World's smallest rocket GPS tracker - Silicdyne Reperix

[Ulyu]

Hey,

I'm the guy behind Silicdyne, a company dedicated to providing the best in advanced rocketry electronics at low cost.

You may have heard of my first product, the Fluctus flight computer. It's a project that's still ongoing development and on the market, but in parallel I'm also developing my next product.

This thread will be dedicated to that new project, called Reperix.

Reperix is a GPS tracker for rocketry.
Its principle is fairly standard: a module, which knows its position via GPS satellites, is placed in the rocket and transmits its coordinates by radio wave to a ground station. The ground station then retransmits the information to a software application (in this case a mobile app) so that you can monitor your flight and be guided back to your rocket on recovery.

In terms of performance, Reperix is up there with the best with its 140mW long-range radio, and latest-generation GPS chipset (ublox M10) for excellent dynamic tracking up to 80km altitude and 500m/s.

One of Reperix's greatest strengths is its size:
the module itself measures down to just 12 by 30mm, making it the world's smallest rocketry GPS tracker. Perfect for your wildest projects!
*For reference, that's more than 2 times smaller than the Featherweight.



And the best part is... I've already got a fully functioning prototype of that thing!

Quick hardware notes:
The battery is intended to be plugged through the bottom USB C connector (capable of voltages from 3.5 to 16 volts), but this might change in next versions.
The actual 915mhz antenna is connected through a robust IPEX radio connector, and there is exposed pad for soldering a thin ~8cm copper wire instead.
All in all you should be able to make a super lightweight and compact tracking setup (reperix+antenna+battery) within 9 grams.




2 euros coin for size reference:




The ground station used - SteadyBluetooth:




I'm planning to do plenty of ground and flight tests soon to properly validate the specs.

On the software side, I'm also making good progress and already have functional firmware/application foundations.
Here's a list of the features that are being / will be implemented:


On the Reperix tracker:

• Configurable radio channel selection with automatic switch on frequency occupancy
• Launch/Apogee/Touchdown detection algorithms
• Flight trajectory recording in internal memory
• Possibility of sending location packets automatically over TheThingsNetwork to track Reperix almost anywhere in the world (useful for potential high altitude balloon usage)
• Battery voltage monitoring, LED status indication...

On the mobile app (Android/iOS), connected to SteadyBluetooth ground station:

• Flight data display / GPS details
• In-app distance/bearing and live tracking on a map
• Voice telemetry during flight
• Settings config
• Convenient and plug and play user experience

For trajectory data download/view, and firmware updates, I'm planning to build a web tool (thus usable anywhere on any PC, without installing anything).


The aim is to have a first user-ready version in about 2 months, in order to launch a small betatest campaign.
I don't have a proper pricing estimate to share yet but it should be quite attractive.
More is coming soon.

If you have any suggestions or questions, feel free to react to this post!

 

[SolarYellow]

With the 12mm width, will it fit in BT-5 (13mm) tubing?

It might be a good idea to move the mounting lugs to the ends rather than sticking out the sides, enabling it to be mounted in even smaller diameters, such as a coupler for BT-5.

 

[darrenf]

Looks like an awesome product. I hope there will be more than 26 channels available as interference between two people using the same channel is going to become a problem very quickly.

 

[OzHybrid]

A lot of the places we launch rockets are remote. No web access. So web based tools have limited use. Stand alone is the way to go. IMHO

 

[Ulyu]

With the 12mm width, will it fit in BT-5 (13mm) tubing?

It might be a good idea to move the mounting lugs to the ends rather than sticking out the sides, enabling it to be mounted in even smaller diameters, such as a coupler for BT-5.

Yes the breakable mounting tabs are not so optimal, they will be changed to a more versatile design.
It can technically fit into a BT5 tube but that's probably the hard limit .

 

[mh9162013]

Cool! Looking forward to further developments.

 

[SolarYellow]

The way I read the description, you only need the app-carrying device to connect via Bluetooth to the ground station. No web service required to recover the rocket. Other features are operable via web.

I think even the 9 grams is too much for people looking to maximize BT-5 apogee. There are ~3gm RF trackers available, but they do require HAM. If you want to set records, it's going to cost.

