hackrf VS hologram-python

Another example: the HackRF SDR board was done in KiCAD

https://github.com/greatscottgadgets/hackrf

keep and eye out for this issue: https://github.com/greatscottgadgets/hackrf/issues/668

I have read about this issue on github (have been some reddit posts over the years as well), originally in #541 which has now culminated in an ongoing investigation #974.

HackRF would be my next choice... https://greatscottgadgets.com/hackrf/

However, unlike your sensitivity issues, i dont get any birdies. i have a TCXO though. (https://github.com/greatscottgadgets/hackrf/issues/216). it seems its related to clock drift calibration without one. However this is something most SDR's suffer from, as a cost saving measure. Most RTL_SDR's suffer from this as well ("rtl sdr blog v3" comes with a stable TCXO, resolving the issue.).

I assume this is the case since I found a GitHub issue talking about blown TX: https://github.com/greatscottgadgets/hackrf/issues/1051 And I followed the recommendation of using hackrf_transfer -c with both -a 0 and -a 1. With a separate RTL SDR tuned to the output frequency I can see a very low power CW signal with -a 0. With -a 1 there is no output. This seems to match the results in the issue.

If you're talking about building attachments to work with a phone, you're almost all the way there to a standalone device anyway. You might want to look into HackRF and pwnagotchi for inspiration.

If you get a HackRF there's a utility called hackrf_transfer which can record a block of spectrum and then play it back.

OVMS is a not cheap module. It comes with a hologram.io SIM card, but you can use any data-only LTE plan. Cost for the module is over $250, and then you'll have to pay somewhere south of $5/mo for a data plan if you go with hologram.io.

An LTE plan from hologram.io is a few bucks a month... and i'd gladly pay it and not give my money to OnStar's broken stuff :-).

You could build out something using Arduino or similar. It's a very heavy lift, especially if you don't have experience using Arduino/similar build-your-own-hardware stuff. But you can find an Arduino as a processor, a GPS module, an IoT/Cell data module, and either battery or some wiring to plug it into another power source, and write your own custom code that will turn the unit on and report location at an interval of your choosing. I'm guessing that'd cost roughly $50-150 for initial hardware depending on options, and you'd need to pair it with monthly cell data service, like hologram.io.

I want to lead off with a big shout-out to Botletics and their (his?) SIM7000 LTE CAT-M1 shield. From the beginning I knew I was going to need wireless connectivity and that WiFi was not going to reach. I considered Blues Wireless, but ultimately went with Botletics + hologram.io and I'm extremely glad I did. I plugged it in, I lightly modified the example code (it was pretty close to what I needed already, I basically just took out the GPS reading and replaced it with an averaged HC-SR04 ultrasonic sensor reading) and it just worked.

Companies use hologram.io sim cars in their devices and trackers and no consumer knows this unless they take the device apart and inspect the sim car and look up what the logo is.

hologram.io

If you can't get Ethernet then Cellular modem is best. For devices I rarely need to talk to I use hologram.io and it costs me a few dollars/year (under $10USD). Otherwise get a real cellular plan. Hologram has some nice software to make it easy to communicate.

i will be trying the mkr nb 1500 with the hologram.io sim card. hologram has a pilot program that includes 1mb of free data per month which should cover texts that aren't sent all the time. i mention this incase anyone else stumbles on this in search of a similar solution.

Depends how open you mean. For a lot of hobbyists and integrators, this works:

https://github.com/hologram-io/nova-hardware

And run this on a Pi:

https://github.com/hologram-io/hologram-python

If you need something one layer deeper on the module or chipset level, there’s not really a lot out there.