$25 GPS Solution

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Oh, one other thing. One can use the UBlox utility, UCenter, before and after radio installation. It didn't occur to me until after I checked my only available Neo7 GPS clone (the $9.00 special) and found it was serviceable. Got a nice lock indoors and could have fired a very small GPS guided missile or bomb to "take me out" without the neighbors hearing or knowing about it! (sic):wink::facepalm: That was feeding it to the computer with the FTDI board.

After installation into the 3DR module there is definitely a difference in the quality of the lock. If O.T.T.'s supposition above is correct in #239, this still could be a dead end for a tight small, cheap tracker. Sure one could buy a "brand GPS chipset" from the csgshop above but there goes the $25.00 appellation.

One thing I don't understand is if these rigs are so sloppy, how can anyone reliably use 'em and expect them to work with quad copters? I presumed it would be a piece o' cake to get them modified to simply transmit a 9600 bps GPS datastream with decent reliable range? Maybe not! Still it's fun to play with.

Perhaps there are some different radio settings that would improve the reliability and increase the expected range. I see the quad people struggling to get
4000 meters with these things. That's only 2.5 miles. I'll try to get some more pictures posted. Will consider trying to double stick a piece of sheet steel to the plastic case of the air module, tie it to the ground and put the GPS on top of that. If the radio design stinks that might not help at all either but I have the stuff
around to try it. Plus, I can fire up UCenter before and after and see the results. I find it works better with the satellites directly overhead. I've sometimes
seen locks of 4 to 8 satellites but the number of satellites held jumps around a lot. It might be 4, 6 , 8 every second so still somewhat unsteady. Kurt
 
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I think Rocket Locator can show the receive signal strength or s/n ratio of the satellites in view. A good indication of your shielding performance would be to have the unit in the open and look at a signal strength for a satellite directly above you. We would be working on the assumption that all satellites are transmitting the same power to your location. Probably a reasonable guess. The way to really guarantee good comparison results would be to have two units, one with and one without shielding, working simultaneously and look at the signal statistics.

Number of satellites jumping around really sounds to me like some of the correlators are having a hard time in the GPS. Modern GPS units are normally quite solid once signal is acquired. Modern units often have more than one correlator per satellite as there is generally only between 8 and 11 visible in the sky. If you look at a modern GPS Rx (say SiRF) it has 48 channel (48 correlators) in the processor. May as well use the extras for something, so they use more than one correlator per satellite and reduce the position error. The early GPS units had one correlator and had to hop from sat to sat. They were horrendously slow. As the electronics became more powerful for the same amount of input power, the number of correlators in the Rx was increased (but battery life expectancy was still similar).
 
One thing is when I connected up the GPS through the FTDI serial board directly to the computer there was a very good lock on 8 or more satellites and there was minimal jitter from indoors. I do have a 3DR 100Mw, 900 Mhz set in the basement I'm going to pull out and try. Now a better quality GPS can be tried but
there goes the economy. Kur t
 
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I have a Neo-M8N clone coming. If that doesn't show improved performance with the 500mW 433Mhz 3DR radio I will call this a dead end.
Perhaps the 100mW radios perform better but why waste your time dinking around when there are 100mW and 250mW commercial solutions that
though they cost a bit more are affordable and reliable on 900Mhz that don't require a Ham license?

Perhaps an $80.00 commercial GPS will deal with the front end noise of the 3DR radio but there goes the economy. Better with a 100mW Beeline GPS on 70cm.
Or if one has the room and just needs to find the rocket an AP510: https://www.sainsonic.com/ap510-apr...th-thermometer-tf-card-support-aprsdroid.html

I'll ride this pony till the end, dead or no. Stay tuned.

One question, if these 3DR radios are so dirty how in the world can anyone use them in a quadcopter that requires absolute positive control? Kurt
 
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Ok, got an 8N clone here: https://www.aliexpress.com/item/UAV...824201295.html?spm=2114.search0305.4.7.RHk2gz We're talking cheap. U-Center allows programming and the son-of-a-gun allows concurrent Glonass use.

I have it running outside now with Glonass active along with GPS and it's working great! I can have it plugged into the 3DR radio and once the positions are fixed, they
come right across! Not like the chipset in the first post.

Bad news is my APRS tracking program APRSISCE/32 can't get a fix with GPS/Glonass both turned on. Shut off Glonass and use GPS only and it works fine with my particular program.
About 6 satellites fixed on GPS. 12 with GPS and Glonass active! UCenter shows a really darned good fix with minimal jitter.

Now............... Have to see if I can program a callsign in there. Will post pictures screen saves tomorrow. I be happy.