 

[Ulyu]

A lot of the places we launch rockets are remote. No web access. So web based tools have limited use. Stand alone is the way to go. IMHO

That's true but I don't think there's really any need to update or download detailed data when you're on the launch site, or am I missing something ?
I can provide a local version of the tool too, that should be a perfectly convenient workaround.

 

[Ulyu]

Looks like an awesome product. I hope there will be more than 26 channels available as interference between two people using the same channel is going to become a problem very quickly.

Yep, working on a better system !

 

[OzHybrid]

The way I read the description, you only need the app-carrying device to connect via Bluetooth to the ground station. No web service required to recover the rocket. Other features are operable via web.

I think even the 9 grams is too much for people looking to maximize BT-5 apogee. There are ~3gm RF trackers available, but they do require HAM. If you want to set records, it's going to cost.

That's a VERY niche market where any of us are worried about 6 grams. The main part of that weight is coming from the GPS receiver chip. If you want a GPS location, you kinda need one of those chips.......

 

[SolarYellow]

That's a VERY niche market where any of us are worried about 6 grams.

Indeed.

This fitting easily in BT-20 couplers is still a worthwhile advantage over the Eggfinder Mini. You have to step up to BT-20+ to fit that larger GPS chip and the board it's mounted on.

 

[Titan II]

Yes the breakable mounting tabs are not so optimal, they will be changed to a more versatile design.

Actually, I like them. They reduce the footprint.

 

[OzHybrid]

Make sure your ground station retains the last known GPS position if it gets powered off...And is the first thing that comes up when powered on.

 

[FMarvinS]

Hey,

I'm the guy behind Silicdyne, a company dedicated to providing the best in advanced rocketry electronics at low cost.

You may have heard of my first product, the Fluctus flight computer. It's a project that's still ongoing development and on the market, but in parallel I'm also developing my next product.

This thread will be dedicated to that new project, called Reperix.

Reperix is a GPS tracker for rocketry.
Its principle is fairly standard: a module, which knows its position via GPS satellites, is placed in the rocket and transmits its coordinates by radio wave to a ground station. The ground station then retransmits the information to a software application (in this case a mobile app) so that you can monitor your flight and be guided back to your rocket on recovery.

In terms of performance, Reperix is up there with the best with its 140mW long-range radio, and latest-generation GPS chipset (ublox M10) for excellent dynamic tracking up to 80km altitude and 500m/s.

One of Reperix's greatest strengths is its size:
the module itself measures down to just 12 by 30mm, making it the world's smallest rocketry GPS tracker. Perfect for your wildest projects!
*For reference, that's more than 2 times smaller than the Featherweight.



And the best part is... I've already got a fully functioning prototype of that thing!

Quick hardware notes:
The battery is intended to be plugged through the bottom USB C connector (capable of voltages from 3.5 to 16 volts), but this might change in next versions.
The actual 915mhz antenna is connected through a robust IPEX radio connector, and there is exposed pad for soldering a thin ~8cm copper wire instead.
All in all you should be able to make a super lightweight and compact tracking setup (reperix+antenna+battery) within 9 grams.

View attachment 653824


2 euros coin for size reference:

View attachment 653832


The ground station used - SteadyBluetooth:

View attachment 653833


I'm planning to do plenty of ground and flight tests soon to properly validate the specs.

On the software side, I'm also making good progress and already have functional firmware/application foundations.
Here's a list of the features that are being / will be implemented:


On the Reperix tracker:

• Configurable radio channel selection with automatic switch on frequency occupancy
• Launch/Apogee/Touchdown detection algorithms
• Flight trajectory recording in internal memory
• Possibility of sending location packets automatically over TheThingsNetwork to track Reperix almost anywhere in the world (useful for potential high altitude balloon usage)
• Battery voltage monitoring, LED status indication...

On the mobile app (Android/iOS), connected to SteadyBluetooth ground station:

• Flight data display / GPS details
• In-app distance/bearing and live tracking on a map
• Voice telemetry during flight
• Settings config
• Convenient and plug and play user experience

For trajectory data download/view, and firmware updates, I'm planning to build a web tool (thus usable anywhere on any PC, without installing anything).


