How does the Eggfinder work?
The Eggfinder GPS Tracking System consists of two boards: A transmitter module that goes into your rocket and a receiver that you keep with you on the ground. The transmitter module contains a GPS module that tracks the latitude and longitude of your rocket as it moves, and that data is transmitted to the receiver on the ground. With the Eggfinder LCD handheld receiver, you get the coordinates right on the LCD display, and with the optional GPS module it will literally point you to your rocket and tell you how far away it is. If you add the optional Voice Module, it will literally “tell” you where your rocket is.
We also offer a USB “dongle” receiver that you can use to set up a fixed “ground station” to log data and create a real-time track with the appropriate software.
How much does it cost?
The Eggfinder Starter Set, consisting of both the TX transmitter and the base LCD Receiver, is $120 for the set of kits. An extra TX transmitter kit is $70, and the Eggfinder LCD receiver kit alone is $55 (you save $5 by purchasing both a transmitter and receiver together). The USB RX “dongle” receiver kit is $35. All of the receiver kits now include the range-boosting external antenna.
We also have a smaller version of the transmitter, the Eggfinder Mini. It’s $5 more than the “standard” Eggfinder TX transmitter ($75), but it’s a lot smaller… only .8″ wide and 3 1/2″ long with the (included!) external antenna. It’s perfect for those minimum-diameter projects or for being wrapped up in a chute protector and taped to your shock cord (like you might do with a RDF tracker).
What is the range?
With the included “rubber duckie” antenna for the receiver , we’ve tracked rockets to over 6 miles with the Eggfinder TX and LCD receiver. Due to a number of factors not necessarily related to the hardware, you may lose contact for a few seconds as your rocket goes through boost, however as it slows down near apogee it will be reacquired and you will be able to track it almost all of the way coming down, which is the real goal of having a tracker in the first place.
If you need more range, AND you have a valid FCC Ameteur Radio (Ham) license, we have a 70cm version of our Eggtimer Quasar GPS transmitter/altimeter and the Eggfinder LCD receiver… you can get about twice the range as the 900 MHz license-free units. Expect over 50,000′ of range in clear-air conditions.
How close will it tell me to where my rocket actually landed?
The GPS module is rated to a typical resolution of 2.5 meters. In reality, you will probably lose your radio signal when the rocket gets very close to the ground, but the last latitude-longitude figure will be very close. It’s not unusual for it to be within a few feet. Unless you land in a tall grassy area, you will almost certainly see your rocket laying on the ground well before you near the last reported GPS position. Once you get close to the rocket, even if you can’t see it, you’ll pick up the updated location and be able to walk right up to it.
Do I need a special license to use an Eggfinder?
The radio module used in the Eggfinder runs on the 900 MHz ISM band, which does not require a license in the US. Like other FCC Part 15 devices, the rule is that it must not cause interference to other licensed-band devices; since it is a low-power device and is intended to be used in a remote location rather than in a home/office environment, it is extremely unlikely to cause any interference to anything at all.
We also make versions for other regions, such as the EU/UK and Australia/NZ, which comply with their specific license-free requirements.
In addition, if you have a valid FCC Amateur Radio (Ham) license, we have a 70cm version of the Eggtimer Quasar and the Eggfinder LCD receiver available. The advantage over the license-free units is that that you get twice the range for the same amount of power (and battery draw), plus there are 300 possible frequency selections.
How does the Eggfinder LCD Receiver work?
The Eggfinder LCD’s 2-line display gives you the GPS coordinates, number of satellites in the fix, and the GPS altitude (although GPS altitude isn’t necessarily real-time, due to a number of factors). With just that information, you can plug the GPS coordinates into a navigation app on your phone (such as hikers use… there are lots of them) and tell the app to “take me there”. You will generally get a track and a compass direction to go.
If you have the Eggfinder LCD receiver and the GPS module option, you don’t need a second device… it gives you an arrow and bearing that literally points to your rocket, no matter which way you’re moving. It’s ridiculously easy to use. If you have the Eggtimer Voice Module in your LCD Receiver, it will literally “tell” you where to go. It’s great for those long recoveries when you may be driving out to the landing spot… you can concentrate on your driving instead of a display.
If I’m using the Eggfinder RX “dongle”, what software can I use to show me where my rocket landed?
We’ve used a number of software programs on the laptop, inclduding Putty just to capture the NMEA serial data stream. VisualGPS View is a nice freebie software that can show you your rocket’s track and coordinates in real-time, it runs on Windows. You can also use Google Earth, but you have to have Internet access at your launch site.
The general procedure is to capture the NMEA data until it stops streaming, which means that your rocket has landed (although if it’s close enough you still might pick it up on the ground as well). You take the last recorded latitude and longitude and set a waypoint in your GPS-enabled phone/tablet’s app, and tell it to navigate to that waypoint. With your handheld device, you simply walk up to that waypoint, and your rocket will be right there.
How does the Eggfinder compare to other GPS radio systems?
The Eggfinder is a little different in that it is a very simple system, its sole purpose is to send the NMEA-formatted GPS data to your laptop/tablet to tell you where your rocket is. There are some other much more expensive systems that have the GPS system integrated with a flight computer, or that use a licensed band such as 70cm to provide more transmitter power and greater range, but for the majority of hobby rocketry sport flyers the Eggfinder is adequate for the vast majority of the flights that you would ever attempt, and it is much more affordable.
If you want an integrated flight computer and GPS tracker, we also offer the Eggtimer Quasar which will do that for you, at a very affordable cost. Besides the GPS data, the Quasar also gives you the barometric altitude during flight, as well as the status of the deployment channels.