Nice thing is the clone GPS chip is programmable. I turned on the jammer protection and that seems to help. Kurt
 
Ok, got an 8N clone here: https://www.aliexpress.com/item/UAV...824201295.html?spm=2114.search0305.4.7.RHk2gz We're talking cheap. U-Center allows programming and the son-of-a-gun allows concurrent Glonass use.

I have it running outside now with Glonass active along with GPS and it's working great! I can have it plugged into the 3DR radio and once the positions are fixed, they
come right across! Not like the chipset in the first post.

Bad news is my APRS tracking program APRSISCE/32 can't get a fix with GPS/Glonass both turned on. Shut off Glonass and use GPS only and it works fine with my particular program.
About 6 satellites fixed on GPS. 12 with GPS and Glonass active! UCenter shows a really darned good fix with minimal jitter.

Now............... Have to see if I can program a callsign in there. Will post pictures screen saves tomorrow. I be happy.

Nice thing is the clone GPS chip is programmable. I turned on the jammer protection and that seems to help. Kurt
Sounds like you might be on to something :D
 
Here is the Rig:
rig.jpg

The little board off to the side is the 5V regulator Pololu https://www.ebay.com/itm/Pololu-5V-...epid=0&hash=item3d419b87c2:g:2r8AAOSwacdZbWdl It's 1amp and I plug a 2S pack to it. 5V out in a very stable fashion.

The GPS is the 8N clone. The radio settings are in this screen:
setup.jpg

My setup is ideal in that the GPS can be disconnected from the radio (unplugged actually) so the radio can be reprogrammed. Can't be attached while you are doing it.
Great.jpgGreat1.jpg

Picture on the left is the NMEA feed coming in with the radio/GPS out in the yard. The screen on the right is the UCenter feed with the GPS attached via the FTDI Basic 5V USB serial
breakout board:
FTDI.jpg

If one is bold, it's essential you have one of these boards because if you lose lock on your radio pairs you're screwed without it. I just so happened to have this around with a variety
of JST cables to fit the radio and GPS.

Good news/bad news:

1. Guess what? The 8N comes with GPS/Glonass systems activated. Guess what? The 3DR radios will duly report all the information coming across in a serial terminal. Very nice indeed
and with the UCenter GPS program monitoring the stream (the right screensave above), there is very little jitter. That is the position jumps around when the tracker is stationary.
(It was late and I didn't get a picture of that.)

2. Good news is one can have their Android device use Bluetooth GPS and select "Allow mock GPS locations": https://play.google.com/store/apps/details?id=googoo.android.btgps
and one can track with the "Blue" GPS as their rocket. Can't navigate but you can see the blue dot where your rocket is. This is using the combined GPS/Glonass stream.
Really helps with the accuracy once locked.

3. Bad news. None of my Ham apps including the Android app "GPS Rocket Locator" can track with the combined Glonass/GPS strings coming in. That trick in #2 can allow you to see the
rocket with "GPS Rocket Locator" as the Blue GPS. That program B/T GPS once running and minimized ignores your internal GPS and pipes the strings coming in over the receiver
as "your" GPS. For some reason, "GPS Rocket Locator" can display the position as the "blue dot" but not as the red push pin. None of my Hams apps could read it either...........But...

4. With that FTDI USB/serial interface, one can go into the GPS units setup with UCenter and shut off using the Glonass system. WAAS and SBAS is fine. Do that and all the programs will work perfectly fine. The picture on the left is with the U.S. GPS positions coming in on APRSISCE/32 using an NMEA port. The constellation was in a very good position last night.

5. One more bad news item. The frontend of the radio intereferes with the GPS even with jamming protection enabled. I couldn't have the GPS lying on top of the radio a' la shrink tubing
it to the case. That's a no go. Spread out from the radio on a cable (and perhaps a ferrite filter might help) and it improved on the GPS reception situation immensely.

Bottom line: Go buy a commercial unit if looking for a 100mW 900Mhz tracker or even a 250mW tracker. The Ham stuff has the potential for better propagation but the unlicensed GPS trackers are doing a darned good job judging by what folks are experiencing.

I'm not so certain that spread spectrum is reasonable for rocket tracking. We only need a one way link from the tracker to the receive station and a two way link is superfluous.
The drone guys seem to gripe about limited range and they are depending on these things for a satisfactory two way link. Besides, the radios are so dirty you can't shrink tube
them together on the GPS.:confused2:

500mW on 70cm seemed like a decent power point but if it won't (and I don't know this) provide long range and reliable high rate position reporting I'd place 3DR on the fringe of
rocket tracking. Again, if you don't have the stuff lying around to experiment nor have an inkling of what's going on (that hasn't stopped me any!) buy commercial.

I'll keep hammering at it. If a callsign can be stuffed in one of the strings, it would at least be worth test flying in a modest sized rocket that could handle the limitations.