The aim is to have a first user-ready version in about 2 months, in order to launch a small betatest campaign.
I don't have a proper pricing estimate to share yet but it should be quite attractive.
More is coming soon.

If you have any suggestions or questions, feel free to react to this post!

Hey,

I'm the guy behind Silicdyne, a company dedicated to providing the best in advanced rocketry electronics at low cost.

You may have heard of my first product, the Fluctus flight computer. It's a project that's still ongoing development and on the market, but in parallel I'm also developing my next product.

This thread will be dedicated to that new project, called Reperix.

Reperix is a GPS tracker for rocketry.
Its principle is fairly standard: a module, which knows its position via GPS satellites, is placed in the rocket and transmits its coordinates by radio wave to a ground station. The ground station then retransmits the information to a software application (in this case a mobile app) so that you can monitor your flight and be guided back to your rocket on recovery.

In terms of performance, Reperix is up there with the best with its 140mW long-range radio, and latest-generation GPS chipset (ublox M10) for excellent dynamic tracking up to 80km altitude and 500m/s.

One of Reperix's greatest strengths is its size:
the module itself measures down to just 12 by 30mm, making it the world's smallest rocketry GPS tracker. Perfect for your wildest projects!
*For reference, that's more than 2 times smaller than the Featherweight.



And the best part is... I've already got a fully functioning prototype of that thing!

Quick hardware notes:
The battery is intended to be plugged through the bottom USB C connector (capable of voltages from 3.5 to 16 volts), but this might change in next versions.
The actual 915mhz antenna is connected through a robust IPEX radio connector, and there is exposed pad for soldering a thin ~8cm copper wire instead.
All in all you should be able to make a super lightweight and compact tracking setup (reperix+antenna+battery) within 9 grams.

View attachment 653824


2 euros coin for size reference:

View attachment 653832


The ground station used - SteadyBluetooth:

View attachment 653833


I'm planning to do plenty of ground and flight tests soon to properly validate the specs.

On the software side, I'm also making good progress and already have functional firmware/application foundations.
Here's a list of the features that are being / will be implemented:


On the Reperix tracker:

• Configurable radio channel selection with automatic switch on frequency occupancy
• Launch/Apogee/Touchdown detection algorithms
• Flight trajectory recording in internal memory
• Possibility of sending location packets automatically over TheThingsNetwork to track Reperix almost anywhere in the world (useful for potential high altitude balloon usage)
• Battery voltage monitoring, LED status indication...

On the mobile app (Android/iOS), connected to SteadyBluetooth ground station:

• Flight data display / GPS details
• In-app distance/bearing and live tracking on a map
• Voice telemetry during flight
• Settings config
• Convenient and plug and play user experience

For trajectory data download/view, and firmware updates, I'm planning to build a web tool (thus usable anywhere on any PC, without installing anything).


The aim is to have a first user-ready version in about 2 months, in order to launch a small betatest campaign.
I don't have a proper pricing estimate to share yet but it should be quite attractive.
More is coming soon.

If you have any suggestions or questions, feel free to react to this post!

Hi Ulyu-many flyers are ham radio operators, how about a 2 meter or second choice a 70 cm band frequency? If possible-APRS based would complement those with APRS capable hand transceivers. One advantage is that the transmision range on 2 meters is significantly better than the 900 MHz band. I'd also like to see 2 meter or 70 cm transmission on the Fluctus. In the USA 1 watt plus transmissions are legal on the above bands-so how about a 500 mw or 1 watt transmitter?

 

[cwbullet]

Nice new product development.

 

[Art Upton]

Hi Ulyu-many flyers are ham radio operators, how about a 2 meter or second choice a 70 cm band frequency? If possible-APRS based would complement those with APRS capable hand transceivers. One advantage is that the transmision range on 2 meters is significantly better than the 900 MHz band. I'd also like to see 2 meter or 70 cm transmission on the Fluctus. In the USA 1 watt plus transmissions are legal on the above bands-so how about a 500 mw or 1 watt transmitter?