How hard is it to put together?
We’re not going to lie, it’s not a good first soldering project, but if you have built other reasonably complex kits with ICs on them (such as an Eggtimer Quark) you shouldn’t have too much trouble with it. There are surface mount parts, but they are relatively large by SMT standards; none of them are under .050″ pitch. To make things easier on you, we include some .020″ low-temperature no-clean solder with the kits, this makes soldering the SMT parts really easy compared to the stuff that you get at your local hardware store. The current version of the Eggfinder TX and Mini kits comes with the GPS module pre-mounted, which makes building the kit MUCH easier than previous versions.
Are there any special mounting requirements in my rocket?
One cardinal rule: Keep the antenna away from anything conductive! That means that you can’t put the Eggfinder inside the AV bay with your altimeter and two allthreads running next to the antenna and expect to get a good signal. We recommend that you mount the Eggfinder in the nose cone of your rocket with the antenna pointing upward. Note that carbon fiber blocks radio signals, so you will need to come up with an external antenna if you have a CF rocket. Note that many CF rockets come with fiberglass nose cones specifically for this reason; mounting your tracker in a fiberglass nose cone with a metal tip will not degrade the performance of your Eggfinder, since the metal tip is in the “dead zone” of the antenna.
What kind of antenna does it use?
The standard included antenna is a very simple 1/4 wave “whip” (about 3″ long), it is simply soldered onto the board right next to the RF module. For more range, you can solder on an RP-SMA connector and use an external antenna… this is a good solution for increasing the range, or if you need to remotely mount the antenna.
The Eggfinder Mini comes with a 2.4 dB gain screw-mount antenna, you should expect similar range out of it compared to the “standard” Eggfinder TX tramsmitter. The Mini may take a bit longer to acquire a GPS signal, however, due to its small size the GPS antenna isn’t as efficient so it takes longer to get a good signal.
What kind of battery does the transmitter require?
We recommend using a 7.4V (“2S”) LiPo battery, at least 300 mAH. You CAN use a smaller one, the Eggfinder TX draws about 70-100 mA when it’s running, but that will reduce your operational time, of course. If you want to use a smaller battery we recommend that you power it up shortly before launch… mounting it in the nose cone or wrapped up in the body tube. usually makes that pretty easy to do. The latest version of the Eggfinder Mini can also use a 1S/3.7V LiPo… we recommend 300 mAH or larger. We do NOT recommend using a 9V alkaline battery… they don’t have enough capacity and don’t source enough current for use with a GPS tracker (ours or anybody else’s…). You CAN use a 9V Lithium battery, such as the Energizer Ultimate battery, but they’re pretty expensive… over $10 each, and they can’t be recharged, so a Lipo is a more cost-effective solution.
Can I fly more than one Eggfinder at a time?
Yes, but you’ll have to make sure they’re on different frequencies/ID’s.
There are nine base frequencies from 909-925 MHz in 2 MHz increments, and eight ID codes, so you can have up to 72 Eggfinders operating simultaneously. The TX transmitter and the LCD receiver can be “paired” up so that they are programmed together to the same frequency, using a simple 3-conductor jumper cable. The RX “dongle” receiver uses a fixed frequency, so it’s not programmable; you’ll have to make sure your TX transmitter matches its frequency if you’re using one of those.
What is the difference between the Eggfinder LCD and Eggfinder RX receivers?
The Eggfinder LCD receiver is a portable receiver with a LCD display that shows you the latitude/longitude in real-time, along with a few other tidbits of useful information (see the Products section). It is designed to be used with a smartphone or portable tablet. You simply enter the coordinates into your smartphone’s navigation app, and walk right up to your rocket. It also has a beeper that lets you know when you have a fix, this is very useful for helping to locate your rocket in the event that it goes out of range. You can configure the displayed coordinates’ format to match your app. You can also set it to any Eggfinder TX frequency, so the same Eggfinder LCD receiver can work with any number of Eggfinder TX transmitters. Finally, you can use the LCD receiver to program the frequency on your TX transmitter, you can’t do that with the RX dongle.
By adding on the optional LCD-GPS module, your LCD receiver becomes a single-device solution for finding your rocket… no more tablet or phone needed. It literally points you to where your rocket is, and tells you how far. All you have to do is to go in the direction of the arrow, and it will take you right to your rocket. Easy peasy!
It’s even easier if you get the optional Eggtimer Voice Module… it will literally TELL you where to go to get your rocket. You can plug it into your vehicle’s stereo AUX jack, and concentrate on your driving instead of looking down at the screen all the time. It’s great for those really long recoveries in rough terrain.
The Eggfinder RX receiver is a “dongle” that has a USB interface that plugs into your laptop or tablet. It is the equivalent to a fixed “ground station”. You configure it on your device as a serial port, and the GPS data from your Eggfinder TX transmitter flows through that serial port. Using any GPS-enabled software package on your laptop/tablet (such as VisualGPS View on Windows), you can get a track of the rocket’s path, and more importantly the landing coordinates. Because it’s connected to a laptop, we DO NOT recommend using it as the primary receiver… but it’s great for gathering in-flight data.
I live outside the USA, can you sell it to me?
Currently, we can ship to the USA, Canada, Australia, and New Zealand, subject to some frequency selection limitations (i.e. Australia/NZ ships from 919-925 MHz since the lower frequencies are allocated for other purposes). In the EU/UK, we can ship on the 869 MHz band since it’s the only license-free band that allows 100 mW output power. The 70cm Ham products can be shipped almost anywhere in the world, but of course we need proof of your license. Shipping will be higher, of course… contact us for details.