The ULTIMATE GPS rocket locator

Discussions about anything electronics, from altimeters to cameras.

Moderator: Moderators

drew
Southern fried goodness
Southern fried goodness
Posts: 1050
Joined: Sat Aug 01, 2009 10:20 pm
Location: Perth

The ULTIMATE GPS rocket locator

Postby drew » Mon May 08, 2017 12:48 pm

So for years we've been talking GPS and how to best receive packets from your transmitter to tell you where your rocket is. Historically my GPS rocket tracking experiences have roughly followed this pattern.

1) receive packets from the GPS tracker/transmitter at a 1Hz frequency during descent.
2) loose radio line of sight at a few hundred feet AGL and no longer receive packets from the transmitter. A directional YAGI might get you a few more packets but rarely the final packet.
3) navigate to "last known good packet" location.
4) hope for an updated "final" on the ground packet OR continue the bearing I took to get the last known good packet location IF I don't receive another packet.
5) Hope I get that final packet that will tell me exactly where my rocket is whilst continuing the bearing.

As you can see the above process could easily be improved upon. Also, the higher you go the harder the above process is due to increased distances on the ground. So for a while now I've been wondering how we could improve our ability to get that crucial final position packet. Boosting radio wattage on the transmitter COULD work but most likely the ground based interference would still absorb the RF and you'd drain your battery more quickly. Improving your Line of Sight could help but I've never attempted to hoist my Yaesu VX-8GR on a tethered balloon or a quad copter. I'm not sure if I want too either. Cellular/mobile internet gateways COULD be of use BUT most likely where extreme altitude projects are launched there is little if any mobile data connection available.

This weekend the Outernet was brought to my attention and I assumed you might be able to integrate an APRS system to it. Sadly I was wrong. That said during the discussion I was pointed to one HELL of a unit called the RockBLOCK Mk2. Effectively it's a Iridium satellite modem. The units are $250 USD each from SparkFun.

https://www.sparkfun.com/products/13745

I can't see any reason why a RockBLOCK Mk2 + Arduino Pro Mini (https://www.sparkfun.com/products/11113) + a uBlox 7 GPS chipset (https://www.sparkfun.com/products/13670) couldn't be leveraged to provide a GPS position reporting system that leverages the Iridium satellite network to provide an email every 10 minutes telling you EXACTLY where your rocket is regardless of location. The RockBLOCK Mk2 unit we'd want would most likely be the naked model with the SMA antenna connector to ensure the antenna has LoS to the sky regardless of final orientation of the unit on the ground. So my expectation is that the process for locating a Iridium network based GPS position transmitting tracker would be as follows.

1) launch rocket and wait until it's back on the ground.
2) go to somewhere with mobile data network coverage (eg Bruno's in Gerlach)
3) drink frosty beverage whilst waiting for an email to arrive.
4) open email, finish beer, and plan excursion for rocket recovery in the comfort of a relaxed environment with no immediate urgency. You know where the rocket is within a meter or two so there's no real chance of losing it unless you can't get to it or someone steals it.

The only negatives of this solution is that you've got to purchase a data plan to get your once per 10 minute slot on the Iridium network AND you only receive one position message every 10 minutes. For the data plan the cheapest cost is 45 pounds for 500 transmission units in a one month window. That should be more than enough for testing and our use case.

Comments? From what I can see this is a $300 USD solution (excluding power) that would allow us to find the final rocket location for extremely high altitude projects simply, reliably, and accurately.
Andrew Hamilton
AMRS 28 L3
AMRS Records Committee Chairman
Max Alt AGL - 26,850ft - L935 - THUNDA 2019
Max V - 3,004 ft/s, ~Mach 2.67 - L935 - THUNDA 2019

drew
Southern fried goodness
Southern fried goodness
Posts: 1050
Joined: Sat Aug 01, 2009 10:20 pm
Location: Perth

Re: The ULTIMATE GPS rocket locator

Postby drew » Mon May 08, 2017 1:01 pm

I should probably also mention that this is a homebrew version of BigRedBee's SBD unit. That said given the SBD unit dimensions it appears the Iridium 9603 data modem is significantly smaller from a footprint perspective when compared to the 9602 modem in the RockBLOCK Mk2. That said I'd expect the Mk3 of the RockBLOCK (assuming one is made) would probably leverage the newer 9603 modem and therefore be smaller from a footprint perspective.
Andrew Hamilton
AMRS 28 L3
AMRS Records Committee Chairman
Max Alt AGL - 26,850ft - L935 - THUNDA 2019
Max V - 3,004 ft/s, ~Mach 2.67 - L935 - THUNDA 2019

drew
Southern fried goodness
Southern fried goodness
Posts: 1050
Joined: Sat Aug 01, 2009 10:20 pm
Location: Perth

