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