I have one of those high power 2m transmitters and it is not really needed for rocketry or ballooning and consumes way too much power. Look at what Pico Balloons are using for APRS and WSPR globally. One got shot down by an F22 remember?

Also the amount of Amateur Radio Operators, sometimes called Hams that are also rocketeers are very tiny market. When trackers went from Amateur 70cm frequencies to 900mhz the market grew exponentially larger about 12 years ago.

Meshtastic on 900mhz is taking over more and more what APRS did/does for networking/messaging. The APRS AX.25 collision domain is very dated now and we need to move forward from it. It needs very good SNR to decode packets also.

There are only two Amateur Radio HTs now made that Receive APRS directly; The Kenwood TH-75 [$750] and the Yaesu FT-5 [$420 street price], both very expensive. Yes I have many of my older HTs that do APRS, but it's expensive for new users. Yaesu is now the only one making mobile 2m/440 radios that have analog APRS in them.

Art - K8XG

 

[Adrian A]

Looks like an awesome product. I hope there will be more than 26 channels available as interference between two people using the same channel is going to become a problem very quickly.

If the product is going to be compliant with FCC part 15 (no HAM license required) then it either needs to do frequency hopping or use >= 500 MHz bandwidth. The latter approach is used by the Featherweight trackers, which why there are 52 channels available, on 26 frequencies.

Ulyu, I’m very impressed by how much development you have done so quickly!

How is the GPS performance with the smaller patch antenna? What are the dimensions before the mounting tabs are removed? What size screw do they accommodate?

 

[Ulyu]

Ulyu, I’m very impressed by how much development you have done so quickly!

Thank you !!

How is the GPS performance with the smaller patch antenna?

It was quite a pain to get the circuit board design RF-efficient, but surprisingly it's pretty good!
With sort of optimal conditions (no antenna obstructions and clear sky), it managed to fix 12 satellites in about 3 or 4 minutes, and it provides me position with a fairly small uncertainty radius (about 2m). I'll be doing more tests soon to see how dynamic tracking performs during a flight.

What are the dimensions before the mounting tabs are removed?

From tip to tip, the board with the mounting tabs is 19mm wide.
I'll have to see if I change them or rotate them to get the true 12mm width without having to break them.
To respond to @Titan II , the idea of placing them like that is to make it easier to install the tracker in a bay, and that the few people who want to go below 19mm won't be bothered to break the tabs and use another mounting method. I've made that choice for this first version because it seemed the most convinient for me. I like them too.

What size screw do they accommodate?

It's intended to be mounted using M1 screws.

 

[Ulyu]

Make sure your ground station retains the last known GPS position if it gets powered off...And is the first thing that comes up when powered on.

I can do that in the application. The ground station itself don't know where the tracker is, it just forwards data to the smartphone.

Hi Ulyu-many flyers are ham radio operators, how about a 2 meter or second choice a 70 cm band frequency? If possible-APRS based would complement those with APRS capable hand transceivers. One advantage is that the transmision range on 2 meters is significantly better than the 900 MHz band. I'd also like to see 2 meter or 70 cm transmission on the Fluctus. In the USA 1 watt plus transmissions are legal on the above bands-so how about a 500 mw or 1 watt transmitter?

The radio used uses modern chirp spread spectrum modulation techniques (LoRa) which, in a nutshell, make it possible to achieve some pretty crazy distances.
In line of sight near ground, I've tested that radio system successfully at a range of more than 10km. In flight, I think it can reach 100km.

It's true that switching to 433mhz might almost double that distance, but that's not all. Decreasing the frequency by 2 times also means that data takes 2 times longer to transmit, and so:
- packets might be more likely to be corrupted (because they are spread over a longer time span)
- radio consumes virtually 2 times more energy
- the data refresh interval is twice as long, which is undesirable if you want smooth real-time flight monitoring
So that's a bit more tricky choice.

I also agree with what @Art Upton said.

 

[KenECoyote]

With the 12mm width, will it fit in BT-5 (13mm) tubing?