$25.00? Naaaahhhh. Not even close to it. Probably more like $75.00 and you won't know if it will work at range. Kurt
 
Hmmmmmmm, I just had a halfed-a**ed idea. With #2 above, I said that GPS Rocket Locator could track the combined GPS/Glonass strings as long as it's coming through the minimized Android
app "Bluetooth GPS". Well, well, stupidhead here had an epiphany when I hit send. I've got four B/T GPS sources around here that are old and can do 9600bps, If I can pair them to my
Android device, velcro it to the top of my ball cap and if I can select the local B/T dongle as the "rocket" might be able to track with the "red pushpin" being "me" and the blue dot
being the rocket. Positions reversed. Well that could be a cool work around!

Shoot, now I got to go reprogram my GPS back to GPS/Glonass and give it a whirl! Still, the cobbled arrangement would only work with GPS Rocket Locator and no other Ham apps I got. Kurt
 
Went for a ride with "GPS Rocket Locator". The local GPS in the phone was the blue dot and the red pushpin was an ancient Royaltek RBT-1000. It works.

Screenshot_2017-09-17-10-36-45[1].pngScreenshot_2017-09-17-10-46-54[1].png

Thing is, is the blue dot or your local position is seemingly sampled once every 5 seconds. The red rocket pushpin is once a second. In this case I was using the B/T Royaltek RBT-1000 as a "local" GPS source.

As I mentioned above, with the Android app B/T GPS I can attach the stream coming in over the 3DR radio that is using both the GPS/Glonass strings to determine position. If one has an internet connection on site, they can
run B/T GPS and "see" the rocket position on the map. B/T GPS is of no use without maps. If B/T GPS is active on one's device and is minimized along with "allow mock GPS locations" the HC-05 or 06 that is feeding
data from the 3DR link can be patched to the blue dot, local position. GPS Rocket Locator cannot decode the native GPS/Glonass strings but if presented to GPS Rocket Locator by B/T GPS the positions will be plotted.

Problem is, is I think the rocket "blue dot" position will now be once every 5 seconds and the red pushpin "local" position coming in over the Royaltek will be the desired once per second.

Oh well, I'll give it a run later tonight after I reprogram the GPS back to GPS/Glonass from just the plain US GPS.

Be aware, if you get an 8N clone like I show, it will come with GPS/Glonass active and none of my local Ham apps or GPS Rocket Locator could decode the strings. Bluetooth GPS was the only thing that plotted the position
but you can't navigate directly with it.

Basically, I'm switching the positions. The rocket is the blue dot and the red pushpin is local. Kurt
 
Ok, Got home, reprogrammed the 3DR radios and reprogrammed the Ublox-8N clone to use both GPS/Glonass. Got the Royaltek RBT NMEA Bluetooth source out.

IMG_20170917_173051[1].jpg

This is the setup. The 3DR radio is obvious along with the little Pololu 5V 1amp stepdown voltage regulator that feeds 5V to the radio and the -8N clone. The Royaltek RBT1000 bluetooth
GPS is down in front. The 3DR ground module is in the back. I used an HC-05 with the angled pin connectors. I can use the Bluetooth or disconnect the + wire on the module and
plug it into a laptop for programming proposes. With the HC-05 module connected the USB plug is just providing power from that big mother black battery

Soooo. I set the air module outside, plugged the ground module into the battery and wait until there is a lock on the GPS. I pair the HC-05 B/T module to the Android phone and then
call up the B/T GPS app: https://play.google.com/store/apps/details?id=googoo.android.btgps&hl=en I select allow mock GPS location and minimize the thing. There will be a small indicator in the upper left of the screen.

Screenshot_2017-09-17-17-05-02[1].png

You can see the little blue ball in the upper left. The blue dot is the "rocket location".

Next step is to pair the outside base station GPS source. We can't use the internal GPS on the phone or tablet using GPS/Glonass sentences combined. They have to run through
the B/T GPS program so GPS rocket locator can "see them". I'm using the Royaltek RBT 1000 and you can get these things used for pretty cheap.
I then pair that up and now fire up "GPS Rocket Locator". Now right off the bat you'll see the "blue dot" which is now the tracker position. Next you have to go to the setup pulldown
and select the B/T source which in my case was the Royaltek. Took a few minutes but the Red pushpin with my local position came up.

You gotta remember the positions are reversed. Blue dot rocket, red push pin your local position.

Screenshot_2017-09-17-17-23-37[1].pngScreenshot_2017-09-17-17-24-36[1].png

Left shot is overview of a drive the right shot is closeup in the driveway. The major surprise is once you get both spots displayed it's almost instantaneous when the positions come in.

With the standard "blue dot" local position and "red pushpin" rocket, it seems the red pushpin is tracked once a second and the blue dot once every 5 seconds. That is perfectly fine for
the ground position to lag.

