GPS for less than $50

TX only. An additional transceiver required for RX/TX. Have fun.

https://www.adafruit.com/products/746

https://www.adafruit.com/products/3070

More reading here:

https://learn.adafruit.com/adafruit-rfm69hcw-and-rfm96-rfm95-rfm98-lora-packet-padio-breakouts

You would need two of the transceivers to communicate so it's closer to $60
Here is a solution for $53 or less right now with the flash sale.
Just add a 1s lipo, connect 4 wires (tx-rx, rx-tx, vcc-vcc-bat+, gnd-gnd-bat-) plug usb in and your away.
Works with most gps software
https://rctimer.com/product-1007.html
https://rctimer.com/product-817.html
I've never bought from this supplier but he was the first that I could think of that wasn't Australian and that would be low cost.
Using radios based of the SI1000 allows for programming a netid which allows more than one set to be used at the same launch with minimal chance of interference

With a different gps unit, I have got it down to fitting into a 20mm tube and still costing under $70 ready to go.
(ignore my soldering, this was just a proof of concept to make sure it all worked together)

vance2loud said:

https://rctimer.com/product-817.html
I've never bought from this supplier but he was the first that I could think of that wasn't Australian and that would be low cost.
Using radios based of the SI1000 allows for programming a netid which allows more than one set to be used at the same launch with minimal chance of interference

Click to expand...

Those are just generic 3DR's. Here is a better deal yet:

https://www.ebay.com/itm/361161198947?_trksid=p2055119.m1438.l2649&ssPageName=STRK:MEBIDX:IT

Yeah, I corrected my post. Add $9.95 for an additional transceiver. You could choose the 433MHz adafruit LoRa for increased range but the modules are slightly more expensive and frankly overkill as most of our rockets fly line-of-sight.

vance2loud said:

With a different gps unit, I have got it down to fitting into a 20mm tube and still costing under $70 ready to go.
(ignore my soldering, this was just a proof of concept to make sure it all worked together)

Click to expand...

Very nice! The first GPS module you suggested was huge compared to adafruit's @ 40.64 x 66.42 x 7.8 mm total size, 12.4 grams. Adafruit dim. = 25.5mm x 35mm x 6.5mm. I initially suggested the breakout version for ease of use because everyone on this site complains about soldering Eggtimer stuff.


Adafruit also offers simple, less expensive, non-breakout GPS module with better specs (e.g. 10Hz update, 20Ma draw):

https://www.adafruit.com/products/790

If you want better range another option is the rf900+ radios from rfdesign.
They give you antenna diversity and 1w output power.
Here in Aus we are limited to 25mw on 433mhz so I tend to avoid them.
There's lots of good deals on ebay and thats where I tend to get mine from.
If you are using the 3dr radios you can also reduce the air transmit speed which apparently gives you better range, most GPS modules only work at 9600 anyway so there's no point trying to transmit at 115200.

Here was my first attempt at this system mounted to a 38mm nosecone sled for a painkiller micro.
If you search ebay for"apm gps", nearly all the modules that show up will be compatible, If possible check the vcc range from the datasheet and if the vcc min is below 3.3v and max above 4.2v then you can hook them direct to a 1s Lipo reducing complexity.

Word up. Do you use a tracker on your Tasmanian Devil when you dispatch him for recovery as well? You never know when those things may go rogue...

Tassie devils are always rogue, no luck using them for recovery we don't have a club or launch site down here yet so I have to go to the big island for any launches that require tracking.
I have however been looking at this 'monkey' tracker https://www.instructables.com/id/MonkeyDogTracker/?ALLSTEPS for ideas for a handheld receiver

Here is some version I made, based on the 3dr radio clones.
It cost less than 40$ including a ground Station with bluetooth.
The tracker weights 11g = 0.4oz and uses a Ublox 7 GPS which is pretty good.


Uses this:
https://de.aliexpress.com/item/1pc-3DR-Radio-Telemetry-Kit-433Mhz-Module-Open-source-for-APM-2-5-2-6-2/32638263766.html

and this:
https://de.aliexpress.com/item/Free-shipping-OP-NZ-NZ32-GPS-for-CC3D-ATOM-CC3D-Revolution-Revo-Nano-NAZE32-MINI-NAZE32/32471751693.html

and for bluetooth
https://www.ebay.de/itm/262396409137?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

thomas said:

Here is some version I made, based on the 3dr radio clones.
It cost less than 40$ including a ground Station with bluetooth.
The tracker weights 11g = 0.4oz and uses a Ublox 7 GPS which is pretty good.
View attachment 291382

Uses this:
https://de.aliexpress.com/item/1pc-...pen-source-for-APM-2-5-2-6-2/32638263766.html

and this:
https://de.aliexpress.com/item/Free...Revo-Nano-NAZE32-MINI-NAZE32/32471751693.html

and for bluetooth
https://www.ebay.de/itm/262396409137?_trksid=p2060353.m2749.l2649&ssPageName=STRK:MEBIDX:IT

Click to expand...

Cool project. What kind of ranges do you get out of it? Have you flown it yet?

I have not flown it yet. I have build it last weekend. The range on the ground is bad without direct sight, but you expect that from 433 Mhz. I have chosen 433 Mhz because it is an amateur radio band in Germany, instead of 860 Mhz or 900 Mhz.