Re: The ULTIMATE GPS rocket locator

Postby drew » Mon May 08, 2017 1:03 pm

Andrew Hamilton
AMRS 28 L3
AMRS Records Committee Chairman
Max Alt AGL - 26,850ft - L935 - THUNDA 2019
Max V - 3,004 ft/s, ~Mach 2.67 - L935 - THUNDA 2019

strud
Engineer
Engineer
Posts: 1077
Joined: Thu Oct 02, 2008 7:37 am
Location: Central Tablelands, NSW

Re: The ULTIMATE GPS rocket locator

Postby strud » Mon May 08, 2017 6:59 pm

Hi Drew,

The Satellite proposal has some merit although the main issue still is that the antenna is one the ground and you cannot guarantee its orientation..... if you use a patch antenna and it ends up on the ground facing down you have the same misery. If it is a

Satellite data plans are also outrageously expensive.... well at lest compared to generic internet access eg dollars per megabyte.

Example costs from their webpage : (works out to be about 50kB for AU$140)

--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Credits are used each time you transmit. 1 credit is used per 50 characters sent or received. 1 credit is also used if you check your mailbox and there are no messages waiting (A mailbox check). Credits do not expire, even if you are paying no line rental.

Bundle per Credit Bundle Price

50 Credits £0.12 £6.00
100 Credits £0.11 £11.00
200 Credits £0.10 £20.00
500 Credits £0.09 £45.00
1000 Credits £0.08 £80.00
2000 Credits £0.07 £150.00
5000 Credits £0.06 £300.00
10000 Credits £0.05 £500.00
20000 Credits £0.04 £800.00

--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

If you location message is say 50 chars (1 credit) it costs you about AU$0.20 per message, so you might want to keep the message rate low.



Maybe the best option is a compromise that gets another antenna in the air in a repeater hence maintaining LOS at both ends, eg Drone ?

drew
Southern fried goodness
Southern fried goodness
Posts: 1050
Joined: Sat Aug 01, 2009 10:20 pm
Location: Perth

Re: The ULTIMATE GPS rocket locator

Postby drew » Tue May 09, 2017 11:26 am

Thanks for the response d00d!

strud wrote:Hi Drew,

The Satellite proposal has some merit although the main issue still is that the antenna is one the ground and you cannot guarantee its orientation..... if you use a patch antenna and it ends up on the ground facing down you have the same misery.


That's why I recommended the variant that doesn't have the patch antenna integrated and instead a SMA connector model. Then we'd be able to use a 1/4 wavelength wire whip antenna which would hopefully resolve that issue. Also, and this is anecdotal, but I've been told these modems don't require full LoS for usage. Apparently they're being used by LE types already for tracking and can be fitted underneath a car and still function.

strud wrote:Satellite data plans are also outrageously expensive.... well at lest compared to generic internet access eg dollars per megabyte.


This is true. BUT, it's prepaid/on demand. So yea, you're up for ~$140AUD in cost per flight but my expectation is that I'd only want to relay simple GPS position coordinates via CSV to keep the bandwidth consumption low. Altitude might be a useful value as well but yea, we'd definitely want to keep the character count low to conserve bandwidth. And you'd only want to use this sort of thing IF you're going ludicrously high.

strud wrote:Maybe the best option is a compromise that gets another antenna in the air in a repeater hence maintaining LOS at both ends, eg Drone ?


Yea, nah. Drones would easily run into the hundreds of dollars, require me to fly one, etc. I'd almost rather attempt some type of hardware repeater distribution over that sort of solution. I want to find rockets, not be a quadcopter pilot!
Andrew Hamilton
AMRS 28 L3
AMRS Records Committee Chairman
Max Alt AGL - 26,850ft - L935 - THUNDA 2019
Max V - 3,004 ft/s, ~Mach 2.67 - L935 - THUNDA 2019

strud
Engineer
Engineer
Posts: 1077
Joined: Thu Oct 02, 2008 7:37 am
Location: Central Tablelands, NSW

Re: The ULTIMATE GPS rocket locator

Postby strud » Tue May 09, 2017 1:09 pm

Hi Drew,

Maybe a rubber duck Omni-directional mounted vertical in the nose cone is the go, however there might not be many off the shelf ie unusual freq for that type of antenna (maybe)
OR
there are some very sexy compact GPS antennae designed for devices such as handheld GPS thingys and they are very close to the satellite band you are thinking of.