Now with the "blue dot" as the rocket and the "red pushpin" representing one's local position, the blue dot jumps once a second and the pushpin follows almost immediately.

Now to try to get a callsign in there and see what happens with a real flight. Kurt
 
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Looks like great progress there Kurt.

If you have a piece of FR4 PCB material (unetched) you can try mounting the Tx module on one side and the GPS, battery, and regulator on the other. Connect the sheet of copper to ground. For extra brownie points you can add feedthrough caps, and/or a ferrite toroid or two, and see what improvement that makes for EMC. That would be a great test. I think a ferrite toroid around the wires to the Tx module is important. Even one or two turns will ensure the return currents are encouraged back along their correct return path, rather than increasing emissions that can worm their way in elsewhere.

If you shape the PCB piece like a sled you can then mount it in a rocket and fly it if the tests come out much improved :)
 
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Looks like great progress there Kurt.

If you have a piece of FR4 PCB material (unetched) you can try mounting the Tx module on one side and the GPS, battery, and regulator on the other. Connect the sheet of copper to ground. For extra brownie points you can add feedthrough caps, and/or a ferrite toroid or two, and see what improvement that makes for EMC. That would be a great test. I think a ferrite toroid around the wires to the Tx module is important. Even one or two turns will ensure the return currents are encouraged back along their correct return path, rather than increasing emissions that can worm their way in elsewhere.

If you shape the PCB piece like a sled you can then mount it in a rocket and fly it if the tests come out much improved :)

I've got some double sided PC board lying around here somewhere. Used to make ematches in the old days. Got good at it too. I have a large collection of toroids lying around. What size you think?

Running GPS Rocket Locator Bass ackwards is weird but actually I like it better than running it in the standard mode with just the GPS satellites. Glonass adds to the accuracy if you ask me. I have no idea why I have to run the B/T GPS program to get the
strings decoded properly and sent to GPS Rocket Locator. None of my Windows tracking apps can read the combined GPS/Glonass strings either.

I have to give my Linux boxes a shot and see. Actually Xastir gives the prettiest screen for APRS or NMEA tracking. With the NMEA trackers, one fires up a python script to intercept the NMEA strings which converts it to a pseudo APRS packet that gets presented to Xastir. It gets displayed on the map very nicely.

I know I'll be able to get the ground module to fire off the strings to an NMEA port (B/T or USB) so I'll see if I can get Xastir to deal with it. If does, that means me and one other guy (the fellow who wrote the python script), Jason KG4WSV can use it! :wink: Jason has the script posted publicly and it has his callsign in the rem notes of the program. Says he flies rockets too. He's out of Alabama.

Also, I discovered last week an Android app ROOT/Gnu Debian and XSDL. It's a bit of a gyration but it fires up Linux and lxde X-windows on top of Android! I did an apt-get install xastir and it installed and I was able to get my maps in.
It connects fine to an -IS server (ie. google aprs or aprs fi) and the only thing left is to see if I can get a B/T device to connect. Sheesh, I attached a B/T keyboard and mouse through Android and it's "just there" when I fire up
X-windows. Same thing with WiFi or the cell data network. If it's connected via the Android side it's "just there" when I fire up X-windows. I've never had be that easy before. I need to see if I can get a user definable device transparent on the linux side so I can pipe my NMEA strings in or use a B/T TNC for APRS stuff. I got GNU/Root and XSDL running in a Nexus 7 2012 3G, 2013 LTE and a cheap Blu Studio G plus. I bought all this stuff used for
way the heck less than a single Apple product. Root 'em and tweak them I say and one can really be surprised.

I'm surprised there aren't a few accomplished 'copter guys on this board. I would'a thought someone would of sounded off to tell me how to optimize the radio settings for what we are trying to do based on their experience but
nary a peep. Probably no one who's an advanced quad copter person flies rockets? Kurt
 
What size you think?

Only need something small. Usually as small as you can and still get the connector through. You could go smaller if you like.

The larger cores saturate (lose their inductance) typically at higher currents, as the magnetic flux increases. We are using it as a common-mode choke, with all the wires to the Tx module passing through. Basically the current flowing in the +Ve flows back out the -Ve (GND) so the magnetic fields cancel to zero. Likewise for the serial lines if they have any signals on them We want to encourage the return currents to go where they are supposed to go (on the wiring loom), and this CM choke helps that. Any signals that want to go "the long way around", via parasitic couplings or other PCBs, end up with the CM choke sensing the imbalance in the return paths and helping by pulling the voltage in the direction that encourages it back through the choke. Anything that is single-ended, does not go out and come back through the CM choke, sees a higher impedance and attenuation.

So, using the cores as a CM choke above you usually don't have to worry about size too much, or saturation, as the normal running current sums to zero.