The system shown on the black sled has flown to 8000 feet and up to 2400 feet away horizontally without any issues, when trying to test them in a residential area I tend to lose signal at around 700 feet. That is using the standard 100mW 3dr style radio (915mhz)
You would expect slightly more with 433mhz, but it should give you a rough idea.

If I could use it up to 8000 feet that would be great, since it is almost impossible to get a permission for higher flights here. `
What antenna did you use on the ground? I will try the arrowantenna 3 element Yagi I normally use with the telemetrum.

I think I was using one of these https://store.rfdesign.com.au/antenna-900mhz-3dbi-dipole-rpsma/
If not that, then I was using the antenna that came with the radio. I tend to avoid directional antennas as I prefer not to have to adjust anything during the flight. YMMV
I don't own any higher gain antennas so it had to be one of those 2.

thomas said:

If I could use it up to 8000 feet that would be great, since it is almost impossible to get a permission for higher flights here. `
What antenna did you use on the ground? I will try the arrowantenna 3 element Yagi I normally use with the telemetrum.

Click to expand...

Be aware that the beamwidth on 900Mhz might be too narrow to be accurately pointed at a rocket in flight. Especially if one can't see the rocket up high well. On 1.25 meters, 2 meters and 70cm bands it's better and doable. On 900Mhz it's desired to use a patch antenna to get some receive gain and have a decent beamwidth. You need something like this:
The square box is the antenna attached to a pole to get it off the ground a bit. I like these tracker designs but be aware it's really klutzy to haul a laptop out in the field to track. It's a lot better to use a tablet inside a flat black painted
box. If the NMEA sentences can be imported into the device via bluetooth, better yet to avoid accidentally yanking the receiver or cable out of the tablet or laptop while actually tracking.
A 10.6" or 11.5" tablet is easier to see. I tried a TW801 with an 8" screen and boy oh boy it can be hard to see. If one throws a blanket over one's head or a curtain like an old fashion photographer used to use to setup and focus a shot, that can make it easier to look at a screen. Kurt

This is all pretty cool stuff...we have a 100mW capable GPS downlink for under $40 that can get into a 24mm tube or less at 15gm all up. You can throw this in the nose cone of almost anything that would need tracking. i think this technology has just gone into the realm where you could use it for some competition events (like E Scale Altitude for the upcoming NARAM).

ksaves2 said:

Be aware that the beamwidth on 900Mhz might be too narrow to be accurately pointed at a rocket in flight. [...] I like these tracker designs but be aware it's really klutzy to haul a laptop out in the field to track.

Click to expand...

As explained in my original post, I am using 433 Mhz, since 900Mhz is not legal in Germany, you can get the same 3dr radios with the hope module in 433 Mhz.
I am not really experienced in antenna design. I bought the 3 element yagi because it was recommended in the Telemetrum documentation. It is not very pointy, but you can still use it for direction finding.

On the ground I use a bluetooth module and the rocket locator app on a mobile phone.
I plan to include OLED display in the ground module to show the coordinates similar to the eggfinder ground station.

thomas said:

As explained in my original post, I am using 433 Mhz, since 900Mhz is not legal in Germany, you can get the same 3dr radios with the hope module in 433 Mhz.
I am not really experienced in antenna design. I bought the 3 element yagi because it was recommended in the Telemetrum documentation. It is not very pointy, but you can still use it for direction finding.

On the ground I use a bluetooth module and the rocket locator app on a mobile phone.
I plan to include OLED display in the ground module to show the coordinates similar to the eggfinder ground station.

Click to expand...

Right, I was pointing out the situation with 900Mhz. On 70cm/400Mhz a Yagi has enough beamwidth to make blind pointing feasible. Once the rocket is down, a yagi on 900Mhz can increase the ground footprint when going to the site of the last
received packet. I've proved that to myself a few times that a 900Mhz Yagi can help with the recovery. Kurt

CORZERO said:

TX only. An additional transceiver required for RX/TX. Have fun.

https://www.adafruit.com/products/746

https://www.adafruit.com/products/3070

More reading here:

https://learn.adafruit.com/adafruit-rfm69hcw-and-rfm96-rfm95-rfm98-lora-packet-padio-breakouts

Click to expand...

From a quick glance of their website, adafruit.com appears to be a company similar in concept to Sparkfun.com

Their products are breakout boards using COTS ICs so the question is how good is the GobalTop Technology GPS chipset in rocket applications. It is my understanding the UBlox-7 chipset is the current champ for hobby rocketry use because it's internal programing permits precision and accuracy optimization selection possible based on the platforms performance and environment. The basic specs appear to be similar but there is not enough detail in the datasheet to find out how the 60 kft/1000mph limits are implemented or how adjustments are made for platform dynamics. Data logging of 4 spm is not useful for in-flight tracking, but I'll assume there is a way to change the rates.

Bob

https://https://www.ausrocketry.com/forum/viewtopic.php?f=32&t=5240
I just finished writing up the basics of getting a system like this working over on the Australian forum.
Hopefully it might be helpful to anyone considering putting one of these together.
Hopefully we will have access to some software soon which will allow the USB radio to be plugged into an android phone for field use.
Otherwise you can connect a Bluetooth module to an air radio module to create a radio bridge to your phone for using the rocket locator app.