It might be a good idea to move the mounting lugs to the ends rather than sticking out the sides, enabling it to be mounted in even smaller diameters, such as a coupler for BT-5.

OOC, why do you need a tracker in a 13mm rocket? Isn't that super-niche and it'd be flying off mini engines unless it's transitioned.

Desert launch altitude shot on a transitoned and staged rocket?

Edit add: Perhaps for a mini tube encased tracker that you can fasten to a shock cord, u-bolt, etc.

 

[jhill9693]

Hey,

I'm the guy behind Silicdyne, a company dedicated to providing the best in advanced rocketry electronics at low cost.

You may have heard of my first product, the Fluctus flight computer. It's a project that's still ongoing development and on the market, but in parallel I'm also developing my next product.

This thread will be dedicated to that new project, called Reperix.

Reperix is a GPS tracker for rocketry.
Its principle is fairly standard: a module, which knows its position via GPS satellites, is placed in the rocket and transmits its coordinates by radio wave to a ground station. The ground station then retransmits the information to a software application (in this case a mobile app) so that you can monitor your flight and be guided back to your rocket on recovery.

In terms of performance, Reperix is up there with the best with its 140mW long-range radio, and latest-generation GPS chipset (ublox M10) for excellent dynamic tracking up to 80km altitude and 500m/s.

One of Reperix's greatest strengths is its size:
the module itself measures down to just 12 by 30mm, making it the world's smallest rocketry GPS tracker. Perfect for your wildest projects!
*For reference, that's more than 2 times smaller than the Featherweight.



And the best part is... I've already got a fully functioning prototype of that thing!

Quick hardware notes:
The battery is intended to be plugged through the bottom USB C connector (capable of voltages from 3.5 to 16 volts), but this might change in next versions.
The actual 915mhz antenna is connected through a robust IPEX radio connector, and there is exposed pad for soldering a thin ~8cm copper wire instead.
All in all you should be able to make a super lightweight and compact tracking setup (reperix+antenna+battery) within 9 grams.

View attachment 653824


2 euros coin for size reference:

View attachment 653832


The ground station used - SteadyBluetooth:

View attachment 653833


I'm planning to do plenty of ground and flight tests soon to properly validate the specs.

On the software side, I'm also making good progress and already have functional firmware/application foundations.
Here's a list of the features that are being / will be implemented:


On the Reperix tracker:

• Configurable radio channel selection with automatic switch on frequency occupancy
• Launch/Apogee/Touchdown detection algorithms
• Flight trajectory recording in internal memory
• Possibility of sending location packets automatically over TheThingsNetwork to track Reperix almost anywhere in the world (useful for potential high altitude balloon usage)
• Battery voltage monitoring, LED status indication...

On the mobile app (Android/iOS), connected to SteadyBluetooth ground station:

• Flight data display / GPS details
• In-app distance/bearing and live tracking on a map
• Voice telemetry during flight
• Settings config
• Convenient and plug and play user experience

For trajectory data download/view, and firmware updates, I'm planning to build a web tool (thus usable anywhere on any PC, without installing anything).


The aim is to have a first user-ready version in about 2 months, in order to launch a small betatest campaign.
I don't have a proper pricing estimate to share yet but it should be quite attractive.
More is coming soon.

If you have any suggestions or questions, feel free to react to this post!

I volunteer for test flights, and can test in parallel with Eggtimer Quasar or Mini GPS for comparison. PM me if interested.

 

[SolarYellow]

From tip to tip, the board with the mounting tabs is 19mm wide.

That won't fit in BT-20, which is 18.1mm ID, 18.7mm OD (off the top of my head).

 

[Titan II]

That won't fit in BT-20, which is 18.1mm ID, 18.7mm OD (off the top of my head).

You just remove the tabs. They are made to be removed if you so chose.

 

[FMarvinS]

I can do that in the application. The ground station itself don't know where the tracker is, it just forwards data to the smartphone.



The radio used uses modern chirp spread spectrum modulation techniques (LoRa) which, in a nutshell, make it possible to achieve some pretty crazy distances.
In line of sight near ground, I've tested that radio system successfully at a range of more than 10km. In flight, I think it can reach 100km.