If you put a toriod on a single wire to create a series inductance, it needs to be sized for the magnetic flux at peak current (DC+AC) through the core. Remember too that more turns increases the magnetic flux induced, as well as the inductance. If you saturate the core it loses its magnetic properties temporarily and the inductance goes down the toilet.
 
Ok, Latest tests:

shield2.jpgshield4.jpg

Right picture is with the GPS lying on the end of its short cable with a filter.
The shot on the left is the GPS lying on top of the shielded case. I put Rf shielding on
both sides of the case of the 3DR radio. Well this kinda stinks.

I guess for 433Mhz, 500mW, Rf noise is too bad to shrink wrap the GPS on the radio.
Perhaps in a large nosecone bay of a 3 or 4 inch rocket it might be workable. The GPS
is on a short cable and it gets pretty good reception as long as it's not lying on the
radio. Using a combination of Russian and US satellites. With a long nosecone it could
work.

Think I'll get a 500mW 900Mhz rig and see if it's just as dirty. It might not be as bad as the 433Mhz rig.

When the weather breaks, I'll put it on top of the roof and do a range test. I can use "GPS Rocket Locator" and see what I get with my Android Tablet and the utility Bluetooth GPS.

Kurt
 
Hmm, tried a second air module and the darned thing lost lock when the GPS starting transmitting strings!! Maybe cheap junk here. Searched about plugging in a ham callsign into the strings and there is no easy way to do it. Scratch the
500mW, 433Mhz radios then. Found a link where a Drone/Rocket guy pulled it off but put an Arduino in between the GPS and the 3DR radio! Up goes the complexity!

Will give the 500mW 900Mhz rig a shot and then if no luck, I'd consider this a dead end. Fun playing with it though.

Note: I can't find anything about programming text into a -m8n module. I saw the link posted above at the beginning of the thread but I can't find anything in UCenter about a text message (ie. callsign) that can be put in the strings. Kurt
 
Sorry you've had such a difficult time with this project, Kurt. My unit, built exactly as described in the original post works great and haven't had any problems, even with losing and reacquiring radio lock at longer distance ground tests (> than 2 miles LOS on the ground with variable terrain and minor obstructions). Hope you find your dream system one day :)
 
Sorry you've had such a difficult time with this project, Kurt. My unit, built exactly as described in the original post works great and haven't had any problems, even with losing and reacquiring radio lock at longer distance ground tests (> than 2 miles LOS on the ground with variable terrain and minor obstructions). Hope you find your dream system one day :)

No problemo, The stuff is not that bad in price and I'm going to give the 500mW 900 Mhz unit a shot. Could be the frequency is what's interfering with the GPS (433Mhz) or the power output 500mW. 900Mhz might be different.
Someone might figure out how to easily and non-destructively get a callsign into the strings. I got a couple of 900Mhz 3DR radios a year ago (100mW) but they are the micro USB version and I can't see how to get the 5V into the USB side.
I took a micro USB rig and put 5V in through the GPS data socket but that didn't work. Didn't hurt the thing but got a red LED lit and not the green one. Power goes in through the micro USB (plus data in out too) and 5V goes out through the
4 or 6 pin socket to the drone rig or in our case the GPS.

If this cost as much as a commercial system to experiment with, it wouldn't have been worth the risk. Might be that 100mW, 900Mhz is the limit for a reasonably reliable tracker for a sport flier that doesn't mind tinkering with 3DR.

Was pretty neat to find out I could get a combined GPS/Glonass string decoded in "GPS Rocket Locator" with the -m8N clone. It didn't cost much more than the GPS you showed. My only issue is I couldn't shrink tube it to the radio without impairing GPS reception. Again, that is probably a frequency/power issue.

Adrian Adamson from Featherweight is showing a prototype system that reads GPS/Glonass strings, is very efficient and looks to have very long range. If I needed long range, I'd stuff a 1 watt AP510 in a nosecone on the 2 meter Ham Band, make sure my deployment electronics used optoisolators on the output channels, thoroughly ground test and let 'er rip. Fellow reported here a year or two ago he loves his AP 510 in his rockets. $95.00 and you got a 3 or maybe 4"nosecone that's long with room for a good antenna and you're good to go. A 3 element Yagi and I'd bet you'd get at least 10 miles from 1000 feet up. That's enough reserve for a crazy stupid flight!

Part of the reason I'm dinking with this is I'd like to see more recovery of in-flight positions than I am seeing now. I'd like to see 'em plotted on a map live. The efficiency with the EggFinder went up with an improved antenna system
stock < vertical dipole < patch antenna on a pole. I've had a revelation that there might be a problem with the software tracking my local position AND the rocket live during the flight. Might be some critical program latency that is
affecting the plotting on the map. I'm running two instances of a program to do this and stupidhead here made the realization I really don't need to know my local position during the rocket flight. I can get it plotted on my map before
launch, shut that monitoring side off just before launch allow the program to devote all its resources to tracking the rocket in flight and then turn on the local position for recovery so I can then see my position move towards the last known position during recovery.

