World's smallest rocket GPS tracker - Silicdyne Reperix

[Ulyu]

Out of curiosity, what's the approximate cost for the unit and a combo with the ground station looking like right now? This looks like a very nice product.

I'm aiming for a retail price of less than 300 USD.

 

[Ulyu]

If you can change the antenna, you'll need a "light weight" cert to confirm you're not radiating too much power with a high-gain antenna. That's what "compliant-ready" means.

Maybe you're right. I've just contacted some french certification labs about this, I'll post here if I get any interesting news.

Note that I'm not at all reluctant to have my product validated to be fully compliant with FCC before "mass producing" it, it's just something that isn't really possible yet since the hardware designs are immature. Once again, I try to be as transparent as possible and I appreciate your comments !

 

[xSwaggyMcjaggyx]

*But I don't live in the USA and have had no contact with the FCC authorities on this subject.

Even though you don't live in the United States, you still have to adhere to the rules and regulations formulated by the FCC. The words "pretty sure, acting in good faith, trusting the guidelines of other small manufacturers in the USA who seem to know what they're doing" only goes so far in the Office of International Affairs (OIA) and makes it seem like you haven't done enough research before mass importing your goods into the United States. The FCC has no problem targeting overseas companies that are importing illegal intentional radiators into the US so I'd advise you to take a step back and realize what you're doing here.

Note that I'm not at all reluctant to have my product validated to be fully compliant with FCC before "mass producing" it, it's just something that isn't really possible yet since the hardware designs are immature.

And that's great to here! I believe you have a great product and it's really benefiting the rocketry community as a whole. However, operations seems a little reversed here. It takes companies years to develop and perfect a board before they submit it to the FCC or CE because they know the process can be daunting with months of ongoing questions, design reiterations, and a large amount of funding. I'm not going to keep beating the dead horse, but I wish you good luck.

 

[Ulyu]

By the way, tell me if I'm wrong but the the AimXTRA doesn't seems to have any certifications either ? The only certificates I found are for its OEM radio module.

And that's great to here! I believe you have a great product and it's really benefiting the rocketry community as a whole. However, operations seems a little reversed here. It takes companies years to develop and perfect a board before they submit it to the FCC or CE because they know the process can be daunting with months of ongoing questions, design reiterations, and a large amount of funding. I'm not going to keep beating the dead horse, but I wish you good luck.

I absolutely understand the concerns, but now we have to look at the practical implications.
If I certify my products today with radio compliances (the necessity of which I do not deny), it would mean that the hardware design would be fixed forever until I re-certify. In fact, I would even have to re-certify every time I updated the firmware (which happens very often).
I'm in no way trying to find an excuse or absolve myself of anything, but please understand that to stay 100% within FCC regulation, even if I took the time to do a whole certification process for a product that will never exist beyond a few hundred copies, I will have to spend several thousand of dollars every time I release a new minor revision.
And even though I've been developing my systems for years and years, there are always minor reiterations to be made, it's unavoidable for the time being.
Once again, I'm not defending myself, I'm just bringing an important and necessary element to this discussion.

It's indeed time to take a closer look at these certification issues, and I DID contact several labs earlier today to find out a proper solution to this.

 

[schworer]

Re these low power TX telemetry and GPS trackers, keep in mind that they are being used in geographic areas with generally extremely low population density and any interference caused by them would be at worst case "below negligible", particularly for the frequency and modulation used. The FCC standards are really intended for high density areas where interference could be an issue and where a company would be selling many thousands of units. My guess is using certified tx chips in accordance with good board design & assembly principles and with their antenna designs will pass any testing.

The bigger issue is potential interference with other electronics colocated with the transmitter. For example, I had the first generation RDAS GPS back around the 1999/2000 time frame along with the 100mW telemetry transmitter. The problem was the roughly 3rd order harmonic from the transmitter was swamping the GPS receiver that was connected to a separate 20db amplified GPS patch antenna (no integrated antenna and receivers available then), so I had to do a lot of shielding with aluminum and copper foil to get the system to function inside a 4" air frame. I had similar issues with the 70cm 1 watt ATV transmitter as well, and end up using low-pass filters on the coax going to the inverted V dipole which projected a couple inches outside of the airframe (elements made out of rigid piano wire). I did a lot of ground testing to make sure both those 70cm transmitters by themselves and also both running at the same time didn't mess up the RDAS boards.....which they didn't. When I mix Eggtimer transmitters with non-Eggtimer boards I always test to make sure the low power RF doesnt cause any problems. So far 100% success rate with being good to go.