Instead of a drone, how about a helium balloon with a tether ? you probably need to get something up in the air say 200 to 400m.

User avatar
Viking
Rocket Crew
Rocket Crew
Posts: 478
Joined: Sat May 16, 2015 2:54 pm
Location: Perth WA

Re: The ULTIMATE GPS rocket locator

Postby Viking » Tue May 09, 2017 3:28 pm

strud wrote:...
there are some very sexy compact GPS antennae designed for devices such as handheld GPS thingys...
...

I have some Maxtena versions of these on the way, the QFH is about as close to isotropic as I could find. Their gain is low but I have my fingers crossed with the NEO-7M's sensitivity this shouldn't be a big issue. I wanted to use an NEO-M8N but couldn't find any at a decent price with short lead time.
Sarantel used to have QFH's with LNA's, but these are almost non-existent now.

A drone repeater is what I have planned, but only as a last resort after leg work.
Simon
WARS #24 / AMRS #54 L2

drew
Southern fried goodness
Southern fried goodness
Posts: 1050
Joined: Sat Aug 01, 2009 10:20 pm
Location: Perth

Re: The ULTIMATE GPS rocket locator

Postby drew » Tue May 09, 2017 4:05 pm

Hey bud.

strud wrote:Hi Drew,

Maybe a rubber duck Omni-directional mounted vertical in the nose cone is the go, however there might not be many off the shelf ie unusual freq for that type of antenna (maybe)

That's what I was thinking. And even if they aren't off the shelf I'm fairly certain one could be somewhat easily made. Here's some RF specs from Iridium's website for a previous version SBD.

RF Interface

Frequency range: 1616 MHz to 1626.5 MHz
Duplexing method: TDD (Time Domain Duplex)
Oscillator stability: ± 1.5 ppm
Input/output impedance: 50 ohms
Multiplexing method: TDMA/FDMA

strud wrote:Instead of a drone, how about a helium balloon with a tether ? you probably need to get something up in the air say 200 to 400m.

Yea, I've considered tethered balloon options. But the further you are from the rocket the higher you need to go to get LoS and that magical "final packet". And for extremely high alt stuff you'd need to tether quite high. Also, wind.
Andrew Hamilton
AMRS 28 L3
AMRS Records Committee Chairman
Max Alt AGL - 26,850ft - L935 - THUNDA 2019
Max V - 3,004 ft/s, ~Mach 2.67 - L935 - THUNDA 2019

User avatar
Viking
Rocket Crew
Rocket Crew
Posts: 478
Joined: Sat May 16, 2015 2:54 pm
Location: Perth WA

Re: The ULTIMATE GPS rocket locator

Postby Viking » Tue May 09, 2017 5:03 pm

I think Iridium is circularly polarised? The linear 'rubber ducky'* would probably be a few dB down if that's the case.
I wonder if a DIY normal-mode helical from some stiff copper-wire would work?

*edit, seems some ducky's are dipole and some are helical....
Simon
WARS #24 / AMRS #54 L2

strud
Engineer
Engineer
Posts: 1077
Joined: Thu Oct 02, 2008 7:37 am
Location: Central Tablelands, NSW

Re: The ULTIMATE GPS rocket locator

Postby strud » Wed May 10, 2017 7:45 pm

Viking, maybe so, but most antennae are patches so no difference in that case.

Ideal compact ones from here :

https://www.maxtena.com/products/helicore/m1621hct-p-ufl/

not sure if they can be bought in low qty though....

User avatar
Viking
Rocket Crew
Rocket Crew
Posts: 478
Joined: Sat May 16, 2015 2:54 pm
Location: Perth WA

Re: The ULTIMATE GPS rocket locator

Postby Viking » Wed May 10, 2017 9:43 pm

Yeah Element14 has them in single quantities, but only the SMA version (sit down before you check the price.... ~$160 each!)
That's why I thought maybe winding a helical would be the go.
I have the same Maxtena QHA's that you linked to but in the GPS flavour, 'only' $32 each in single qty from E14

RichardsonRFPD sell single quantities but they're not showing a price for the M1621HCT-P-UFL, though going on the other prices on their site, they'd be way less than E14!
http://www.richardsonrfpd.com/Pages/Pro ... Id=1142184

Shipping however was a killer for me, they wanted US$50 to ship two $11 (yes $11) M1575's that weigh maybe 2 or 3g each!
I cancelled that order and went to E14.
Simon
WARS #24 / AMRS #54 L2

drew
Southern fried goodness
Southern fried goodness
Posts: 1050
Joined: Sat Aug 01, 2009 10:20 pm
Location: Perth