It's true that switching to 433mhz might almost double that distance, but that's not all. Decreasing the frequency by 2 times also means that data takes 2 times longer to transmit, and so:
- packets might be more likely to be corrupted (because they are spread over a longer time span)
- radio consumes virtually 2 times more energy
- the data refresh interval is twice as long, which is undesirable if you want smooth real-time flight monitoring
So that's a bit more tricky choice.

I also agree with what @Art Upton said.

Thanks for your timely response. Others (Big Red Bee GPS,Byonics, Eggfinder)) have offered 2 meter and 70 cm GPS/transmitter units with no or minimal packet corruption. These companies offer both ham band and 900 MHz band units. Also, as you acknowledged, the use of 2 meters and 1 watt significantly increases the potential transmission distance which is offered by Byonics and Big Red Bee..My purpose is to only suggest that in addition to 900 MHz, please consider the additional production of units that transmit in the ham bands too.

 

[SolarYellow]

You just remove the tabs. They are made to be removed if you so chose.

I still think it would be better if the tabs were on the end, so they could be used or not, but without the choice being permanent. This will be significantly more expensive than an Eggfinder Mini, so it would be nice to have it be useable indefinitely on the maximum variety of rockets.

 

[FMarvinS]

I have one of those high power 2m transmitters and it is not really needed for rocketry or ballooning and consumes way too much power. Look at what Pico Balloons are using for APRS and WSPR globally. One got shot down by an F22 remember?

Also the amount of Amateur Radio Operators, sometimes called Hams that are also rocketeers are very tiny market. When trackers went from Amateur 70cm frequencies to 900mhz the market grew exponentially larger about 12 years ago.

Meshtastic on 900mhz is taking over more and more what APRS did/does for networking/messaging. The APRS AX.25 collision domain is very dated now and we need to move forward from it. It needs very good SNR to decode packets also.

There are only two Amateur Radio HTs now made that Receive APRS directly; The Kenwood TH-75 [$750] and the Yaesu FT-5 [$420 street price], both very expensive. Yes I have many of my older HTs that do APRS, but it's expensive for new users. Yaesu is now the only one making mobile 2m/440 radios that have analog APRS in them.

Art - K8XG

Art-I agree that LORA has significantly improved 900 MHz transmission. But,as you know, APRS is still very popular in Ham circles. Furthermore, for the uninitiated, APRS transmission via repeaters on towers, enables multiple receivers to acquire messages (e.g. GPS coordinates) at distances far exceeding simplex (e.g. 900 MHz) transmissions. Thus, favoring rocket recoverability. Kenwood and Yeasu produce APRS capable hand transceivers and mobile units used in cars. I personally have found that transmission distance from a 1 watt GPS unit,in flight and particularly after landing, far exceeds that of a 100 mw or 250 mw unit. Again, this favors recoverability. High Altitude Balloon enthusiasts often utilize higher wattage APRS units for similar reasons. I respect the differences in opinion and I don't want to utilize any more of Ulyu's time. The only request was to offer ham based units in addition.
Fred,
KG4YGP

 

[Art Upton]

Thanks for your timely response. Others (Big Red Bee GPS,Byonics, Eggfinder)) have offered 2 meter and 70 cm GPS/transmitter units with no or minimal packet corruption. These companies offer both ham band and 900 MHz band units. Also, as you acknowledged, the use of 2 meters and 1 watt significantly increases the potential transmission distance which is offered by Byonics and Big Red Bee..My purpose is to only suggest that in addition to 900 MHz, please consider the additional production of units that transmit in the ham bands too.

I am curious what rocketry/balloon type application you have that needs 1+ watt? Going to the edge of space is going to require special programming in the GPS RX unit to make sure it works for the Speed/Altitude limit imposed on them. But I suspect you know that.

FYI the Byonics units are mostly for Ham tracking use in 2D, not for Balloons or rocketry. Their small 2 watt unit needs a separate GPS receiver. They have been out of stock on that and some of that stuff for awhile. I don't think there is that much market for it.