This wasn't apparent of course during a testing drive around. Both units were inside the vehicle. No range problems or decoding issues with a strong signal. With a rocket flight, I was surprised I didn't see plotting of that many
positions on my map although that might change next time I fly and do the modification in technique as I mention above.

Me thinks this will enhance my chances of better live plots. I base that on the fact that many folks have posted they get plenty of positions at altitude and I am so wired when I track, I can't tell if I am getting the beep signal and position plots at the same time. Some close in flights didn't seem to have as many beeps off the LCD as I would have expected. Of course enough positions get through that folks can get a good recovery otherwise the EggFinders wouldn't have
become so popular. (And the associated tracker board now available for a better log to be had after recovery). Kurt
 
Got back from continuing education and received a 500mW 915Mhz radio. Plugged in two different GPS units after pairing and tweaking the settings like for the 433Mhz radios. Good news is the Neo 7 chipset
can be plugged in from the get go and when positions start coming in, there's capture and transmission. With the 433Mhz, wouldn't work unless the GPS was already receiving positions. The Neo 8 GPS
worked out of the box too. The default is GPS/Glonass so most tracking software will not decode to a map in realtime. On Android, I can run "Bluetooth GPS" and by selecting "Allow Mock Locations" I can minimize
the "Bluetooth GPS" program and the "blue dot" in the "GPS Rocket Locator" program is the rocket. One then has to pair a little Bluetooth GPS source and tell "GPS Rocket Locator" to use this device.
The red pushpin then becomes your local position. It's in reverse.

Now, I tested the setup with the Neo 8 GPS extended a couple of inches away from the 3DR radio:
915off2.jpg
Ran the Ublox utility and got this visual signal strength above.

Then, I set the Neo8 GPS "on top of the radio case like it was attached by heat shrink "able" tubing:
915on2.jpg
I got this shot and the signal strength of the satellites is a bit lower. It's the third bar graph from the bottom. I suspect it's usable but
I think when I get around to fly it, I'd use it in a nosecone bay I can keep the radio and the GPS separate on a cable as opposed to
shrink wrapped on top of each other.

If one wanted to use the Neo 8 with the US GPS alone, they'd have to plug the GPS into a USB serial card and use the Ublox Ucenter program to reprogram and shut off
Glonass. (Unless they want to use "GPS Rocket Locator" and "Bluetooth GPS" like I described above for live tracking.)

As I mentioned before, I did a drive around post and saw satisfactory handling for the positions. Kurt
 
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Settings used for the above setup with the 915Mhz 500Mw radio:

9153DRsetup.jpg

Might be able to get away with an airspeed of "19" instead of "24".

Kurt

P.S. Tried 19 for the airspeed and 24 is better. Those settings with error correcting off like I show is a good starting point for someone else to experiment with. To recap it appears that 900Mhz 3DR rigs don't interfere as much with the GPS receiver
at least at the "alleged" 500mW Rf output. The better situation is with the GPS receiver placed away from the radio. So much for shrink wrapping the GPS to the radio. With 900Mhz it's doable but I would suspect the accuracy of position is much
decreased with the GPS shrink wrapped on top of the radio. I'm going to try to eventually test this out next year.
 
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Bump

Any more work on this or has it fallen by the wayside?
Other stuff got in the way. What remains for me to try is see if I can shut off two-way communication at the ground station and have it act as a passive, reliable receiver while the tracker simply transmits.

Also as it stands, I couldn't get a Ham Callsign into the NMEA strings. I did get the
"comment" line transmitted in the NMEA strings but my alpha numeric data did not come
across with a Callsign. This would only be helpful with the 400Mhz rigs that technically
require a Ham ticket to "operate". I could probably hack this over time but that is
something of a commodity now. (And probably not worth it.)

The 400mhz 3DR radios are noisy and interfere with the GPS receiver. The 900Mhz less so.
I found that out by "setting" the GPS receiver on the 3DR case and noticed the reception
signal strength of the satellites dropped by quite a bit. Something one doesn't want inside
of a rocket otherwise that cuts down on the accuracy of the position. I tried shielding
but it didn't work very well. 900Mhz was more resistant. If I had the GPS a couple of inches away from the radio on a cable, all was fine. Only problem there is a nice, neat shrink wrapped package makes for a nice neat payload on a rocket. A stretched out tracker package would then be confined to larger rockets.

