EggFinder with outboard GPS

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Nov 25, 2009
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Central Illinois
I busted my first EggFinder a long time ago and pulled it out of my junkbox after dorking
the GPS removal. I decided to bridge the cut traces from the cut-off wheel and use it as a
development board type of thing.

Funny thing is when I plugged in a Ublox Neo6M: with a Sarantel antenna, it worked quite nicely with seemingly better performance then the Maestro SirfIV chipset with the promise of better altitude reporting. The 3.3V terminal was nice too to simply power the outboard GPS from.
The picture shows 4 wires, +,-, transmit and receive but actually 3 are only needed the
transmit out from the GPS to the receive in on the EggFinder is all that is necessary.

Alas, I dropped the danged thing bringing it out to allow it to get a fix and never got a chance to fly it. Broke the GPS antenna. In the meantime, the antenna maker stopped making the quadrifilar GPS antenna that seems suited for flying in a rocket and a replacement was
difficult to find:

I found this one: the price was right and I gave it a go:IMG_20170404_215349.jpg View attachment 316603IMG_20170404_214740.jpg

$35.00 was tolerable and the altitude specs of 164,000' was a lot more I'd ever need.
Nice green LED for when there is a lock.

Well I found out it can lock on more than one GPS constellation and can get really tight accuracy as far as positioning is concerned. Only problem is that the location sentences
come across so fast from so many systems that most of my decoding software can't get a plot. The EggFinder does fine with it though:

There is more than the standard NMEA sentences in there. To be brief, I found out that the Android program "Bluetooth GPS" ( can decode and display positions on a Google map as long as one has internet service for the map (no caching of maps possible):

The pics with the little man are the ones with from the B/T GPS program.

Now when Bluetooth GPS is exited out of, it minimizes and if one has developer options enabled like "allow mock GPS locations", the paired HC-06 can be used "instead of" one's device's internal GPS. The B/T GPS app will pipe the positions to "GPS Rocket Locator" as your base station position (the blue dot). At least I could get it displayed as shown above. I couldn't get any other tracking programs to display the incoming code from the EggFinder like I can do with the usual SirfIV strings or Ublox that are strictly NMEA sentences and start with GPXXX. Xastir, GPS Rocket Locator and YAAC all could not get a position plotted on the map though the EggFinder was dutifully and reliably was sending the data across. Xastir and YAAC both showed the strings coming in but couldn't decode them to place the position on the map.
Only the Android app Bluetooth GPS could do that trick.

The number of satellites locked really goes up:


I had to take two screenpics by sliding the bottom bar across to show all the satellites in sight.

This shows that even more accurate positioning is out there and affordable but the current
open source software has difficulties handling it. Something to look forward to when the
programmers catch up. I think the Quadrifilar antenna is better suited
for rockets than the patch but the current patch antennas are fine to
simply find a sport rocket. Kurt Savegnago
Those Sarantel/Maruwa helical GPS antennas are really nice. They have an active one that gets 24 dB of gain with no ground plane (it's like $125, though). Unfortunately, they're also hard to get unless you buy 10,000 of them... they sell directly to OEMs, no US distributor.
The Neo6M I had, had an active Sarantel on it and if I knew I was going to dork it, I would have bought two. Sarantel got out of the business or Maruwa took it over. I guess they can charge whatever they want now.
I'm impressed with this $35.00 unit though most software can't decode it. I used a stock EF dongle/receiver (no beeper, doesn't drive one crazy with testing) and the strings are sent fine. The EggFinder LCD also will send
the datastream to an outboard device but can't get a lock and decode the position on the screen. When I open Bluetooth GPS on Android, it has no trouble decoding the stream (the site says it supports GNSS also). I found out last night that the Android app GPS Coordinates NOW: will display the Eggfinder position fine as long as the B/T GPS app is running
minimized. I like this program Coordinates NOW because it shows the conversions on the different units on the screen and for 99 cents it's worth it to me. Potentially eliminates conversion error if going the manual tracking route.

