I'm a total novice when it comes to RF beyond basic concepts.

I'm trying to use a HackRF One to pull the data coming off of this transponder, which theoretically transmits data on a 3.59MHz carrier.

I've followed some tutorials on BPSK demodulation, but while I expect the constellation to look like this:

Ideal BPSK constellation

I'm getting points all over the I and Q axis with no consistency whenever it transmits (having trouble getting a screenshot of just when the device is transmitting). Here's my current setup - is there a parameter I have incorrect or am missing?

GNU Radio

  • \$\begingroup\$ I don't think the hackrf supports an extremely low sampling rate like that. If you used a normal sampling rate like e.g. 8 MHz and look at the received spectrum (qt frequency sink), do you see your transmission? \$\endgroup\$
    – mmmm
    Commented Apr 19, 2021 at 0:04
  • \$\begingroup\$ Is it dots randomly everywhere, dots populating a disk, or dots on (or roughly on) a circle? Maybe give us a hand sketch if you can't take a screenshot. \$\endgroup\$
    – TimWescott
    Commented Apr 19, 2021 at 1:02


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