVE MATERIALS (i.e. CF tubing, metallic trim, metal flake paint).  Anything metal near the antenna will affect the range, and the effect can be very unpredictable, ranging from insignificant to "Dang, I just lost the signal and my rocket is 15,000' in the air..."

o  If you have to mount the Eggfinder TX in an AV bay with allthreads, you'll need to install an RP-SMA connector and use a cable and external antenna to get the signal away from the allthreads.  Keep anything conductive away from the GPS module too... it will significantly reduce the sensitivity of the GPS receiver.

o  If you are installing the RP-SMA connector, you'll need a RP-SMA antenna or pigtail cable to match your external antenna.  Make sure that it is RP-SMA; the antenna or cable will have INSIDE threads with a center SOCKET (NOT a center PIN).  We've seen some eBay and other Internet sellers that are selling standard SMA antennae/cables and calling them RP-SMA.

o  You can run a cable outside your AV bay and tape the antenna to your drogue shock cord, this works very well.  Just make sure that you tape it down securely so that it can't come loose (don't use electrical tape, it can melt from the heat of the ejection charge).

o  You can also mount the Eggfinder TX in a 8" piece of BT55 tubing, taped to the shock cord.  Make sure it's securely taped to the shock cord, and that your Eggfinder can't come out and get lost.  (Actually, you'll probably find the Eggfinder and lose the rocket...)

o  If you have an Eggfinder Mini, mounting it in your body tube is real easy.  Just connect the battery (and tape the connector shut so it won't come loose!) and wrap the Mini and battery in a chute protector, or slide them into a piece of Kevlar shock cord protector.  Use duct tape or lots of masking tape (NOT electrical tape... it melts!) and securely wrap it around the end of your shock cord.  No special AV or nose cone mount required!  You DO want to make sure that the battery isn't mounted directly on top of the GPS module's antenna though, since that will reduce it's effectiveness.


o  Turn on your Eggfinder receiver before the transmitter, and let it sit for a few minutes to make sure that you DO NOT get a fix, or you DO NOT see the green LED on the receiver's RF module flash.  If you DO get a fix or see the green LED flash, DO NOT turn on your transmitter... that means that somebody else is already using your frequency.  You don't want to be the one that keeps somebody else from finding their rocket.  Either change your transmitter's frequency using the LCD receiver, or wait until they're done.

o   If you DO find that somebody is on your frequency, you can use your mapping program to find them... or just walk over to the LCO and find out who's using an Eggfinder on your frequency.   They'll be impessed when you tell them that it's on Pad 14...

o  It wouldn't hurt to put your Eggfinder's frequency on your flight card... in fact, this goes for other telemetry systems, as well.  We know of some clubs that keep track of frequencies, since it's not uncommon for beacon transmitters to be shipped on the same frequency, if you're not sure then ask the LCO/RSO.

o  Once you have retrieved your rocket, turn off the transmitter as soon as practical, to free up the frequency.  It saves battery power, too.

o We've seen excellent results with the Linx Technologies line of 900 MHz antennas, specifically ANT-916-CW-QW for the transmitter and ANT-916-CW-HW for the receiver.  It's about $20 for the pair from electronics distributors like Mouser or DigiKey.  With these antennas we've heard reports of good tracking data to flights over 25,000'... higher than our waiver (and budget!) will allow.

o  If you are going to use a directional external antenna on the Eggfinder RX receiver to improve the range, we recommend a PANEL antenna, NOT a Yagi.  Yagi antennas are highly directional, which is good for beacon-type transmitters but not so good for GPS transmitters.  With a panel antenna, you only need to point the antenna in the general direction of the rocket; chances are excellent that you'll get enough signal to pick up the GPS' fix.


o  If you have the cable with the BLACK shell, download the Prolific PL2303 drivers from the Eggtimer Rocketry web site if the current ones on the Prolific site don't work on your PC.  Apparently the newer "universal" drivers don't work quite as well as the ones that were written specifically for Windows 2000/XP and Vista/7/8.  The Prolific universal drivers work just fine with the cable with the BLUE shell.

o  Pick a low-numbered COM port, some software doesn't like to see COM ports above COM4.  You can change it in Control Panel/Administrative Tools/Computer Management/Device Manager/Ports.   Select Advanced... and pick a port that you know isn't being used (COM3 or COM4 is usually safe).