I have two ultra small/sub-miniature coaxial connectors on my circuit board - one for a cellular (4G) antenna and one for a GPS antenna. I accidentally connected the cellular antenna to the GPS connector and the GPS antenna to the cellular connector.

With the wrong setup, I powered the device and started seeing errors when trying to get the GPS signal through AT (modem) commands. However, when I connected the antennas properly the errors went away and I was able to get GPS and cellular signals. The board seemingly functions fine now.

What can go wrong in this case? Is there a chance I could have damaged my circuit board or the antennas with a setup like that? If so, then why?

Board schematic: https://www.waveshare.com/w/upload/c/c8/SIM7600E-H-4G-HAT-Schematic.pdf

The entire circuit board with antennas is shown on the photo below.to

Schematic for the antenna connectors:

enter image description here

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    \$\begingroup\$ are you experiencing a problem? \$\endgroup\$ – jsotola Jan 13 at 0:00
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    \$\begingroup\$ somebody got their signals crossed \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jan 13 at 0:00
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    \$\begingroup\$ @jsotola No, it started working fine when I swapped the antennas back. Thank you for the suggestions. I made edits to the post. \$\endgroup\$ – Ben N. Jan 13 at 0:13
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    \$\begingroup\$ @ReinstateMonica-ζ-- I'd suspect that GPS antenna (with l-o-n-g, lossy coax) is active. So DC is likely provided with a bias-T from the board. Does the cellular antenna require a bias-T as well? Hard to tell. OP is lucky the board's bias-T and DC supply to it survived the swap. \$\endgroup\$ – glen_geek Jan 13 at 18:12

Looks like you are using an active GPS antenna which certainly means it has a LNA built-in. If you are setting-up the modem in GSM mode, at higher transmit power (if I recall correctly can go up to +30dBm) you may eventually damage the LNA output stage and therefore not get anything out of your GPS antenna. It does seem like an unlikely scenario though, you could try and report :)

Connecting the cellular antenna to GPS will likely "capture" no satellite signal because it is not designed for these frequencies. There is a chance you get few satellites (the stronger ones) if your antenna is broadband and crosses GPS frequencies (~1.6G), however I don't think you can get any usable location application with that setup. It shouldn't do any damage if your GPS module has a proper notch filter (very common).

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