 

[xSwaggyMcjaggyx]

If I certify my products today with radio compliances (the necessity of which I do not deny), it would mean that the hardware design would be fixed forever until I re-certify. In fact, I would even have to re-certify every time I updated the firmware (which happens very often).
I'm in no way trying to find an excuse or absolve myself of anything, but please understand that to stay 100% within FCC regulation, even if I took the time to do a whole certification process for a product that will never exist beyond a few hundred copies, I will have to spend several thousand of dollars every time I release a new minor revision.
And even though I've been developing my systems for years and years, there are always minor reiterations to be made, it's unavoidable for the time being.

Trust me. Your frustration has been shared with many small creators across the world. You are not the first person to have dealt with these road blocks created by the FCC. However, these road blocks are created for a reason and therefore we should abide by the rules and regulations set in place. Doesn't matter the quantity of units sold either...

Re these low power TX telemetry and GPS trackers, keep in mind that they are being used in geographic areas with generally extremely low population density and any interference caused by them would be at worst case "below negligible", particularly for the frequency and modulation used.

That is correct, but I haven't met many people who would drive 15 min to 45 min out to a launch site to be able to test a GPS tracker. Usually people assemble and test them in the comfort of their home before going out to the launch field. Therefore, doing so potentially puts high density areas at risk of interference.

 

[Titan II]

I'm not going to keep beating the dead horse, but I wish you good luck.

Then why are you still beating it?

 

[xSwaggyMcjaggyx]

Then why are you still beating it?

Touché

 

[schworer]

That is correct, but I haven't met many people who would drive 15 min to 45 min out to a launch site to be able to test a GPS tracker. Usually people assemble and test them in the comfort of their home before going out to the launch field. Therefore, doing so potentially puts high density areas at risk of interference.

Re testing at home in a high density area, I was talking about checking for RF interference to the flight computer. And when testing in a high density area, I doubt there will be anyone or anything within in range at that particular frequency, particularly at that low level of power or modulation, that it would be an issue with. That would certainly be the case with spread spectrum type systems like LoRa. If you want a high density example of spread spectrum avoiding interference, just look at your WiFi settings on your computer or phone. If you are in a dense area you will see both your router and everybody else's router or WiFi device nearby all operating on basically the same frequency band and not interfering with each other That is because they are using different spreading sequences. For more conventional type modulations, the inverse square law applies plus RF absorption by physical objects, so for low power devices the range at ground level is probably no more than a few hundred feet. Regulations may be regulations, but for real world functional purposes these devices are just not a big deal and the FCC has a lot bigger fish to fry than to get all wound up over amateur rocket GPS or telemetry transmitters, powered by factory certified compliant transmitter modules, that are really only used infrequently out in the hinterlands for short periods of time.

 

[Simon Auty]

Ulyu just another plug for a Tx-Rx in the 921mHz frequency so your unit is legal for Australia and New Zealand

 

[Ulyu]

Hey

I took a short break on this project because I had a lot to deal with with Fluctus and other products in the pipeline.

Several trackers made a few flights during these last few weeks.
From a functional point of view, they have all worked fine, but I've still got some work to do:
unfortunately the tracking performance aren't as optimal as I had hoped and as a result the tracker typically loses fix on take-off.

Realtistically it's not a problem for 80% of the use because the main function is to find the rocket on landing, to know where it is during descent or to get the apogee altitude. But I feel that it's still quite a waste to cut these capabilities.

For example the following trajectory was recorded at Balls32 at over 6km (20kft) altitude. Radio communication was maintained throughout the flight.
As expected, most of the ascent trajectory is missing.
By contrast, the tracking accuracy at apogee and during descent is really f* good. (sometimes down to an HDoP of 0.6 !)




So while continuing testing and software development, I'm designing a third version that's even more compact (yes, even more compact than what it already is ...) and that should improve GNSS performance to keep a better fix during ascent.

And thank y'all again for your interest !

 

[Flare]

Image in the above post is my flight (L1000 subminimum diameter, 20k ft, Mach 2.8). I was very happy with the Reperix tracker. Super nice and small which is a huge selling point for high performance flights where having a compact avbay is crucial, and it's easy to use. Highly recommend checking this out once it hits the full market.

 

[JoeTekcor]

Your work on these projects has been exciting to watch. I just added the Fluctus to my letter to Santa. I'm sure the Reperix will be on the wish list once it is available.

 

[dhbarr]

A GPS for getting 13mm, 18mm, 24mm experiments back is pretty exciting stuff.