Time sensitive advice from the 900 mhz experts.

Discussion in 'Rocketry Electronics and Software' started by School of Rock'et', Aug 18, 2019.

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  1. Aug 18, 2019 #1

    School of Rock'et'

    School of Rock'et'

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    Hey all!

    LDRS in 12-13 days. No access to the nosecone. (Apoxee clay sealed, wish I would have thought of this ahead of time.). 4'' diameter DD 6ft madcow fiberglass Level-2. No ham radio cert. No soldering skills or soldering station. Would like to be south of $500 overall investment and still be able to recover the rocket loaded with a L1000 w potential to breach 10k feet @ mach 1.25. Would need to order, construct/retrofit and ground test between now and launch. Already have avionics bay w stratologger cf fer DD and data telemetry.

    Suggestions for the right GPS 900 mhz tracker system very welcome.

    Thanks in advance for the advice!
    Eric
     
  2. Aug 18, 2019 #2

    BryRocket

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  3. Aug 18, 2019 #3

    School of Rock'et'

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  4. Aug 18, 2019 #4

    School of Rock'et'

    School of Rock'et'

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    Although my daughter has an iPhone and she coming with us...
     
  5. Aug 18, 2019 #5

    School of Rock'et'

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    Would I also need to mount this inside my payload bay somehow ( maybe labratrocketry or someone with 3D printing can help) or drill and retrofit somehow into the nosecone that is sealed? Really don't want to invest and ruin via ejection charges either...
     
  6. Aug 18, 2019 #6

    mikec

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    Should be possible to cut a hole in the nose cone bulkhead (I used a Dremel and a rotozip bit for something similar) and put a removable cover on it with screws tapped into the remaining fiberglass. Mounting something on your avbay sled might also work, depends on how much space you have.

    Missileworks T3 is inexpensive and in stock.

    Using an RDF beacon like the Com-spec tied to the shock cord would be simpler at this stage if you can borrow a receiver from someone.
     
  7. Aug 18, 2019 #7

    kjs

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    Nothing would prevent you from using your daughter's iPhone for the launch - we would just need her Apple ID in order to add her to the TestFlight list.

    It is harder for me to comment on the mounting situation. You would want it protected from the ejection charges. If you had a sealed 'container', you might be able to attach it to the shock cord I guess as it doesn't need vent holes (since it is just a tracker). You might be able to do a sealed PVC container quick and cheap and tape it to the shock cord [but I have never done this myself before so I would want someone with experience in that area to comment as well...]
     
  8. Aug 18, 2019 #8

    BryRocket

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    FWIW you can get an iPhone 5 for less than $40 on eBay.

    Also, I know it can be frowned upon and not best practice to put your tracker in the normal eBay with all threads, but I haven’t had a problem doing that. The app has a page that you can see signal strengths and I haven’t found any appreciable difference between mounted in the nose cone and mounted in the regular eBay.
     
  9. Aug 18, 2019 #9

    School of Rock'et'

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    Will the T3 work mounted inside pvc and harnessed somehow to the shock cord in the payload bay?
     
  10. Aug 18, 2019 #10

    School of Rock'et'

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    Thought of trying to squeeze something in the ebay but with my luck the signals will mess with my altimeter and the drogue and/or main will fire prematurely. I already seem to be constantly browning out for a second upon ascension...(Error code 2) and the connections all test good when checked via computer program diagnostics upon recovery...
     
  11. Aug 18, 2019 #11

    mikec

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    No electronic reason why this wouldn't work that I know of, although such mounting will probably place more mechanical shock on the unit and no GPS is as mechanically robust as a Com-spec.

    FWIW I've flown 900 MHz trackers right next to SL CFs in an avbay with no ill effect. Your report of brownouts is troubling though. Sounds like a bad connection somewhere.
     