The other thing is over time the 3DR costs have gone up since I started and I found on the
Drone blogs one had the specialized metering equipment to measure power output and
Chinese milliwatts abound. Fellow said he measured anywhere from 80mW to 270mW and this was with purportedly 500mW radios! I recognize it as the same results as with the
lithium batteries the Chinese sources touted as 3000mW/hr when one was lucky to get 1600 out of them (some years ago).

The radios when operated normally tend to require a "lock" in order to communicate except as I said there is a "one-way" transmit receive mode I didn't test yet. Psychologically I want the receiver to be listening and the transmitter transmitting and I want the range to be as far as possible. The Drone folks generally keep their vehicles in sight. Well at least the hobbyists do! The guys and gals who do the long range goggles thing are spending more for
out of sight 900Mhz 1+watt two-way telemetry. Defeats the purpose of "economical" for rocket fliers. I think the 1 watt 900Mhz radio was quite a bit over $200.00.

I will admit I learned a lot even though I didn't get this to my satisfaction or fruition.

There are el cheapo Ublox GPS chipsets (like $8.00 to $15.00) that can monitor and use both the US and Russian Glonast satellite systems that really gets accuracy to the point of absurdity. What is seen is the position on the ground doesn't jump around as much.
I believe it's called horizontal dilution of precision, (HDOP). I set a GPS/Glonass tracker outside and the position doesn't jump around as much on the map as using the singular
GPS system. (Plus it depends upon the position of the satellite constellation).

Oh, BTW the Ublox utility U-center was wonderful for testing by a neophyte. Pulls up a map and one can see how a chipset does with GPS, Glonass or GPS/Glonass together. Most of the
-8M GPS chipsets I could configure the receiver to whatever system I wanted to use or test.
Again, I had to climb a learning curve to mess with this but it certainly helped me with GPS tracking concepts.

Disadvantages to 3Dr? Besides the unknown range (which I think is less than current one-way methods) I had to get a voltage regulator for 5V to make certain I could use 2S batteries and provide "healthy" current to the radio. That of course limited me to 5V GPS chipsets and a lot of the newer ones like 3.3V or less now as they can be so sensitive and power efficient.
The voltage regulator adds to the cost. The noisiness of the 3DR rigs to interfere with the
GPS reception really turned me off too. This was more with the 400Mhz rigs but still.
The ly'in power output specs. Another turnoff. Oh, programming these things can be
a real bear if one gets them out of sync. Need a USB serial board, voltage regulator and
connectors to sync an air module to a receiver if one muffs it up. Believe me when experimenting it's going to happen. I lucked out with all the messing around with GPS for the last 10 years I had the hardware (it is pretty cheap I have to admit) lying around to do this. The learning curve, that's another matter!

I think CORZERO had success with flying these but I haven't heard much from anyone using these hacked 3DR in rockets. I think the 900Mhz is still a possibility but again a real PITA to prove reliability.

Overall, I call it a worthwhile experience. Certainly it would have been nice to have a reliable
$35.00 GPS tracker one could lose or crash ballistic and not bat an eye. Believe me, doing a Beeline GPS ballistic is cause to shed a tear (done that 10 years ago) whereas a $75.00 EggFinder is a "less" tearful experience especially when the unit gives its "life" and one finds the fiberglass rocket sticking out of the ground that is easily made flyable again with little work.

Recommendations? Technically adept neophyte, of course, the EggFinder clan. If one doesn't want to build? The Beeline 900Mhz GPS tracker has been around quite some time and proven itself. The Missileworks line especially the T3 if one just wants a GPS tracker. The T3 has a 250mW power output that "might" have an edge on the EggFinders. Suffice it to say, I haven't had nary a problem with recoveries with EggFinders although I haven't had one land more than 2 miles away. Folks have flown some of this stuff towards 20k with success at finding their projects. Oh the impending Featherweight tracker looks extremely promising
and it is the only dedicated Rocket tracker that will do GPS/GNSS monitoring and use simultaneously. Has what appears to be mesh technology for "group" tracking too. Also
looks like to be in the very long range category with the LoRa technology $300 for complete system. Only unknown is what if any live-mapping capability can be had. It should find rockets and proved itself on a 96k rocket ride and >90% recovery of positions over Rf.

Stupendously far ranging rockets would likely benefit from the Multitronix product or
the Ham band trackers from Beeline GPS and the controllers from AltusMetrum.

When I started out 11 years ago the Ham band APRS stuff was a bit cheaper than the dedicated
rocketry RDF hardware so that's where I headed.

Very long range tracking on a shoestring? Ham band Beeline GPS products, Byonics (very DIY), the high learning curve Sainsonic ap510 (1 watt on 144Mhz, 2 meter band) PicoAPRS and the Featherweight GPS tracking system outlined above. For non-Hams the Featherweight is likely going to be the "economical" go to for the extreme. The 100mW 70cm Beeline GPS's are solid performers at long range (and there is the turnkey 900Mhz Beeline GPS too that many have flown satisfactorily). One of Gregs 2 meter GPS trackers made it across the Atlantic in a balloon and was recovered in Africa. The group that flew it, got it back!

