hackrf VS hardware

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.

I tried looking in the schematic here: https://github.com/rad1o/hardware/blob/master/datasheets/else/hackrf-one-schematic.pdf I'm not great at reading schematics, but from what I'm able to gather it seems that should be a 22pF capacitor? I assume 0402 size SMD. Anyone able to confirm?

Here's a schematic for the HackRF One. The official source is here but those aren't rendered out to PDF, you'd need KiCAD and such to get anything out of them.

Here is the schematic