  12. Aug 18, 2019 #12

    mikec

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    I guess I'll also mention that a big flight where you really need the tracking is the wrong time to be using any tracker for the first time -- much better IMHO to build up experience with a flight or two where the tracker isn't so critical.
     
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  13. Aug 18, 2019 #13

    School of Rock'et'

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    Yep! Feel stupid for putting LDRS on the calendar entirely without the previous tracker experience. Agree 100%.
     
  14. Aug 18, 2019 #14

    School of Rock'et'

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    T3 does sound like a great investment, or the featherweight. Wonder why such a cost difference in total systems?
    T3 ~ $165
    Featherweight ~ $352
     
  15. Aug 19, 2019 #15

    Adrian A

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    The Featherweight GPS price includes a lot of custom software for things like a real-time pointer display on your phone that points toward the rocket using the compass and gyros of your phone, an over-the-horizon relay of lost rocket location from other trackers, voice telemetry, using one ground station for multiple trackers, etc.
     
  16. Aug 19, 2019 #16

    dshmel

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    I own 3 Featherweight devices (2 trackers and 1 ground station). I have walked straight to my rocket every time I have used it. I also have the Eggfinder GPS system and use CommSpec trackers. I cannot speak to the T3 system since I don't own it or have seen it in action. Whether or not you consider the Featherweight system to be expensive is relative, it is under your $500 budget. I do not regret my purchase.
     
  17. Aug 19, 2019 #17

    School of Rock'et'

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    Thank you all for your input. I have much to consider.
     
  18. Aug 19, 2019 #18

    BryRocket

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    One other point to consider is that the Featherweight has its own dedicated and updated app. That can’t be said for the T3 (as far as I know). I had one for a little while and didn’t have a ton of luck with the available finicky apps. The featherweight is very easy and just works really good.
     
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  19. Aug 23, 2019 #19

    Cameron Anderson

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    T3 has walked me 4 miles to a rocket below ground in an irrigation ditch. I let all my friends use mine. I think it did 5 flights in a weekend, all without issue.

    You can't beat the range of a Featherweight without a HAM licence though.
     
  20. Aug 26, 2019 #20

    ksaves2

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    T3 uses a 250mW xbee unit and might have a little extra edge over 100mW units. The key is getting the last known position as close to the ground as possible. If a tracker is in a ditch, the ground footprint can be quite poor. If the last known position is from 25 to 50 feet in the air, it will get one darned close. A beeper or noisemaker on the harness can help with vegetation if one has the room. The ears are still a good tracking device.
    The Featherweight uses a different LoRa technology that henceforth is giving the fine performance reports. I’ve tracked on a map with a 100mW tracker, not a Featherweight,and made the mistake of not zooming in close enough while recovering. Once I zoomed in, I walked straight to the rocket. Kurt
     
    Last edited: Aug 26, 2019
  21. Aug 26, 2019 #21

    OverTheTop

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    I think the Featherweight Tracker fits your constraints well. I personally run Android, but annoyed my daughter to borrow her iPad (I bought it years ago for her anyway). Proved to be an easy and zero expense Crapple option for me ;).
     
  22. Aug 26, 2019 #22

    ksaves2

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    One can consider the loss ratio. Save $700.00 worth of a rocket, electronics and motor hardware more than once and the $352 or whatever one invests in a tracking system sort of pales in comparison. I’ve saved 18 rockets with my APRS Ham trackers and even though that was a $1000.00 option 12 years ago. I consider it paid for itself with hardware saved. We’re talking rockets that disappear sight unseen and are not found until I walked up to them.
    A D72a connected to a Garmin 60gs or gsx using an APRS tracker gives a live map capability and ability to indirectly track altitude via the APRS packet. All the while monitoring the flight on the map.
    The 900Mhz trackers one can shunt/hack the nmea GPS sentences through other software to achieve that end but it’s a pain.
    Yes RDF works but can be a challenge. I’d rather be flying than trying to reacquire a lost signal.
     

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