When I pipe the data to the NMEA ports of mainstream tracking programs they can't get a fix.

Let me be perfectly clear, this is only an issue with this GPS chipset not with the EggFinder. In fact even with the higher volume of data, the EF is blasting it out over Bluetooth perfectly. The red led on the Hope module is on most of the time and doesn't flicker as much as with the SirfIV stock chip.

This just presages what is going to be available in the near future. Kurt
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Maestro Wireless now has a SIRFStar V pin-compatible GPS module, they say that the SIRF V gets a fix quicker. I might go to that one, if the price comes down a bit... most of the distributors raised the prices on the SIRFStar IV chips about 20% last year, but the one that I buy from did not.
Can you give the app, Rocket Locator a try? I like that one, because I don't need a network connection for it to work. It simply displays a black screen with dots for my location and the rocket. The compass and directions still work fine to lead me to the rocket.

That app also doesn't require that you go to developer settings and allow GPS data from another source.

The dev also has a site with a lot of good info.
Have you tried to filter the stream? Might be able to get a lot more apps working if you simple ditch the non GPS entries.
Mark, The last picture on the right is from "GPS Rocket Locator" on a Nexus 7 2013 though the "B/T GPS program" was running in the background. In that condition, the positions from the EggFinder were piped to GPSRL as the "base"
station position. I did run GPSRL stock after I paired the EF receiver and the positions were not plotted
from the EggFinder at all with the red pushpin. I only saw the blue dot from the onboard GPS of the Nexus 7.

SpaceNMan, Filtering would then get one back to the limit of precision of the US GPS system. I haven't been through the data/setup set of the Neo8Q chipset yet to see if it could be set to read the US system only.
It does show that combined use of GPS/GNSS yields higher accuracy that seemed more stable than one satellite
system alone. I noticed less jitter and jumping around when zoomed in. The quadrifilar GPS antenna I believe
is better suited for rocket flight but since Sarantel is not making them, whomever picks it up has a monopoly
and can charge what they want for the technology. (Like Cris implies above.)

I did try feeding the strings through NMEA ports on Xastir, YAAC and APRSIS32 with the datastreams seen on the terminal but nothing plotted. I'm not going to try UI-View as the code is so old it won't do it. I've done this with a variety of older GPS chipsets connected to my two "dorked" EggFinder boards and it works every time. The positions
are plotted no sweat.

I believe the use of two combination satellite systems simultaneously is too far ahead of the free software out there
except that B/T GPS app can handle it.

I'm going to post a message on the Xastir newsgroups to reference this thread. Wouldn't hurt to see what happens.

I did this before with respect to feeding NMEA strings to Xastir and in 36hours Jason Winningham KG4WSV
posted this python script: to the group that
converted the NMEA strings into a "pseudo" APRS position packet that is plotted 1/sec instead of
once every 5/sec with standard APRS. Lest you think I'm violating confidentiality, Jason put his full name
and callsign in that program that is publicly available at that link. Just pair the EF receiver, click on the Interface pulldown and select enable server ports. Run Xastir, pull up an Xterminal, run the script and one
will see the strings coming in from the EggFinder. Can minimize the terminal and the rocket will be on the map.
The rocket will be plotted on the map and one can save the NMEA port for the base station position.

I actually have this working on a Pocket CHIP:

This takes some Linux smarts but the "Game" crap can be ditched, a standard Jessie version of Debian flashed from
the manufacturers site and with 8Gb available, Xastir can be run. Takes awhile to start Xastir but once it's up
it does a surprising job of tracking. I'm hoping to try it out soon. Pretty easy to carry. Kurt

Forgot to mention, Google maps no longer work with GPS Rocket Locator in new installations. I cached a pile of the maps on my tablets. If going to use the program, it defaults to Google and just sits there. You have to go to the
pull down and hit OSM as the source to get the simple roadmaps. Can cache those for off line use.
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