These are used on PICO balloons: https://www.wimo.com/en/picoaprslite
US seller: https://www.dxengineering.com/parts/wmo-picoaprslite
I have one in my electronics bin, was waiting on making a balloon that never happened, at least I got it years ago for less.

The high power really drains a battery faster on the 2 I have , compared to the same brand unit in lower power amplifier. I have a BigRedBee 2 meter high power and an AVRT5 China unit. The China unit is too heavy and not really good for rocketry.

I have also used Big Red Bee GPS 440 standard power units since about when they came out*, on most all my high L2 and 3 flights and they worked well. I used BigBee RDF 440 trackers and still do.

I've lost two of the BeeGPS, one to a supersonic Shred that separated the nose cone from it's shoulder and the Green Bee-GPS board was never seen again in the grass, even after seeing it float to the ground. [They come in Red now it seems, my last two were] The other one was reporting right were it was, in a tree in the Middle of a Bog next to Manchester TN Sod farm. I still have one left.

*PS, I have a video where the M1400 rocket in my avatar has one in the nose, and Greg from Big Red Bee who's camp was next to our club's trailer camp, is calling out the Altitude up and down on my fight to the LCO.

** I've also flown the old OOP OZARK/Loki GPS/900mhz telemetry add-on for the ARTS flight computer on an M1400 as well. I have a video of that kicking around some place on the web. After it went OPP, I sold it here to someone who wanted it for their ARTS boards on a project they were doing. It worked well, but cost seems to have limited the market for it.

 

[Adrian A]

Thank you !!



It was quite a pain to get the circuit board design RF-efficient, but surprisingly it's pretty good!
With sort of optimal conditions (no antenna obstructions and clear sky), it managed to fix 12 satellites in about 3 or 4 minutes, and it provides me position with a fairly small uncertainty radius (about 2m). I'll be doing more tests soon to see how dynamic tracking performs during a flight.

That is surprisingly good performance for that size of antenna and ground plane. Good job! If you want to benchmark against the Featherweight GPS performance, this is from the ground station log of a test I did on my deck just now:



I turned on the tracker at and got the first packet at 11:00:14 AM. The first lock was 21 seconds later, and 12 satellites was 37 seconds after the cold start. It was locked on 20 satellites 1:25 after power on. The numbers >40, >32, etc. are the reported signal strength in dB. I have read once (not sure if it's still true for this generation of receivers) that a signal strength >=32 is needed to download the ephermeris data (orbital elements) from the satellites initially, but once the receiver has the data it can continue to track at lower signal strength. If there is a rocket installation that blocks most of the GPS signal, then it can help to get a lock with the av-bay out in the open where the receiver can download the data, and then install the av-bay inside the rocket. I took advantage of that with my carbon fiber booster, where I cut the CF and made a small FG-covered window next to the tracker. This was needed when I was flying a uBlox 8. Later with the uBlox 10, the window was enough to get a lock when the av-bay was in place inside the booster.

 

[rfjustin]

Make sure you can power the unit by a 9V battery off the shelf with the USB adapter. Sometimes when you are in remote locations, having a power source option like a 9V is really convenient.

 

[Ulyu]

Thanks for your timely response. Others (Big Red Bee GPS,Byonics, Eggfinder)) have offered 2 meter and 70 cm GPS/transmitter units with no or minimal packet corruption. These companies offer both ham band and 900 MHz band units. Also, as you acknowledged, the use of 2 meters and 1 watt significantly increases the potential transmission distance which is offered by Byonics and Big Red Bee..My purpose is to only suggest that in addition to 900 MHz, please consider the additional production of units that transmit in the ham bands too.

2m band requires entirely different radio modulation and will thus require an entirely different hardware product. Maybe one time I will make a HAM band-able tracker, but unfortnuately Reperix will never be because that's just not physically possible!
In fact, even a 433mhz (70cm) version wouldn't be doable because my chip manufacturer don't produce chipsets on this frequency band.

I can only offer 868 or 915 depending world regions.

Make sure you can power the unit by a 9V battery off the shelf with the USB adapter. Sometimes when you are in remote locations, having a power source option like a 9V is really convenient.

I can confirm it can !