The PicoAPRS looks promising except in it's current state not acceptable for rockets. Smallest tracker with 1 watt out on the 2 meter 144Mhz band switchable to 500mW. Tunable off the National APRS frequency (as is the ap510) but the beacon triggering is by distance traveled
AND time. I've had contact with the developer and he sent me a firmware that allows beaconing every 5 seconds but still has the distance moved restriction. Problem there is once the tracker is down, it will "clam up" and no signal sent. Hardly a way for a tracker to behave. I sent him a long tome on loosening up this "distance moved" triggering and he said for me, he'll send me a firmware with my callsign hardwired so I can set the tracker to beacon off the National APRS frequency once every 5 seconds come heck or high water. Oh, I forgot to add that
the developer of the PicoAPRS is coming up with a balloon tracker with a Ublox chipset that might accommodate to
rockets better. I told him to feel free to bounce ideas off me.

Advantages to 2 meter and 70cm Ham band GPS tracking is one can slap an electronic attenuator on their Yagi antenna plugged into their handitalkie and can convert to RDF tracking as long as a carrier is coming out of their GPS tracker! I've never had to do it with my
Beelines but the facility is there to do it. Ok, enough of this long winded diatribe.
Merry Christmas and any questions?

Kurt
https://aprs.fi/#!mt=hybrid&z=11&call=a/QCRS&timerange=3600&tail=3600
https://aprs.fi/#!mt=hybrid&z=11&call=a/PARS&timerange=3600&tail=3600
 
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This project is stalled for me temporarily. Work is getting in the way of things mostly, but have been concentrating on my vertical trajectory system completion and a kit-bash on a Go Devil 38 rather than this. Electronics is my day job :)
 
I saw that I had slipped that one in on ya :)

I'm with OTT in that work has consumed me lately. I haven't touched a rocket anything for several months. I've also been distracted recently. I saw a youtube video by pure chance that caught my attention, so now I have an itch to delve into knife making. I'm working on a 2"x72" belt grinder build. I just received a completely CNC'd chassis and a Baldor 3hp drive motor. Still waiting on a few other components before I can start putting it all together. Can't wait to grind my first decent bevel, even if this is just another hobby I'll ignore in a year from now.

Who knew a decent belt grinder would set a guy back a couple thousand? Whatever. Good thing I love tools!

Speaking of electronic components, hey OTT, do you know anything about VFD's? I'm going to supply single phase 110 (130 what they call it down under, I believe?) to a 3hp, 3ph motor through said VFD inverter. So as not to detract from the thread, perhaps you could shoot me a pm? Would be much appreciated!

Merry Christmas, folks!
 
I think there are so many economical remedies for tracking now it really isn't worth ones time and effort to pursue this. That said, what I found problematic was I couldn't shrink wrap the GPS on top of the 3DR radio without interference cutting the signal strength of the incoming NMEA strings from the satellites. That was a big turn off for me. Sure maybe it would work fine for modest flights but I'd like to have some reserve for something above 10k "just in case".

Now, what I did find out was if I put the voltage regulator (ie. 2S 7.4 battery to 5V regulator) on the 3DR case, put the battery underneath and then have the GPS chipset a few inches aft of the 3DR radio on the unshielded cable connector, the incoming
signal strength was great. Lay the GPS on top of the 3DR radio and the signal dropped by a 1/3 or more as indicated by the Ublox Ucenter software: https://www.u-blox.com/en/product/u-center-windows.

Conceivably if one mounts the components on a sled with the GPS on the end of it's 3 to 4 inch cable and the radio/Vregulator/battery ahead of it, it should work as long as the Rf signal output is good. Some of the drone fliers had the appropriate meters to measure the Rf output on the digital 3DR rigs and the "rated" outputs were outright lies. Some of the cheap radios put out alot less than they were rated from the maker. Since they are digital, it takes more than a simple analog meter to get an accurate output reading.

If one moves up to the 1 watt output 900Mhz radios the cost is so much it simply isn't worth trying to hack it. If I needed that capability and couldn't afford Kate, I'd take my Ham license and use the APRS mode on 1 meter or 70cm Ham bands.

If you've followed this thread, one has to hack the 3DR receiver to solder an HC05 BT board to the receiver board. I found the HC05 worked better for me than the HC06. Once the two 3DR radios are "paired" If you don't record your
settings somewhere you might have to "desolder" your receiver to "reset" it. Yeah a real PITA.

The short answer is with a lot of work, a viable system is possible but I would prefer to toss a "known" tracker in the rocket (with care) and go fly not to be worried about my hacked up reliability. Kurt
 
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