Sooooo several comments: 1) It's very possible your signal is too strong. IIRC, GPS signals are usually around -150 to -160 dBm at the receiver. The HackRF can transmit at about +10 dBm. That is SIGNIFICANTLY stronger than most GPS receivers expect.
2) BE VERY CAREFUL ABOUT TRANSMITTING GPS SIGNALS. Even Faraday cages don't provide perfect isolation -- I've used one with 90 dB of isolation before. Of course, +10 dBm - 90 dB is... -80 dBm, which is 80 dB louder than a typical GPS signal! Even if you hard-wire your HackRF to your receivers (through attenuators, of course), you'll likely be leaking a relatively strong signal. 3) You will likely have to transmit a signal for at least 15 minutes to get a lock, as your transmitter isn't synced to actual GPS time. See https://en.wikipedia.org/wiki/Time_to_first_fix. Phones may also have trouble locking because they might rely on A-GPS for the ephemeris and almanac data, as well as coarse time sync. On Thu, Jul 9, 2020 at 1:59 PM John Akin <ja...@asset-intertech.com> wrote: > I am working on a project that involves a GPS receiver and I need a GPS > generating device to produce test data. I thought the HackRF One sounded > perfect for the job. > > I have gone through the tutorial videos on Great Scott Gadget’s site and > implemented the FM radio project, so I believe that I have verified my > HackRF is definitely working as an FM receiver. Now I am seeking guidance > in the transmitting of GPS. > > I found several tutorial videos on line that make it look easy enough and, > following their examples, I have been using the HackRF transfer command to > transmit the GPS signal (the command syntax I have used is, > “hackrf_transfer -t .\gpssim.bin -f 1575420000 -s 2600000 -a 1 -x 0 -C 2 > -R.”) > > I see the Transmit LED is on, as I would expect, but I am not having luck > in verifying the transfers are occurring using apps for either Android > phones, or iPhones. The GPS location reported by these aps is my physical > location no matter what coordinates I supply. > > I have also connected, via SMA cable, the HackRF to my project and the GPS > receiver does not appear to be receiving GPS coordinates either. The GPS > sentences it reports contain no latitude or longitude values. > > Anyone have any recommendations? > > Thanks! > > _______________________________________________ > HackRF-dev mailing list > HackRF-dev@greatscottgadgets.com > https://pairlist9.pair.net/mailman/listinfo/hackrf-dev >
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