Re: The ULTIMATE GPS rocket locator

Postby drew » Thu May 11, 2017 12:42 pm

Viking wrote:Yeah Element14 has them in single quantities, but only the SMA version (sit down before you check the price.... ~$160 each!)
That's why I thought maybe winding a helical would be the go.
I have the same Maxtena QHA's that you linked to but in the GPS flavour, 'only' $32 each in single qty from E14

RichardsonRFPD sell single quantities but they're not showing a price for the M1621HCT-P-UFL, though going on the other prices on their site, they'd be way less than E14!
http://www.richardsonrfpd.com/Pages/Pro ... Id=1142184

Shipping however was a killer for me, they wanted US$50 to ship two $11 (yes $11) M1575's that weigh maybe 2 or 3g each!
I cancelled that order and went to E14.


Don't worry about that shipping d00d, I've got a workaround. :wink:

Those M1621HCT-P-UFL Antennas look very well suited to our use case. And 33.00 mm H x 13.20 mm D is plenty small enough to fit in a nose cone!
Andrew Hamilton
AMRS 28 L3
AMRS Records Committee Chairman
Max Alt AGL - 26,850ft - L935 - THUNDA 2019
Max V - 3,004 ft/s, ~Mach 2.67 - L935 - THUNDA 2019

martymonsta
Engineer
Engineer
Posts: 709
Joined: Mon Oct 13, 2014 11:57 am
Location: Drouin Vic.

Re: The ULTIMATE GPS rocket locator

Postby martymonsta » Fri May 12, 2017 10:42 pm

I just noticed this thread. It reminded me of the Spot Gen3 https://au.findmespot.com/en/index.php?cid=100 I had thought about attaching one as a rocket tracker when I first started out in the hobby. They are widely used in offroad racing and can provide a tracking down to 2.5-minute intervals. I never pursued the idea due to not being able to control which way up was going to be at landing, however, I believe it could be a very valid way of providing an accurate landing location. The price of the service plans doesn't seem too extravagant with 5-minute intervals costing PA US$49 and 2.5-minute intervals costing PA US$149.
Many years ago the great British explorer George Mallory, who was to die on Mount Everest, was asked why did he want to climb it. He said, "Because it is there."
Well, space is there, and we're going to climb it

MARS #21
AMRS #41 L2/LCO/RSO/CO

User avatar
ROCKet STAR
Astronaut
Astronaut
Posts: 1725
Joined: Mon Mar 16, 2009 1:40 pm
Location: Blue Mountains, NSW
Contact:

Re: The ULTIMATE GPS rocket locator

Postby ROCKet STAR » Fri May 19, 2017 10:16 am

I looked at the original RockBLOCK units a few years ago, and initially had the same concern as Strud regarding unpreductable antenna orientation upon landing. Giving it some more thought though, any project that requires this level of sophistication and expense in terms of tracking, is likely going to be of a fairly large diameter, so mounting the unit in some kind of gravity oriented, gimballed cradle within the airframe, to ensure the antenna is pointing towards the sky, could be a possibility.

I'll be following your progress closely. :)
Chris Barnes

AMRS# 29 - L3

UKRA - L3

strud
Engineer
Engineer
Posts: 1077
Joined: Thu Oct 02, 2008 7:37 am
Location: Central Tablelands, NSW

Re: The ULTIMATE GPS rocket locator

Postby strud » Mon May 29, 2017 8:37 pm

I've ordered a couple of the Maxtena GPS antennae from Richardson and am having them shipped to my work colleague's place in the US (will be visiting him next week).

Not sure how much benefit these will be in the rocket under normal operation but maybe there will be some improvement under unusual orientations...
Main application I have in mind is for a hand held pendant for use when tracking after flight ie need local GPS info to determine heading and distance to target.
Ground shipping within US was $15.

Still the main issue is getting a transmission out of the landed rocket.

Another approach is to simply improve the RX sensitivity of the user end, all other things being equal.

Previous module I have been using is one of these : http://www.hoperf.com/rf_transceiver/Enhanced_Power/RFM23BPW.html and it has best case RF link budget of 150dBm.

With this in mind, some new transceiver modules from Hope RF have come out with a huge signal budget of 166dB ie Tx power of 30dBm and RX sensitivity of -136dBm !!
This is a LORA module with a PA (to get 30dBm) http://www.hoperf.com/rf_transceiver/Enhanced_Power/RFM98PW.html

There is a 900MHz band unit as well but essentially the same.

Anyway, this is likely a 20dB improvement on the signal budget many of the better units out there have at the moment, so might be worth a try.


Return to “Electronics”

Who is online

Users browsing this forum: No registered users and 2 guests